Updated December 3, 2023:
Many agronomic practices and standards need periodic evaluation. Soybean population studies are being evaluated across the United States and observing that lower populations do not necessarily result in lower yield. While Delaware results may be like those of other regions, our climate and soil types will still have an interaction with plant population. This study observed yield results from 5 different planting populations between 60-180,000 seeds per acre. Additional treatments were added to include row spacing (15 and 30”) as well as plots that were irrigated and rainfed at our variable rate irrigation research farm in Harbeson, DE. Plots were planted in May 2022 and harvested with a plot combine in November 2022.
For the 2022 dataset, there was no difference in populations (maturity group 4.3) for full season soybeans ranging from 60-180,000 seeds per acre. Yields ranged from 62-68 bushels per acre based on populations averaged across row spacing and irrigation status. This certainly gives flexibility for Delaware farmers in lowering seeding rates in an era of higher costs. However, this represents one year at one site, and local on-farm seeding rates should be performed by each producer. Row spacing remains best for full season soybeans at 15 inches, with a 10 bushel advantage. This was only based on one variety, however this matches most nationwide research.
Irrigation remains one of the best methods for Delaware farmers to remain competitive for higher soybean yields, providing a 25-bushel advantage averaged across all row spacings and populations. The interesting observation from this study is that there was no interaction with population, so lower populations on rainfed and irrigated fields have similar differences to higher populations under the same scenarios. This type of work should be performed annually to keep up with varying weather conditions.
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Many agronomic practices and standards need periodic evaluation. Soybean population studies are being evaluated across the United States and observing that lower populations do not necessarily result in lower yield. While Delaware results may be like those of other regions, our climate and soil types will still have an interaction with plant population. This study observed yield results from 5 different planting populations between 60-180,000 seeds per acre. Additional treatments were added to include row spacing (15 and 30”) as well as plots that were irrigated and rainfed at our variable rate irrigation research farm in Harbeson, DE. Plots were planted in May 2022 and harvested with a plot combine in November 2022.
For the 2022 dataset, there was no difference in populations (maturity group 4.3) for full season soybeans ranging from 60-180,000 seeds per acre. Yields ranged from 62-68 bushels per acre based on populations averaged across row spacing and irrigation status. This certainly gives flexibility for Delaware farmers in lowering seeding rates in an era of higher costs. However, this represents one year at one site, and local on-farm seeding rates should be performed by each producer. Row spacing remains best for full season soybeans at 15 inches, with a 10 bushel advantage. This was only based on one variety, however this matches most nationwide research.
Irrigation remains one of the best methods for Delaware farmers to remain competitive for higher soybean yields, providing a 25-bushel advantage averaged across all row spacings and populations. The interesting observation from this study is that there was no interaction with population, so lower populations on rainfed and irrigated fields have similar differences to higher populations under the same scenarios. This type of work should be performed annually to keep up with varying weather conditions.