Corn yield response to nitrogen rate and timing in sandy irrigated soils

Efficient use of N fertilizer for corn (Zea mays L.) production is important for maximizing economic return and minimizing NO3 leaching to groundwater. The objective of this study was to evaluate grain yield response to irrigation rate and N rate and timing for irrigated corn in the sandy soils along major Kansas waterways. Nitrogen treatments included 300 and 250 kg N ha(-1) applied at planting; 250 kg N ha(-1) applied at planting (one-half) and sidedress (one-half); 185 kg N ha(-1) applied at planting (one-third) and sidedress (two-thirds); 125 kg N ha(-1) applied at planting (one-fifth) and sidedress (two-fifths, two-fifths); and 0 kg N ha(-1). Nitrogen treatments were duplicated at one site for each of two irrigation treatments (IS): 1.0x (optimal) and 1.25x (25% > optimal). A split application of 185 kg N ha(-1) was sufficient to achieve maximum corn yield at every location, and in most instances 125 kg N ha(-1) was sufficient. These rates were on average 88 kg N ha(-1) less than the current N recommendation for corn in Kansas, indicating that N rates could be reduced for these soils by an average of about 40% of the current N recommendation when N is split applied. The environmental risk associated with irrigated corn production on these sandy-textured soils, specifically, NO3 leaching to groundwater, will be minimized only when N fertilizer and irrigation inputs do not exceed crop requirements and N fertilizer is applied to more closely match crop demand (e.g., in-season applications).