Spatial and temporal variation of soil nitrogen parameters related to soil texture and corn yield

The spatial variability of soil properties that affect the soil N budget and corn (Zea mays L.) grain yield were studied for 2 yr in southcentral Texas to better assess the potential for variable-rate N fertilization. Residual soil NO3 N with depth and soil N mineralization (Nmin) potential and their relationships with soil total N, soil organic C, and clay content were characterized. Residual soil NO3-N to 60-cm depth was more related to corn yield than NO3-N at shallower depths. Residual soil NO3-N showed temporal variation with spatial structure existing for NO3-N in the first year when NO3-N concentrations were high, but this variation was absent in the second year when NO3-N concentrations were low. The opposite trend was observed for soil Nmin. Soil total N exhibited temporal persistence. Soil Nmin showed significant correlations with soil clay content in both years. Temporal persistence of soil texture and variation in spatial structure for N parameters would likely result in different strategies for soil N management zones in 2002 vs. 2003. This experiment demonstrated the potential importance of soil texture for modifying fertilizer N recommendations. Texture generally is more easily determined than soil N parameters at the scale and intensity necessary for site-specific N management.