Drainage system impacts on surface runoff, nitrate loss, and crop yield on a southern alluvial soil
2003
Grigg, B.C. | Southwick, L.M. | Fouss, J.L. | Kornecki, T.S.
Excess rainfall and subsequent surface runoff is a challenge to farmers of the Lower Mississippi River Valley region. In 1993, we established an experimental field site in Baton Rouge, Louisiana, consisting of 16 hydraulically isolated plots (0.2 ha) on a Commerce soil (Aeric Fluvaquents). Our objective was to determine drainage system impacts on surface runoff, subsurface drainage effluent, nitrate loss, and corn (Zea mays L.) yield. We evaluated the following drainage systems (four replications) in 1995 and 1996: surface drainage only (SUR), controlled subsurface drainage at 1.1 m below the soil surface (DCD), and shallow water table control at a 0.8 m depth via controlled-drainage/subirrigation (CDSI). Planting date, fertility management, and minimum tillage were consistent across treatments. When compared to SUR, DCD and CDSI did not reduce surface runoff or nitrate loss in runoff. This is in contrast to previous research showing that subsurface drainage systems decreased runoff on this soil, the difference being that we did not use deep tillage. Our results suggest that subsurface drainage systems should be coupled with deep tillage to reduce nutrient loss in runoff from this alluvial soil. DCD and CDSI controlled the shallow water table, but the increased annual effluent from subsurface drainage increased nitrate loss compared to SUR. DCD and CDSI had no affect on corn yield under these rainfall conditions. With respect to nitrate loss and crop yield in this region, typical SUR drainage may be the best management practice (BMP) in the absence of effective runoff mitigation, such as deep tillage.
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