Spatial and temporal processes affecting nitrogen availability at the landscape scale |
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Authors: | J. M. Sogbedji H. M. van Es S. D. Klausner D. R. Bouldin W. J. Cox |
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Affiliation: | Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853-1901, USA |
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Abstract: | Nitrogen dynamics in soils are affected by spatial and temporal processes. Drainage class is generally regarded to be the most significant source of variability for N in temperate humid climates. A 5-year study was conducted including four rates of N fertilizer and three drainage classes within a 15 ha maize (Zea mays L.) field. Variance component analysis showed that N response was minimally affected by drainage class, but showed strong yearly variations, apparently related to early-season precipitation. Annual field-averaged economic optimum N rates had a range of 65 kg ha−1 with lower rates being associated with years with low early-season precipitation. A calibrated LEACHMN model and site-specific weather data were used to evaluate the effects of early-season weather conditions on N rate and availability. During wet years, soil N availability was reduced by approximately 35–50 kg ha−1 compared to dry years, largely independent of drainage class. For well-drained soils, most losses were attributed to leaching (especially in years with wet early-season), while poorly drained soils mainly experienced denitrification. It is concluded that limited benefits may be gained from spatially variable N applications within fields based on drainage class or soil type, but considerable economic and environmental gains are possible from yearly adjustment of supplemental N rates based on model simulations of N dynamics using information on early-season weather conditions. |
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Keywords: | Author Keywords: Soil variability Spatial variability Temporal variability Nitrogen Maize Drainage class Weather LEACHMN |
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