Presentation on theme: "Fig. 13-13, p. 281 Evaporation Transpiration Evaporation Waterlogging Salinization Waterlogging 1. Irrigation water contains small amounts of dissolved."— Presentation transcript:
Fig. 13-13, p. 281 Evaporation Transpiration Evaporation Waterlogging Salinization Waterlogging 1. Irrigation water contains small amounts of dissolved salts 2. Evaporation and transpiration leave salts behind. 3. Salt builds up in soil. 1. Precipitation and irrigation water percolate downward. 2. Water table rises. Less permeable clay layer
Fig. 13-15, p. 281 Cleanup Prevention 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)
Salinization and Waterlogging of Soils: A Downside of Irrigation Example of high evaporation, poor drainage, and severe salinization. White alkaline salts have displaced cops. Figure 13-14
Erosion Control (see Miller pg. 282) Shelterbelts – can reduce wind erosion. Long rows of trees are planted to partially block the wind. They can also help retain soil moisture, supply some wood for fuel, and provide habitats for birds.
Minimum Tillage – (conservation tillage) to disturb the soil as little as possible while planting crops. Special tillers break up and loosen the subsurface soil without turning over the topsoil, previous crop residues, and any cover vegetation.
SUSTAINABLE AGRICULTURE THROUGH SOIL CONSERVATION Modern farm machinery can plant crops without disturbing soil (no-till and minimum tillage. Conservation-tillage farming: Increases crop yield. Raises soil carbon content. Lowers water use. Lowers pesticides. Uses less tractor fuel.
Contour Farming –sloping your growing crops, etc. You run terraces parallel to the ground to stop soil from running down a steep slope. Plowing and planting crops in rows across, rather than up and down, the sloped contour of the land.
Terracing – (what you use for contour farming.) Dirt goes up to hold the dirt in place. Broad, nearly level terraces that run across the land contour. Helps to retain water for crops at each level and reduce soil erosion by controlling runoff.
SUSTAINABLE AGRICULTURE THROUGH SOIL CONSERVATION Terracing, contour planting, strip cropping, alley cropping, and windbreaks can reduce soil erosion. Figure 13-16
Strip Cropping – a row crop such as corn alternates in strips with another crop that completely covers the soil, reducing erosion. It catches and reduces water runoff and helps prevent the spread of pests and plant diseases.