The Relationship of Nitrification Rate of the Soil and Nitrogen Content of the Corn Leaf to the Yield of Corn

In this study the capacity of the soil to supply available nitrogen to corn was measured by nitrification rate of the soil and by the nitrogen content of corn leaves.Rotation plots on the Agronomy Farm, Lincoln (NE), offered an opportunity to study the relationship of both the nitrification rate of the soil and of the nitrogen content of the corn leaf to yields of corn on a typical non-irrigated soil.A moisture-fertility-spacing experiment of the North Platte Experiment Substation provided a source of samples for studying the relationship of nitrogen content of corn leaves to yield of corn on an irrigated soil. In the rotation plots a highly significant correlation was obtained between nitrification rate of the soil and yield of corn.In these plots the highest yields have been obtained from the rotation that included two years of sweet clover and an application of manure. Yields of corn and nitrification rates were highest immediately following a legume in the rotation or an application of manure and decreased as the length of time between the crop of corn and the legume or an application of manure increased.The very low yield of corn immediately following alfalfa was one outstanding exception to this.This was probably due to a moisture deficiency induced by the alfalfa. In the rotation plots the nitrification rate was correlated with the total nitrogen content of the soil.Total nitrogen content of the soil was about 0.008 per cent greater in plots having rotations that contained two years of a legume or an application of manure than it was in those plots where rotations contained no legume or manure.Total nitrogen content of the soil in plots where rotations contained two years of legume and application of manure exceeded by about 0.018 per cent that in plots where rotations contained no legume or manure. In the moisture-fertility-spacing experiment, the nitrogen content of the corn leaves was influenced by fertility levels and plant population and was highly significantly correlated with yield (r = 0.84). Advisor: H. F. Rhoade