Interactions encountered when supplying iron, phosphorus and nitrogen fertilizer to two cultivars of soybeans

Abstract

Abstract An Fe‐efficient and an Fe‐inefficient cultivar of soybean were grown in calcareous Hacienda loam soil with FeEDDHA, P and N fertilizers in factorial combination. With the Fe‐efficient cultivar (Hawkeye), there was response to Fe alone (40 percent) and very small responses to P alone (5 percent) and N alone (13 percent). When N and P were combined there was antagonism. The Fe with P and Fe with N both gave sequentially additive interactions or very near. When all three inputs were combined the responses to Fe, P and N, respectively, were 80, 35, and 44 percent, and the interaction was synergistic. Each nutrient was a Liebig‐type limiting factor. With T‐203 soybean, FeEDDHA gave no response when used alone, and N and P singly and together were very antagonistic. When all three nutrients were supplied simultaneously, the interaction was synergistic with responses to Fe, P and N, respectively, 569, 471, and 116 percent. Even after Fe had been supplied, the N and P were Liebig‐type limiting factors. Y...