CHAPTER 2 Review of literatures - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/5052/11/11_chapter 2.pdfReview of literatures ... toxicity and the amount of exposure to that

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CHAPTER 2

Review of literatures Pesticide usage and sustainability of cardamom ecosystem are the important research

areas of this thesis. Therefore the available information on these two important fields has

been arranged to cover these two aspects, which are pesticides in agroecosystems,

climate variability and change in tropical mountains and Indian cardamom hills,

agroecosystem intensification and sustainability as well as forest degradation. Since,

agroecosystem sustainability is more closely related and important to water resources the

quality of surface water both in cardamom and tea ecosystems is reviewed in detail.

Forest and cardamom growth and development as well as yield are interrelated

therefore, the impact of biodiversity and its loss is covered in depth in this chapter.

2.1 Pesticides in agroecosystems History of pesticides

The humans enticed high productivity through the breeding and management of

food plants and animals. Through scientific knowledge and technology, we controlled

crop diseases, weeds, nematodes, insect pests, rodents and other pests that would

otherwise shorten our lives or compete with us for food and fiber. In nature, there were no

pests. Humans labeled as “pest” any plants and animals that endanger our food supply,

health or comfort. To manage these pests, we have “pesticides”. These were products

“intended for preventing, destroying, repelling or mitigating any pest” (US FIFRA,). The

only thing all pesticides have in common was that they are used to control pests.

Otherwise they come from almost every imaginable class of chemicals. Every one

associated with pesticide use viz., farmers, extensionists, environmental protection

specialists, state regulatory experts, manufacturers and environmentalists-needs

information that will allow them to distinguish between pesticides that may be a problem

as pollutants in certain situations and those which may not. There were five basic

properties that were combined with information about use, provide much information

about the potential of a pesticide to be a pollutant. These five properties were solubility in

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water, volatility, soil absorption tendency, persistence and ionization potential

(Wauchope, 1998). Pesticides were designed to be toxic to living things; so by their very

nature, they pose risks. The risk of a substance has been a function of the substance’s

toxicity and the amount of exposure to that substance. The risks of pesticides, however,

whether real or perceived, may force changes in the way these chemicals were used.

Scientists and lawmakers are working toward pest control plans that were

environmentally sound, effective and profitable. The best pesticide policies will reconcile

environmental concerns with economic realities. Pests must be managed, and farmers

must survive economically. Humans have practiced agriculture for more than 10,000

years, but only in the past 50 years or so farmers have become heavily dependent on

synthetic chemical fertilizers and pesticides (Horrigan et al., 2002). Pesticides were not

new for farming. Ancient Romans killed insect pests by burning sulfur and controlled

weeds with salt. In the 1600s, ants were controlled with mixture of honey and arsenic

compounds. By the 19th century, the US farmers were using arsenate, nicotine sulfate and

sulfur to control insect pests in field crops, but results were often unsatisfactory because

of primitive chemistry and application methods.

The major classes of pesticides were acaricide, antimicrobial, attractant, avicide,

fumigant, fungicide, herbicide, insecticide, molluscide, nematicide, piscicide, predacide,

repellent, rodenticide surfactant, and synergist. An emergence in pesticide use began after

World War II with the introduction of dichloro diphenyl trichloroethane (DDT),

hexachlorobenzene (BHC), aldrin, endrin and 2,4-dichlorophenoxy acetic acid (2,4-D).

These chemicals were inexpensive, effective and enormously popular. DDT was

especially favored for its broad spectrum activity against insect pests of agriculture and

human health. 2, 4-D was an inexpensive and effective way of controlling weeds in grass

crops such as corn. Lulled into a false sense of security, users applied pesticides liberally

in pursuit of habitats sterilized of pests. Under constant chemical pressure, some pests

became genetically resistant to pesticides, non-target animals were harmed and pesticide

residues appeared in unexpected places.

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Benefits of pesticides

Studies of the benefits of pesticides have estimated the economic consequences of

a ban on pesticide use. These ‘what if” studies deal with extreme-case possibilities, but

they served as a starting point for putting pesticides in perspective. Possible effects on the

United States society of a hypothetical ban of herbicides, insecticides and fungicides had

indicated that the US food production would drop and food price would soar besides the

farmers would be less competitive. A pesticide ban in the United States would decrease

year-ending supplies of corn, wheat and soybeans by 73 per cent, trigger price instability,

slow U.S. food aid programs to poor countries, and increase worldwide hunger. Similarly

ban on fungicides would increase consumer food prices by 13 per cent, reduce the gross

national product by about $28 billion, and eliminate 235,000 jobs including 125,000 jobs

in the farm sector, which represented 4 per cent of total agricultural employment

(Barrons, 1981; NRC, 1989).

An estimate of crops losses to pest for the first three years (2001-2003) of the

present decade was 26-29% for maize, rice and potatoes respectively. The efficiency of

crop protection was higher in cash crops than in food crops. Despite a clear increase in

pesticide use, crop losses have not significantly reduced during the past 40 years (Oerke,

2006). The distribution of pesticides on crops is uneven for example, 50% of all

insecticides used in the US is applied to non food crops (Cotton and Tobacco). Only a

few food crops, mainly fruits and vegetables, have more than 75% of their acreage treated

with insecticides (Pimental et al., 1978). Widespread use of synthetic organic pesticides

has contributed enormous benefits to consumers. Chemical pest control has contributed to

dramatics increases in yields of most major fruit and vegetable crops (Gianessi, 1999).

Some of the new generation insecticides were found to increase the cardamom

yield significantly in Ceylon. Thrips and borers in combinations damaged 91% of the

capsules when no spraying of pesticides was taken up. The insecticides thiamethoxam,

lufenuron, fipronil and thiacloprid successfully reduced capsule damage while

chromofenozide, tebufenocide and acetamiprid did not reduce the damage percentage.

Higher yields were obtained for thimethoxam (335 g/plant) and lufenuron (304.9g/plant)

(Dharmadasa et al., 2008).

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Risks of pesticides and their residues

With the publication of Rachel Carson’s book Silent Spring in 1962, public

confidence in pesticide use was shaken. Carson painted a picture of environmental

consequences of careless pesticide use. Although the quality of her reporting has been

severely criticized, Carson, more than anyone before, had pointed out the risks of

pesticides (Carson, 1962). The result has been a direction of research toward more pest-

specific pesticides and cropping methods that reduce reliance on pesticides. For instance,

“pyrethroid” insecticides were modeled after natural “pyrethrins”, which were natural,

plant-derived poisons that have been used as insecticides for hundred years. Insect growth

regulators (IGR) mimic hormones that affected insect growth, but they have little effect

on non-target organisms. These products and similar ones using bacteria, viruses or other

natural pest control agents were called “bio-rational” pesticides. Epidemiologic studies

from a number of countries indicated that farmers were most vulnerable to be at higher

risk for selected cancers than the general population (Pearce and Reif, 1990; Blair and

Zahm, 1995) because farmers world wide were more exposed to pesticides than common

public.

Li (1983) screened around 75 pesticides for mutagenicity in the microbial systems

for the assessment of the safety of the system, among them surflan, zincofol were

mutagenic on strain TA 100 Salmonella. Li (1983) also found higher concentrations of

herbicide residues in paddy soils which caused phytotoxic effects on cucumber, radish,

rape, broccoli, maize and black bean during the next season. In a study from the U.S. with

225 food samples comprising of apples, lettuce, peaches, peppers, potatoes, snap beans,

spinach, sweet corn and tomatoes were analyzed for residues from 26 pesticides, 15 of

which were classed by EPA as possible causing cancer residues, (Hodgson and Levi,

1996). There were reasons to focus on pesticides because the carcinogenic potential of a

number of these chemicals has been demonstrated in animal bioassays. For about 50% of

the pesticides evaluated, the International Agency for Research on Cancer has concluded

that there was limited or sufficient evidence for carcinogenicity in experimental studies

(IARC, 1987). Pesticides have produced both short- and long-term effects on human

health. The UN has estimated that about 2 million poisonings and 10,000 deaths occur

each year from pesticides, with about three-fourths of these occurring in developing

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countries (Quijano, 2002). The elevated level of cancer risks and disruption of body’s

reproductive, immune, endocrine, and nervous systems were reported due to long-term

exposures of pesticides. Population based studies have shown associations between

certain types of pesticide and certain cancers (Blair and Zahm (1995). Repetto and Baliga

(1996) have showed evidence of an association between pesticide exposure and increased

incidence of human disease, particularly the susceptible immunocompromised

individuals.

Many of the pesticides used in developing countries have not been tested for their

toxicity, and testing in the past has focused on acute effects rather than long-term effects.

In an inventory of commonly used chemicals in 1984, the NRC found that data required

for complete health hazard evaluations were available only for 105 of the pesticides.

Human exposure to pesticides can come through residues in food-either on or within

fruits and vegetables, or in the tissues of fish and animals, human eat or through

contaminated drinking water and through the air the human breathe (NRC, 1993).

In a review of the status of contamination and safety of plant food in Arab

countries, Nahhal (2004) found a range of low contamination and concentration levels in

cucumber and tomato in Palestine, Jordan and Egypt. Elevated levels of contaminations

with pesticides were detected in vegetables from Pakistan, Egypt and in grapes from

Jordan. Several poisonous cases and plant food contamination were reported in Morocco,

Egypt, Iraq, Saudi Arabia, Sudan, Syria, Jordan, UAE, Pakistan and Yemen in the past

years. Further detailed studies of these problems showed accumulation of these organic

contaminants in consumer bodies and farm workers who worked directly with the

chemicals. This problem occurred due to over and misuse of pesticides in the

environment. Lee et al., (2004) found an association between chloripyrifos use and

incidence of lung cancers among applicators in agricultural health study. The increased

risk of lung cancer with increasing chlorpyrifos use was consistent after controlling the

state of residence and for a variety of lifestyle factors, including smoking, other

occupational exposures, previous lung disease, type and form of food intake. However,

lung cancer was not an a priori hypothesized site linked to chlorpyrifos exposure. Luchini

et al., (2000) reported various pesticide residues in soils after continuous application of

pesticides for cotton in Brazil. The residues ranged from 0.1-0.4 ppm, and among the

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pesticides studied endosulfan was found to be degraded fast in soils into sulphate

metabolites. In India, monocrotophos and endosulfan were considered the most frequently

used or consumed pesticides for intentional poisoning during 1997-2002 and the average

fatality ratio was 22.6 % (Rao et al., 2005). Epidemiological studies have found

carbomates and organophosphates to be carcinogenic (producing cancer), mutagenic

(causing genetic damage), teratogenic (damaging fetus) or allergenic (Zahm et al., 1997).

During the next 50 years from now, which is likely to be the final period of rapid

agricultural expansion there will be a major global environmental change. Should past

dependencies of the global environmental impacts of agriculture on human population

and consumption continue, 109 hectares of natural ecosystems would be converted to

agricultural production by 2050. This would be accomplished by 2.4-2.7 fold increase in

nitrogen and phosphorous driven eutrophication of terrestrial, fresh water and near shore

marine ecosystem and comparable increases in pesticide use. During the first 50 years of

Green Revolution, global grain production doubled, greatly reducing food shortages, but

at high environmental cost. Agriculture affected ecosystem by the use and release of

limiting resources that influenced ecosystem functioning (N, P and water) through release

of pesticides and conversion of natural ecosystem to agriculture. Although society

benefits from pesticides, many caused environmental degradation or affected human

health (WHO, 1990). Some pesticides, depending on persistence and volatility, disperse

globally, bioaccumulate in food chains and had impacts on human and other species far

from the points of release and that too many years after release. If past pattern continue,

global pesticide production which has increased over 40 years, would be 1.7 times than

that at present by 2020. World trade in pesticides, another estimate of trends in pesticide

use, would be 1.6 times present levels by 2010. Should trends continue, by 2050, humans

and other organisms in natural and managed ecosystem would be exposed to markedly

elevated levels of pesticides. According to Aspelin et al., (1997) the worldwide

consumption of pesticides has reached 5 million metric tons. Of this, 85% has been used

in agriculture. Although the largest volume of pesticide use has been reported in

developed countries, its use has been growing rapidly in developing countries too

(Matson et al., 1997).

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Li (1983) worked on the pesticide residues and toxicity problems associated with

pesticide use in Taiwan and reported that higher levels of arsenic and mercuric

compounds were found in paddy soils. He also studied various pesticides that were

commonly used on various crops in Taiwan and found residues of some pesticides like

chlorpyrifos (0.25 ppm), profenophos (0.1 ppm), acephate (2.5 ppm), carbofuran

(0.1ppm) etc. above the maximum permissible intake (MPI). Residue levels of some of

the chlorinated hydrocarbon insecticides (DDT, DDD and DDE) in the paddy soils of

Taiwan were reported to be highest in the surface soils (top 5 inches) than those of deeper

layers (10 and 15 inches). The arsenic content of paddy soils varied greatly from place to

place, ranging from 1.3 ppm to 176 ppm. The average arsenic content in paddy soils was

8.22 ppm in the upper most layer, and then increased to 14.07 ppm in the next layer,

lastly to 18.85 ppm at the third layer (15 inches).

Pesticide use on crops

In addition to the increase in quantity of pesticides used, farmers generally have

used stronger concentrations of pesticides, they have increased the frequency of pesticide

applications and increasingly gone for several pesticides together to combat (WRI, 1999)

various pest attacks. In fact, the amount of pesticide impinging on target pests is generally

an extremely small percentage of the amount applied. For example, pesticide consumed

by Pieris rapae caterpillars in collards showed that 0.003% of the 1 kg/ha of the pesticide

applied was consumed by the target pests. Joyce (1982) reported that only 0.0000001% of

the DDT applied for Heliothis spp reached these target pests. Amounts of pesticide

applied and amounts reaching target pests were often reported to be less than 0.1% of

pesticide applied to crops (Pimental, 1995). Therefore, the excess pesticide moves

throughout the environment, containing soil, water, and biota. The quantity of insecticides

used, on the other hand, varied with insecticide type. Newer synthetic insecticides,

phosphates, and carbomates, for example required smaller quantities per season than did

the chlorinated hydrocarbons of an earlier generation pesticides, such as toxaphene. In

1981, 74 million kg of insecticides were applied to some 34 million ha of cropland.

Nearly 40% of the total amount was used on cotton alone.

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The state of California in United States America has the most extensive reporting

system for agricultural pesticide use with approximately 2.4 million pesticide application

reports per year (Epstein, 2006). Recently, the UK had reliable data on pesticide use for

major crops (Thomas and Garthwaite 1998). India and all other developing countries had

no reporting system of pesticide use so far therefore no reliable data were available on

pesticides used in different states under different crops.

The pesticide consumption in India has reached nearly 85,000 MT (41020 MT

active ingredient) during 2007 with 204 registered pesticides in the Indian markets. Even

today, the bulk of the pesticide production is insecticides. India is currently the second

largest manufacturer and consumer of pesticides in Asia, and it ranks 12th globally. The

worldwide consumption of pesticides is about five million tones per year, of which 24%

is consumed in the US alone, 45% in Europe and 25% in the rest of the world. India’s

share is just 3.75%. Presently, the consumption of pesticide is showing a slight declining

trend. Despite huge consumption of pesticides, it has been estimated that crop losses

varied between 10-30% due to pest alone. In monetary terms, these losses amounted to

5800 million USD per year (Agnihotri, 1999). Pesticide residues from food commodities

were very high in India, and it was found that 51% of food commodities were

contaminated with pesticide residues. Out of these 20% had pesticide residues above

MRL (maximum residue level) values as compared to 21% contamination with only 2%

above the MRL on worldwide basis (Agnihotri, 1999).

The share of crop yields lost to insects has nearly doubled during the last 40 years

despite more than a ten-fold increase in both the amount and toxicity of synthetic

insecticide used (Pimentel et al.,, 1991). The increase in crop losses despite increased

insecticide use was due to several major changes that have taken place in agricultural

practices including crop varieties that were more susceptible to insect pests, the

destruction of natural enemies of certain pests, the reduction in crop rotations, the

monoculture and reduced crop diversity, the use of herbicides and plant growth regulators

that have been found to alter the physiology of crop plants, making them more vulnerable

to insect attack (Pimentel et al., 1991). As a whole, the world has very limited data on the

amount of agricultural pesticide used on major crops for considerable time period. It has

been difficult to assign causes for year to year fluctuations in pesticide use. Greater pest

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pressure in monoculture plantation increased profits, which resulted in greater pesticide

use. Overall, the pesticide use in any particular region or ecosystem could depend on

individual and total cropped area; climate variability and change; soil properties and

nutrient availability; crop and agronomic factors; socioeconomic and institutional aspects.

Climate conditions exerted a significant influence on the spread, population

dynamics, life cycle duration, infestation pressure and overall occurrence of the majority

of agricultural pests (Smatas et al., 2008). For instance, California’s dry summer climate

in inland limited the development of many foliar plant diseases. Consequently, fungicide

and bactericide used was less intensive than it would be in a region in which rain fell

more frequently during the growing seasons. Indeed, fungicide use was typically lower in

years when there was little or no rain in the spring and fall. The patterns of pesticide use

were generally crop dependent world wide (Epstein and Bassein, 2003). In cardamom

pest population was correlated with climatic factors such as rainfall, temperature, air

relative humidity and sunshine hours. The severity of the pests is above 15 per cent (Naik

et al., 2010)

Khan et al., (2010) observed six types of pesticides used in the tobacco growing

areas of Swabi. The farmers commonly used Methomyl; WHO toxicity class Ib, highly

hazardous marketed under the trade name of Lannate (63%) and Thiodicarb, Class II,

moderately hazardous (56%). Methamidophos, marketed under the trade name Grip

belonging to OP; Class Ib, highly hazardous was used by 62% of the farmers.

Cypermethrin, toxicity Class II, moderately hazardous, was used by 36%of farmers. The

organochlorinated compounds Thiodan (endosulphan) and Confidor (imidacloprid;

toxicity ClassII, moderately hazardous) were used occasionally. The participants had a

casual attitude towards storage, handling and disposal of the pesticides. A large majority

of the farmers 67 (64%) did not store pesticide containers in proper storage places and

were thus accessible to children and females at home. Only 38 (36%) stored pesticides in

proper storage rooms. Most of the farmers did not use basic protective equipments during

pesticide handling and applications on the tobacco crop. Gloves and face masks were not

commonly used while mixing pesticide and during the refilling of tanks. None wore any

protective head cover. However, many farmers reported washing their hands and bodies

after spraying of pesticides. Twenty-one (20%) farmers’ had knapsack sprayer tanks with

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ill-fitting nozzle. Most farmers wore traditional cotton salwar kameez while working in

the fields and covered their faces with a cotton cloth while spraying which cannot be

considered as a separate protective equipment gear. The pesticide applicators’ back (9%)

was in direct contact with pesticide mixtures owing to leakage of the tanks .Disposal of

empty pesticide containers was also not satisfactory. A majority of the farmers (65%)

threw these containers either in the fields, (62%), or in canals. We have collected 84

empty pesticide containers from the tobacco farms of the two villages. Almost 40 (38%)

farmers discarded the empty containers either by burning or burying them in the soil.

Most of the pesticides were organophosphates, but carbamates, organochlorines,

and pyrethroids were also represented. The pesticides included aldrin, endosulfan, DDT,

dieldrin, camphechlor and lindane, which were either endocrine disruptors or persistent

organic pollutants, and were banned or restricted in their countries of origin. Some of

these pesticides were classified by World Health Organization as extremely or highly

hazardous. More pesticide formulations were used on coffee compared with cotton, and in

individually owned compared with cooperative farms. Hazardous practices were more

pronounced at the individually owned than the cooperative farms, with significant

differences for pesticide storage areas, unlabeled and non-original containers. Acute

health effects assessment of the extent and intensity of organophosphate exposure showed

that erythrocyte acetyl cholinesterase activities during spraying and non-spraying period

were comparable (Khan et al., 2010).

Cardamom is one of the most susceptible crops in the tropics; the loss could be up

to 75-80%, if no crop protection measures were not taken against major insect pests

(capsule and shoot bores, thrips and root grubs) and disease causing pathogens (rot

diseases). Planters cannot afford to lose even a kg of produce because one kg of cured

cardamom could fetch more than Rs. 2000 in the local market. Therefore the use of

pesticides could play primary role for both agronomic and socio-environmental

sustainability; and they were considered cutting edge issues to be studied for overall

ecosystem sustainability and stewardship activities. Current projections in cardamom

agroecosystem suggested that the productivity of cardamom needs to be increased

because of higher costs of inputs and increasing labor costs. Given both formal and

informal evidence to date, pesticide use warrants a careful assessment of the current

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situation as well as experimentation for which various factors affecting pesticide use

directly and indirectly must be understood comprehensively. Use of comprehensive IPM

strategies in cardamom plantations is very limited. Although biological controls in

general are environmentally safer than pesticides, most non chemical control poses some

threat to environment and public health. Central to all IPM programs is a thorough

assessment of the benefits and risks of all combined controlled technologies, including

nonchemical biological controls. Since the benefits and risks vary with agroecosystem

involved (particular pest complex, crop, climate and soil), these assessments have to be

carried out for specific regions. Only then we can expect to have truly long lasting,

effective pest management programs that are environmentally safe (Pimental et al., 1984).

Pesticide consumption and contamination

According to Aspelin (1997) the world wide consumption of pesticides has

reached 2.6 MT. Of this, 85% has been used in agriculture. Although the largest volume

of pesticides used was in the developed countries, its use has been growing rapidly in

developing countries (World Resource Institute (WRI, 1999). The quantity of pesticides

used per hectare of land has also increased (WRI, 1999). In addition to the increase in

quantity of pesticides used, farmers have used stronger concentrations of pesticides; they

have increased the frequency of pesticide applications and increasingly mix several

pesticides together to combat pesticide resistance by pests (Chandrasekhara et al., 1985;

WRI, 1999). These trends were particularly true for Asia and Africa. While majority of

pesticides used in developed countries were herbicides (which can be as toxic as

insecticides) the bulk of the pesticides used in developing countries were insecticides

which lead to insecticide-resistance by insect pests and caused more damage to human

health (WRI, 1999). Report of the WRI (1999) have revealed that majority of insecticides

used in the developing countries of Asia and Africa consisted of organochlorines

(endosulfan and lindane), organophosphates (monocrotophos and parathion) and

carbomates (carbofuran and tiodicarb) noted for their higher toxicity. Carlson and

Wetzstein, (1993) cautioned that organophosphates and carbomates were less persistent

than organochlorines but were potentially toxic to field workers and therefore should be

used with more caution.

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Pimental et al., (1992) pointed out that honey bees which were vital for the

pollination of crops including spices, vegetables and fruits were affected by most of the

insecticides used. There were reports on agricultural yield loss due to reduced pollination

of crops attributed to higher uses of pesticides (Pimental et al., 1992). Wilson (1998)

reported based on a field work in Sri Lanka that pesticides easily find their way into soils

and become toxic to arthropods, earthworms, fungi, bacteria, protozoa. These were vital

to ecosystem because they dominate both structure and function of natural systems.

According to the USFDA (United States Food and Drug Administration (1990)

approximately 35% of foods purchased by the consumers had detectable levels of

pesticide residues and 1-3% of the food samples had pesticide residue levels above legal

tolerance levels. Kegley and Wise (1998) studied sample extract of the foods and reported

that many vegetables (cucumbers, carrots, turnips, radish and tomatoes) and fruits

(strawberries) exceeded the allowable tolerance limits of pesticide residues

(organophosphates, organochlorines and carbomates) in the USA.

Bakore and Bhatnagar (2004) have reported that all of the wheat and water

samples collected from Jaipur, Rajasthan were found to be contaminated with various

organochlorine residues of DDT and its metabolites, HCH and its isomers. The amount of

pesticides detected in wheat flour was higher than the permissible limits prescribed by

WHO/FAO. Wilson and Tisdell (2001) stated the reasons for continuous applications of

pesticides despite a great deal of paradox. They differed widely across regions and

countries. According to the neoclassical theory, farmers will use pesticides if the

discounted net present value of stream of returns from doing so was positive. They also

reported that farmers were not informed about pesticide ill in developing countries.

Mekonnen and Agonafir (2002) have studied pesticide sprayers’ knowledge,

attitude and practice of pesticide use on agricultural farms of Ethiopia and recommended

for pesticide safety education to the applicators. They also found inappropriate use of

personal protection devices and recommended for proper replacement of worn-out parts.

Studies on sociodemographic characteristics, knowledge and experience of adverse health

effects related to pesticide use, details of work practices, and an inventory of pesticides

used on the farm showed that of the 112 farmers interviewed, 111 (99.1%) used

pesticides. Respondents had good knowledge about the acute health effects of pesticides

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and their exposure routes. Some of the risk behaviors identified were frequent pesticide

use, washing pesticide equipment in water sources used by humans, inadequate disposal

of empty pesticide containers, eating and drinking during pesticide application, and using

inadequate protective clothing. Respondents had good knowledge about the acute health

effects of pesticides and their exposure routes. Burleigh et al., (1998) studied pesticide

use pattern among chilli growers in Sri Lanka and reported that the growers had used

higher doses of pesticides than the department recommendations, and cautioned that the

use could be very high and excessive and the pesticide treatments were found to be

ineffective because the reduction in pest and disease intensity was not significant and

there was no significant increase in yield from the pesticide treatments.

Blair and Zahm (1995) stated that the reliability and validity of data on pesticide

use obtained by recall, often years after the event, have been questioned. Pesticide use,

however, was an integral component in most agricultural operations, and the farmers’

knowledge and recall of chemicals used may be better than many other occupations.

Contrary to general belief, many farmers typically used only a few pesticides during their

lifetimes and made only a few applications per year. Data from the USDA surveys

indicated that herbicides were applied to wheat, corn, soybeans, and cotton and that

application of insecticides to corn averaged two or fewer times a year.

Frazier et al., (2008) detected unprecedented amounts of fluvalinate (up to 204

ppm) along with fungicides. Herbicides that had been widely used were detected in hive

matrices. For the large numbers and multiple kinds of pesticides that have been found

potentially toxic for which there are no scientific studies to date. Europe researchers have

also reported similar results for pesticides and frequencies in hive matrices and express

similar concerns (Martel et al., 2007). These chronic levels of pesticides in pollen and

wax at potentially acute levels needed to be further investigated with regard to their

potential interactions with other stress givers on foraging activities. Nafees et al., (2008)

found that the entire soil sample studied contained residues of pesticides, two of them

were known to be toxic and accumulated in soil system. He also opined that pesticide use

was heavy in Swat Valley, Pakistan. The residual concentration varied from place to

place and crops to crops. Six pesticides were identified in all the soil samples. These

included dieldrin, DDT, malathion, lindane along with restricted levels of methyl

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parathion and heptachlor. The concentration of these pesticides ranged from

6 to 45 mg kg-1.

Chu Chi- Lo (2010) reviewed guidelines for the approval of pesticides and

information about effects of pesticides on soil microorganisms and soil fertility. He also

found some stimulation of pesticides and the growth of microorganisms, but some other

pesticides had depressive effects or no effects on microorganisms. For examples,

carbofuran stimulated the population of Azospirillum and other anaerobic nitrogen fixers

in flooded and non-flooded soil, but butachlor reduced the population of Azospirillum and

aerobic nitrogen fixers in non-flooded soil. Diuron and chlorotoluron showed no

difference between treated and nontreated soil, and linuron showed a strong difference.

Phosphorus (P)-contains herbicides glyphosate, and insecticide methamidophos

stimulated soil microbial growth, but other P-containing insecticides were detrimental to

nitrification bacteria.

Pesticide application had higher effect on fungal population (50-70% reduction)

than on bacterial population (23-38.4 % reduction) in the soil. Dithane suppressed most of

the bacterial population where as karate suppressed fungal most of the population

(Amengor and Tetteh, 2008). The detoxification capacity of soil depended on its

microbial activity. The higher the microbial activity the greater was the capacity of soil to

counteract the effect of a pesticide. Pesticide residual effect varied depending on the

dosage, Bliev et al. (1985) observed that there were no traces of hexazinone in the soil

after 450 days when 5 kg ha-1, it took 750 days for the pesticide to completely degrade in

the soil. Regarding soil organisms, it has been shown that insecticides which were oily in

nature affected soil bacteria considerably. Chlorinated hydrocarbons and carbomates had

adverse effect on nitrifying and ammonifying bacteria (Dialo, 1986).

2.2 Soil bio-physicochemical properties and quality

Intensively managed soil has been subjected to change in many aspects

continuously therefore the soil properties and processes must be assessed and understood.

There has been a considerable interest in the problem of how to monitor the soil so as to

ensure that its critical functions were conserved, these functions could have been

damaged by contamination, pollution or by poor management or may deteriorate under

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environment change (Lark et al., 2006). Varying perceptions of soil quality have emerged

since the concept was suggested in the early 1990’s. Soil quality was defined as the

capacity of specific kind of soil to function, within natural and managed ecosystem

boundaries, to sustain plant and animal productivity, maintain or enhance water and air

quality, and support human health and habitation (Karlen et al., 1997). With regard to

post-World war II “technological fixes” worked to produce more food, fiber and feed,

every one associated with agricultural expansion was caught in change that side effects

were not always noticed and experimentally unverified conclusions were drawn

sometimes. Soil and crop management practices were rapidly adopted without

recognizing the consequences on long-term productivity and environmental quality

(Doran et al., 1996). Off-site impacts including contamination of streams, rivers, lakes

and road ditches with pesticides and fertilizers in our water resources were often

overlooked (NRC, 1993).

Wilcke et al., (2005) studied the influences of pH and land use pattern and found

evidence that Al, Cu, Cd, Pb, and Zn were generally more mobile in forest soil system

than in grass land and arable soil systems indicating significantly higher contributions of

these heavy metals to total metal concentrations. They attributed this increased mobility

of metals to the presence of higher dissolved organic matter acting as complexing agents.

They found that an overwhelming metal partitioning in top soil was affected by pH and

Fe oxides. In anthropogenically contaminated soil, the type of heavy metal sources,

chemical and physical soil modifications, and co-deposition of other contaminants such as

acids and complexing agents like fluoride played a more important role for the chemical

forms and solubility of heavy metals in soils (Totsche et al., 2000).

Fenner et al., (2006) worked on a novel approach to study the effect of

temperature on soil biogeochemistry using thermal gradient bar and reported that nitrate

availability in the peat decreased by 90% between 2 and 18˚C, whereas the concentration

did not respond in forest soil. Sulphate availability in the peat decreased significantly with

warming, while the forest soil showed the opposite response (30% reduction).

Productivity changes within a field or soil type due to management were recognized

especially with the modern farming. Changes in productivity were positive due to

drainage, tillage, and addition of organic matter and physical structure, and other

�%�

degrading processes. Both positive and negative processes occurred simultaneously,

making it difficult to assess the change in the yields with certain individual cultural

practices. Farmers manipulate soils intensively; therefore, a comparative measure of soil

quality has traditionally included more than a simple measure of crop yield. Soils were

being degraded worldwide through erosion, nutrient imbalance; organic matter depletion

etc. central to sustainable agroecosystems must be the protection and enhancement of soil

quality. Soil function would be defined in terms of physical and chemical and biological

properties and processes, and measured against some definable standard to determine

whether a soil was being improved or degraded (Karlen et al., 1997). In acid forest soils

CEC, pH was less important in nutrient supply power than base saturation (BS) (nothing

but relative abundance of base nutrients on the soil exchange complex) (Reuss, 1983;

Reuss and Johnson, 1986).

Changes in soil chemical properties under perennial cropping systems were found

to be different depending on the soil-climatic and agronomic practices. Studies have

indicated that the original C and N levels under natural forest were not attained again in

perennial cropping systems, although levels of P and exchangeable cations, in particular

K, may be much higher in soils under perennial cropping system due to the use of

inorganic fertilizers. The change in soil chemical properties may reflect the decrease in

nutrient stocks of forest soils, but it also reflected on the immobilization of nutrients in

the biomass. Therefore it was very difficult to assess soil fertility decline and its causes in

perennial crop system than in annual cropping systems (Hartemink, 2003). The coffee

plantations in San Jose, Costa Rica were subjected to heavy metal inputs as a result of the

regular use of fungicides and inorganic fertilizers. However studies on this showed no

marked increase in heavy metals in soils under coffee plantations, it was likely that the

continuous use of agrochemicals had resulted in a built up-of heavy metals, comparable

with some of the problems encountered in soils under high input temperate agriculture

(Tinker, 1997). Also research on tea plantations near Kyushu, Japan, showed that the

heavy use of inorganic fertilizers on the plantations markedly increased nitrate and

sulphate in neighboring water sources (Li, 2001).

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Soil microbial diversity and response to agricultural intensification

In tropical agroecosystems, where climate and edaphic factors had less constraint

on microbial activity, and farmers have limited access to inputs, the turn over of organic

matter was rapid. Degradation processes such as losses in soil carbon, nutrient depletion,

and reduced water holding capacity occurred quickly and difficult to reverse. The land

use and management factors were considered to be playing important role in regulating

microbial communities in tropical soils than in many temperate systems, where favorable

climatic factors, combined with fertilizers, helped to buffer changes in soil environment

(Sanchez, 1976; Giller et al., 1997).

The soil habitat was considered to be highly heterogeneous environment for

microbiota inhabiting it. Therefore, microorganisms resident in soils were exposed to

varied abiotic and nutritional conditions. These organisms collectively were responsible

for underlying catalysis of the biochemical process in soils including those resulting in

disease suppressiveness at the scale of microhabitats and organismal biosphere. And,

these processes were susceptible to major changes in the surroundings. Three major and

inherently complex factors, plant and crop type, soil type, and soil management and

treatment were found to be important since these factors can have major repercussions on

soil quality, as reflected in suppressiveness of soil to plant diseases (Garbeva et al., 2004).

Microorganism in soils played a critical role in the maintenance of soil function in

both natural and managed agricultural soils because of their involvement in key processes

such as soil structure formation; decomposition of organic matter; toxin removal; and the

recycling of carbon, nitrogen, phosphorus and sulphur; besides suppressing of soil borne

plant diseases and promoting plant growth and development (van Elsas and Trevors,

1997; Doran et al., 1996). Relationships were observed between the extent of microbial

diversity in soil, soil and plant quality, and ecosystem sustainability. Studies have

documented the relationship between the degree of soil suppressiveness to plant diseases

and the diversity and abundance of soil microbial communities (Abawi and Widmer,

2000; Nagamulli et al.,1997).

Malajczuk (1983) suggested that the main agents in soil suppressiveness were

microbial, because sterilization by autoclaving, steam pasteurization, and irradiation

rendered the soils conducive to pathogen studied. Several studies reported that

�'�

mechanisms within the microbial activity of soils were responsible for the suppression of

pathogens. For instance, van Os and van Ginkel (2001) showed a clear relationship

between the suppression of Pythium root rot in bulbous Iris and soil microbial biomass

and activity: high microbial biomass and activity induced suppression of Pythium growth

through soil. Suppression of root diseases has been reported for higher microbial diversity

(Nitta, 1991; Workneh and van Bruggen, 1994). Studies indicated that the microbiota in

organic rich soils tended to reduce the severity of attack by many soil borne plant

pathogens. Disease suppression by microorganisms was reported by monocropping

system of wheat where the infection of Rhizoctonia solani was contained (Huber and

Watson, 1970).

Several recent studies have shown that soil management practices, such as

application of fertilizers, pesticides, composts, manures and irrigation greatly affected soil

microbial parameters (Omay et al., 1997; Schonfeld et al., 2002). Buyer et al., (1999)

studied the effect of soil and seed type on the microbial community structure around

germinating seeds. They examined two soil types namely loamy and sandy with

differences in soil pH and in humic acid content, and five seed types: maize, cucumber,

radish, soybean and sunflower. Soil type was shown to exert greater effect on the

spermosphere microbial community structure than seed type. In addition, the soil with

higher organic matter content had a greater microbial biomass.

Huber et al., (1970) modified the level of suppressiveness to Fusarium wilt by

adding clay minerals to a conducive soil. Higher microbial densities resulted from this

treatment and the degree of soil suppressiveness was increased. Minimum-till or no-till

cultivation lead to increased disease severity by pathogens that survive better when

infested crop debris remained on or near the soil surface. Knowledge on microbial

communities and the major groups of microorganisms involved in the disease

suppressiveness of soil was fundamental to better understanding of the relevance of

microbial diversity to disease suppression. Van Bruggen and Semenov (2000) proposed

that microbial community structure and the time required to return to the initial state after

application of various disturbances or stress could be characteristic for disease

suppression in soil. Agricultural management had to be directed toward maximizing the

�(�

quality of the soil microbial community in terms of disease suppression, if it was to

reduce the use of pesticides in agroecosystems.

2.3 Climate variability and change

Climate change has become more and more significant across the world. The

recent Fourth Assessment Report of the Intergovernmental Panel on Climate Change

(IPCC, 2007) has reported a world average surface temperature rise by about 0.74 ˚C over

the past 100 years (1906-2005). The global mean surface temperature was projected to

increase by 1.1-6.4 ˚C by the year 2100 (IPCC, 2007). Annual global temperatures have

increased by 0.4 ˚C since 1980, with larger changes observed in several regions (IPCC,

2001). While many studies have considered the impact of future climate changes on food

production, the effects of these past changes on agriculture remain unclear. It is likely that

warming has improved yields (food production per unit land area) in some areas, reduced

them in other areas and has negligible impact in still others (Rosenzweig and Parry, 1994;

Parry et al., 2005; Edmands and Rosenberg, 2005). Lobell and Field (2007) showed the

variance in year-to-year yield changes explained by the recent climate change. For some

crops, such as rice and soybeans, much of the model explanatory power came from a

positive relationship with precipitation. For other crops, however, temperature provided

the most of the explanatory power. The inferred temperature sensivities were negative to

all crops, many studies gave explanation as increased crop development rates, water stress

and canopy respiration with warmer temperatures (USDA, 1994; Rosenzweig and Parry,

1994; Parry et al., 2005; Edmands and Rosenberg, 2005).

The availability and capture of solar radiation, water, and soil nutrients were the

basic factors for plant growth and survival. Temperature played an important role in

general biological activity, defining in the case of plants the length of the available season

suitable for growth, the speed of phenological development, and the level of enzymatic

activity associated with photosynthesis and respiration. Plant growth and development

were reduced at low temperatures, and high temperatures can be detrimental during

flowering and initial stages of yield formation. The interaction of these factors will

determine the impact on crop productivity, insect pest and disease management, and

economics of agriculture under climatic change.

�)�

Lobell and Field (2007) studied recent climate trends attributable to human

activity. They reported that the impact of warming was likely to be offset to some extent

by fertilization effects of increased CO2 levels, although the magnitude of these effects

were uncertain and the subject of much debate (Long et al., 2005; Tubiello et al., 2007).

These researchers attempted to estimate CO2 effects using the same approach for

temperature by Lobell and Field (2007), but year to year differences in the size of the CO2

increment were too small to result in a measurable yield. If each additional ppm of CO2

resulted in 0.1% yield increase for C3 crops (a increase of 17% yield increase for a

concentration increase from current 380 ppm to frequently studied 550 ppm), then the 35

ppm increase since 1981 corresponds to a roughly 3.5% yield increase, about the same as

the 3% decrease in wheat yield due to climate trends over this period. Thus, the effects of

CO2 and climate trends had likely largely cancelled each other over the past two decades,

with a small net effect on yields.

Rainfall was the most important natural factor that determined the agricultural

production in any agroecosystem of the world. The variability of rainfall and pattern of

extreme high or low precipitation were very important for the agriculture as well as the

economy of the country. It was well established that the rainfall was changing on both

global (Hulme et al., 1998) and the regional scales due to global warming. The

implications of these changes were particularly significant for mountainous regions

(IPCC, 2007). Studies in different parts of the world indicated that global warming had

altered the precipitation patterns and resulted in a frequent extreme weather events such

as floods, droughts (WMO,2005).

Assessment efforts worldwide have focused mostly on wheat and corn, while

much is known about possible effects of climate change even on important crops like

potato and other crops. Published studies addressing the effect of climate change on

cardamom were scarce (Murugan et al., 2000; Murugan et al., 2008). The reason for rise

in atmospheric temperature had been attributed to global warming due to increased

concentration of CO2 in atmospheric air. The increasing concentrations of atmospheric

CO2 and concurrent changes in temperature and precipitation patterns were expected to

affect many aspects of human activities including agriculture (IPCC, 2007).

�+�

There were abundant experimental evidences indicating that elevated CO2

increases plant growth, biomass accumulation, and yields, the later depending on the

increases of sink (e.g., grains and tubers) strength proportional to gains in total biomass.

The beneficial effect of CO2 was more significant for crops with C3 photosynthetic

pathway (e.g., wheat, soybeans, potatoes and majority of domesticated plants) and minor

for crops with C4 photosynthetic pathway (e.g., corn and sorghum). In addition elevated

CO2 caused partial stomatal closure thus reducing crop water loss by transpiration, which

coupled with biomass gains result in some gains in water use efficiency, providing

advantages to rainfed crops (Stockle et al., 2003).

Schlenkar and Roberts (2009) related temperature patterns and yields of corn, soy

bean and cotton for the period 1950-2005 in most counties in the US by calculating the

length of time a crop was exposed to each one degree rise Celsius temperature in each

day of growing season. They found yield as a function of temperature increased modestly

up to a critical temperature and then decreased sharply. Using these functions and climate

prediction from Hadley 3 model, the authors projected nationwide average yields for

corn, soy beans and cotton for the years 2070-2090. They conceived a decline of yield by

43%, 36%, and 31% correspondingly, under slow warming scenario, and by 79%, 74%,

and 67% under rapid warming scenario. In general, depending on the application, seasons

were defined in a number of ways, such as astronomical seasons, meteorological seasons

(e.g. Argiriou et al., 2004) and standard seasons. Seasons were divided based on

meteorological variables (namely, rainfall, temperature and wind), as they affect

agriculture and irrigation of the region and also they were commonly used in climate

change impact studies.

A number of studies have analyzed the rainfall and temperatures simulated by the

IPCC AR4 GCMs and regional climate model (RCM) for different regions of India

(Rupakumar et al., 2006; Kripalini et al., 2007).�These studies showed an increase in

mean monsoon rainfall and temperature towards the end of 21st century under scenarios

of increasing greenhouse gas concentrations and sulphate aerosols. Though a number of

studies have analyzed the changes in rainfall and temperatures for the different seasons in

India, there has been a lacuna in research to study the changes in season length for the

future scenarios. The season length may be defined as conventional (fixed) length or

�*�

‘floating’ length. In a fixed season length, the starting dates and length of seasons remain

the same for every year. In contrast, in a ‘floating’ season length, the date of onset and

duration of each season was allowed to change from year to year. Studies have shown that

floating seasons reflect ‘natural’ seasons contained in the climate data better than fixed

seasons, especially under changing climate conditions (Anandhi et al., 2008).

Soil temperature

Whole-plant response to global atmospheric change was the product of a complex

set of processes that resulted from coordinated interactions between root and shoot (Farrar

and Jones, 2000). As the main organ involved in water and nutrient uptake and as one of

the major sinks for assimilated C, roots played a critical role in determining plant and

ecosystem response to various facets of global change ranging from N deposition and

elevated CO2 (Norby, 1998; van Noordwijk et al., 1998) to elevated ozone and UV-B

(Kilironomos and Allen, 1995).

An important root-shoot interaction that might determine the overall response of

plants was the ability of the root system to adjust nutrient acquisition capacity to meet

variations in shoot demand caused by environmental changes. Even though the

physiological capacity of root nutrient uptake was one of the number of adjustments that

influences nutrient acquisition, it’s response to changes in plant environment might

provide a key mechanistic explanations of why some species were more sensitive to

global change than others. However it should be highlighted that the degree to which

kinetics of nutrient uptake or other potential adjustments were expressed would ultimately

depend on soil nutrient availability and soil factors like soil temperature that can

determine nutrient transport to the root surface (Bassirirad, 2000). Houghton (1997)

estimated that the temperature of the globe might increase by as much as 2-4˚C during the

twenty first century and would result in increasing mean soil temperature in many

terrestrial ecosystems. Such changes will have a marked effect on soil biology including

growth and physiological characteristics of roots.

A number of studies have demonstrated that changes in soil temperature can

directly effect plant nutrient acquisition by changing root transport properties for NH4+

,

NO3 - , PO4

- and K+ (Chapin et al., 1974; Chapin et al., 1986; Siddiqui et al., 1984). The

���

exact mechanism for temperature induced changes in nutrient uptake capacity was not

fully understood. Root zone temperature might also affect nutrient absorption capacity by

changing the fluidity of the fatty acids in root plasmalemma (Clarkson et al., 1988). A

few studies have shown that the temperature sensitivity of NO3 - uptake capacity was

highly modulated by the N status of the roots or the whole plant (Bassirirad et al., 1993).

Climates in Tropical Mountains and Indian Cardamom Hills (ICH)

Climate and soil are the basis and substrate of all life forms both vegetal and

animal. High tropical mountain climates are extremely peculiar in their combination of

features. The position of tropical belt on the planet earth and general circulation of air

masses at low latitudes are the major features of tropical climates. In tropical systems air

temperature decrease with increasing altitudes without the confounding effects of its

seasonal change. Air temperature changes by a much larger degree in a day than

seasonally, and the growing period is the same from low land to forest limit, which is

quite different from temperate systems where the growing period usually shortens with

increasing altitudes. In tropical mountain systems with abrupt and irregular relief,

horizontal surfaces are either reduced to small areas or nearly inexistent. Under such

circumstances, the concept of regional climate looses most of its value. Therefore

topoclimates become ecologically more meaningful than regional climates.

Environmental conditions at higher altitudes have been characterized by low temperature,

low air pressure, low humidity, and distribution of light and high speed wind

(Tranquillini, 1964).

Barry and van Wie (1974) stressed the effects of three factors on topoclimate:

slope angle, slope aspect and relative topographic position. The first two modified the

diurnal temperature and humidity through their action on insolation while topography

influences night climate through its action on downward cold air movement and the daily

cycle of valley winds. In many tropical mountains, the daily weather pattern actually

determines the insolation on the westfacing slopes to be significantly reduced by

cloudiness or fog during afternoon, in contrast to eastfacing slopes receiving early

morning sunshine. Sites of easterly aspect receive greater direct insolation and therefore

experience drier, higher maxima and lower minima temperatures.

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Hnatiuk et al., (1976) attributed the higher maxima on eastfacing slopes to a

longer period of insolation due to a lower frequency of clouds in the morning than in the

afternoon. The lower minimum temperatures reported due to drier soils, were possibly

because of greater evaporation under conditions of greater insolation. The soil

temperatures on the easterly slopes averaged up to 10 ºC warmer at 1 cm, in the morning

before cloud had built up. But in the afternoon, the west facing slope was just a few

degrees warmer because cloud cover reduced the warming effect of direct sunshine. This

result supported the view that differences in the east-west aspect could be an important

ecological factor in tropical mountains.

The relatively high variability of daily cycles, contrasting with the relatively low

variability yearly cycles, is thus the major features of tropical mountain climate. In the

tropics high altitude areas are the sole regions where low temperature predominates and is

an important factor in plant, animal and human life. Cyclic changes of climate in the

tropics are best illustrated by comparing solar radiation along the latitudinal gradient from

the equator (0˚) to middle latitudes (50˚). Therefore the tropical climates differ sharply

from the middle-and-high latitude climates in having reduced month-to-month variation

in both the mean temperatures and the duration of the day, a fact that surely permits us to

consider tropical environments to be remarkably constant. For this reason seasons do not

have the same meaning in the tropics as in the higher latitudes, even when they can be

recognized by rainfall patterns or by sunlight variations in temperature (List, 1971).

On the equator, the daily total amount of solar radiation at the equinoxes, when it

reaches its annual maximum, is only about 13 % higher than the minimum amount of

radiation intercepted at the solstices. At first this percentage increases slowly with

latitude, together with solar declination at the solstices, so that at 23˚ 27� (at the tropics)

the annual range of extraterrestrial irradiation was still only about 60% of the winter

solstice minimum. This percentage increases sharply outside the tropical belt, and reaches

almost 400% at 50˚ latitude. At this middle latitude, the amount of solar radiation is

nearly five times that of daily value at the winter solstice (List, 1971).

Climatic factors such as relative humidity show regular variations and are

inversely correlated with air temperature. Mean air temperature is therefore relatively

constant year round in the tropics. In wet tropical mountains air temperature decreases at

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an average rate of about 0.6oC per 100 m elevation, with slight variation according to

local conditions. The altitudinal gradient in temperature determines the occurrence of

various thermal belts in tropical mountains (Boughey, 1965).

The trade winds and atmospheric circulation associated with them are responsible

for the widespread occurrence of highly seasonal rainfall climates within tropical

latitudes. Besides their year-round constancy in the mean temperature, some tropical

climates show distinctive patterns in the distribution of precipitation and consequently in

the relative humidity and soil water availability. This is particularly true in areas under

the direct influence of the trade winds, with their cyclic displacement across the thermal

equator. These winds and the atmospheric circulation associated with them are

responsible for the widespread occurrence of highly seasonal rainfall climates within

tropical latitudes. Rain, with condensational heat in its formation, is the driving force for

the atmospheric circulation in the tropics, while the convergence of moisture-laden air in

the lower atmosphere fuels convection. However, the monsoon rain is highly organized in

space depending on the distinct connective centers, and abnormal changes in these give

rise to floods and droughts, causing economic damage to crop agriculture (Barry, 1978).

Irrespective of the causes of rainfall seasonality, many tropical areas have either

two or four contrasted seasons, including rainless periods that extend from 1 to 6 or 7

months. This annual pulsation may induce slight but significant changes in the

temperature regime. Since high cloudiness prevailed during the rainy seasons, the total

solar radiation at ground level decreased, whereas high relative humidity at night greatly

diminished the coldness due to long wave of out going radiation from the ground and

vegetation. These combined effects decreased the amplitude of daily temperature

variation. The opposite conditions prevailed during rainless period, when low cloudiness,

clear skies, and dry atmosphere lead to higher day and lower night temperatures that

increased the amplitude of daily temperature fluctuations. In this way, seasonality in

rainfall brought thermoperiodism, an annual cycle with dampened temperature

oscillations and higher night minima during the wet seasons and with greater temperature

fluctuations and lower night minima during dry seasons. This variability in oscillations of

temperature combined with humidity seasons became a conspicuous feature of mountain

climates.

�%�

Rainfall varied much more than temperature in tropical mountains since rainfall

heavily depended on the precise geographic conditions of each mountain system. List

(1971) analysed these patterns along the slopes of various tropical mountain regions. And

he showed that, as general rule, the amount of precipitation increased from low altitudes

to a maximum at a middle altitude, roughly corresponding to the occurrence of montane

or the cloud forests and then decreased more or less steadily to the highest elevations. All

tropical mountains differed from adjacent lowlands and high rhythmic higher latitudes,

principally by the lower temperatures prevailing throughout the annual cycle. Therefore

the climate of the high tropical mountains was responsible for these areas with peculiar

environments that are ecologically apart from both extra tropical mountains and from

tropical low lands.

The ICH enjoys typical monsoon rainy climate except the eastern most slopes

where the annual mean maximum and minimum temperatures attained correspondingly

38ºC and 16ºC. The mean annual rainfall in the eastern most slopes were reported to be

1500 mm while the west facing slopes in Elappara range reported a maximum of 7000

mm. The changes in climatic elements mainly temperature and rainfall for the last century

in the ICH have been studied (Murugan et al., 2000) in relation to cardamom

productivity.

The tree cover in the tropical mountains has been used to modify the heat budget

of a land surface by its influence on incoming and outgoing radiation, as well as by its

direct modification of humidity and temperature below canopy. Mean and maximum

temperatures were lower under the forest canopy than under the sparse cover, but the

minimum temperatures were higher in the forest 10 cm above the forest vegetation. The

forest canopy functioned effectively as a screen for short and long wave radiation.

Temperature fluctuations were thus dampened and the daily climatic cycle was less

contrasted in forested tropical mountains.

Microclimatic conditions in a forested system has been playing a crucial role in

the development and severity of plant diseases, and crop diversifications either

encouraged or inhibited the pathogen growth, depending on the particular requirements of

the organisms. Macroclimate played a very important role in the population dynamics of

sucking pests (Boudreau and Mundt, 1994).

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2.4 Influence of plant biodiversity and shade levels on the level of

infestations of disease pathogens and pest insects on crops The effects of the diversity of plant species present in a field especially on crop

pests has received considerable attention by intercropping specialists (Risch et al., 1983;

Altieri, 1991). The effect of a plant species on the pests and diseases of another species

would change from one place to another, causing regional differences in

recommendations for species associations. Erythrina species, which were widely used in

Latin America as cocoa shade, have been reported to be hosts for cocoa tree borers in

central Africa (Poncin, 1957).

Diversification of the tree component of agroforestry systems by broadening the

genetic base of the species and mixing different species were used to reduce pest and

disease risks. A reduced development of pest and disease organisms in agroforestry

systems compared with simpler agricultural systems would be expected if either the crop

or tree species which were sensitive to certain pests or pathogens which were effectively

diluted by non-host species that formed barriers to their propagation within the

agroforestry system. Insect pests and disease vectors were more effectively controlled by

their natural enemies due to the greater complexity of the agroforestry compared with a

pure agricultural system. For employing these diversity effects strategically in

agroforestry design, more has been required than simply adding more plant species to a

species-poor system (Altieri, 1991).

Comparisons of species-rich and species-poor agroecosystems have often

demonstrated lower populations of specialist herbivores in polyculture systems which

contained both host and non-host plants than in monocultures of host plants. This

characteristic of polycultures has been explained with the lower resource concentration

for the pest and an increased abundance of predators and parasitoids due to the higher

availability of alternate food sources and suitable microhabitats (Altieri, 1991; Power and

Flecker, 1996; Stamps and Linit, 1998).

Similarly, fungal disease infection was often lower when the host plant density

was lower (Burdon and Chilvers, 1982), which has been usually the case in more diverse

systems. It could thus be expected that high plant diversity protects agroforestry systems

�'�

to some extent from pest and disease outbreaks. Pest and disease outbreaks have also

been reported from tropical rainforest (Augspurger, 1984; Newman, 1993) and

sclerophyll Eucalyptus forest, indicating that such problems occur even in highly diverse

natural vegetation.

For diseases, the host plant density would especially influence the progress of the

infection in a field when the mechanism of dispersal was only effective over short

distances, as was the case for autonomous or nematode-dispersal (Burdon and Chilvers,

1982). Conidia of the fungal disease agent in coffee, Colletotrichum gloeosporioides have

been rain-dispersed as far as eight meters from infected coffee trees. Planting the coffee

bushes further apart than this had reduced the spread of the disease through the plantation

if the conidia fell on the soil or on non-host plants and inactive before they were further

transported. Phytophthora species spread from one host to the another by rain splash,

flowing water and root channels etc., and their dispersal would thus be expected to be

slower in mixed plantations of host and non-host species than in host monocultures

(Schroth et al., 2000).

Distances in the range of several meters between individuals (or small groups) of

the same species were obviously unrealistic in monoculture plantations, but may not be so

in agroforestry systems composed of several annual and perennial crop species

interspersed with trees. For wind-dispersed diseases, on the other hand, the host-plant

density within a plantation may be of little importance because the propagules spread

readily through the whole system. Phytophthora has been dispersed by soil and water,

including wind-blown rain, and the chance that its propagation in a plantation has been

reduced by an alternation of host and non-host species. The three Phytophthora species

P.capsici, P. citrophthora and P. palmivora attacked both rubber and cocoa (where they

cause Phytophthora pod rot black pod disease), but individual strains isolated from one

host did not infect the other one (Schroth et al., 2000).

In another study, cross-inoculations of P. palmivora isolates from cocoa, rubber

and black pepper (Piper nigrum) gave variable results, but in general the aggressiveness

of the pathogen was highest on its original host (Resnik et al., 1980). P. palmivora from

cocoa did not infect coconut, although some coconut isolates elicited symptoms on cocoa

at a slower rate than cocoa isolates. Especially insect pests as well as nematodes and

�(�

viruses often affected numerous crop and trees species, whereas many fungal and

bacterial diseases were too specific in their host range to pose a threat to other plant

species that are associated with their primary host. The probability that associated plant

species shared pests and diseases, increased for closely related species (Resnik et al.,

1980).

A biological (specific) effect would be if a tree species increased the pest or

disease incidence in an associated crop because it was an alternative or intermediate host

of the pest or pathogen. In this case, the appropriate management decision would be to

remove this species from the system and to replace it by another one which would not

serve as a alternate host. A physical (unspecific) effect, on the other hand, would be if the

tree species increased the pest or disease incidence by creating a suitable (e.g., moist,

shaded) microclimate for the respective organism. In this case, it may not be necessary to

change the tree species, but rather to reduce its shade by a partial crown pruning, or to

thin it to obtain a wider spacing. Both biological and physical effects can also be

favorable, e.g., when the species encourages parasitoided and predators of pests present in

the system by providing them with nectar and pollen (biological),or when its shade was

unfavorable for the development of a pest (physical) (Ortíz, 1996).

Shade and the accompanying increase in humidity and reduction in temperature

affected both the insect pests and their predators and disease organisms. In coffee, the

effect of shade on insect pests was less clear than in cocoa, as the leaf miner (Leucoptera

meyricki) was reduced by shade, whereas the coffee berry borer (Hypothenemus hampei)

increased under shade (Willey, 1975).Similarly, unshaded tea suffered more from attack

by thrips and mites, such as the red spider mite (Oligonychus coffeae) and the pink mite

(Acaphylla theae), whereas heavily shaded and moist plantations were more damaged by

mirids (Helopeltis spp.) (Muraleedharan and Chen, 1997).

Shade can influence plant diseases through numerous mechanisms which often act

simultaneously. Shading altered both the quantity and the quality of light. Light, in

particular near UV frequencies around 350 nm can stimulate sexual and asexual

sporulation in many fungal species, whereas short and long wavelengths triggered spore

release (Kranz, 1974; Aylor, 1990). Shading also reduced air and soil temperatures and

buffered against high and low temperature extremes. Atmospheric humidity and

�)�

consequently the surface wetness of plants were increased under shade. High humidity

triggered the release of fungal spores in many species, and free moisture was considered

essential for spore germination (Barradas and Fanjul, 1986).

Fungal and bacterial pathogens grew best at moderate temperature and high

humidity, which were both provided by a shade canopy. A reduction of leaf spot

(Drechslera incurvata) on three varieties of dwarf coconut under 30% and even more so

under 50% artificial shade compared with full sunlight was attributed to the reduction of

temperature fluctuations and consequently reduced dew formation on the leaves (Fagan,

1987). Shade trees also intercepted rainfall and altered through fall distribution (Schroth

et al., 1999). Reduced impact of rain drops had reduced spore dispersal by splash effects

(Evans, 1998); although large-leaved shade trees may coalesce rain drops which

subsequently have increased impact of spore dispersal (Beer et al., 1998).

Given this multitude of interacting mechanisms, the interpretation and especially

the prediction of shade effects on crop diseases in agroforestry has not been always

straight-forward. For example, the sporulation of Exobasidium vexans, the causal agent of

blister blight in tea, was proportional to daily hours of sunshine, whereas the disease

progress was negatively related to hour’s sunshine, because the basidiospores were

sensitive to UV radiation, and the infection and lesion development required free

moisture and high humidity (Kranz, 1974; Ventkataram, 1979; Muraleedharan and Chen,

1997). As a consequence, epidemics of blister blight of shaded tea have been reported

from many countries (Muraleedharan and Chen, 1997).

In cool areas where shade by an associated crop decreased soil temperatures to

below the optimum of the pathogen, the disease was reduced by shade, whereas in hot

areas, the temperature of exposed soil was above the optimum of the fungus, so that

shading favored its development. As far as the elements of agroforestry were concerned,

shade management for pest and disease control was obviously a question of optimization

of shade. Which shade level was the best for a certain crop depends on its management

(e.g., fertilization), local environmental conditions (e.g., temperature, rainfall) and the

principal pests’ and pathogens at the respective site. In some cases, shade management

for pest control had been given priority over shade management for the control of

diseases (e.g., cocoa in Africa and Asia). In other cases, diseases were the major threat for

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a crop (e.g., black and yellow sigatoka in banana and plantain), and the shade level was

selected according to optimum control of the respective pathogens. An important

principle was to manage shade for minimizing physiological stress of the crops

themselves (e.g., avoid excessive irradiation, too high or low temperatures, drought

stress), thereby increasing their resistance to pest and disease attack. Optimum shade

usually had a range which was sufficiently wide to accommodate seasonal and year-to-

year fluctuations of weather conditions. However, even if the overall shade level of a plot

was in the optimum range, pathogens may develop in micro-niches of high humidity

which were created by patches of dense shade, and these may subsequently act as

inoculum sources (Rao et al., 2000; Schroth et al., 2000).

Besides drought, one of the dominating stress factors at many tropical sites was

nutrient deficiency, caused by inherently infertile or degraded soil conditions. Such

conditions can affect crop health by reducing the resistance (i.e., ability to avoid damage)

and tolerance (i.e., ability to compensate for damage) of crops against pests and diseases.

Vigorously growing plants with an optimum nutritional status were better able to replace

leaf area or roots lost to a pathogen than nutrient-limited and thus slow-growing crop

plants (Marschner, 1995). On the other hand, competition between trees and crops for

nutrients and nutrient sequestration in the tree biomass can reduce the availability of

nutrients for the crops and could increase their susceptibility to certain pests and diseases.

Nitrogen, whose availability was easiest to increase in soils through agroforestry

measures, may reduce crop resistance against pests and diseases when supplied in

excessive quantities. High N supply especially increased the infection by obligate

parasites such as rust fungi (Puccinia spp.), whereas the infection by facultative parasites

such as Fusarium reduced considerably. High N and low K supply also favored the attack

of field crops by insect pests, mainly because of increased contents of amino acids in the

plant (Marschner, 1995).

In trees, the relationship between N supply and pest incidence has been less clear

than in herbaceous crops, because repellents and toxic plant compounds had a

pronounced influence on pest attack. Besides increasing the nutritional value of the plant

tissue for herbivorous insects, high N availability can also reduce the levels of defensive,

carbon-based metabolites such as tannins and terpenoids and increase levels of defensive,

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N-containing metabolites such as alkaloids or cyanogenic glycosides (Kytö et al., 1996).

Further N, K were the important nutrients through which agroforestry techniques are most

likely to affect crop health. A high K supply generally improved the resistance of plants

to fungal and bacterial parasites up to the level required for optimum plant growth

(Marschner, 1995). High K also reduced nematode and borer damage in tea

(Muraleedharan and Chen, 1997).

2.5 Agroecosystem Intensification and Sustainability

Next to the genetic potential of species, soil fertility and climatic conditions, pests

and diseases played a significant role in determining plant productivity and yield

sustainability in crop plants. Among invertebrates insects formed the most dominant

group of herbivores that attacked plants and crops. The current and future food production

methods need to be accounted for the potential conflicts between optimal nutritional

quality for humans and agricultural animals and the physiological needs of crop plants for

growth and defense against pests and diseases (Rao et al., 2000).

Cropping systems have been performing multiple functions in their role as

ecosystems. In addition to food, feed, and fiber production, cropping systems have been

helping nutrient cycling, influencing water partitioning within landscapes, and regulating

green house gas flux, thereby influencing environmental quality as well as human and

animal health (Costanza et al., 1997; Daily et al., 1997). The long-term viability of

cropping systems- or any agricultural production system was largely determined by how

well these functions were executed within the context of the production, economic, and

resource conservation goals of agricultural producers. Consequently, quantifying the

effects of management practices on agroecosystem functions was necessary to determine

the sustainability of cropping systems (Liebig and Varvel, 2003).

The composition, abundance, and activity levels of soil community have been

shown to be markedly different in agricultural systems from those in the natural

ecosystems from which they were derived. In comparisons of tropical forest and

agricultural systems, it was reported that taxonomic diversity and population abundance

of the macro fauna in the agricultural systems were typically less than half that in primary

forest; similar changes were evident across a wide range of tropical ecosystems. However

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the trend was not absolute; the abundance and biomass of the fauna in tropical pastures,

for instance, were enhanced. These soil communities were usually dominated by single or

small number of species, highly adapted to the changed environment (Lavelle et al.,

1997).

Agroecosystems high in sustainability can be taken as those that aim to make the

best use of environmental goods and services while not damaging these assets (Altieri,

1995; Pretty, 2005; Conway, 1997; Tilman et al., 2002; Scherr and McNeely, 2008;

Kesavan and Swaminathan, 2008). The primary principles for sustainability were to:1)

integrate biological and ecological processes such as nutrient cycling, nitrogen fixation,

soil regeneration, allelopathy, competition, predation and parasitism in to food production

process, 2) minimize the use of those non renewable inputs that cause harm to

environment or the health of the farmers and consumers, 3) make productive use of the

knowledge and skills of planters, thus improving their self reliance and substituting

human capital for costly external inputs, and 4) make productive use of people’s

collective capacities to work together to solve common agricultural and natural resource

problems, such as pest, watershed, irrigation, forest and credit management (Pretty, 2005;

Kesavan and Swaminathan, 2008) .

The idea of sustainability, though, did not mean ruling out any technologies or

practices on ideological grounds. If a technology works to improve productivity for

farmers and did not cause undue harm to the environment, then it was to be considered to

have some sustainability benefits. They jointly produce food and other goods for farmers

and markets, and also contribute to a range of valued public goods, such as clean water,

wildlife and habitats, carbon sequestration, flood protection, ground water recharge,

landscape amenity value and leisure/tourism. In this way sustainability can be seen to be

both relative and case dependent and implied a balance between a range of agricultural

and environmental goods and services. A common, though erroneous, assumption about

agricultural sustainability is that it implies a net reduction in input use, thus making such

systems essentially extensive. This means more land is required to produce the same

amount of food. Agricultural systems emphasizing these principles also tend to be

multifunctional within landscape and economies (Dobbs and Pretty, 2004).

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Recent empirical evidence showed successful agricultural sustainability initiatives

from projects arise from shifts in the factors of agricultural production, for instance from

use of fertilizers to nitrogen fixing legumes; from pesticides to emphasis on natural

enemies. Therefore the critical question centers on the ‘type of intensification’ which

meant using natural, social and human capital assets, combined with use of best available

technologies and inputs (best genotypes and best ecological management) that minimize

or eliminate harm to the environment, and this can be termed ‘sustainable agricultural

intensification’. The use of fertilizers and pesticides has increased in many of the crop

monoculture systems. But the efficiency of use of applied inputs has been decreasing and

crop yields in most key crops were leveled off. In some systems the yields continued to

be declining and there were different opinions as to the underlying causes of this

phenomenon. Some believed that yields were leveling off because the maximum yield

potential of current varieties has already been approached, and therefore genetic

engineering must be applied to the task of redesigning crop. Agroecologists, on the other

hand, opined that the leveling off was because of the steady erosion of the productive

base of agriculture through unsustainable practices (Altieri, 1995).

Most agriculturists had assumed that the agroecosystem/natural ecosystem

dichotomy need not lead to undesirable consequences, yet, unfortunately, a number of

ecological diseases have been associated with the intensification of crop production. They

were grouped into two categories; diseases of ecotope, which included erosion, loss of

soil fertility, depletion of nutrient reserves, salinization and alkalinization, pollution of

water system, loss of fertile crop lands and diseases of the biocoenosis, which included

loss of crop, wild plant, and animal genetic resources, elimination of natural enemies, pest

resurgence and genetic resistance to pesticides, chemical contamination, and destruction

of natural control mechanisms(Altieri, 1995; Dobbs and Pretty, 2004).

The loss yields due to pests in many crops (reaching about 20-30% in most crops);

despite the substantial increase in the use of pesticides (about 500 million kg of active

ingredient worldwide) signaled a symptom of the environmental crisis affecting

agriculture. It has been well understood that cultivated plants grown in genetically

homogenous monocultures did not possess the necessary ecological defense mechanisms

to tolerate the impact of the out break of pest populations.

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Modern agriculturists have selected crops for high yields and high palatability,

making them more susceptible to pests by sacrificing natural resistance for productivity.

On the other hand, modern agricultural practices negatively affected the pest natural

enemies, which in turn would not find the necessary environmental resources and

opportunities in monocultures to effectively and biologically suppress the pests. Due to

this lack in the natural controls, an investment of about 40 billion dollars in pesticide

controls has been incurred yearly by US farmers, which saved approximately $6 billion in

US crops. However, the indirect costs of pesticide use to the environment and public

health have to be balanced against these benefits. Based on the available data, the

environmental and social costs of human pesticide use reached about $8 billion each year.

Currently, crop pest management has been primarily accomplished through the use of

pesticides, and 5 million tons of pesticides were being applied annually to crops

worldwide. As a result, pesticide resistance has become a ubiquitous problem, as have the

environmental and human health threats associated with pesticide transfers to

environmental components. Although IPM has been promoted for decades and has had

some successes, it has been widely adopted in few crops and has yet to significantly affect

the amount of pesticides used worldwide. In 1998, the world used 137 million MT tons of

chemical fertilizers. High nutrient inputs to agricultural systems often had significant,

positive effects on pathogens and insect pest populations. Response to nitrogen

concentration in crops were reported to be strong for many insects and fungal pathogens.

Because nitrogen fertilization often had its strongest effects on plant soluble nitrogen, sap

feeding insects such as aphids, leafhoppers and plant hoppers were likely to show strong

population increase in response to nitrogen fertilization that accompanied the introduction

of high yielding varieties (Huber et al., 1970).

A range of crop pathogens, including fungi, bacteria, and viruses, caused more

damage when nitrogen inputs were high particularly in ammoniacal forms. Soil process

that affected the form of N available to crop plants also had increased disease severity. In

contrast, the response of insect pests to N fertilization did not appear to depend on the

form of N applied (Scriber, 1984). Between 1950 and 1998, worldwide use of fertilizers

increased more than 10-fold. Each year the world has been using about five million tons

of pesticides, formulated from about 1,600 different chemicals. Complete toxicity data are

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lacking for many of these substances. In the United States, insecticides use increased 10-

fold between 1945 and 1989.

Cho (2002) studied the characteristics of soils in environment friendly rice-wheat

cropping system in southern Korea and found out that a no tilled, unfertilized, direct

sown, wheat-rice cropping system was likely to sustain grain yield by improving soil bio-

physicochemical factors and was one of the most ecologically stable, economically sound

and socially supportive wheat-rice production systems.

Effect of continuous application of manures and fertilizers on soil chemical

properties and yield under long term monocropping

There has been currently world-wide concern regarding the impact of modern

farming and intensive practices on soil and water quality and much recent works have

focused on management options for reducing nutrient run-off and leaching (Sharpley et

al.,1994; Gillingham and Thorrold, 2000; Ledgard et al., 2000) and improving the soil

quality (Dick, 1992; Liebig and Doran, 1999). Review of 14 field trials comparing long-

term effects of fertilizers and manures (FYM and slurry etc.) on soil properties recorded

higher contents of organic matter and numbers of microfauna than the fertilized soils, and

were more enriched in P, K, Ca and Mg in top soils. However there was no significant

difference between fertilizers and manures in their long-term effects on crop production

(yield) but increased biological properties particularly bacteria and actinomycetes were

registered for manured soils (Edmeades, 2003).

The results of the six long-term fertilizers experiment trials which measured the

effects of nutrient inputs, either as manure or fertilizer, on crop yields, demonstrated

clearly the combined effects of nutrient inputs, improved cultivars and appropriate weed

and pest control on long-term crop yields The size of this effect was site specific and

ranged from 150% to 1000% and typically was the order of 300-400%. The size of this

effect was dependent of initial soil fertility and the rate at which weathering and net

mineralization of organic matter as well as crop and cultivar being grown. Therefore,

nutrients inputs must be regarded as essential on most soils to maintain long-term

sustainability (Edmeades, 2003).

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While the addition of organic matter to the soils found to be beneficial, it was

necessary to consider the possible negative effects of applying manures. The evidence of

long term-term trials showed that the use of manures relative to the fertilizers had resulted

in soils becoming excessively enriched with some nutrients, particularly P, K, Ca and Mg

in the top soils. The accumulation of excessive levels of these nutrients, while not

desirable in terms of nutrient efficiency, was likely to pose an environmental risk.

However, levels of P and N above the required for optimal crop production would

increase the potential for nutrient runoff and leaching (Sharpley et al.,1994; Ledgard et

al., 2000). Nicholes et al., (1994) compared poultry litter and fertilizer (ammonium

nitrate) and found that there was no difference in the amounts of total N and P in the run

off but the Catabolic Oxygen Demand (COD) was higher for the manure treatment. It has

been generally concluded that compared on an equal nutrient basis, losses of N and P,

either from leaching or runoff could be similar in the long-term basis (Edmeades, 2003).

Soils of high rainfall tropical mountains have reduced soil fertility owing to lower pH

levels. In order to reduce soil acidity soil liming has been recommended, so that free

hydrogen ions could be replaced by calcium ions in soils. The results of experiments on

liming practices showed greater variations in both calcium - to - magnesium and

potassium - to - magnesium ratios of the soil that can be detrimental to crops leading to

lower crop yields (Loide, 2004).

Within agroecosystems, soils have played major role in food production and

considered the interface between human activities and other parts of the environment, to

be extremely important to protect this resource and ensure sustainability (Gou et al.,

2007). In addition to their essentiality for plant growth and or human nutrition, some

heavy metal elements were found to be toxic to both animals and humans at high

concentrations viz., copper (Cu), chromium (Cr), molybdenum (Mo), nickel (Ni),

selenium (Se), mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd) or zinc (Zn). As a

result of long-term applications of inorganic fertilizers and organic wastes to agricultural

soils, periodic risk assessment of heavy metal accumulation was imperative considering

long-term environmental and health threat (Williams et al., 1987). Gou et al., (2007)

studied heavy metals accumulations from Chinese soils and found higher concentration of

all heavy metals (Cd, Pb, As, Cu and Hg) except Cr than the background values.

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Some of the important heavy metals that have most commonly gave rise to health

concerns about food safety were the heavy metals Cd, Hg and Pb, together with the

anionic metalloids As and Se (Reilly, 1991). In a review of health risks posed by metals

in organic composts entering the food chain, Chaney (1980) introduced the concept of the

‘soil-plant-barrier’ and classified metals into four groups. Group1 was comprised of the

elements Ag, Cr, Sn, Ti, Y and Zr which posed little risk because they were not taken up

to any extent by crops and plants owing to lower solubility in soils. Group2 include As,

Hg and Pb which was strongly absorbed by plant roots but not translocated readily to

edible tissues. Group 3 comprised of metal elements B, Cu, Mo, Ni and Zn which was

immediately taken up by plants but phytotoxic at concentration that posed little risk to

human health. Group 4 consisted of Cd, cobalt (Co), Mo and Se which caused human or

animal health risks at plant tissue concentrations that were generally phytotoxic.

McLaughlin et al., (1999) reported that of all heavy metals, the most important to

consider in terms of food chain contamination were As, Cd, Hg, Pb and Se. Hellal et al.,

(2009) worked on the effects of mercury on soil microbial communities in tropical soils

and reported that enzyme activities, respiration and functional diversity were modified at

higher concentrations of soil available mercury (1 ppm). The results demonstrated that in

the tropical soils, mercury affected the soil microbial communities in a different manager

than was previously reported in temperate soils. Furthermore, mercury toxicity on soil

microbes may be modulated by tropical soil characteristics.

2.6 The CHR and forest degradation

The evergreen forests of CH and PTR were the richest in terms of plant

biodiversity within the Western Ghats (WG) (Pascal, 1988). At the local scale, the

diversity was attributed to the multiplicity of the forest and species types that adapted to

different climatic conditions (gamma diversity). But high species richness and diversity

were also noticed within a forest type (alpha and beta diversity). The humid forest of this

area reported with the highest rates of endemism for the Western Ghats (Ramesh and

Pascal 1977). The rate of deforestation in these hills had increased considerably during

the last few years (Ramesh et al., 1996).

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The rapid growth of encroachment of forest lands while contributing to the

expansion of area under cultivation of various crops has resulted in unscrupulous tree

felling causing significant changes in micro and macro climatic condition in the CHR

region. One of the primary reasons for drastic decline in the acreage of cardamom

cultivation was that, most of the planters who migrated from the plains of Kerala and

Tamil Nadu came in quest of agricultural lands for livelihood, had introduced a variety of

subsistence crops like rice, tapioca, vegetables etc. These crops were cultivated in the

grass lands of deciduous forest areas adjacent to the ever green forest canopy where

cardamom was being cultivated. Since the migrant farmers adopted a cropping pattern not

conducive to the forest ecosystem, there has been major shifts in the cropping pattern in

the CHR area.

In the initial stages, the cultivation of these crops required substantial removal of

forest tree growth. Although the rules of land assignment on lease prohibited the removal

of forest trees, the dual control of the revenue department and forest departments on the

CHR areas made it possible for the cultivators to indulge freely in such activity. Thus the

introduction of other crops in the CHR areas had paved way for degradation of CHR

forests. Apart from this, various cultural practices used for the cultivation of introduced

crops were not conducive to the CHR environment for instance, tillage and ploughing

operation in steep slopes which lead to serious problems of soil erosion and fertility

degradation. As a consequences of these activities both large scale deforestation and

decline in soil fertility and productivity as well as the conducive micro climatic condition

necessary for the normal growth and development of cardamom had undergone near

irreversible alteration (Miniraj and Murugan, 2000). Several studies have shown that the

fertility status of CHR soils was generally high due to closed nutrient cycling which

occurred in almost in all forest ecosystems (Korikanthimath et al., 2001; Murugan et al.,

2008). In such environments certain cultural practices like frequent soil wok, severe

pruning of forest trees for the purpose of shade removal and regulation, that were

practiced in many of the cardamom plantations have proved to be unsustainable for CHR

system because these practices lead to depletion of soil moisture, poor nutrient absorption

and high degree of soil erosion in the region. In the recent years the conditions further

aggravated by the pest insects and disease attacks due to various reasons including

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climate change. Overall, the far-reaching human interaction into the CHR forest system

through intensive cardamom agriculture has undoubtedly affected the sustainability of

cardamom ecosystem (Miniraj and Murugan, 2000).

2.7 Water quality

The quality of surface and ground water samples has shown variations particularly

among the samples collected from plantation areas. Majority of the ground water samples

were found to have EC less than 500 �s cm-1. Nitrate concentration was within

permissible limit but in plantation samples the values were above 100 ppm. Fluoride

concentration of the ground water samples was in the range of 0.1 to 0.98 ppm. Humans

have been exposed to agriculturally derived chemicals and pathogens in the environment

through water and soil by a number of routes, including the consumption of crops that

have been treated with pesticides or have taken up contaminants from soils and ground

waters and surface waters used for drinking water. Climate change has important impacts

on the dispersion of pathogens and chemicals in the environment. In addition, changes in

climate were likely to affect the types of pathogens occurring as well as amounts and

types of chemicals used for a wide range of scenarios and crops. The main environmental

pathways from the farm to the wider population could be the consumption of

contaminated drinking waters and food. In the United Kingdom, other pathways like

aerial and direct contact were currently of less importance to the general population

(Boxall et al., 2009).

Pesticide use patterns have changed as agriculture and pest species shift

(expansion of pest pressures) in response to climate change. As a result, human and

wildlife pesticide exposures could be increased (Chen and McCarl, 200l; Reilly et al.,

2003). Climate change has a powerful effect on the environmental fate and behavior of

chemical toxicants by altering physical, chemical, and biological drivers of partitioning

between the atmosphere, water, soil/sediment, and biota. Surface air temperature and

precipitation as altered by climate change were expected to have the largest influence on

the partitioning of chemical toxicants. In addition, an array of important processes

including organic carbon cycling, significant increase in fugacity (thermodynamic

measure of substance tendency to prefer one phase over the other) and contaminant

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concentration was expected by potential climate change (MacDonald et al., 2002).

Increase in nutrient concentrations in surface water, soils and sediments were reported

due to higher run-off coupled with lower water levels, which had negatively affected the

water quality (IPCC, 2007). In region where intense rainfall was expected to increase

pesticides, organic matter and heavy metals washed off from soils to water bodies

therefore, deterioration of water quality was envisaged.