The Soil System

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Soil formation is a slow process:Soil formation is a slow process:

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Mature soils are arranged in a series of zones called SOIL HORIZONS:

“O” HORIZON = freshly fallen and partially decomposed leaves, twigs, animal waste. You can find fungi and other organic materials.

“A” HORIZON = porous mixture of partially decomposed organic matter (humus) as well as bacteria, fungi, earthworms, and other decomposer organisms interacting in complex ways. inorganic

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

“B” (subsoil) and “C” (parent material)

HORIZON contain most of the soil’s inorganic matter, mostly broken-downrock consisting of varying mixtures of sand, silt, clay, and gravel..

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Clay (very fine particles) <0.002mmSilt (fine particles) 0.002-0.05mmSand (medium-size particles) 0.05-2.0mmGravel (coarse to very coarse particles) >2.0mm Soil Texture is determined by the relative amounts of the different types and sizes of mineral particles.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Soil Content

Loam is soil composed of sand, silt, and clay in relatively even concentration (about 40-40-20% concentration respectively). Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils. Loams are gritty, moist, and retain water easily.

100%clay

Increasingpercentage silt

Increasingpercentage clay

0

20

40

60

80

80

60

40

20

0

100%sand 80 60 40 20 100%silt

Increasing percentage sand

sandyclay

clay

siltyclay

silty clayloam

clayloam

loam siltyloam

silt

sandy clayloam

sandyloam

loamy sandsand

http://www.youtube.com/watch?v=knrmCbctGEA

Soil Texture TriangleTopic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems.-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Soil texture helps determine SOIL POROSITY, a measure of the volume of pores or spaces per volume of soil and the average space between those spaces.INFILTRATIONINFILTRATION is the downward movement of is the downward movement of water through soils.water through soils.As the water seeps down, it dissolves various soil components in upper layers and carries them down to lower layers in a process called LEACHING.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

SOIL PERMEABILITY is the rate at which water and air move from upper to lower soil layers.

Water Water

High permeability Low permeability

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Properties of Soils with Different TexturesProperties of Soils with Different Textures

Texture Nutrient Capacity

Infiltration Water-Holding Capacity

Aeration Workability

Clay Good Poor Good Poor Poor

Silt Medium Medium Medium Medium Medium

Sand Poor Good Poor Good Good

Loam Good Good Good Good Good

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Soil erosion is the movement of soil components, Soil erosion is the movement of soil components, especially surface litter and topsoil.especially surface litter and topsoil.

• The two main agents of erosion are:1. wind2. flowing water

• Loss of plant cover by farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation and other activities leave soil vulnerable to erosion.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Two major harmful effects of soil erosion:1. Loss of soil fertility and its ability to hold water2. Runoff of sediment that pollutes water, kills fish

and shellfish, and clog irrigation ditches, boat channels, reservoirs, and lakes.

serious concernsome concernStable areas

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

DesertificationDesertification is the enlargement of deserts through human activities.

ConsequencesCauses

Worsening drought

Famine

Economic losses

Lower living standards

Environmentalrefugees

Overgrazing

Deforestation

Surface mining

Erosion

Salinization

Soil compaction

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

SALINATION

1. Irrigation water contains small amounts of dissolved salts.

2. Evaporation and transpiration leave salts behind.

3. Salt builds up in soil.

WATERLOGGING

• Precipitation and irrigation water percolate downward.

• Water table rises.

• Causes roots to drown.

Both result in stunted plant growth, lower crop yields, dead plants and ruined land.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Soil Conservation involves reducing Soil Conservation involves reducing soil erosion and restoring soil fertility.soil erosion and restoring soil fertility.

http://www.youtube.com/watch?v=MQQcnId3Z7A

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Contour planting and strip cropping: each row acts as a small dam to help hold soil and slow water runoff.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Alley cropping or agroforestry: several crops are planted together in strips or alleys between trees and shrubs that can provide fruit or fuel-wood, shade, help retain and slowly release soil moisture,

and fodder for livestock.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Windbreaks or shelterbelts of trees reduce wind erosion, help retain soil, supply wood for fuel, and provide habitats for birds,

pest-eating and pollinating insects, and other animals.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Terracing retains water for crops at each level

and reduces soil erosion

by controlling runoff.

Topic 3The Soil System and Food Production

Students will be able to:-to outline how soil systems integrate aspects of living systems .-compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

Soil Restoration• Organic fertilizer• Manure• Compost crop rotation• No till farming• Contour farming• Terracing• Nitrogen fixation-legumes