Mineral Nitrogen Movement into Subsoils Following Continued Annual Fertilization for Corn
1974
MacGregor, J. M. | Blake, G. R. | Evans, S. D.
Two clay loam soils were fertilized for corn (Zea mays L.) at planting for 10 or 15 growing seasons at annual rates of 0, 44.8, or 268.8 kg N/ha as NH₄NO₃. After 10 growing seasons, little NO₃-N remained below drainage tile depth in Le Sueur clay loam. After 11 growing seasons on untiled Forman clay loam, considerable NO₃-N was found at depths to 6 or 7 meters. After 15 years, appreciable nitrate occurred to at least the 10-m depth. The average rates of movement of the NO₃ front for the 10 and the 15-year periods were 1.7 and 1.9 mm/day, respectively. Concentrations of ammonium N were similar under all fertilizer treatments. Annual N additions failed to significantly increase corn grain yields on Le Sueur clay loam but significantly increased yields on Forman clay loam.
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