Items of Interest for Soybean Producers--July 2025
Soybean producers are always looking for information and research results that can lead to increased profit from and/or more efficient production of their harvested product. Information in the following articles can be used by producers to learn of happenings or production practices that can or will affect cost of production and/or seed yield and quality.
An article titled Soybean water-use efficiency increased over 80 years of breeding by Netto et al. provides the following details.
• The research was conducted for 4 years under rainfed conditions using soybean varieties released between 1930 and 2005 to determine if water use efficiency [WUE] has changed with the year of variety release [YOR]. It also looked at the relationship among canopy temperature [CT], WUE, and seed yield.
• Across all environments of the study, results showed a positive correlation between WUE and YOR of varieties.
• The research also showed that midday CT at early seedfill was negatively correlated with YOR and WUE, suggesting that recently released varieties had greater WUE while maintaining cooler canopies. This indicates that more recently released varieties experienced greater transpiration during times of high atmospheric water demand.
• The authors concluded that these findings suggest differences in patterns of water use between old and new varieties.
• The authors also concluded that further studies dealing with water use by soybeans are needed to decipher the relationships indicated by these results. This is needed so that plant breeders can target the specific mechanisms that are involved in enhanced WUE in soybean varieties that are grown in both irrigated and nonirrigated environments.
The results reported in the above article should not be misconstrued by soybean producers who irrigate that increases in WUE in newly-released varieties can supplant the irrigation water conservation measures that are highlighted here and here.
In an article titled US soybean seed protein concentrations–Current status, challenges, and some potential crop management solutions, the following is reported.
• Nitrogen [N] limitation during the seedfill period in high yielding U.S. soybean varieties has resulted in a decrease in seed protein. This means that soybean meal in some U.S. locations fails to meet quality standards established for animal feed.
• Soybean requires a very high amount of N during the seedfill period, and most of this N will have to come from biological N fixation since soil inorganic N will mostly be depleted at this time. Limited N during this time will negatively affect soybean yield and seed protein concentration.
• Soybean breeding over the past decades has resulted in increased soybean yield, but not seed protein content.
• Supplemental N application to soybean during the seedfill period could improve seed protein concentration, but this practice is not economically practical. This means that improving soybean’s biological N fixation ability via breeding and biotechnology should be the long-term goal to remedy this problem.
• Finally, the author states that “late-season N application and improved crop cultivation and soil management practices would be a more effective solution to avoid N limitation and improve seed protein concentration” in U.S. soybeans.
As stated above and in the White Paper on this website, N application to soybeans is not economical. Thus, breeding efforts to improve/enhance soybean’s N-fixing ability during seedfill will likely provide the most economical, long-lasting solution to lowered seed protein content in new varieties.
An article titled Soybean yield and seed quality in equidistant versus non-equidistant plant arrangements under different densities provides the following information.
• A 2-year study [2021 & 2022] was conducted in Kansas, Mississippi, and South Dakota to 1) assess the effects of equidistant vs. non-equidistant plant spacing on soybean seed yield and quality, and 2) determine the effect of modified soybean plant canopy that resulted from different plant arrangements on soybean seed yield and quality.
• Treatments were plants spaced 1) 5 in. apart [250,000 seeds/acre], 2) 6 in. apart [175,000 seeds/acre], and 3) 8 in. apart [98,000 seeds/acre]. A non-equidistant spacing of plants following planting of soybean at 130,000 seeds/acre in 15-in.-wide rows was also included.
• In all of the studies, there was no evidence of an advantage of soybean planted at equidistant spacing.
• Protein and oil content of seed remained constant across all plant arrangements.
• In this study, there was no correlation between canopy coverage development and yield.
• The authors concluded from these limited results that an equidistant arrangement of soybean plants provides no advantage relative to a non-equidistant spacing.
From an economic standpoint, these results offer no justification for investing in a new planter that is designed to plant soybean seed in an equidistant arrangement.
Composed by Larry G. Heatherly, July 2025, larryh91746@gmail.com