Nitrogen, Climate, and Previous Crop Effect on Corn Yield and Grain N1

Abstract

AbstractTwo N response experiments, previously cropped with alfalfa and small grain, were conducted for 4 years (1977 to 1980) on Mexico silt loam soil, (fine, montmorillonitic, mesic Udollic Ochraqualf). The study included the evaluation of temperature and precipitation effects upon corn (Zea mays L.) yield, predicting the N requirement for maximum yield, based on N content of corn grain. A fertilizer N gradient of 0, 45, 90, 135, 180, and 225 kg N ha−1 with four replications was established. By dividing the growing season into 3 monthly periods (June, July, and August) the monthly heat units and precipitation were included as independent variables. Regression analysis related relative yield to monthly precipitation, monthly heat units and their products of grain N and the square of grain N. There was a significant yield response to N fertilizer 3 of 4 years where corn followed a small grain, but corn yield was not increased by N fertilization following alfalfa. Corn grain N content was significantly increased by N fertilization with the N content always higher where corn followed alfalfa (Glycine max L.). Relative yield of 100% was obtained with grain N content of 1.09 mol kg−1. June precipitation did not significantly effect corn yield, while above average heat units in June showed a positive effect on corn yield. The models showed that above average precipitation in July will increase corn yield and above average heat units would decrease yield. The effect of above average July heat units could be offset with a higher quantity of precipitation. To reach 100% relative yield, 114.3 mm of precipitation would be required in July (36.9 mm above mean) with mean of 450 heat units. On this soil, this 114.3 mm precipitation predicted corn yield of 9.36 Mg ha−1 requiring 136 kg N ha−1 of fertilizer N.