Placement of preplant liquid nitrogen and phosphorus fertilizer and nitrogen rate affects no-till wheat following different summer crops

Because of improved equipment technology, many producers in the eastern Great Plains are planting winter wheat (Triticum aestivum L.) no-till (NT) into previous crop residues, but management of fertilizer N and P remains critical. This Held study was conducted from 1998 through 2003 in southeastern Kansas on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf). The objectives were to determine effects and interactions of previous crop [corn, Zea mays L.; grain sorghum, Sorghum bicolor (L.); and soybean, Glycine max (L.) Mem], preplant placement method of liquid N-P fertilizer [subsurface-knife (KN), surface-band (SB), and surface-broadcast (BC)], and fertilizer N rate (22, 45, 90, and 134 kg N ha(-1)) on NT winter wheat yield, yield components, and nutrient uptake in a 2-yr cropping rotation. Wheat yields averaged 3.73, 3.56, and 2.97 Mg ha(-1) following soybean, corn, and grain sorghum, respectively. However, as fertilizer N rate increased, yield differences between previous crops decreased. Grain yields also were influenced by placement of N-P fertilizer, averaging 3.68 Mg ha(-1) for KIN, 3.40 Mg ha(-1) for SB, and 3.19 Mg ha(-1) for BC. Plant and grain N responses indicated that grain yield differences were primarily related to greater immobilization of both fertilizer and soil N following grain sorghum, compared with soybean and corn, and to better utilization of KIN N-P than surface-applied. Fertilizing with greater N rates applied as a subsurface band, especially if following grain sorghum, may be necessary to maximize NT wheat yield potential in the eastern Great Plains.