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Title: DRAINAGE SYSTEM IMPACTS ON SURFACE RUNOFF, NITRATE LOSS, AND CROP YIELD ON A SOUTHERN ALLUVIAL SOIL

Author
item Grigg, Brandon
item Southwick Jr, Lloyd
item Fouss, James
item Kornecki, Ted

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2003
Publication Date: 10/3/2003
Citation: Grigg, B.C., Southwick Jr, L.M., Fouss, J.L., Kornecki, T.S. 2003. Drainage system impacts on surface runoff, nitrate loss, and crop yield on a southern alluvial soil. Transactions of the ASAE. American Soc. Agr. Engrs. Nov-Dec. Vol. 46(6) 1531-1537.

Interpretive Summary: Runoff from heavy rains typical of the Lower Mississippi River Valley (LMRV) can carry large quantities of fertilizer nutrients and soil particles to rivers, lakes, and wetlands. We conducted an experiment in 1995 and 1996 at the USDA, ARS, Water Quality Field Site in Baton Rouge, LA. The objective was to determine if subsurface drainage systems could increase infiltration of rainfall, thereby reducing nutrient and sediment losses from agricultural fields. The site consisted of 16 hydraulically isolated plots, 0.2 ha in size, 12 of which were planted to corn and used for this experiment. The soil was a poorly drained Commerce silt loam. We evaluated four replications of the following treatments: Surface drainage only (SUR), controlled drainage at a depth of 100 cm (CD), and controlled drainage with subirrigation at a depth of 75 cm (CDSI). Minimum tillage and fertility management were the same for all treatments. Neither CD nor CDSI reduced runoff or nitrate loss. Moreover, because of the additional subsurface drainage effluent, more nitrate was transported to surface waters by CD and CDSI when compared to the SUR treatment. There was also no treatment impact on corn yield. These data contradict earlier findings on the same soil, primarily a result of our minimum tillage practices when compared to regular deep tillage used for the previous experiment. Deep tillage breaks up the surface layer of this alluvial soil, allowing for increased infiltration of rainfall. In the absence of deep tillage, SUR is likely the Best Management Practice for this region. However, CD and CDSI could improve the quality of agricultural drainage waters in the LMRV region, if part of an integrated management system that includes periodic deep tillage.

Technical Abstract: Management of excess rainfall and surface runoff is a challenge to farmers of the Lower Mississippi River Valley region. In 1993, we established a water quality field site in Baton Rouge, LA consisting of 16 hydraulically isolated plots (0.2 ha) on a Commerce silt loam soil (Aeric Fluvaquents). Our objective for this site was to determine drainage system impacts on surface runoff, sub-drainage effluent, nitrate loss, and corn (Zea mays L.) yield. We evaluated the following drainage systems (four replications) on 12 of the available plots in 1995 and 1996: Surface drainage only (SUR), controlled sub-drainage at 100 cm below the soil surface (CD), and shallow water table control at a 75-cm depth via controlled drainage/subirrigation (CDSI). Minimum tillage and fertility management were the same for all treatments. When compared to SUR, CD and CDSI did not reduce surface runoff or nitrate loss in runoff. This was in contrast to similar research on the same soil; the primary difference being our disuse of deep tillage. CD and CDSI increased total nitrate loss compared to SUR, solely because of additional sub-drainage effluent. Drainage management also did not significantly affect corn yield. It appeared that sub-drainage systems must be coupled with deep tillage to effectively reduce runoff and loss of nutrients from this alluvial soil. With respect to nitrate loss and crop yield, the widely used SUR drainage system appears the Best Management Practice in the absence of effective strategies for reducing runoff.