Growing 100 Bushel Soybeans In South Dakota!

Currently in year four of a five year project, the overall goal of this project is to increase production and profitability of South Dakota’s soybean producers. Using a combination of on-farm research and targeted University studies, the project provides information to maximize advances in crop genetics under a variety of environmental conditions and management. Components include the feasibility of double-cropping soybeans into small grain stubble and use of cover crops in soybean-corn rotations. Also being researched is the effect of weed stress at different stages in the growing season, along with the effect of water stress on overall yield. To address producers’ yearly budgeting needs, crop planning budgets comparing alternative and no-till rotation systems as compared to traditional corn/soybean rotations are being developed. Results of some components can be applied immediately, such as the planting date and seeding rate research highlighted below. Others focus on a longer term impact, such as responses to stress based on genetics, which may be incorporated into future variety development.

Capturing sunlight is one of the keys to high yielding soybeans. Soybeans convert sunlight to chemical energy. Higher energy conversion means higher yields. Research from this project has shown that to maximize light energy capture, it is critical that soybeans be seeded as early as possible, yet late enough to avoid frost. The most sunlight in SD occurs in June or July. Therefore, earlier seeding means a bigger plant, more leaf area, and greater conversion of light energy to soybeans during these months. Review of recent SD Soybean Yield Contest winners shows that a common factor was planting prior to May 15. Research data suggests that high yielding soybeans will lose .25 to 1 bu/acre/day when planted after the optimum planting date. Optimum planting date will vary based on location and variety selection. Short season varieties will respond differently to later planting dates than full season varieties.  As a general rule for South Dakota, 1.5 to 2 maturity beans out-yield beans with maturity categories less than one or greater than 2.5, but exceptions can be found. For example, during years with extremely dry July, August and Septembers, early beans (less than 1), win. In years with below normal moisture in June and July, but above normal August and September moisture, long season (greater than 2.5) varieties win. As on goes from north to south, optimum maturity group numbers increase.

Row spacing and seeding rates can impact yield. University research on small plots suggests that reducing row spacing increases yields by as much as 20 bushels/acre. However, as part of this project, on-farm research was conducted with soybean producers, with results indicating the differences in yield may not be as large as anticipated. Some on farm research in 2011 showed only a 2 bushel/acre difference between narrow 10 inch rows and 30 inch rows. Additional on-farm research was conducted in 2012. Final analysis is still in process, but data indicated that seed treatment (fungicide and insecticide) response correlates with planting date. That is, the earlier the planting date (late April to early May), the more likely that a seed treatment will provide a positive yield response. Late planting (late May) seems to not show a significant response to seed treatments.