Assessing irrigation water use efficiency and economy of twin‐row soybean in the Mississippi Delta

Abstract

AbstractTwin‐row planting in soybean (Glycine max L.) has been proposed for optimizing resource use and seed yield. Experiments were conducted in 2018 and 2019 on a Dundee silt loam to assess soybean seed yield and irrigation water use efficiency (IWUE) in response to single‐row (SR) and twin‐row (TR) planting geometries under rainfed (RF), all row or full irrigation (FI), and alternate row or half irrigations (HI). Averaged across two crop years and three irrigation regimes, TR enhanced seed yield by 13% over SR (4.5 vs. 4.0 Mg ha−1). The final plant stands established in the FI, HI, and RF under TR were 32, 33, and 31 plants m−2, whereas 30, 31, and 27 plants m−2 were established under SR. Under both SR and TR, irrigations produced a higher number of pods per plant than of RF. Averaged across crop years, yields in the irrigation–planting geometry combinations were 4.8 Mg ha−1 in FI‐TR, 4.7 in Mg ha−1 in HI‐TR, 4.2 Mg ha−1 in FI‐SR, 4.1 Mg ha−1 each in RF‐TR and HI‐SR, and 3.6 Mg ha−1 in RF‐SR. The HI‐TR combination had the highest IWUE of about 0.0063 Mg ha−1 mm−1 of water, followed by HI‐SR with 0.0053 Mg ha−1 mm−1. The seed yield in FI‐TR was not significantly higher than that of HI‐TR. Thus, conversion from FI‐TR to HI‐TR can save half the amount of irrigation without compromising yield or economic returns. Conversion from SR to TR is profitable regardless of the irrigations.