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Fluid Journal : Fluid Journal 1993-1995
3 Fluid Journal Spring 1993 chemical and biological properties of the soil. Perhaps the single, most important effect is that of protection of the soil from water and wind erosion. Other important effects include increased water infiltration, reduced moisture evaporation and generally an increased supply of plant-available water for crops. Dense residue covers result in cooler soil temperatures below the mulch. Lower temperatures can delay planting and increase seedling emergence time. Leaching losses of soluble nutrients, such as nitrates, are often greater in a no-till system. Crop residues play an important role in nitrogen fertilizer efficiency. The zone near the soil surface is rich with microbial activity. This increased activity can result in greater nitrogen immobilization. Nitrogen immobilization can be from native N sources and applied nitrogen fertilizers. Furthermore, if soil moisture is excessively high, nitrogen losses from denitrification can occur in this surface zone. Since there is a greater activity of soil bacteria and other microbes, there is also an increased amount of urease in the surface soil and increased urease activity results in high ammonia volatilization losses of applied urea nitrogen fertilizers. Dr. Varsa is associate professor and Hnetkovsky is a former graduate assistant in the Plant and Soil Science Department at Southern Illinois University in Carbondale, Illinois. Acknowledgment: The Fluid Fertilizer Foundation provided partial funding for this research as a grant. May June 86 84 82 80 78 76 74 72 70 68 0% 100% 50% 200% from: S. Hnetjivsjy, M.S. theels, SUC (1992) 13151719212930 4 8 121418 Degrees F Figure 4. Influence of residue levels on noon-day soil temperature at 4-inch depth, May 13 to June 20, 1991.
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