Spatial and Temporal Variability of Soil Nitrate and Corn Yield: multifractal Analysis
2003
Eghball, B. | Schepers, J.S. | Nigahbān, Muḥammad | Schlemmer, M.R.
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 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 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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