Nitrogen Leaching and Retention Under Alfalfa and Bare Fallow at the LTER Root Turnover Site

Kavdir,Y., D.P. Rasse, A.J.M. Smucker

Presented at the All Scientist Meeting (1998-07-21 to 1998-07-22 )

Contributions of a legume crop to the soil nitrogen dynamics were evaluated at the LTER root turnover site which compared soluble soil nitrogen pools among treatments of bare soil in the presence and absence of alfalfa roots and shoots in a Kalamazoo loam soil (mixed, mesic Typic Hapludalf). Spring spray-killing of the alfalfa generated 310 kg N ha-1 in the 0-120 cm soil profile during the 8-month period from April 29 to December 17, 1997, Table 1. After three years without plant growth, mineralization of SOM in the bare soils produced 170 kg N ha-1 during the same 8-month period of time. Therefore, decomposition of a two-year alfalfa crop produced 140 kg N ha-1 during the subsequent 1997 growing season. The best cover crop management system for transferring this excessive soil nitrogen to subsequent cash crops is currently being studied in a rye-cover crop and Roundup-Ready corn management system.Table 1. Total mineral N content over the upper 120 cm of Kalamazoo loam soils at the LTER root turnover study.— kg NO3-N + NH4-N ha-1 —* Excludes C horizons, which were not available.Return to Contents

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