Nitrogen Mass Balance of a Tile-drained Agricultural Watershed in East-Central Illinois

摘要: Simple nitrogen (N) input/output balance calculations in agricultural systems are used to evaluate performance of nutrient management; however, they generally rely on extensive assumptions that do not consider leaching, denitrification, or annual depletion soil N. We constructed a relatively complete N mass for the Big Ditch watershed, an extensively tile-drained watershed east-central Illinois. conducted direct measurements wide range pools and fluxes 2-yr period, including mineralization, soybean N(2) fixation, tile river loads, ground water in-stream denitrification. Fertilizer inputs were from survey yield data county estimates combined with estimated protein contents obtain grain By using maize fertilizer recovery fixation estimate total derived soil, we calculated explicit change storage each year. Overall, dominated inputs, export outputs. Precipitation during 2001 was below average (78 cm), whereas precipitation 2002 exceeded 30-yr 97 cm; monthly rainfall above April, May, June 2002, which flooded fields produced large riverine loads. In 2001, greater than outputs, suggesting carryover subsequent year may occur. less outputs due leaching losses likely substantial field The (67 kg ha(-1)) offsets this shortfall. Although climatically unusual, current production trends yields N, is occur maize/soybean rotations, especially years above-average extremely wet spring periods.