Spatial and Temporal Variation of Soil Nitrogen Parameters Related to Soil Texture and Corn Yield

Received for publication November 23, 2004. 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 south-central 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 sitespecific N management.