Effect of Nitrapyrin and N Fertilizer on Yield and Mineral Composition of Corn

Fertilizer N applied in the fall or early spring is often used less efficiently than N applied closer to the time of maximum N demand by plants. Nitrification inhibitors make it possible to delay nitrification of applied NH₄⁺-N in the soil and thereby reduce overwinter and early spring N loss from leaching and denitrification. Because NH₄⁺ absorption may induce changes in plant mineral composition, we evaluated under field conditions, the effect of inhibiting nitrification of NH₄⁺-N on the mineral composition of corn leaf tissue as well as on grain yield and protein content. Anhydrous ammonia with and without nitrapyrin [ 2-chloro-6-(trichloromethyl) pyridine] at 0.55 kg/ha was applied in the fall and spring on soils of three types. Addition of nitrapyrin to fall-applied NH₄⁺ significantly increased grain yield and grain protein. Grain protein was sometimes increased when nitrapyrin was applied with NH₄⁺ in the spring. Grain protein content was increased by N and nitrapyrin and from 10 to 33%. Protein generally continued to increase even after the maximum yield had been reached. The mineral composition of leaves was more dependent on soil type than on N treatment. The minerals K, Ba, and Mn were higher, and Ca, Mg, and A1 were lower in plants grown in Tracy sandy loam (Ultic Hapludalfs, coarse-loamy, mixed, mesic) than in those grown in either Runnymede loam (Typic Argiaquolls, fine-loamy, mixed, mesic) or Chalmers silty clay loam (Typic Haplaquolls, fine-silty, mixed, mesic) soils. The concentrations of minerals in plants were similar with fertilizer treatments and time of application. Zinc was the only mineral in plants that significantly increased when nitrapyrin was added to NH₄⁺. Nitrification inhibitors can effectively reduce N losses without adversely affecting the uptake of other minerals or the mineral composition of corn leaf tissue.