Effects of Soil Nitrogen Fertility on the Protein and Lysine Content and Nutritional Value of Normal and Opaque-2 Corn

Abstract

An experiment was conducted to determine the effects of level of N fertilization on the yield, protein and lysine content and nutritional value of normal and opaque-2 corn. Three normal endosperm hybrids and their nearisogenic opaque-2 counterparts were grown on three replicate plots on a low-N soil in Kentucky. Plots were fertilized with 0, 112, 224 or 448 kg of N/ha. The normal hybrids outyielded the opaque-2 hybrids (7,947 vs 6,765 kg/ha; P<.01). Yields increased quadratically (P<.01) with increasing level of N in both types of corn. Protein content was similar for the two corn types (8.1%), but the opaque-2 corns were higher in lysine (.36 vs .26%, P<.001). Protein and lysine increased in both corn types with increasing level of N. Protein level was correlated with lysine level in normal corn (r = .71) and in opaque-2 corn (r = .55). Chicks fed opaque-2 corn grew faster (P<.001) and required less feed/unit of gain (P<.001) than those fed normal corn. Nitrogen fertilization resulted in improved gain and feed/gain (P<.01) in chicks fed opaque-2 corn, but not in chicks fed normal corn. Gain and feed/gain were more highly correlated with lysine content of the corn (r = .73; −.81) than with protein content (r = .11; −.26). The results indicate that the protein and lysine content of both normal and opaque-2 corn is influenced by soil N fertility. The increased lysine and protein content resulted in an increased nutritional value of opaque-2 corn, but not normal corn.