Alternate and Every Row Irrigation Management Effects on Soybean Yield and Economics on Very Fine Sandy Loam Soil

Investigators: Gurbir Singh, Nicolas E. Quintana Ashwell, Gurpreet Kaur, and Himmy Lo

Date: 2022

Project Summary

Introduction

Early Soybean Production System (ESPS) was developed to improve seed yield and water use efficiency (WUE) allowing farmers to plant early maturing varieties (Maturity Group III and IV) to capture spring season rainfall, achieve faster canopy closure, avoid reproductive growth under hot summer temperatures, prevent late-season insect feeding, and harvest early for higher profit (Hoeft et al. 2000; Alsajri et al., 2021, 2019). Traditionally, soybeans were planted in a single-row geometry on raised beds spaced 36 or 38 inches like other cash crops (cotton and corn) in the delta states. However, soybean planting in the last two decades shifted to a narrow or twin-row arrangement to take full advantage of ESPS (Smith et al., 2019b). Soybean planted in twin-row typically consists of two rows 10 inches apart on the same raised bed, with the beds 36 or 38 inches apart (Bruns, 2011). Twin-row planting of soybean results in several benefits including enhanced cold tolerance, high sunlight interception, rapid canopy closure, weed suppression and reduced evaporation under non-irrigated conditions (Smith et al., 2019 a,b; Pinnamaneni et al., 2020). The objective of this study was to evaluate individual and combined effects of irrigation management and planting patterns single row and twin row on soybean yield, quality, water productivity, irrigation water use efficiency, and net returns. The hypothesis is that alternate irrigation and twin-row will increase yield and irrigation water use efficiency (IWUE) resulting in enhanced soybean productivity.

Materials and Methods

The experiment was conducted for three years (2019, 2020, 2021) at the National Center for Alluvial Aquifer Research (NCAAR) near Leland, Mississippi (33 °25'45.5"N; -90 °57'21.1"W). The soil series of the research site was Bosket very fine sandy loam (Fine-loamy, mixed, active, thermic Mollic Hapludalfs) (USDA-NRCS). The experimental layout was a randomized complete block design with four replications consisting of a factorial arrangement of row spacing single row planted at 40-inch spacing (SR) and twin-rows with 10 inches between planted rows on 40-inch beds (TR) and three irrigation treatments [(every row irrigated (ERI), alternate row irrigated (ARI), and non-irrigated (NI)]. The plot dimensions for every treatment were 26.67 x 200 ft. Tillage, fertilization, and weeds were managed according to Mississippi State University Extension Service recommendations. Soil water potential sensors (Watermark Model 200SS, Irrometer Company, Inc., Riverside, CA) were installed at 6-, 12-, and 24-inch depths in one replication of every treatment (Wood et al., 2020). An irrigation threshold of -40 kPa was used to trigger irrigation initiation. Irrigation was applied based on the weighted average of the soil water potential sensors in a 0- to 24-inch rooting depth (the weighted sum was calculated as 0 to 6-inch sensor x 0.25 + -12-inch sensor x 0.25 + -24 inch sensor x 0.5).

Plant population data from 3 feet of the row was determined from four random locations in each plot to calculate plants/ac. After physiological maturity, the two middle rows of the plot were harvested with a Kincaid 8XP plot combine (Haven, KS) equipped with Harvest Master H2 Grain Gauge (Juniper systems, Logan, UT). The seed yield (bu/ac) was adjusted to 13% moisture prior to analysis. Water productivity was calculated by dividing the soybean yield by the total water use (total rainfall + irrigation water applied). The irrigation water use efficiency was calculated by dividing the soybean yield by the amount of irrigation applied in a plot. The collected data was analyzed using the GLIMMIX procedure in SAS 9.4 (SAS Institute, Cary, NC). The partial budget analyses was performed to compare the expected levels and variability of returns under each of the three irrigation treatments across the two planting geometries using the crop planning budgets (Mississippi State University's Department of Agricultural Economics, 2020, 2021, 2022).

Results and Discussion

Soybean seed yield was significantly affected by year, irrigation management, and their interaction (Table 1). Soybean yield was not affected by the planting patterns. The available soil water among irrigation treatments was ranked ERI > ARI > NI considering uniform rainfall and furrow-irrigated water across the field site. Every row irrigation showed no statistically significant (P >0.05) increase in the yield with twice the amount of water applied by ERI compared to ARI in 2019 and 2020 (Table 1). The ERI had 20% increase in yield over ARI in 2021. In all three years, the soybean yields were increased with application of irrigation either as ERI or ARI as compared to NI. The ERI had greater soybean yield than the NI by 26, 30, and 79% in 2019, 2020, and 2021, respectively. The ARI had 20% greater yield than NI in 2019 and 2020, whereas it had 50% greater yield than the NI in 2021 (Table 1). Further, yields with ERI were similar in all three years, while soybean yields significantly differed under the ARI and NI over years.

Significant irrigation-by-year interaction was observed for water productivity and IWUE (Table 1). The

IWUE in 2020 was ~35% lower than 2019 or 2021, when data were averaged over-irrigation methods and row spacings. Averaged over row spacing, IWUE was 66 to 91% greater with ARI compared to ERI (Figure 1). Water productivity was 4.7 kg ha-1 mm-1 in 2019 and 4.24 kg ha-1 mm-1 in 2020 (Figure 1). The water productivity showed no significant differences among irrigation methods in 2019 and 2020. Water supplied with a low rainfall scenario in 2021 was not enough to reach maximum water productivity compared to the previous two years, and therefore, water productivity increased with ARI and ERI than the NI (Figure 1). Irrigation water from ARI showed a 34% increase in water productivity over NI. Additional water supplied by ERI showed no significant increase in water productivity compared to ARI in all three years.

The relationship between expected returns and variability (Table 2 and Figure 2), a measure of risk, is an important consideration for farmers making decisions on these practices and conservation agencies providing incentives and policies related to irrigation water conservation. Considering ERI as the benchmark to evaluate ARI and NI cropping systems, TR soybean produced the greatest average risk-return than other treatments. The ARI with TR had the second highest overall risk-return tradeoff. For SR soybean, ARI resulted in an equivalent risk-return production system as ERI which is evident from the ray origin including both points (Figure 2).

Conclusion

This study revealed a positive soybean yield, quality, and water productivity response to a conservation furrow irrigation practice. However, the amount of water required through furrow irrigation could be modified by rainfall amounts. In terms of risk-return, planting soybean in twin-row and irrigating every row presents the best risk-return proposition. For SR planting, both irrigated systems offered an equivalent risk-return proposition as the reduction in expected returns is associated with a reduction in the variability of those expected returns.

References

Alsajri, F. A., Singh, B., Wijewardana, C., Irby, J.T., Gao, W., Reddy, K.R., 2019. Evaluating soybean cultivars for low-and high-temperature tolerance during the seedling growth stage. Agron., 9(1), 13. https://doi.org/10.3390/agronomy9010013

Alsajri, F. A., Wijewardana, C., Rosselot, R., Singh, B., Krutz, L.J., Gao, W., Reddy, K.R., 2020. Temperature effects on soybean seedling shoot and root growth and developmental dynamics. J. Mississippi Academy Sci., 65(3), 247-258.

Hoeft, R.G., Aldrich, S.R., Nafziger, E.D., Johnson, R.R., 2000. Modern corn and soybean production (1st Ed.). MCSP Publications: Champaign, IL, USA.

Bruns, H.A., 2011a. Comparisons of single?row and twin?row soybean production in the Mid? South. Agron. J., 103(3), 702-708. https://doi. org/10.2134/agronj2010.0475

Smith, R.M., Kaur, G., Orlowski, J.M., Mahaffey, J., Edwards, C.B., Singh, G., Irby, T., Krutz, L.J., Falconer, L., Cook, D.R., Chastain, D., 2019. Evaluation of planter errors associated with twin?row soybean production in Mississippi. Agron. J., 111(4), 1643-1649. https://doi. org/10.2134/agronj2018.08.0488

Smith, R.M., Kaur, G., Orlowski, J.M., Singh, G., Chastain, D., Irby, T., Krutz, L.J., Falconer, L., Cook, D.R., 2019. Narrow?Row Production System for Soybeans in Mississippi Delta. Crop Forage Turfgrass Manage., 5(1), 1-6. https:// doi.org/10.2134/cftm2019.02.0015

Pinnamaneni, S.R., Anapalli, S.S., Reddy, K.N., Fisher, D.K., Quintana?Ashwell, N.E. 2020a. Assessing irrigation water use efficiency and economy of twin?row soybean in the Mississippi Delta. Agron. J., 112(5), 4219-4231. https:// doi.org/10.1002/agj2.20321

Project Photos

• Crop Type:
• Soybean

• Topic:
• Irrigation scheduling
• Irrigation