Genetic Gain × Management Interactions in Soybean: I. Planting Date

Abstract

Planting date is a commonly manipulated management practice in soybean [Glycine max (L.) Merr.] production; however, the impacts of past and ongoing agronomic improvements, such as earlier planting, on genetic yield improvement and associated changes in seed protein and oil have not been evaluated. The objectives of this study were to determine if a 30‐d difference in planting date affected measured rates of genetic improvement in (i) yield, (ii) seed mass, and (iii) seed protein and oil in the midwestern United States. Research was conducted at Arlington, WI, Urbana, IL, and Lafayette, IN, during 2010 and 2011, using 59 Maturity Group (MG) II cultivars (released 1928–2008) at Wisconsin, and 57 MG III cultivars (released 1923–2007) at Illinois and Indiana, with targeted planting dates of 1 May and 1 June. Earlier planting provided higher yields (+3.1 kg ha−1 yr−1) than late planting in MG III soybean. Seed protein concentration decreased linearly over cultivar year of release at a rate of 0.191 (± 0.069) g kg−1 yr−1 for MG II, and 0.242 (± 0.063) g kg−1 yr−1 for MG III. Seed oil concentration increased over year of release at a rate of 0.142 (± 0.037) g kg−1 yr−1 for MG II, and 0.127 (± 0.039) g kg−1 yr−1 for MG III. The interaction between planting date and cultivar year of release for MG III yield suggested that the trend toward earlier planting is one agronomic improvement that, when coupled with genetic improvement, has provided a synergistic increase in on‐farm soybean yields in the midwestern United States.

Drivers of spatial and temporal variation in soybean yield and irrigation requirements in the western US Corn Belt

“…Sowing date is the management factor with the greatest impact on soybean yields in the US Corn Belt (Bastidas et al, 2008;De Bruin and Pedersen, 2008;Villamil et al, 2012;Rowntree et al, 2013). Linear regression analysis was used in the present study to assess the impact of sowing date on inter-annual yield variation in irrigated and rainfed soybean.…”

Genetic Gain × Management Interactions in Soybean: II. Nitrogen Utilization

“…Rowntree et al (2013) Genetic improvements of soybean have increased yield through changes in seed quality and physiology across release years. Soybean yield and oil increased as protein concentration decreased with the advancement of soybean cultivars over time (Rowntree et al, 2013;Wilcox et al, 1979).…”

“…Rowntree et al (2013) Genetic improvements of soybean have increased yield through changes in seed quality and physiology across release years. Soybean yield and oil increased as protein concentration decreased with the advancement of soybean cultivars over time (Rowntree et al, 2013;Wilcox et al, 1979). Boerma (1979), Morrison et al (2000), and Voldeng et al (1997) reported seed mass was not well correlated with cultivar release year, but Specht and Williams (1984) noted an annual increase in seed mass (0.10 g per 100 seeds).…”

“…), seed mass (100-seed weight), and seed quality were collected as described by Rowntree et al (2013). Grain subsamples (approximately 500 g) were collected from each plot to determine seed protein and oil with a Perten DA 7200 Feed Analyzer (Perten Instruments).…”

“…Statistical analysis was similar to Rowntree et al (2013), which included the mixed-effect regression analysis using PROC MIXED procedure in SAS version 9.2 (SAS Institute,…”