Agronomy and Horticulture Department

 

Date of this Version

June 2003

Comments

Published in Agron. J. 95:339–346 (2003).

Abstract

High levels of residual soil NO 3–N can contaminate ground water by leaching through the soil. Our objective was to reduce the level and spatial variability of residual soil NO 3–N while maintaining optimum corn (Zea mays L. ) production by variable rate N fertilizer application. The experiment was located on a 60-ha sprinkler-irrigated corn field in central Nebraska and included four N management practices: uniform rate, variable rate (VRAT), variable rate at 75% of recommended amount (VRAT + 75%), and variable rate plus 10% (VRAT + 10%). VRAT + 75% decreased the amount of residual NO 3–N in the soil while maintaining similar grain yield to the other treatments, indicating over-application of N with treatments receiving the recommended rate. Increasing the recommended rate by 10% (VRAT + 10%) did not increase corn yield or residual soil NO 3–N. Based on multifractal spectrum, no consistent pattern of spatial variability of soil NO3–N was observed for each treatment across years. Spatial variability in corn grain yield was much lower than that for soil NO 3–N, indicating noneffectiveness of using soil NO 3–N spatial distribution for variable rate N application unless some areas in the field are severely N deficient. Variable rate N application did not reduce variability of residual soil NO 3–N or corn grain yield as com- pared with uniform N. Multifractal analysis quantitatively characterized the extent and pattern of spatial and temporal variability in corn grain yield and residual soil nitrate.

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