HR: 13:55h
AN: H53J-02 INVITED    [Abstracts]
TI: Effects of Crop Rotation, N Management, Tillage, and Controlled Drainage on nitrate-N Loss in Drain Flow
AU: * Ma, L
EM: liwang.ma@ars.usda.gov
AF: USDA-ARS, Agricultural Systems Research Unit, Fort Collins, CO 80521, United States
AU: Malone, R
EM: malone@nstl.gov
AF: USDA-ARS, National Soil Tilth Lab, Ames, IA 50011, United States
AU: Ahuja, L
EM: laj.ahuja@ars.usda.gov
AF: USDA-ARS, Agricultural Systems Research Unit, Fort Collins, CO 80521, United States
AU: Kanwar, R S
EM: rskanwar@iastate.edu
AF: Iowa State University, Dept. of Agricultural and Biological Engineering, Ames, IA 50011, United States
AB: Accurate simulation of agricultural management effects on N loss in tile drainage is vitally important for understanding hypoxia in the Gulf of Mexico. An experimental study was initiated in 1978 at Nashua, Iowa of the USA to study long-term effects of tillage, crop rotation, and N management practices on subsurface drainage flow and associated N losses. The Root Zone Water Quality Model (RZWQM) was applied to evaluate management effects (tillage, crop rotation, N application, and controlled drainage) on N loss in drain flow. RZWQM simulated the observed increase in N concentration in drain flow with increasing tillage intensity from NT (no-till) to RT (ridge till) to CP (chisel plow) and to MP (moldboard plow). It also adequately simulated tillage effects on yearly drain flow and yearly N loss in drain flow. On the other hand, RZWQM adequately simulated lower yearly drain flow and lower flow-weighted N concentration in drain flow under CS (corn-soybean) and SC (soybean-corn) than under CC (continuous corn). The model also simulated higher N loss from fertilizer-N applications than from manure-N applications. Applying the newly suggested N management practice for the Midwest of controlled drainage, the model simulated a 30% reduction in drain flow and a 29% decrease in N losses in drain flow under controlled drainage (CD) compared to free drainage (FD). With most of the simulations in reasonably close agreement with observations, we concluded that RZWQM is a promising tool for quantifying the relative effects of tillage, crop rotation, N application, and controlled drainage on N loss in drainage flow. Further improvements on simulated management effects on N mineralization and plant N uptake are needed, however.
DE: 0402 Agricultural systems
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0466 Modeling
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
SC: Hydrology [H]
MN: 2007 Fall Meeting