Flooded fields, replanting considerations for Ark. soybeans
A large soybean project funded jointly by the United Soybean Board and the MidSouth Soybean Board was conducted at eight locations in the US Midsouth in 2012 and 10 locations in 2013, with four planting dates at each location, and 16 soybean cultivars from MG 3 to 6. The MG 4 cultivars had the highest yields, or were not significantly different from the highest yield, in 100% of the environments studied in both early- and late-planting. When considering only locations in east-Arkansas and nearby experimental sites (Rohwer and Keiser, AR, Stoneville, MS; Portageville, MO, and Milan, TN) results indicate that average soybean yields were highest with MG 4 soybean cultivars (70 bu ac-1) with plantings from June 1to June 15. For plantings from June 15 to June 30, average yields were nearly identical (50 to 51 bu ac-1) for MG 4, 5, and 6 cultivars. Finally, with plantings in July, average yields were highest with MG 4 soybeans (50 bu ac-1).
click image to zoom Figure 1 shows the average yield over all 18 environments for MG 3 through 6 cultivars for early and late planting dates. The asterisks above the data points indicate that the early-planting dates were significantly greater than the late planting dates. The solid symbols, within the early or late planting dates, indicate that the average MG yields were not different from the yield of the MG with the greatest yield.
5. Seeding rate - Our recommendations for Full-Season soybean production ranges from 110,000 – 185,000 seed/ac. For late plantings, we recommend increasing your normal seeding rate by 10 – 15%. The reason for this increased seeding rate is to obtain quicker canopy closure and increase the number of nodes per acre since the number of nodes per plant will be reduced due to shortened growing season.
6. Row spacing - At this point in the planting window, our recommendations would be to plant on narrow rows less than 20 inches. Narrow rows will increase the likelihood of canopy closure. Complete canopy closure will decrease weed competition, increase irrigation efficiency, increase light interception, and possibly decrease late-season insect problems.
7. Late season pest concerns - Scout, Scout, Scout and Scout. When considering an extremely late replant of soybeans, growers should budget in at least 1-2 applications of an insecticide and a fungicide. With the tremendous numbers of soybean insects we are currently expecting in the state, these late-planted fields will more than likely need insecticides applications.
8. Average frost date - For the area affected by the flooding, the average frost date is November 1. Planted in mid-July, mid-MG IV and early-MG V’s soybean varieties will require 110 to 115 days to reach R8. These late plantings will be reaching maturity very close to the average frost date.
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