Deep banding phosphorus and potassium fertilizers for corn managed with ridge tillage

Broadcast fertilization leads to stratification of soil P and K in the ridge-till system, which may reduce fertilizer use efficiency, This study evaluated the response of corn (Zea mays L.) to broadcast or deep-band (15- to 20-cm depth) placements in 15 site-years. Fertilization rates were 0 to 56 kg P ha(-1) and 0 to 132 kg K ha(-1). Soil-test P (STP) and K (STK) were higher in the top 15-cm layer of the ridges. Phosphorus increased early plant growth (V5 stage) in five sites, early P uptake in nine sites, and grain yield in seven sites. Yield was increased by P when STP was < 22 mg P kg(-1) (Bray-l) in the top 15cm layer of ridges or < 18 mg P kg(-1) in the top 15 cm of ridges and valleys. The P placements seldom differed (the deep-band P was better in one site). Potassium increased growth in 6 sites, K uptake in 14 sites, and grain yield in nine sites. The deep-band K increased yield over the broadcast K in four sites. The yield response to broadcast K across sites was not correlated with STK, but the response to deep-band K was negatively and linearly correlated with STK from various sampling positions. Corn responded to deep-band K in soils with above-optimum STK according to current soil-test interpretations. The results showed that both placements usually were similarly effective for P, and that deep banding often was superior for K.