Reducing nitrate loss in tile drainage water with cover crops and water-table management systems.
Drury, C.F., Tan, C.S., Welacky, T.W., Reynolds, W.D., Zhang, T.Q., Oloya, T.O., McLaughlin, N.B., and Gaynor, J.D. (2014). "Reducing nitrate loss in tile drainage water with cover crops and water-table management systems.", Journal of Environmental Quality, 43(2), pp. 587-598. doi : 10.2134/jeq2012.0495 Access to full text
Nitrate lost from agricultural soils is an economic cost to producers, an environmental concern when it enters rivers and lakes, and a health risk when it enters wells and aquifers used for drinking water. Planting a winter wheat cover crop (CC) and/or use of controlled tile drainage–subirrigation (CDS) may reduce losses of nitrate (NO3−) relative to no cover crop (NCC) and/or traditional unrestricted tile drainage (UTD). A 6-yr (1999–2005) corn–soybean study was conducted to determine the effectiveness of CC+CDS, CC+UTD, NCC+CDS, and NCC+UTD treatments for reducing NO3− loss. Flow volume and NO3− concentration in surface runoff and tile drainage were measured continuously, and CC reduced the 5-yr flow-weighted mean (FWM) NO3− concentration in tile drainage water by 21 to 38% and cumulative NO3− loss by 14 to 16% relative to NCC. Controlled tile drainage–subirrigation reduced FWM NO3− concentration by 15 to 33% and cumulative NO3− loss by 38 to 39% relative to UTD. When CC and CDS were combined, 5-yr cumulative FWM NO3− concentrations and loss in tile drainage were decreased by 47% (from 9.45 to 4.99 mg N L−1 and from 102 to 53.6 kg N ha−1) relative to NCC+UTD. The reductions in runoff and concomitant increases in tile drainage under CC occurred primarily because of increases in near-surface soil hydraulic conductivity. Cover crops increased corn grain yields by 4 to 7% in 2004 increased 3-yr average soybean yields by 8 to 15%, whereas CDS did not affect corn or soybean yields over the 6 yr. The combined use of a cover crop and water-table management system was highly effective for reducing NO3− loss from cool, humid agricultural soils.
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