Mid‐South Soybean Yield and Net Return as Affected by Plant Population and Row Spacing

Abstract

Traditionally grown soybean [Glycine max (L.) Merr.] Maturity Groups V and VI are subject to late-season drought in the US Mid-South, resulting in yield reductions when planted in mid-May. Earlier maturing soybean, such as the more recently adapted Maturity Group III cultivars, have generated interest among farmers as a way to avoid the e ects of late-season drought. We investigated economically optimal plant population density for soybean considering seeding rate, row spacing, seed and soybean prices, and weather for Maturity Groups V, IV, and III grown on the rainfed soils in the rolling uplands region of the US Mid-South. ree separate experiments were conducted for Maturity Groups V, IV, and III in 2005 through 2007. Soybean was planted in mid-May in narrow (38-cm) and wide (76-cm) rows at seeding rates of 60 to 593 (´ 10 3 ) seeds ha -1 . ree key implications resulted from this study. First, yield did not respond to plant population density, and an extended yield plateau was found in each maturity group experiment, implying an economic incentive to reduce seed costs to achieve the plant population density at the minimum point on the yield plateau. Second, yield and net-return responses to row spacing were inconsistent and primarily in uenced by weather, but if Maturity Group III soybean were planted, narrow row spacing may provide higher expected yields and net returns. ird, planting Maturity Group III soybean may not overcome the susceptibility of Maturity Groups V and IV soybean to the late-season drought conditions in the rolling uplands region of the Mid-South.

Minimum optimal seeding rate for indeterminate soybean cultivars grown in the tropics

“…For a detailed analysis of the response of each cultivar to SR, it was decided to unfold the results for SY, OY, and PY, even though there were no significant interactions among these factors. For these variables, a segmented regression (linear‐plateau) was chosen as a function of the biological behavior of soybean in response to the reduction in SR (Thompson et al., 2015, Corassa et al., 2018). For the other variables, linear or quadratic regression was adopted.…”

“…Optimizing the seeding rate (SR) is one approach to improve profitability of soybean production (De Bruin & Pedersen, 2008; Thompson et al., 2015). Optimization requires that soybean is sown at the appropriate SR, on many farms this results in lowering the seeding rate.…”

Profitability and Risk Analysis of Soybean Planting Date by Maturity Group

“…Soybean was planted in 2010 on 21 April, 7 and 24 May, 2 and 16 June, and 6 and 19 July. Figure 1 shows soybean yields by planting date as Day of the Year (DOY) by MG. Seeding rate was not considered in the analysis because yields were not impacted by seeding rates and soybean did not respond to various seeding rates in Tennessee (Thompson et al, 2015). There were a few observations for each of the MGs with near‐zero yields, which were probably due to late planting and wildlife damage.…”

Analysis of phenotypic plasticity in indeterminate soybean cultivars under different row spacing

“…Similarly, De Bruin and Pedersen (2008) also observed soybean higher capacity to increase grain yield per plant at low densities when water was available during the crop development cycle. Thus, we may assume that under favorable environments, soybeansowing density can be reduced without changing grain yield; however, with a substantial decrease in cost of seeds as discussed by Thompson et al (2015).…”