A number of agriculture news sources released an article last week reporting extraordinary yields in soybean trials at Weslaco, Texas ( EG: http://www.prweb.com/releases/2014/09/prweb12151978.htm). The trials were conducted by Stoller Enterprises, Inc. at the Texas A&M AgriLIFE Research center in Weslaco, Texas and reported yields of 214 bushels per acre in replicated trials. This may offer a little insight into soybean genetic yield potential and what Minnesota farmers should consider when trying to maximize their own yield and profit line as well as limitations that may be present in any farm operation.
The trials at Weslaco were irrigated under a drip line and received supplemental fertilization (610 lb/ac N, 40 lb/ac P, 200 lb/ac K) to alleviate those factors as yield limiting. When looking at fertility needs and soybean yield, Salvagiotti et al reported that rhizobium ability to supply N demand in high yielding environments (yield above 5 Mg ha-1 or 74 bu/ac) was uncertain based on their review of the literature. (F. Salvagiotti, K.G Cassman, J.E. Specht, D.T. Walters, A Weiss, and A Dobermann, 2008. Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review. Field Crops Res 108:1-13). John Schmitt, DuPont Pioneer Research Scientist, reported that soil residual and fixed nitrogen were sufficient up to 60 bu/ac but that nitrogen may be limiting as soybean yields approach 80 bu/ac (https://www.pioneer.com/home/site/us/agronomy/library/nitrogen-fertilizer-for-soybean/).
University of Minnesota Extension publication AG-FO-03813-C “Fertilizing soybean in Minnesota” by Daniel E. Kaiser and John A. Lamb cited early UMN research that showed conclusively that application of additional nitrogen had no effect on Minnesota soybean yield. It is also commonly reported that the Rhizobium become “lazy” under fertilization and cease fixation. The results reported in this Texas trial indicated that this was not the case here and that the nodules appeared healthy and functional. Finally, keep in mind that Salvagiotti et al reported that unless the soybean to N price ratio was large (high soybean price – low N price), supplemental fertilization would not provide a significant return on investment for the years 2002-2006 that the data was examined. The financial return on additional N remains a vital question that UMN research indicated was not sufficient to warrant application and Salvagiotti et al indicated would only be profitable in specific scenarios in their publication.
Possible questions you might ask are: Can we dramatically increase yields like those in Texas here in Minnesota?; and Could we do it profitably? There are a couple of things to keep in mind as you ask those questions. First what is the true yield potential in our growing environment? Here in Minnesota, yield trials at Becker last year had a few lines at just above 90 bushels, but that yield was not achieved across the state in similar trials. Water, rhizobium activity and soil fertility must be adequate and yield limiting pests and/or pathogens reduced or eliminated to realize full yield potential in the range of relative maturity zones from south to north in Minnesota. Certainly the potential observed at that single location/year and relative maturity group grown at Becker encourages us to consider what might be possible given an optimum field environment over the relative maturities grown across the rest of Minnesota. A solid response to the report out of Texas is to begin now to improve your strategy for soybean production from cultivar selection, rotation, tillage and soil health, and pest management for next year. The best management practices (BMP) and integrated pest management (IPM) strategies available from University of Minnesota Extension and Research should also be part of the seed selection and the planning phase examining how each might be more efficiently integrated into your farming practice.
Will you be able to produce 214 bushel beans next year? Maybe not, but our strategy at Minnesota Soybean is to work with our research and extension partners to increase your yield 10% over trend line in the next five years. That is the goal driving the kind of research and technology transfer the Production Action Team looks to support to assist Minnesota soybean farmers in achieving the maximum yields and profit in any given growing season.