Evaluation of Potential Inputs to Improve Late-planted Soybean Yield

Trial Objective

• Limited research is performed on late-planted soybean and farmers are actively seeking information on what input(s) will provide the most value to his/her operation when soybean is planted late.
• The objective of this trial was to evaluate the impact that potential inputs have on the yield potential of late-planted soybean.

Research Site Details

• This study was comprised of ten treatments in a randomized complete block design with three replications. Four treatments added one component to the base management (BM) treatment as indicated with a ‘+’ and four treatments removed one component from the high management (HM) treatment as indicated with a ‘-‘ (Table 1).
• A 2.7 MG soybean product was planted in all treatments.
• Row spacing was 30 inches.
• Weeds were uniformly managed.
• Hero® insecticide at 5 fl oz/acre was applied across all treatments at R6 to control salt marsh caterpillars, except the HM-InFu treatment.
• Soil test values: phosphorous – 14 ppm, potassium – 576 ppm, organic matter – 3.6%, pH – 7.0.

Understanding the Results

    Base Management

• Good yields were obtained with the BM treatment considering that the soybean was planted six weeks past the optimum planting date of the first week in May.
• Increasing the seeding rate, adding sulfur and zinc, or applying a fungicide and insecticide all had similar yield increases over the BM treatment.

— Diseases, such as septoria brown spot or anthracnose, could be controlled with a fungicide.

— Insects, such as wooly bear caterpillars, grasshoppers, or bean leaf beetles, could be controlled with an insecticide.

• Potassium thiosulfate reduced yield and the most visual symptom was severe burning of the leaves. Potassium provided a positive yield response in 2017, but in that year, potassium was applied as potassium chloride to the base of the plants rather than using a foliar application, as was done in this trial.
• It is important to note that potassium thiosulfate can be safely applied but too high a rate was used with too little water and the fertilizer damaged the soybean plants.

High Management

• The HM treatment yielded more than the BM treatment.
• The highest yield in the study was obtained when removing the potassium thiosulfate treatment from the HM system, because the crop was not damaged by the foliar fertilizer application.
• Reducing the seeding rate from 180,000 to 120,000 seeds/acre, or removing the insecticide and fungicide application equally reduced yields compared to the HM treatment.

What Does This Mean for Your Farm?

• In late-planted soybean, the addition of a fungicide and insecticide or planting a higher seeding rate of 180,000 seeds/acre consistently provided higher yields and greater returns to the soybean production system.