Soil – A Renewable Resource

Soil – A Renewable ResourceSoil – A Renewable Resource

Chapter 13: Food, Soil, Conservation, Chapter 13: Food, Soil, Conservation, and Pest Managementand Pest Management

January 2012January 2012

What is Soil?What is Soil?

• “Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, air, and billions of living organisms”

• Produced by physical, chemical, and biological weathering

Soil HorizonsSoil Horizons

Layers in Mature SoilsLayers in Mature Soils

• Infiltration: the downward movement of water through soil.

• Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers.

• The soil type determines the degree of infiltration and leaching.

Fig. 3-24a, p. 69

Mosaic of closely packed pebbles, boulders

Weak humus-mineral mixture

Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts

Alkaline, dark, and rich in humusClay, calcium compounds

Desert Soil(hot, dry climate)

Grassland Soilsemiarid climate)

Fig. 3-24b, p. 69

Deciduous Forest Soil(humid, mild climate)

Forest litter leaf moldHumus-mineral mixtureLight, grayish-brown, silt loamDark brown firm clay

Fig. 3-24b, p. 69

Tropical Rain Forest Soil(humid, tropical climate)

Acidic light-colored humus

Iron and aluminum compounds mixed with clay

Fig. 3-24b, p. 69

Coniferous Forest Soil(humid, cold climate)

Light-colored and acidic

Acid litter and humus

Humus and iron and aluminum compounds

Soil PropertiesSoil Properties

• Particle size: clay, silt, and sand• Soil texture: relative amounts of each different

particle size • Porosity: how well water infiltrates the soil• Soil Moisture: how much water is retained in the

soil• % Organic Matter• Percolation Rate – how fast water infiltrates the

soil

Fig. 3-25, p. 70

0.05–2 mmdiameter

High permeability Low permeability

WaterWater

Clay

less than 0.002 mmDiameter

Silt

0.002–0.05 mmdiameter

Sand

SOIL QUIZ WHIP AROUNDDIRECTIONS:

1. Select a partner.2. Find an open area where

you can move around.3. Stand back to back. 4. Take one step away

from each other.5. Make sure that you both

can see the screen.6. Wait for further

directions.

SOIL EROSION AND DEGRADATIONSOIL EROSION AND DEGRADATION

• Soil erosion is the movement of soil components, especially surface litter and topsoil, by wind or water.– lowers soil fertility – overload nearby bodies of water with eroded

sediment. – increases through activities such as farming,

logging, construction, overgrazing, and off-road vehicles.

TYPES OF SOIL EROSIONTYPES OF SOIL EROSION

– Sheet erosion: surface water or wind peel off thin layers of soil.

– Rill erosion: fast-flowing little rivulets of surface water make small channels.

– Gully erosion: fast-flowing water join together to cut wider and deeper ditches or gullies.

Sheet erosionSheet erosion

Rill erosionRill erosion

Gully erosionGully erosion

Global Outlook: Soil ErosionGlobal Outlook: Soil Erosion

Figure 13-10Figure 13-10

Soil Erosion in the U.S. Soil Erosion in the U.S.

• Soil erodes faster than it forms on most U.S. cropland, but since 1985, has been cut by about 40%.– 1985 Food Security Act (Farm Act): farmers receive a

subsidy for taking highly erodible land out of production and replanting it with soil saving plants like grasses and trees for 10-15 years.

DesertificationDesertification

• “Occurs when the productive potential of drylands falls by 10% or more because of a combination of natural climate change that causes drought and human activities that reduce or degrade topsoil.”

– Natural oscillating process that has been accelerated by human activities

– Affects 1/3 of world’s land and 70% of all dry lands.

Fig. 13-11, p. 280

Very severe (>50% drop)

Severe (25-50% drop)

Moderate (10-25% drop)

Causes and Consequences of Causes and Consequences of DesertificationDesertification

Fig. 13-12, p. 280

Causes Overgrazing

Deforestation

Erosion

Salinization

Soil compaction

Natural climate change

Consequences Worsening drought

Famine

Economic losses

Lower living standards

Environmental refugees

Salinization and WaterloggingSalinization and WaterloggingSalinization results from repeated irrigation in dry climates where salts gradually accumulate in the upper soil layers.

Waterlogging occurs when farmers apply too much irrigation water to leach salts deeper into the soil.

Figure 13-13Figure 13-13

The Effects of Soil SalinizationThe Effects of Soil Salinization

Figure 13-14Figure 13-14

Fig. 13-15, p. 281

CleanupPrevention

Soil Salinization

Solutions

Reduce irrigation

Switch to salt-tolerant crops (such as barley, cotton, sugarbeet)

Flush soil (expensive and wastes water)

Stop growing crops for 2–5 years

Install underground drainage systems (expensive)

Agricultural Best Management Agricultural Best Management Practices and the Consequences of Practices and the Consequences of

Traditional AgricultureTraditional AgricultureChapter 13: Food, Soil, Conservation, Chapter 13: Food, Soil, Conservation,

and Pest Managementand Pest ManagementFebruary 2011February 2011

DIRECTIONS:1. Select a partner.2. Find an open area where

you can move around.3. Stand back to back. 4. Take one step away

from each other.5. Make sure that you both

can see the screen.6. Wait for further

directions.

Question #1

How many plants are known to have parts that can be eaten?

1. 1,0002. 10,0003. 30,0004. 100,000

Question #2

A cash crop is a plant grown primarily to be sold as cash rather than consumed by the farmer. What is the largest cash crop in the U.S.?

1. corn2. rice3. marijuana4. soybeans

http://www.epa.gov/oecaagct/ag101/cropmajor.html

Question #3U.S. Consumers spend about 2% of their annual income on food. About what percentage of income do the poorest billion people in the world spend on food?

1. 10%2. 30%3. 70%4. 100%

Question #4When the energy required to plant, grow, store, process, package, transport, refrigerate, and cook plant and animal food in developed countries is considered, how much more nonrenewable energy is consumed to produce 1 unit of food energy?

1. 2 units2. 5 units3. 10 units4. 15 units

Question #5An alternative to traditional agriculture is interplanting in which several crops are grown on a plot of land together. Which of the following interplanting types involves growing trees along with crops?

1. Polyvarietal cultivation2. Alley cropping3. Intercropping4. Polyculture

Question #6In 1999, Ingo Potrykus and Peter Beyer developed a genetically modified crop designed to supplement vitamin A, a nutrient deficient in the diet of millions of children in developing countries. What is this GMO crop?

1. sugarbeet 1312. α-sweet potatoes3. Hybrid corn4. Golden rice

Question #7First generation pesticides are derived from the natural defensive chemicals in plants. Which of the following first generation pesticides was derived from the heads of chrysanthemum flowers?

1. rotenone2. pyrethrum3. DDT4. atrazine

Three Types of AgricultureThree Types of Agriculture

Traditional Agriculture – Low input– Usually multiple crops/animals are grown– Two varieties

• Traditional subsistence agriculture• Traditional intensive agriculture

Industrialized Agriculture/Agribusiness – high input– monoculture

From King Corn…What we’ve learned about industrialized agriculture

Case Study of Industrial Case Study of Industrial Food ProductionFood Production

• 30,000 plants are known with edible parts• 90% of world food is provided by just 14 of these - plus 9 terrestrial animal• Industrialized agriculture (high-input agriculture) is a northern hemisphere

phenomenon devoted primarily to just 3 of these crops (wheat, rice, and corn).

• Major cash crops in U.S. are corn, soybeans, hay, and wheat. Major black market cash crop is marijuana.

• Southern hemisphere sometimes practices plantation agriculture mostly for commodity crops consumed in the north (i.e. cocoa, coffee, bananas, sugarcane, soybeans, and peanuts.)

• Livestock (mostly cattle, pigs, and chickens) are grown in feedlots or animal factories.

• Agribusiness is the largest industry in the United States - makes up over 18% of U.S. GDP

10 units of nonrenewable energy are used to produce 1 unit of food energy in the U.S. In traditional subsistence agriculture the ratio is 1 to 10.

Alternatives to MonoculturesAlternatives to Monocultures

• Interplanting – growing several crops on the same plot simultaneously–Polyvarietal cultivation–Intercropping–Agroforestry (alley cropping)–Polyculture

Polyvarietal cultivationPolyvarietal cultivationDefinition:Planting a plot of land with several genetic varieties (natural or transgenic) of the same plant.

Example: hybrid rice and sticky rice grown together to provide greater genetic resistance to rice blast (Magnaporthe grisea), a fungus that produces necrotic holes in rice leaves.

IntercroppingIntercropping

Definition:Two or more different crops are grown at the same time on a plot.

Example:Seed corn in is rotated with wheat and soybeans (right) in Nebraska) to replenish soil nutrients and produce multiple yields from the same plot.

Alley CroppingAlley CroppingDefinition:Crops and trees are grown together

Example:Left: Corn is grown between two strips of black walnut trees.Below: Crop between banana trees

PolyculturePolyculture

Definition:Many different plants are planted together.

Advantages to InterplantingAdvantages to Interplanting

• Crops maturing at different times extend the harvest.

• Reduces erosion• Reduces need for fertilizers• Reduces need for water• Reduced need for herbicides and pesticides• Higher yields per hectare than high-input

monoculture

SOIL CONSERVATIONSOIL CONSERVATION

• Soil conservation involves reducing soil erosion and restoring soil fertility mostly by employing vegetation.

• Conservation tillage• Strip cropping/contour planting• Terracing• Alley cropping• Shelter breaks/windbreaks• Cover crops• Livestock rotation

Conservation TillageConservation Tillage

Strip Cropping/ Contour PlantingStrip Cropping/ Contour Planting

TerracingTerracing

Shelter Belts / WindbreaksShelter Belts / Windbreaks

Cover CropsCover Crops

Cover CropsCover Crops• Planting of a grass or grain that establishes well in fall and winter on a field shortly before

(early) or not long after (late) the main cash crop has been harvested

Cover Crops Benefit Ground and Cover Crops Benefit Ground and GroundwaterGroundwater

• Reduce nutrient concentrations in groundwater.

• Promotes root growth of subsequent cash crop especially in compacted soils.

• Especially effective against nitrogen.

Costs of Cover CropsCosts of Cover Crops

• Costs– Require extra management by the

farmer in order to perform well– Not always an available market/use for

the cover crop– Few programs advocate for them in MD

and VA – Requires farmers to incur the cost of the

cover crop (seeds) – Horton estimates this at $56 million/year in Chesapeake Bay watershed

• In 2005, Gov. Robert L. Ehrlich Jr. provided $5 million in grants to MD farmers to plant cover crops through the Maryland Agricultural Water Quality Cost-Share (MACS) Program .

Hairy vetch and winter rye at Clagett Farm

Livestock RotationLivestock Rotation• the movement of cattle or other grazing livestock from pasture to pasture• Benefits

– Prevents over-grazing of pastureland and excess soil erosion– Reduces the need for equipment intensive “hay” operations and the

expense of fertilizers and pesticides that go with them– Cattle require fewer medicines, antibiotics, and hormones– Rotation of livestock reduces the impact of animal waste and reduces

run-off of nutrients– Produce healthier meat products

In addition, converting crop land into pasture can broaden a farm’s economic base.

Costs Often means a reduction in gross sales

for the farmer Reduces the amount of land farmer

has for crop production

SUSTAINABLE AGRICULTURE SUSTAINABLE AGRICULTURE THROUGH SOIL CONSERVATIONTHROUGH SOIL CONSERVATION

• Fertilizers can help restore soil nutrients, but runoff of inorganic fertilizers can cause water pollution.– Organic fertilizers: from plant and animal (fresh,

manure, or compost) materials.– Commercial inorganic fertilizers: Active ingredients

contain nitrogen, phosphorous, and potassium and other trace nutrients.

““Green” Alternatives to Green” Alternatives to Inorganic FertilizersInorganic Fertilizers

• Less likely to run-off, more sustainable, and do not involve intense energy input to make

• Provide organic material, not just nutrients• Types

– Animal manure• Especially if anaerobic methane digester is used

– Green manure– Compost– Crop rotation

Work CitedWork CitedBrophy, Alan. "So What's This All about Eh?" Web log post. The Bizz. 30 Nov. 2010. Web. 28 Feb.

2011. http://alsbizz.blogspot.com/.Clark, A. (ed.) 2007. Managing cover crops profitably. 3rd ed. National SARE Outreach Handbook

Series Book 9. National Agricultural Laboratory, Beltsville, MD.Darring, Gerald. Hunger. Theology Library. Photo. 27 Feb. 2011.

<http://www.shc.edu/theolibrary/graphics/hunger.jpg>."Discovering Profits in Unlikely Places: Agroforestry Opportunities for Added Income." University of

Minnesota Extension. Regents of the University of Minnesota, 2011. Web. 27 Feb. 2011. <http://www.extension.umn.edu/distribution/naturalresources/components/DD7407b.html>.

"Health Care Reform Bill Gives Power to FDA Shut Down Organic Food Industry." Politicol News. 3 Aug. 2011. Web. 27 Feb. 2011. <http://www.politicolnews.com/health-reform-fda-power/>.