Soybean continues to be important to many Louisiana farmers, with approximately one million acres dedicated to the crop. The LSU AgCenter uses official variety trials (OVTs) and on-farm demonstrations to provide research that can help growers increase crop efficiency and maximize yield.

In 2023-24, official variety trials at seven AgCenter research stations included small plot tests for nearly 100 varieties, while 20 core-block varieties were grown at 27 on-farm demonstrations in 14 parishes.

“There was a three-bushel-per-acre difference from the top-yielding to the middle variety, and a seven-bushel-per-acre difference from the top to the bottom variety,” said LSU AgCenter soybean specialist David Moseley.

The average yield and top yielding varieties could produce an additional profit of $33-$77 per acre compared with the lowest yielding variety, and this could help the soybean industry collect an additional $77 million, according to Moseley.

The on-farm demonstrations were divided into three maturity group sections. Data from these trials was published in the LSU AgCenter 2024 Soybean Variety Yields and Production Practices publication.

AgCenter researchers also did nematode resistance screening trials and conventional soybean variety demonstrations.

Other testing focused on management practices to correct low potassium, phosphorus, sulfur, manganese and zinc levels. Currently, research at two on-farm trials is comparing different fertilizer formulations and treatments — specifically examining fertilizer rates and application timings to establish the most economical fertilizer plan.

“One trial showed a potential economic benefit of applying less potassium oxide per acre than the recommended amount,” said Moseley.

Phosphorous application timing trials on alkaline, low-phosphorous soils showed a significant increase in yields when applying recommended amounts at planting dates and at reproductive stages, as compared to no applications. However, the most significant yield bump came when phosphorous was applied at planting.

Tests done on biological seed treatments, for the most part, had small and inconsistent effects on yield. Bradyrhizobium, a nitrogen-fixing bacteria, outperformed the other treatments, achieving a small but consistent increase in yield.

Planting date trials were another important aspect of soybean research. Findings indicated optimum planting dates were April 8 for the northern region, April 21 for the central region and May 17 for the southern region.

Data also indicated farmers can increase mature seed protein and oil content through variety selection and proper planting dates. Some initial data shows an increase of soybean oil content when planting in May or later, and an increase in protein when planting in March.

The AgCenter has recently published a paper showing data on planting date findings in the three regions to help farmers select the best times for them to plant.

Additional current and upcoming research analyzes:

• Desiccant harvest aids across multiple maturity groups — understanding optimum timing for application, whether soybean plants are developed enough to be desiccated without losing yield because of decreased seed size and potential effectiveness of a new desiccant, Reviton.
• Macro nutrient fertilizer applications — investigating correlations between phosphorous uptake and yield, potential benefits of inputs like humic acid and other biological products and evaluating impacts of foliar nutrients applied at planting and during the growing season.
• Planting date trials — identifying the best maturity groups and seeding rates to maximize yield potential in extremely early and late planting dates, evaluating the effects of fungicide treatments and researching the impact of planting date by populations.
• The economic feasibility of growing two cash groups in one season.
• The potential benefits of deer repellants for soybean fields.