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Adjust Seeding Rates for Delayed Soybean Planting


Whether it’s too cold, too rainy or perhaps a combination of both, Mother Nature can keep you from getting out to your soybean fields as early as you’d like. Or maybe you were able to get your seed in the ground but weather conditions later have you facing a replant situation. Below are some tips to help maximize yield when faced with those situations.

Increase Seeding Rates when Planting is Delayed

Starting off the season behind schedule increases the potential for reduced yields. This occurs because soybeans react to changes in day length by flowering at approximately the same time regardless of when they were planted. As planting is delayed, the period during which vegetative growth occurs is shortened, causing shorter plants with fewer nodes and flowers as a result of reduced pod set. Reduction in pods per plant can quickly lead to less yield potential.

Fortunately, agronomists and farmers have discovered that increasing seeding rates when planting is delayed can sometimes counteract some yield loss by increasing the number of plants and pods set per acre. A 4-year, multi-state study was done by Golden Harvest Research Agronomy to understand how much yield potential could be recovered in late planted soybeans if populations were increased (see chart below). 

Chart source: Golden Harvest

5 seeding rates ranging from 60,000 to 220,000 seeds/acre were tested at planting dates spread from late April through late June. The data confirmed an increased yield response with increased seeding rates when planting dates were delayed from late May to late June. However, no statistical benefit to increasing seeding rates within normal planting dates (early April to mid-May) was observed. These results warrant considering a 10 to 15,000 increase in seed drop in delayed planting/replant situations.

Selecting the Best Relative Maturity (RM) when planting is delayed

Golden Harvest also conducted planting date trials to understand the need to reduce RM of later planted soybeans. Studies were done at both northern (I-90 corridor) and southern (I-80 corridor) locations to better understand how latitude impacts the decision, pictured in the charts below. In northern locations maintaining full season varieties up until end of May provided the best yield potential.  As planting was delayed into June, earlier varieties (0.6 to 0.8 RM earlier than full season) performed the best. However, reducing RM any further could start to minimize yield potential.

Chart source: Golden Harvest

In Southern locations (I-80 corridor), planting the fullest season variety option always maximized yield potential, regardless of the planting date. It will be important to consider which fullest season RM can be planted in your area to still reach maturity prior to your normal first frost date.

Chart source: Golden Harvest

Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

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Syngenta hereby disclaims liability for third-party websites.

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