Effect of residual profile nitrate on corn response to applied nitrogen
1988
Bundy, L.G. | Malone, E.S.
Residual profile NO3 significantly affects crop N fertilizer requirements in semiarid regions, but little information is available on the influence of profile NO3 on crop response to applied N in humid climates. Experiments were conducted on three well-drained silt loam soils to investigate profile NO3 accumulation and retention and to determine the effect of profile NO3-N on corn (Zea mays L.) response to applied N under humid climatic conditions. In 1983, spring pre-plant N (0, 134, 268, or 402 kg N ha-1) was applied to corn at each location. Fall 1983 profile NO3-N to 90 or 120 cm was linearly related to 1983 N rate and ranged from 52 to 644 kg N ha-1. Overwinter retention of fall profile NO3-N varied from 45 to 66% among locations in a year with above normal tall to spring precipitation. Original plots at all locations were split in 1984, and preplant N rates of 0, 78, 156 or 234 kg N ha-1 were superimposed on each 1983 N treatment. Corn yields in the absence of applied N and yield response to added N were significantly affected by spring profile NO3-N content. With no applied N, profile NO3-N to 90 cm accounted for 84% of the variation in yield at the most responsive site. Grain yields weremaximized (8.5 to 9.5 Mg ha-1) in the absence of applied N where profile NO3-N to 90 cm was >150 kg N ha-1. Similarly, yields were not increased by applied N where profile NO3-N exceeded 150 kg N ha-1. These results indicate that profile NO3-N significantly affects corn response to applied N on some Wisconsin soils. Adjustment of N recommendations for profile NO3-N should allow more accurate prediction of corn N fertilizer requirements on these soils when substantial overwinter carryover of profile NO3-N occurs.
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