A Tale of Two States' Soybean Production

In a report by Rachel Vann et al. titled “Production practices that maximize soybean yield: What we have learned from the North Carolina soybean yield contest” that appears in Agronomy Journal (2021, Vol 113, Issue 3; https://doi:10.1002/agj2.20728), 18 years (2002-2019) of entries (877 total) into the North Carolina Soybean Yield Contest (NCSYC) were analyzed to identify the production practices that were associated with high-yielding soybean in the state. The following is a short summary of the results of that analysis.

•    Eleven management practices were evaluated for their influence on soybean yield achieved by NCSYC entrants over the 18-year period.

•    Average contest yields over the 18 years averaged 65.2 bu/acre, which was 102% higher than the state average yields over this period. This was also higher than the average U.S. soybean yields during the same period.

•    The three most important contributors to the high yields of winners of the NYSYC were maturity group (MG), planting date, and foliar fungicide application.

•    MG was the most significant predictor of yield. In 2002, more than 75% of the entries were a MG V or later variety, whereas in 2019, fewer than 25% were MG V or later. In 2006, 56% of the entries were MG VI or later varieties, whereas in 2019, there were 0% entries of MG VI or later.

•    Use of early-maturing varieties increased over time–in 2002, 0% of the entries were MG III or earlier varieties, whereas in 2019, 24% of the entries were MG III or earlier varieties. Across the years of the contest, highest yields were associated with MG III varieties (67.5 bu/acre) followed by MG IV varieties (64.0 bu/acre). Using a MG IV or earlier variety provided a 17.8 bu/acre yield advantage across all entries.

•    In 2002, fewer than 10% of the entrants planted before May, while in 2019, over 50% of the entrants planted before May. Planting dates earlier than May 12 generally provided more yield benefit when earlier maturing varieties were used.

•    In 2002, no entrants used a foliar fungicide, whereas in the 2015 to 2019 period, more than 60% of the entrants used at least one foliar fungicide application. When a MG IV or earlier variety was used, foliar fungicide use provided a 11.2 bu/acre yield protection. Foliar fungicide use was especially important when MG IV or earlier varieties were planted early.

•    The farmer-supplied data used in this analysis allowed for the identification of management practices that are consistent contributors to yield. The planting date and MG practices that consistently impacted yield in this analysis can be modified without additional cost to the producer.

•    According to NASS, harvested wheat acres in North Carolina over the 2016-2020 period averaged 21% of the harvested soybean acres in the state (<2% in Mississippi). It is assumed that essentially all of these wheat acres were doublecropped with soybeans. Thus, results from this analysis of the NCSYC entries justifies an economic assessment of the wheat-soybean doublecropping system to determine its overall profitability vs. that of a non-doublecropped soybean system where the above high-yield factors can be fully utilized to raise soybean yields to the level achieved by the NCSYC entrants.

According to NASS, planting progress by the end of April and state average soybean yields for Mississippi and North Carolina for the 2011-2020 period, plus the average soybean yield for the U.S. for the years in that period, show that early planting in Mississippi is associated with high yields that are greater than the U.S. average. This is depicted in the below table, which shows a high percentage of early planting in Mississippi over the last 10 years and state yields that exceed the national average in most of those years.. These data, coupled with results from a 2019 survey of production practices deemed important by Mississippi soybean farmers and the results from the above NCSYC analysis, support the following conclusions.

Soybean producers in the southeastern U.S. should be: 1) planting soybeans before May; 2) using early-maturing varieties–i.e., MG 4 and earlier; and 3) applying a foliar fungicide to protect the potential high yields from these plantings.

Composed by Larry G. Heatherly, June 2021, larryh91746@gmail.com