Agronomy and Horticulture Department

 

Date of this Version

March 2003

Comments

Published in Agron. J. 95:339–346 (2003). MARCH–APRIL 2003. Permission to use.

Abstract

High levels of residual soil NO3–N can contaminate ground water by leaching through the soil. Our objective was to reduce the level and spatial variability of residual soil NO3–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 prac- tices: 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 NO3–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 NO3–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 NO3–N, indicating noneffectiveness of using soil NO3–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 NO3–N or corn grain yield as compared 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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