Maize (Zea mays L.) yield response to nitrogen as influenced by spatio-temporal variations of soil-water-topography dynamics

Applying N fertilizer at rates that satisfy both economic and environmental objectives are critical for sustainable agriculture. The hypothesis of this study was that the spatial variability in maize (Zea mays L.) yield and its response to N rate were influenced by soil-water-topography dynamics. In 2008 and 2009, a study was conducted along an agricultural hillslope in the Northern Appalachian Ridge and Valley Physiographic Province in the USA with Cambisols according to FAO soil classification. Minimum, maximum, and delta yields and optimum N rate at different slope positions were determined using quadratic-plateau maize yield - N rate models. Results confirmed our hypothesis. The spatial variability of maize yield and its response to N rate was influenced by silt content, soil depth, profile curvature, slope, soil wetness and degree of soil water content temporal variation. In both dry year (2008) and wet year (2009), optimum N rates positively correlated (P<0.05) with the temporal variation of soil water content, which is an indicator of subsurface flow paths. In 2008, maize yield was little varied along this hillslope (11.7-12.0Mgha^-1), while greater yield response to N rate (represented as delta yield, 5.6Mgha^-1) was observed in upper convex and steep slope areas with low minimum yield (6.1Mgha^-1). However, in 2009, greater maximum maize yield (13.5Mgha^-1) and yield response to N rate (8.7Mgha^-1) were observed in lower concave slope areas with deeper soil depth and thus greater water storage. Results from this study suggested that site-specific N applications could be improved by considering within field variability of soil, topography and hydrology.