Proceedings of the 2019 Mississippi Water Resources Conference

Year: 2019 Authors: Pinnamaneni S.R., Anapalli S.S., Reddy K.N., Fisher D.K., Bellaloui N., Sui R., Boykin D.L.

In the humid climate of the Mississippi (MS) Delta, high intra-seasonal variability in the rainfall received during the critical periods of crop growth often makes irrigation necessary to maximize crop yields. Farmers in this region, generally, meet their crop irrigation water demands by pumping water from the shallow MS valley alluvial aquifer underlying this region. However, water withdrawal beyond the aquifer's natural recharge levels is resulting in significant groundwater-level declines, thereby threatening future water availability. A field study was initiated in the summer of 2018 to compare the water use efficiencies between twin-row and single-row planted soybean (Glycine max L.) cropping system under varying irrigation levels in a Dundee silt loam soil in the humid climate of MS Delta. The soybean was planted on ridges spaced 102 cm apart and furrow irrigated. In the twin-row plantings, soybean was planted in two rows of 25 cm apart on a 102 cm center. The experimental design used in this study was a split-plot with irrigation as main unit and row spacing as subunit, replicated six times. Irrigation levels were full irrigation (FI), half irrigation (HI), and rainfed (RF). Irrigations were scheduled based on soil water measurements. Twin-row planting had a significant impact on grain yield over single rows in all the irrigation treatments (5.03 t ha^-1 vs. 3.01 t ha^-1 RF; 5.70 t ha^-1 vs. 3.84 t ha^-1 HI and 6.14 t ha^-1 vs. 5.06 t ha^-1 FI). Similarly, seed test weight increased considerably due to irrigation: 14.76 g RF vs. 16.29 g HI vs. 17.79 g FI in single rows and 14.76 g RF vs. 16.67 g HI vs. 17.48 g FI in twin rows, respectively. Nutritional quality was assessed using a standardized near-infrared reflectance (NIR) diode array feed analyzer protocol. Significant enhancement in the levels of seed protein, palmitic acid, aspartic acid, glycine, methionine was observed in FI and HI while sucrose levels were elevated in the rainfed soybean. The growers can consider transitioning to twin row system of soybean production with alternate row irrigation during critical periods of crop growth for enhanced water use efficiency and crop profitability.