Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 1998
Publication Date: N/A
Technical Abstract: Variability in soil productivity can cause large within-field differences in fertilizer N removal by summer crops, especially when drought limits yield of the summer crop. A spatial assessment of the ability of winter cover crops to scavenge residual N will help optimize cover crop use for protecting ground water quality and improve the determination of the following season's fertilizer needs. The objective was to determine the spatial N accumulation of a wheat (Triticum aestivum) winter cover crop following a droughted corn (Zea maize) crop. In 1993, corn was grown on an 8-ha field with a uniform application of 129 kg N/ha. Corn grain N removal ranged from 14 to 41 kg/ha across 10 locations (which included six soil map units). Wheat was planted in November without fertilizer N. At each location, soil NH4-N and NO3-N were measured to a depth of 0.9 m on 22 March 1994, and aboveground wheat biomass and N content measurements were made on 14 March and 14 April. Inherent soil productivity factors were important for determining the effectiveness of using this cover crop to trap residual N. Soil NH4-N ranged from 30 to 86 kg/ha, and NO3-N ranged from 5 to 20 kg/ha. Total N in the wheat averaged 21 (range 5 to 35) and 43 (range 24 to 64) kg/ha in March and April, respectively. The amount of N sequestered by the wheat was almost as variable within as across soil map units.