Nitrate leaching from residual fertilizer N after spring thaw in two corn agro-ecosystems

Abstract

Water samples at zero tension were collected using an open-ended lysimeter and analyzed for NO3−-N from a Chicot sandy clay loam and a Ste. Rosalie clay soil under continuous corn (Zea mays L.) in 1993 and 1994, shortly after spring thaw. There was negligible leaching of NO3−-N at previous fertilizer N rates of 0 and 170 kg ha-1 in both soils. However, NO3−-N concentrations of the leachates from soils receiving 285 and 400 kg N ha-1 yr-1 varied from 1.4 to 80 mg L-1, depending on the initial levels of soil residual NO3−-N and the supply of percolation water. When the initial levels of soil NO3−-N were relatively high and percolation of water was relatively slow in 1993, NO3−-N concentrations of the leachates ranged from 20 to 80 mg L-1. Nitrite-N concentrations were from 1.4 to 15.6 mg L-1 when the initial levels of soil residual NO3−-N were relatively low and percolation was relatively fast in 1994. The occasional higher NO3−-N concentrations in the leachate from the previous higher N applications indicated a potential for contaminating surface and ground waters as a result of NO3−-N leaching in the early spring. Key words: Residual N, nitrate-N leaching, soil solution, continuous corn, N fertilization