Chapter 12 Soil Resources

Soil Problems o Soil Erosion Def: wearing away or removal of soil from the land Def: wearing away or removal of soil from the land Caused primarily by water and wind Caused primarily by water and wind o Why a problem? Causes a loss in soil fertility as organic material and nutrients are eroded Causes a loss in soil fertility as organic material and nutrients are eroded More fertilizers must be used to replace nutrients lost to erosion More fertilizers must be used to replace nutrients lost to erosion o Accelerated by poor soil management practices

Three types of soil erosion o Sheet erosion – water moves down a slope and erodes topsoil evenly o Rill erosion – cuts shallow channels in the soil o Gully erosion - is the most severe- cuts deep channels in the soil. Usually occurs on steep slopes o Soil erosion destroys the soil profile, decreasing the water-holding capacity and increasing compaction. Because water cannot percolate through, it runs off the land, taking more soil with it. Is this a positive or negative feedback loop? o POSITIVE

Case in Point: American Dust Bowl o Great Plains have low precipitation and subject to drought severe drought severe drought No natural vegetation roots to hold soil in place No natural vegetation roots to hold soil in place Replaced by annual crops Replaced by annual crops Winds blew soil as far east as NYC and DC. Winds blew soil as far east as NYC and DC. Farmers went bankrupt Farmers went bankrupt

Poor agricultural techniques can lead to soil erosion o Monoculture crops o Row cropping o Overgrazing o Improper plowing o Removing crops wastes o Soil erosion causes damage to agriculture, waterways(canals) and infrastructures (dams)

Soil Problems o Nutrient Mineral Depletion

Soil Problems o Soil Salinization The gradual accumulation of salt in the soil, usually due to improper irrigation techniques The gradual accumulation of salt in the soil, usually due to improper irrigation techniques often occurs in arid and semiarid regions due to the high natural concentrations of inorganic compounds (mineral salts) in the soil often occurs in arid and semiarid regions due to the high natural concentrations of inorganic compounds (mineral salts) in the soil o Salt concentrations get to levels toxic to plants

Soil Problems o Desertification the degradation of once- fertile rangeland or forest into nonproductive desert caused partly by soil erosion, forest removal, overcultivation, and overgrazing the degradation of once- fertile rangeland or forest into nonproductive desert caused partly by soil erosion, forest removal, overcultivation, and overgrazing o Change in vegetation changes climate, further decreasing precipitation levels

Soil Conservation o Conservation Tillage a method of cultivation in which residues from previous crops are left in the soil, partially covering it and helping to hold in place until the newly planted seeds are established a method of cultivation in which residues from previous crops are left in the soil, partially covering it and helping to hold in place until the newly planted seeds are established Conservation tillage reduces soil erosion, increases organic matter, and improves water-holding capacity No-tillage leaves the soil undisturbed in the winter; it saves on fuel costs, machinery wear and tear, and labor time

Crop Rotation Planting a series of different crops in the same field over a period of years Planting a series of different crops in the same field over a period of years It lessens insect damage and disease, helps retain essential nutrient minerals, decrease erosion, and helps maintains soil fertility It lessens insect damage and disease, helps retain essential nutrient minerals, decrease erosion, and helps maintains soil fertility

Soil Conservation o Contour Plowing Plowing around hill instead of up-down Plowing around hill instead of up-down Decreases soil erosion Decreases soil erosion o Strip Cropping Alternating strips of different crops along natural contours Alternating strips of different crops along natural contours o Terracing Creating terraces on steep slopes to prevent erosion Creating terraces on steep slopes to prevent erosion Strip Cropping Terracing Contour plowing, strip cropping, and terracing help control erosion of farmland with variable topography

Preserving Soil Fertility o Preserving soil fertility can be accomplished through the use of both organic and commercial inorganic fertilizers o Organic fertilizers Animal manure, crop residue, bone meal and compost Animal manure, crop residue, bone meal and compost Nutrient available to plants only as material decomposes Nutrient available to plants only as material decomposes Slow acting and long lasting Slow acting and long lasting o Inorganic fertilizers Manufactured from chemical compounds Manufactured from chemical compounds Soluble Soluble Fast acting, short lasting Fast acting, short lasting Environmentally sound to limit use Environmentally sound to limit use Mobile- easily leach and pollute groundwater Mobile- easily leach and pollute groundwater

Soil Reclamation o Soil reclamation involves two steps, stabilizing the land to prevent further erosion (seeding and eventual ground cover)and restoring the soil to its former fertility o Shelterbelts are one of the best ways to reduce the effects of wind on soil erosion (Row of trees planted to reduce wind erosion of soil.)

o Agroforestry uses both forestry and agricultural techniques to improve degraded areas and offer economic benefits

Soil Conservation Policies in US The Soil Conservation Act of 1935 authorized the formation of the Soil Conservation Service (now the NRCS); Mandates the protection of the nation’s soil reserves. Deals with erosion, carries out soil survey and does research on soil salinity. o Food Security Act (Farm Bill) 1985 contained provisions for two main soil conservation programs contained provisions for two main soil conservation programs –Conservation Compliance Program –Conservation Reserve Program (CRP)

Just some factoids o Soil on cultivated land in the USA is eroding 16x faster than it can form. o More soil is lost each year in the US than during the dust bowl due to soil erosion. o 15% of all land on Earth (mostly in Africa/Asia) is no longer available to grow crops due to overgrazing (35%) deforestation(30%) and unsustainable farming (28%).