The properties of most Iowa soils allow for a single fertilizer or manure application to be successful for up to two crops in a rotation. Most Iowa farmers apply the P needed for the corn-soybean rotation once. The efficiency of applied P with this practice is similar to that of annual applications if the needs of the two crops are considered and the application method is such that P losses with erosion or water runoff are minimized. This practice also reduces application costs. Producers should use proven yields for the crops involved, especially when only maintenance fertilization is needed.
Broadcasting is a popular and low-cost method for applying P fertilizers and manure.
Concentrating P in bands could increase plant uptake in soils with unusually high capacity to fix P and when root growth is restricted by unfavorable weather or soil conditions. Iowa research has shown, however, that in most situations any yield advantage from P banding does not offset increased application costs. Banded P often results in accelerated early growth and development, but yield levels remain comparable with the broadcast method. Still, Iowa producers could consider banding all or part of the P in some situations. Also, the producers' cash availability may not allow for application of the recommended optimum rate, and banding can be more effective when suboptimal P rates are used.