Nitrogen Fertilization I. Nitrate Accumulation and Losses Under Continuous Corn Cropping

Abstract

Abstract Selected treatments were chosen from three field experiments with corn ( Zea mays L.) to determine effects of N rates on the vertical distribution of nitrates in the soil. The experiments were located on three different soil types and corn was grown for 5 consecutive years. Irrigation was a variable in two of the experiments. Appreciable amounts of NO 3 ‐N accumulated in the soils when the optimum rate of 140 kg N/ha at Blacksburg and Charlotte Courthouse and 168 kg N/ha at Orange had been exceeded. Amounts of vertical distributions of NO 3 ‐N accumulations were highly dependent on soil type, and on amounts of irrigation and rainfall. Lowest NO 3 ‐N accumulations and highest NO 3 ‐N losses were encountered in the Cecil fsl. An increase in NO 3 ‐N was found in the Davidson clay loam whereas no loss or gain was observed in the Groseclose silt loam. Irrigation markedly reduced the maximum NO 3 ‐N accumulation in the Davidson clay loam especially in the 120 to 195‐cm depth. Irrigation on the Cecil fine sandy loam had less influence on NO 3 ‐N and hardly affected the spread of the accumulation zone. The data indicated that proper irrigation of soils with high internal drainage can markedly reduce NO 3 ‐N loss through leaching; the reduction in NO 3 ‐N loss in the Cecil fine sandy loam was from 48 to 5% at near optimum N rate of application.