Soil resources

Soil Resources

Submission by: Ankit Chhabra Roll No: 01315603615

Project Guide: Dr. Tanuja Nautiyal

Department of ChemistryNorthern India Engineering College

New Delhi

Read dust storm in china and measures taken to control it

Millions of trees defend China against raging dust storms from the Gobi desert. Shown are pines and poplars developed by Chinese scientists to grow rapidly in poor soil. The agricultural land is protected by the Great Green Wall.

1)The unconsolidated organic and mineral material on the earth’s surface that is capable of supporting plants.

2)A dynamic natural body, in which plants grow, that is composed of mineral and organic materials and living organisms.

Soil Definitions

Soil-Forming Factors

Parent material (rock that is slowly broken down by biological, chemical, and physical weathering processes in nature.)

Climate (when temperatures are below freezing decomposition of organic matter and water movement are slow, soil dvelopment in the humid tropics is accelerated by the rapid weathering of rock and soil minerals, the leaching of nutrients, and the decompostion of organic detritus.)precipitation and temperature changes

Soil-Forming Factors

Topography (presence or absence of mountains and valleys, steep slopes have little or no soil on them because soil and rock are continually transported down the slopes by gravity; moderate slopes and valleys, may encourage the formation of deep soils)

Organisms (plant roots, lichens produce acids, animals that burrow or tunnel, such as earthworms, voles, mix the soil, distributing organic and mineral matter

Time Grasslands soil have rich organic matterHow long climate has been altering parent material

over geologic time

Soil Composition

Soil Composition

• 45% Mineral particles (broken down pieces of rock)• 5% Organic matter (humus - from dead organisms, worm castings, leaf litter)• 25% Water (precipitation)• 25% Air (More with sandy soil, less with clay soil)

Soil Composition

Soil organisms - Millions in one teaspoon of fertile agricultural soil! bacteria, fungi, algae, microscopic worms. •provide ecological services such as worm castings, •decomposition to humus, •breaking down of toxic materials, •cleansing water, •nutrient cycling from decomposers or upon death

Soil Nutrients (NPK)

Organic - animal manure, bone meal, compost (slow-acting, long-lasting)

•Delay in availability to plants, needs time for the organic material to decompose•Delay causes low level of nutrient leaching•Improves water holding capacity

Soil Nutrients (NPK)

Inorganic - Manufactured from chemical compounds (fast-acting, short-lasting)

•Highly soluble so immediately available to plants•High solubility also makes it leach quickly (pollutes water)•Suppresses growth of microorganisms •Source of nitrogen gases that increase air pollution•Production requires much energy from fossil fuels, increasing CO2 emissions.

Soil Horizons

Soil horizon

O Horizon: Organic or litter layer, topmost layerA Horizon: Topsoil; mostly inorganic minerals with some

organic material and humus mixed in; crucial for plant growth

E Horizon: Eluviation horizon; loss of minerals by leaching, a process whereby solid materials are dissolved and transported away, only found in forested areas, light colored

B Horizon: Subsoil; zone of accumulation or deposition of leached minerals and organic acids from above, clay and minerals, (iron, aluminum and calcium)

C Horizon: Slightly altered parent materialR Horizon: Bedrock

Soil Organisms

Soil organisms

•Ants live in the soil in enormous numbers, constructing tunnels •and chambers that aerate it. •Food brought in by the ants and the left Over is eventually decomposed and add to the organic matter in the• soil. •Ants also bury seeds in the soil and help in reproduction

Soil organisms

•Symbiotic association between the roots of plants and fungi.

•When mycorrhizal fungi are absent from the soil, the reestablishment of certain tree species is retarded.

Nutrient Cycling

•Leaching causes some nutrient minerals to be lost from the soil ecosystem to groundwater, the weathering of the parent material replaces much or all of them.

•Dusts carried in the atmosphere help replace nutrient minerals in certain soils.

•Hawaiian rainforest soils, for example, receive dust inputs from central Asia, a distance more than 600km away.

Nutrient Cycling

Soil characterizationSoil can be characterized by color and several

other traits:• Texture• Structure• pH

Soil Texture

Determined by size of particles

Three main categories:

Clay = particles < 0.002 mm diameter

Silt = particles 0.002–0.05 mm diameter

Sand = particles 0.05–2.0 mm diameter

Soil Texture

Best for plant growth is loam, an even mix of these three types.

Loam

Is an ideal agricultural soil. Has an optimum combination of different soil particle sizes. It contains 40% each of sand and silt, and about 20% of clay.

Generally larger particles provide structural support, aeration, and permeability to the soil, whereas smaller particles bind into aggregates, or clumps, and hold nutrients and water.

Loam

Sandy soil is not desirable because they do not hold mineral or water and plants grown in such soils are more susceptible to mineral deficiencies and drought.

Clayey soil provide poor drainage and often do not contain enough oxygen.

Soil Texture Chart

It is possible find the type of soil by making use of the soil texture chart.

We can determine the percentage of each component in a soil sample and then plot the results. (make sure the sum of the sand plus silt plus clay will always be 100 percent.

Soil Characteristics

Understand what soil is and how it forms.

•1) clay = “layer silicates that are formed as products of chemical weathering of other silicate minerals at the earth's surface. They are found most often in shales, the most common type of sedimentary rock.” •2) silt = rock worn into tiny pieces (coarser than clay, but finer than sand). usually 1/20 millimeter or less in diameter

Soil Characteristics

•3) sand = quartz or silica worn down over time. grains with diameters between 0.06 mm to 2 mm •4) organic matter (humus)

•5) Loam = soil containing a mixture of clay, sand, silt and humus. Good for growing most crops.

Soil pH

Most soil ranges from 4 to 8The soil of the Pygmy forest in Mendocino County,

California, is acidic, with a pH of 2.8 to 3.9Soils in Death Valley, California, have a pH of 10.5At a low pH, the aluminum and manganese in soil

water are more soluble, and the roots absorb them in toxic concentrations.

Certain mineral salts essential for plant growth, such as calcium phosphate, become less soluble and less available to plant at a higher pH.

An acidic soil has a relatively reduced ability to bind postiviely charged ions to it.

Soil Porosity and Permeability

Porosity - volume of water that “fits between” the soil particles

Permeability - rate of flow of water through soil

% retention - how much water is “trapped” by soil

Porosity and Permeability are directly related; when one is high, the other is high as well. % water retention is inversely related to both.

Soil Porosity and Permeability

• 1) Clay - porosity permeability, retention

• 2) Silt - porosity, permeability, retention

• 3) Sand - porosity, permeability, retention

• 4) Organic matter - porosity, permeability, retention

Alfisol

Brown to gray-brown A-horizon

Moderately weathered forest soils

Found: Moist temperate forest biomes Most organic material is found in living plants

Adequate for agriculture if supplemented with fertilizer or organic material

Mollisols

Primarily found in temperate, semiarid grasslands

Fertile soilsDark brown to black A –horizon rich in humusSoluble minerals remain in the upper layers

because precipitation is not great enough to leach them into lower layers.

Best agricultural soilMost of the world’s grain crops are grown in

mollisols.

Aridisols

Thin light colored and contain a lot of sand.

Found: Dry lands and deserts

Susceptible to salinization

Crops can be grown on aridisols, if water is supplied by irrigation

Oxisols

Low in nutrient mineralsExist in tropical and subtropical areas with

ample precipitationLittle organic material accumulates on the

forest floor (O-hroizon) because leaves and twigs are rapidly decomposed.

A-horizon is rich with humusMost organic matter is found in living plants

Soil Erosion

Wind, water, ice, and other agents promote soil erosionRainfall loosens soil particles, and then transported by

moving water.Effects of soil erosion Reduces the amount of soil in an area and limits the

growth of plantsCauses a soil to lose its fertility because essential nutrient

mineral and organic matter in the soil are removed. Leads to loss of productivity of crops and use of more fertilizers

Sediments that gets into water bodies affect water quality and fish habitats.

Sediments with pesticides add to pollution

Cause and prevention of soil erosion

Poor soil management practicesPoor agricultural practicesRemoval of natural plant communitiesUnsound logging practicesClearcutting large forested areasSufficient plant cover limits the amount of soil

erosion. Roots help to hold the soil in place.

Nutrient mineral depletion

As plant and animal detritus decomposes innatural ecosystems, nutrient minerals are cycled back to the soil for reuse. In agriculture, much of the plant material is harvested. Because the nutrient minerals in the harvested portions are unavailable to the soil, the nutrient cycle is broken, and fertilizer must be added periodically to the soil.

Soil Salinization

The gradual accumulation of salt in a soil, often as a result of improper irrigation methods.

Irrigation water contains small amounts of dissolved salts. The continued application of such water, leads to the gradual accumulation of salt in the soil.

When the water evaporates, the salts are left behind, particularly in the upper layers of the soil, which are the layers important for agriculture.

The level can get high to an extent that plants can get poisoned or their roots get dehydrated.

When soil is waterlogged , capillary movement may carry salts from groundwater to the soil surface, where they are deposited as a crust of salt.

Salinization & Waterlogging

Salinization & Waterlogging

Desertification

Desertification

Asia and Africa the largest land areas with extensive soil damage, and rapid population growth is the main cause.

Prolonged periods of drought (Sahel). During droughts the soil cannot support crop or grazing animals. The Sahelians must use the land to grow crops or they will starve. Overexploitation leds to desertification

To reclaim the land would require restricting its use for many years so it could recover.

Soil conservation and Regeneration

Conservation tillageCrop rotationContour plowingStrip croppingTerracingShelterbelts

Preserving Soil Fertility

List and describe some of the pros and cons of using fertilizers. What different sorts of fertilizers are available?

Experimental data comparing methods!

Click on the picture!

Organic and Inorganic Fertilizers

Organic fertilizers include natural materials as animal manure, crop residues, and compost. They are complex and their exact composition vary. The nutrient minerals in the organic fertilizers become available to plants only as the organic material decomposes. They are slow-acting and long-lasting

Inorganic fertilizers are manufactured from chemical compounds and their exact composition are known. They are immediately available to plants . They also quickly leach away.

Soil Reclamation

Stabilizing the land to prevent further erosionRestoring the soil to its former fertilityTo stabilize the land, the bare ground is seeded with

plants that eventually grow to cover the soil, holding it in place. After the Dust Bowl, land in Oklahoma and Texas was seeded with drought-resistant native grasses.

Plant shelterbelts to lessen the impact of wind ( a row of trees planted as a windbreak to reduce soil erosion of agricultural land.

Restoration of soil fertility to its original level is a slow process. Use of the land must be restricted it cannot be farmed or grazed

Thank You

Submission by: Ankit Chhabra Roll No: 01315603615

Project Guide: Dr. Tanuja Nautiyal

Department of ChemistryNorthern India Engineering College

New Delhi