NASS production records for 1979 and 1980 and 2012 and 2013 give a definitive acreage and yield picture for the nine Mississippi reporting districts in those two periods. These data can be used to determine how both acreage and yield trends have changed for Mississippi soybeans over the years. A summary of that information is shown in the below tables.

Table 1 Summary.

In 1979 and 1980, there was not a large numerical difference in annual average yields among the districts, with a range of 26.8 to 31.9 bu/acre in 1979 and 13.3 to 19.5 bu/acre in 1980.

In 2012 and 2013, there was considerable numerical difference in average yields among the districts; e.g., South Delta vs. all other districts.

In 1979, average yields in all districts ranged from 25 to 31.5 bu/acre. In 1980, average yields in all districts were below 19.5 bu/acre. Total state acreage was about 4 million in both years.

In 2012 and 2013, average yields in the North Central and Northeast Districts were the only ones that did not exceed 40 bu/acre in either year. Total state acreage was about 2 million in both years.

The above data show just how much change has occurred in Mississippi soybean production in the 3+ decades since 1980. Statewide acreage has declined by about one-half, average yields are much higher statewide, and acreage and yield patterns among districts have changed.

Table 2 Summary.

The percentage of the state’s total soybean acreage has increased in the Delta and declined in all other districts. The acreage in south Mississippi has declined precipitously.

Perspective.

I came to Stoneville as a USDA-ARS Research Agronomist in 1975. During my tenure there, several significant occurrences made an indelible imprint on my agronomic psyche. One of the most profound was the contrast in soybean yields between 1979 and 1980. A second was the change in yield patterns that occurred during my 30 years there.

1979 was the most nearly perfect growing season for soybeans ever at Stoneville. Rainfall during the July, August, and Sept. 1-20 periods totaled 6.3, 3.0, and 2.3 in., respectively. Maximum daily air temperatures during these same periods averaged 92, 91, and 83 deg. F, respectively. The Mississippi average soybean yield was 29 bu/acre from 4.1 million acres, a state record that stood until 1992.

1980 was the most devastating growing season weather-wise for soybeans ever at Stoneville. Rainfall during the July, August, and Sept. 1-20 periods totaled 1.8, 1.4, and 0 in., respectively. Maximum daily air temperatures during these same periods averaged 99, 96, and 96 deg. F, respectively. The Mississippi average soybean yield was 16 bu/acre from 3.85 million acres, the lowest state average yield to date.

Both 1979 and 1980 soybean crops were pre-ESPS, and varieties were conventional or pre-GMO that were in MG’s 5, 6, and 7. Tillage was used for preplant weed control and Treflan was often incorporated prior to planting. There were no effective seed treatments. The majority of soybeans were planted in wide rows; i.e., 38-40 in. The 5-yr. average for planted soybean acres before May 10 was only 11%. Post-plant cultivation was the norm for weed control because most of the now-common broadleaf and grass herbicides for use on conventional soybean varieties were not yet available. Irrigation was applied to only a small amount of acreage. There were no effective foliar fungicides that had efficacy against the prominent foliar diseases.

In 2012, rainfall at Stoneville during the July, August, and Sept. 1-20 periods totaled 4.6, 4.3, and 1.4 in., respectively. Maximum daily air temperatures during these same periods averaged 93, 93, and 88 deg. F, respectively. July and August rainfall totals would be considered adequate. The Mississippi average soybean yield was 45 bu/acre from 1.95 million acres, a new state yield record.

In 2013, rainfall at Stoneville during the July, August, and Sept. 1-20 periods totaled 1.4, 1.9, and 2.0 in., respectively. Maximum daily air temperatures during these same periods averaged 89, 93, and 94 deg. F, respectively. July and August rainfall totals would be considered inadequate. The Mississippi average soybean yield was 45 bu/acre from 1.99 million acres.

The 2012 and 2013 Mississippi soybean crop was mostly MG 4 and early MG 5 herbicide-resistant varieties planted in narrow rows in a stale seedbed following herbicide burndown of weeds prior to planting. About 75% of the soybean crop was planted before May 10. Seed treatments that were effective against the prominent seed- and soil-borne pathogens were widely used. There was little or no postemergence cultivation for weed control. Irrigation was widely used in the Delta. Effective foliar fungicides were used to manage prominent foliar diseases.

Since 2008, Mississippi soybean acreage has averaged 1.95 million (range 1.8 to 2.03 million), and annual average yields have ranged from 38 to 45 bu/acre. A subjective conclusion from these data is that 2 million soybean acres seems sustainable in Mississippi, and that state average yields can now be expected to be around 40 bu/acre. This compares to the average 3.5 million acres in the 1979-1984 period that produced an annual average yield of about 23 bu/acre.

I realize that drawing subjective conclusions about Mississippi soybean production based on arbitrary periods can be viewed as less than scientific. However, the chosen periods do represent a time of two very distinct and different management systems, and it is obvious that what is being done now is producing much better and more consistent results that what was being done previously.

So what’s next? Can we sustain the 40+ bu/acre state yield average? Can this “high” yield trend continue in Mississippi?

In my opinion, the answer is yes, but with the following caveats.

●          Seed treatments. There are now seed treatments for control of seed- and soil-borne fungal pathogens, early-season insects, and soybean cyst nematode. Each of these pesticide classes should be considered for use where the target organism(s) is known to persist or be present.

●          Soil fertility. The recent trend toward higher soybean yields will result in an increased demand on the soil nutrient reservoir. Thus, it is imperative that soil sampling is regularly used to determine soil nutrient levels, and that soil fertilizer additions are made to replenish those fertility elements that will be rapidly depleted as a result of these high yields.

●          GMO’s. Transgenic breeding of soybeans for pest control will likely be the area where technological advances will have the greatest impact on yield advances. The production agriculture sector in the US must therefore continue to counter and debunk the misguided and counter-productive opponents of GMO crops.

●          Weed control. Few if any new herbicide chemistries are or will be forthcoming. Therefore, producers must increasingly use resistance management practices in their weed control programs to prevent or delay selection of weeds that have the potential to become resistant to current herbicides.

●          Irrigation. There is no doubt that irrigation of roughly half of the state’s soybean crop has contributed to the yield increase trend. Thus, it has become imperative that the water resource that is used for irrigation be protected from overuse and subsequent decline. Current research and demonstration efforts are showing that this can be done, but it is up to producers who irrigate to quickly adopt water conservation tools that are proven effective.

●          Foliar fungicides. There is no doubt that use of foliar fungicides during the last decade has been a contributing factor to increased yields. However, producers must increasingly use resistance management practices in their fungicide programs to prevent or delay selection of fungal pathogens that are resistant to current fungicides, and to ensure the longest possible utility of current fungicides. The recent selection of the frogeye leaf spot pathogen for types that are resistant to strobilurin fungicides is a wake-up call to support this.

●          Variety development. This is probably the most dynamic contributor to the increased yield trend. It is also the part of the equation that receives the most attention and resources. New varieties that are developed must continue to incorporate those traits that are known to contribute to or protect yield advances, as well as incorporate new traits for pest resistance as they are developed.

●          Host plant resistance. Both public and private soybean breeding programs must increase their efforts to produce soybean lines and varieties that are resistant to major insect, disease, and nematode pathogens using both conventional and transgenic methods. Host plant resistance will reduce reliance on chemical control products as well as prolong the usefulness of present and forthcoming products.

Composed by Larry G. Heatherly, April 2014, larryheatherly@bellsouth.net