Best Management Practices to Improve Mid-South Soybean Irrigation Efficiency.

Irrigation capabilities are vital for profitable Mid-South soybean (Glycine max (L.)) production.  Furrow irrigation systems are of predominant use in Midsouthern agriculture.  Inefficiencies inherent to furrow irrigation, including increased runoff volumes and reduced infiltration, result in application efficiencies of approximately 50%.  Therefore, efficiency of this application system must be improved to ensure the sustainability of Mid-South irrigated soybean production.  This study seeks to determine the effects of conservation tillage practices and cover crops on irrigation application efficiency in the Mississippi River Delta under continuous soybean production.  Treatments include conventional tillage without cover crop (CT/NC), reduced tillage without cover crop (RT/NC), reduced tillage with sub-soiling and no cover crop (RT/SS), reduced tillage with cereal rye (Secale cereale L.) cover crop (RT/RC), reduced tillage with tillage radish (Raphanus sativus L.) cover crop (RT/TR), zone tillage without cover crop (ZT/NC), and zone tillage with tillage radish cover crop (ZT/TR).  Reduced tillage/sub-soiling, RT/TR, and ZT/TR treatments were added in the second year of the trial.  Experimental units (8.13-m wide by 153-m long) were separated by 3-m wide levees and planted with soybean at 345,935 seeds ha^-1 and instrumented to mass balance irrigation water runoff volume.  Year one results indicate no difference among tillage and cover crop systems for soybean yield and economic return.  Zone tillage without cover crop and RT/RC increased furrow advance times by at least 65% relative to CT/NC and RT/NC, while irrigation application efficiency decreased in the order of ZT/NC (87%) = RT/RC (82%) > CT/NC (69%) > RT/NC (44%).  Second year results and multi-year trends, including irrigation application efficiency, water use efficiency, infiltration, yield and economic return, will be discussed at length.