Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 1993-1995
180 170 160 150 140 130 120 110 Broadcast Broadcast Inject Inject April Plant Plant V6 Yields - bu/A With Starter Figure 4. Interaction of starter fertilizer and N timing and placement on yield of no-till corn. N applied with herbicides in early preplant applications is not efficiently used and a high percentage of N is lost through denitrification. Broadcast vs. injection. Applying N on the surface of residue-covered soils can increase the risk of N loss. It has been well established that the efficiency of surface- applying N is generally lower and less predictable than injecting or incorporating N into the soil of no-till systems. Two mecha- nisms responsible for these reductions in efficacy of surface-applied N are: 1) immobi- lization of N in decomposing residue, and 2) ammonia volatilization from the hydrolysis of urea-based fertilizers. Moisture retention. In no-till systems, the residue layer left on the soil surface en- hances infiltration of precipitation and reduces evaporation of soil water. Thus, soil water content is generally higher than in conventionally-tilled soils, and soil tempera- tures are lower. Conditions in and directly under the residue cover also are conducive to microbial activity. Populations of soil organisms responsible for nitrification and denitrification are normally higher than those found in a clean-tilled soil. These conditions can lead to increased N losses from leaching and denitrification. Mann is a former graduate student, Dr. Mengel is professor and Dr. Hawkins is extension agronomist in the Department of Agronomy at Purdue University. ! Summer 1995
Fluid Journal 1996-1998