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

Authors: PINNAMANENI, SRINIVASA - Oak Ridge Institute For Science And Education (ORISE); Anapalli, Saseendran; Reddy, Krishna; Fisher, Daniel; QUINTANTA ASHWELL, NICOLAS - Mississippi State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2020
Publication Date: 8/18/2020
Citation: Pinnamaneni, S.R., Anapalli, S.S., Reddy, K.N., Fisher, D.K., Quintanta Ashwell, N.E. 2020. Assessing irrigation water use efficiency and economy of twin-row soybean in the Mississippi Delta. Agronomy Journal. 112(5):4219-4231. https://doi.org/10.1002/agj2.20321.
DOI: https://doi.org/10.1002/agj2.20321

Interpretive Summary: Water level in the Mississippi (MS) River Valley Alluvial aquifer has started reducing appreciably in recent years due to irrigation water withdrawals disproportionate to their recharge levels, challenging the sustainability of irrigated agriculture in the Mississippi Delta region. In order to reduce further loss of this aquifer water resource, crop-irrigation practices need to be efficient while enhancing farm output and economic returns. To address this, scientists with the USDA ARS Sustainable Water Management Research Unit and Crop Production Systems Research Unit, Stoneville, MS, conducted an experiment by varying planting patterns and adapting three irrigation rates in the Lower MS Delta, USA, during 2018-19. The results of the study indicated a 13 % yield advantage in soybean production by adopting a twin-row production system with skip-row irrigations. The skip-row irrigations reduced water use for irrigation by about half without any yield reduction in soybean yield and economic returns compared to all-row irrigation. This study is anticipated to help soybean producers to use water more efficiently for conserving the limited ground water resources in the aquifer for sustainable irrigated agricultural production in the region.

Technical Abstract: win-row planting geometry in soybean [Glycine max (L.) Merr.] has been proposed as an alternative spatial arrangement that would optimize resource use and grain yield by decreasing inter-plant competition and improving radiation interception. A field study was conducted in 2018 and 2019 at Stoneville, Mississippi (MS), on a Dundee silt loam to assess grain yield components and irrigation water use efficiency (IWUE), and soybean phenology in response to single-row (SR) and twin-row (TR) planting geometries under three irrigation regimes: (i) rainfed (RF), (ii) all row or full irrigation (FI), and (iii) alternate row or half irrigation (HI). There were no differences observed among the irrigation regimes and planting geometries for different phenological stages. Averaged across the two crop years and the three irrigation regimes TR enhanced grain yield by 13% over SR. (4.5 Mg ha-1 vs. 4.0 Mg ha-1). The final plant stand established in the FI, HI, and RF treatments under TR were 32, 33, and 31 plants m-2 respectively, while 30, 31, and 27 plants m-2 were recorded under SR. Under both SR and TR, irrigations (both FI and HI) produced a higher number of pods per plant than RF. Averaged across crop years, soybean yields in the irrigation and 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 grain yield in FI-TR was not significantly greater than that of HI-TR. Hence, conversion from FI-TR to HI-TR can save half the amount of water used in irrigations, without compromising yield or economic returns. Conversion from SR to TR is profitable regardless of irrigation scheme.