Updated December 17, 2020:

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Funding supported multiple projects including an on-farm state soybean yield contest, multi-year soybean maturity group x planting date study, and evaluation of broiler litter for fit into soybean production. The Top Bean Tennessee Soybean Yield Contest seeks to recognize those producers in five contest districts who grow high-yielding soybeans, and to gather data on the production practices utilized by these outstanding producers in order to promote the use of sound cultural practices to increase soybean profitability. Sixty-two producers entered the 2020 contest, and 22 completed contests were received.

Cultural practices such as planting date can influence soybean yield and profitability. In 2020, our focus was on completing a multi-year planting date and maturity group study to identify a) best maturity group fit for early, optimal or late planting, b) best time to plant by maturity group, and c) impact of planting date on soybean development and seed quality in a dryland environment. Data generated in 2020 completes a multi-year project and data, and will be summarized and used to refine current Extension publications and be shared during winter producer meetings and statewide grain conferences.

Studies were conducted to determine impact of broiler litter to yield of soybeans 1) from prior applications to corn, 2) applied directly to soybeans, and 3) the liming effect of poultry litter in soybean production. Single applications of litter to prior year corn can be expected to increase plant available soil phosphorus and potassium concentrations for a rotational soybean crop (Figure 1). Other plant available macronutrients (sulfur) and micronutrients (zinc and boron), are likely present in litter and may benefit the soil nutrient profile. There is some indication that prior year litter applications improve soybean yield. Depending on the cost of litter, these soil and production benefits could be obtained at reduced cost and perhaps in fewer trips over a field versus commercial fertilizers. Litter application to corn could increase soil organic matter, releasing nitrogen and other nutrients to soybean crop.

In the direct litter study, applying 2 to 3 Tons/Ac broiler litter to soybeans increased soybean height both early and late season, improved early leaf concentration of the micronutrient Boron, pod retention and yield, but did not affect seed nutrient concentration or the tissue levels of other macro and micronutrients in our study. The development of N fixing nodules on roots was delayed particularly in treatments that included ammonium nitrate or litter, but supplemental nitrogen from these sources offset any reduced N fixation in nodulation early season because yield was not reduced. Broiler litter at 2 T/Ac appeared to be as effective as the 3 T/Ac rate with respect to improved yields. Nitrogen uptake appeared to have some bearing on yield as the N, P, K, S control out yielded the P, K, S control. The additional increase in yield with litter is thought to be related to boron uptake and enhanced pod retention at higher (2 to 3 Tons/Ac) rates of broiler litter.

In the liming study, the addition of broiler litter treatment did not influence soil pH. Seasonal fluctuation may partly explain the lack of significant difference among the treatments. Grain yield from un-limed plots were comparable to all of the limed plots except one, indicating that soil pH may not have been a yield-limiting factor.