Excerpt
Crops grow by opening their stomata, which allow CO2 to enter their leaves, where CO2 and water can be photosynthesized into carbohydrates using the sun's energy. Photosynthesis occurs in the light only if CO2 continues to diffuse from the atmosphere into the interior of the leaves. However, stomata cannot remain open for CO2 diffusion if water is not continually supplied to the stomata to replenish the water these cells lose via transpiration. If the water flux from the soil is limited under drought conditions, stomata initiate closure and crop growth decreases. The soil profile is the critical storage reservoir, which can absorb and hold the rainfall until it is needed by the crop. The amount of rainfall that can be absorbed, stored, and made available for crop use depends on the porosity and texture of the soil and depth to which crop roots penetrate the soil.
EFFECTS OF TILLAGE ON ABSORPTION AND RETENTION OF WATER AND CROP YIELDS One aspect of the absorption and holding capacity of soils that appears amenable to significant change by management is the runoff-infiltration tradeoff. Edwards and Norton (1986) found that with rainfall averaging about 100 cm y-1 (40 in yr-1) at…
Footnotes
W. Doral Kemper is a soil physicist, retired from the USDA Agricultural Research Service. He is now consulting with the Pakistan Council of Research in Water Resources and the Water and Power Development Authority. Nicholas N. Schneider is the agricultural agent for Winnebago County, Wisconsin, and an associate professor at University of Wisconsin Extension, Oshkosh, Wisconsin. Thomas R. Sinclair is a professor at the Department of Crop Science, North Carolina State University, Raleigh, North Carolina.
- © 2011 by the Soil and Water Conservation Society
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