Phosphorus Absorption by Sod-Planted Corn (Zea mays L.) from Surface-Applied Phosphorus

The no-till method of planting makes it difficult to incorporate fertilizer into the surface soil. The reason for doing the study was to determine if fertilizer placed on the surface of the soil was sufficiently available to corn (Zea mays L.) planted by the no-till method in order to produce high yields. Because P is the least mobile of the major plant nutrients, it was chosen as the fertilizer variable in the study. Corn was planted in a fescue sod killed with herbicides. Four rates of superphosphate (O, 56, 112, and 224 kg P/ha) were applied by two methods and the effects were measured in terms of corn grain yield and P content in the forage at four stages of plant development. All of the P was broadcast on the soil surface as one of the methods of application. The second method consisted of placing 28 kg P/ha into the soil near the seed and the remainder of the added P broadcast on the soil surface. At 29 days after emergence dry matter accumulation was greater on plots receiving surface-applied P than on plots receiving no P fertilizer. Although the percentage of P in the plants increased with increasing rates of applied P, maximum yields of dry matter were attained with 56 kg P/ha, as were yields of grain and stover. Applying all of the P on the soil surface was equally effective to banding part of the P in the row and the remainder on the soil surface. The data support the conclusion that under conditions of no-till, corn planted in a killed sod can effectively absorb surface-applied P. The P does not have to be incorporated into the soil in order to obtain high yields. It should be pointed out, however, that different results might have occurred had lower rates of P been used in the study. The lowest rate of added fertilizer (56 kg P/ha) produced grain yields just as great as the intermediate and the highest rates of added P.