In late spring of 2011, flooding of a large acreage in the lower Mississippi River Valley floodplain left soybean producers with a dilemma–how to manage the late planting in Mississippi soybean farming environs that would result from this event.

In my previous blog, I presented a summary of results from a soybean yield trial conducted by Dr. Ernie Flint, Area Agronomist–MSU Extension Service, in cooperation with Mr. Brad Burgess, Operations Manager–MSU Variety Testing, and Mr. Philip Vandevere, County Director–Yazoo County Extension, following the flood on the farm of Mr. Bob Ragland, a soybean grower in the Satartia area of Yazoo County.

This article summarizes their results from an adjacent study that was conducted to evaluate the effect of seed treatments and inoculants applied to soybeans that were planted in the same infrequently-occurring environment.

A mid-MG V variety (REV 55R21) was planted on a Sharkey clay loam soil on June 28 . The study site had been inundated with flood water for approximately 6 weeks to a depth of 6 to 8 feet before planting. Seeding rate was approximately 7 seed per ft. in rows spaced 18 in. apart, or about 200,000 seeds/acre. Soil moisture was near optimum at planting, and seedlings were emerged to a stand at 5 days after planting.

Seed treatments were: No treatment (NONE); FI–fungicide (F) + insecticide (I); RM–Rhizobium (R) and mycorrhizal (M) inoculants; FI + RM; FI + R; FI + M; R only; and M only. All treatments were applied to the seed at labeled rates 5 days prior to planting.

Results from this one-year study follow.

Results from post-flood soybean planting made in Yazoo County, MS in 2011.
Seed treatment	Seed yield–bu/acre	Mature height–in.	1000 plants/acre
NONE	36.5	24	116
FI	50.6	26	151
RM	36.9	23	104
FI + RM	41.9	23	133
FI + R	41.4	22	121
FI + M	32.4	21	110
R only	31.0	22	102
M only	15.4	19	81

Conclusions from this study are based on numerical trends since no statistical comparisons were made. However, these results can be useful for future reference in Mississippi soybean farming systems since duplication of this experiment in time is dependent on the infrequent occurrence of flooding.

• It is apparent from the values in the above table that use of a fungicide + insecticide (FI) seed treatment was valuable for ensuring the highest yield. Plants in this treatment were also the tallest numerically. This is further validation for the current recommendation to growers that seed be treated with these products.


• The fungicide + insecticide (FI) seed treatment generally ensured the greatest plant population.


• The study site had a high population of three-corned alfalfa hoppers soon after emergence. The insecticide seed treatment can likely be credited with suppressing this pest enough to allow for the greater plant populations, especially in the fungicide + insecticide (FI) treatment.


• Soybean seeds planted following a flood where soybeans had been grown in previous years did not need a Rhizobium inoculant to achieve the highest yield. Thus, the existing native populations of Rhizobium in soil at this site were apparently sufficient to effect a level of nodulation that resulted in the highest yield in the fungicide + insecticide (FI) treatment following an inundating flood period.

Again, these are results from only one year; however, this type of research that usually cannot be replicated in time provides invaluable information for Mississippi soybean farming systems should these conditions reoccur in the future.

The MSPB thanks the above-listed persons for going the extra mile in conducting this study, and for quickly getting the results to producers.

Reviewed by Dr. Ernie Flint.
larryheatherly@bellsouth.net