1. Soil and Agriculture
Chapter 9

2. Soil: The Foundation for Sustainable Agriculture
Agriculture – raising of crops and livestock for human use
Agriculture can increase need for irrigation and fertilizer
Cropland – land used to raise crops
Rangeland or pasture – land used for grazing
38% of Earth’s land used for agriculture
Soil – combination of mineral, rock, water, air, microorganisms, gases, and decaying organic matter (humus) that supports plant growth
Soil is a renewable resource that could be depleted

3. Sustainable agriculture - agriculture practices that can be employed far into the future without compromising the resource
Healthy soil is necessary for:
Productive agriculture
Soil retention
Water retention
Many living things depends on healthy soil in some way for their food

5. Agricultural Revolution
10,000 years ago agriculture arose independently in several areas:
China
Middle east
Americas
Africa
Societies switched from hunter-gather to fixed
Fixed societies grew larger leading to first cities requiring increased food production

7. Industrial Agriculture Dominates Today
Traditional agriculture – agriculture powered by human and animal
Uses simple hand tools and machines
Subsistence agriculture – agriculture that only produces enough food for the family that grows it
Polyculture – having several crops planted in one field
Market economies allow farmers to sell their products

8. Industrialized agriculture – agriculture relying on mechanization and fossil fuels to boost yields
Monoculture - planting of a single crop
Green Revolution s introduced new technologies, crop varieties, and farming practices to developing nations
Increased food production, decreased starvation
Soil degradation increased

9. Soil as a System Living organisms Decaying organic matter Soil is:
50% mineral and rock
Up to 5% organic matter
Living organisms
Bacteria, algae, protists, fungi, earthworms, insects, mammals, reptiles, and amphibians
Decaying organic matter
Remaining space is air and water
Soil is made of biotic and abiotic factors, therefore is considered an ecosystem

11. Soil Forms Slowly: Parent material – the geologic base of soil
Lava, volcanic ash, rock, dunes
Bedrock - solid rock that makes up Earth’s crust
Weathering is a key process in the rock and mineral makeup of soil formation is also influenced by
Climate – soils form faster is warmer more humid climates than in cooler drier climates
Organisms – add organic matter
Topography - soils is thicker at the base of a slope that on the side of a slope, amount of exposure to sunlight, wind, and precipitation all affect soil formation

12. Parent material – determines that type of rock and mineral soil contains
Time – soils can take a few years to a few thousand years to form

13. Soil Profiles and Horizons:
Soil profile – a vertical column of soil horizons
Soil horizon – the individual layers within a soil profile
Can be up to six horizons in a profile
Leaching – as rain infiltrates soil, particles are moved through horizons
Particles may become part of drinking water
If particles are toxic, water could become inconsumable
Topsoil – the horizons most beneficial to plants
Usually the O and A horizons

15. Soils Differ: Soil color indicates composition and productiveness
The darker the more organic matter it has meaning soil is nutrient rich
Pale soil shows leaching often meaning soil is nutrient poor
Texture is determined by particle size
From smallest to largest
Clay
Silt
Sand

17. Loam – soil with good mix of silt, clay, and sand
Allows water and air to move freely through soil without allowing it to move to quickly
Loam soils are easy to cultivate
Structure refers to its “clumpiness”
Medium clumpiness is good
Over tilling or repeated tilling compacts soils, preventing water movement
pH affects soil ability to support plant growth
To acidic or basic will kill plants

18. Cation Exchange: Cation exchange is vital for plant growth
Cation exchange - a process allowing plants to gain needed nutrients
Negatively charged soil holds cations of Ca, Mg, and K
Roots donate H to soil in exchange for these nutrients
Cation exchange capacity – soil’s ability to hold cations
Cations that don’t leach from upper horizons become available to plants
Soils with fine texture or rich in organic matter have higher cation exchange capacity

19. Soil Conservation Soil Conservation is Vital:
Increased population requires increased food production
Arable land (suitable for farming) is being depleted and mismanagement is causing
Deforestation
Diminishing biodiversity
Encouraging growth of non-native species
Soil, air, and water pollution
Loss of topsoil from wind and water runoff

20. Soil degradation – decline in quality and productivity of soil
Caused mainly by deforestation, crop agriculture, and overgrazing
Land degradation – overall decline of land’s productivity and biodiversity

21. Wind and flowing water generate erosion
Vegetation holds soil in place
No-till agriculture reduces exposure
Cover crops protects soil between seasonal plantings
Desertification – land degradation with more than a 10% productivity loss
Caused by, deforestation, overgrazing, drought, and climate change
Arid regions are prone more
Arid regions cover nearly 40% of Earth’s surface

22. The Dust Bowl:
During the 1930s in the southern Great Plains, the Dust Bowl formed as a response to prolonged drought, over cultivation, and overgrazing
Tons of valuable topsoil were blown away leading to the formation of the Soil Conservation Service in 1935.
The service developed conservation plans through the creation of conservation districts that dealt with farms at the county level
1994 the service was renamed the Natural Resources Conservation Services (NRCS)
Expanded to include water quality and pollution control

23. Farming to Protect Soil:
Crop rotation – changing what’s grown from year to year
Contour farming – planting crops perpendicular to the slope of the land to provide a barrier to erosion
Terracing – cutting platforms into hillsides to create flat areas like stair steps
Intercropping – alternating rows of crops creating a mixed arrangement
Shelterbelts (windbreaks) – rows of tress planted along the perimeter of a field to provide wind protection

24. Conservation tilling – reduces the amount of tilling needed
No-till reduced erosion even more
Better soil quality, more humus, carbon storage
Less labor, less machinery wear, less fossil fuel used
40% of U.S. farmland uses conservation tillage

25. Overgrazing - too many animals eating too much plant cover

26. Watering and Fertilizing Crops
Irrigation:
Irrigation - providing water to support agriculture
70% of all freshwater is used in agriculture
Used in regions normally not arable or for water intensive crops like rice and cotton
Matching crops to climate can reduce need for irrigation
Traditional irrigational causes up to 45% of water evaporate, drip irrigation puts more water to plants up to 90%

27. Salinization – the buildup of salts in soils surface layers
Easier to prevent than fix
Caused by continual irrigation, evaporation leaves salt behind
Plant salt tolerant plants
Flush soil with low salt water
Let soil rest and let rainfall flush soil
Waterlogging – over-irrigating until gas exchange in plant roots is prohibited
Can lead to crop loss

28. Fertilizers
Soil can be remediated by adding fertilizers
Fertilizers – substances that contain essential nutrients
N, Ph, K which limit plant growth if not proper amounts
Organic fertilizers – the wastes or remains of living things
Manure, compost, crop leftovers
Compost - mixture of organic matter broken down by decomposers

29. The Green Revolution of the 19470s saw a rise in food production with:
Genetically altered crops
Improved pesticides
Improved mechanization
Inorganic fertilizers – mineral supplements that are mined or manufactured
Increase soil compaction
Decrease soils capacity to hold water
Runoff can create dead zones
Nitrate and phosphate build in drinking water can cause cancer and blue-baby syndrome
Are cheap, easy to transport, and greatly increase food production

30. Agricultural Policy Government Policies and Agriculture:
Policy has encouraged production
Recent policy tries to lessen environmental impact
Markets should discourage land degradation
Governments spend billions on subsidizes, some are unsustainable
Water intensive crops in arid regions
Agriculture in areas where land degrades easily

31. Wetlands:
Wetlands – marshes, swamps, bogs, and river floodplains
More than 50% have been drained for agriculture in US
US policy encouraged draining
Swamp Lands Acts (1849, 1860, 1950) drained/converted wetlands to for flood and malaria control
Wetlands now considered vital
Wetlands Reserve Program – payment encourages landowners to restore, protect, and enhance wetlands

32. Programs Promoting Soil Conservation:
2008 “farm bill” funded 15 programs providing subsidies for farmers adopting soil conservation plans
1985 Conservation Reserve Program – farmers are paid to out easily eroded land into reserve, meaning it’s not used
Income for farmers
Money spent saves topsoil
Better water quality
Wildlife habitat

33. 2012 farm bill never voted on, leaving future conservation programs in limbo
Food and Agriculture Organization (FAO) is the UN main agriculture program
Supports innovation in resource management and sustainable agriculture in Asia
China and India both part of Asia
Communities educate and encourage soil conservation and secure the food supply