David Moseley, LSU AgCenter Soybean Specialist

Many areas of Louisiana received several consecutive days of rain between August 28 to September 12 (Table 1). The rainy period was capped off with Hurricane Francine on September 11. The continuous precipitation caused weather damage in soybean plants that were mature or near maturity.

Fields planted on or before April 16 at the Dean Lee Research and Extension Center were harvested by August 28 and had good yield and quality. In addition, fields planted on May 6 or later did not show weather damage on September 12. In this case, fields planted from approximately April 16 to May 6 (35% of the statewide crop) have the largest percent chance of weather damage from the extended rainy period (Figures 1 – 7).

The USDA-NASS reported 40% of the Louisiana soybean crop was harvested by September 8, 2024. At this time, the crop condition was rated as 82% good to excellent (Figure 1). However, 28% and 19% of the crop was dropping leaves and mature, respectively, and not yet harvested. These plants would be the most sensitive to continuous rain events.

With this set of data and observations, it is difficult to determine how much weather damage was caused statewide by the rain events. It appears approximately 20-30% of the crop was in a sensitive growth stage from August 28 to September 12. However, at times, the rain fell in isolated areas and would not have caused as much damage in some areas as others.

Table 1. Rain totals in different regions across the state according to the Louisiana Agriclimatic Information System

Figure 1. The USDA-NASS reported 40% of the Louisiana soybean crop was harvested by September 8. However, harvest progress slowed down in places beginning on August 28 due to rain events. 35% of the crop was planted between April 16 and May 6 and may be the most sensitive plants to the continuous rain events between August 28 and September 12.

Figure 2. Soybean seeds from a March 28th planting date. On September 12, the seed from all maturity group 4 plants and most of the maturity group 5 plants were rotten (left). The timely harvest date for these plants was August 26. The seed from a late maturing group 5 plant was still green and had good quality (right).

Figure 3. Soybean plants from a March 28 planting date at the Dean Lee Research and Extension Center. On September 12, the seeds from all maturity group 4 plants and most of the maturity group 5 plants were rotten (left). The pods and seed from a late maturing group 5 plant was still green and had good quality (right).

Figure 4. Soybean plants from an April 19 planting date at the Dean Lee Research and Extension Center. These plants were beginning to mature in mid-August and matured in late August or early September during the days of continuous rain events. On September 12, the seed from all maturity group 4 plants and most of the maturity group 5 plants had some degree of weather damage.

Figure 5. Soybean plants from an April 19 planting date at the Dean Lee Research and Extension Center. On September 12, the pods and seeds from a late maturing group 5 plant were still green with no damage.

Figure 6. Soybean plants from a May 9 planting date at the Dean Lee Research and Extension Center. On September 12, the pods and seeds from two MG 4.2 plants were at different growth stages but had little to no weather damage.

Figure 7. Soybean plants from a May 21 planting date at the Dean Lee Research and Extension Center. On September 12, the pods and seeds from a MG 4.1 (left) and MG 4.3 (right) variety were at different growth stages but had little to no weather damage.