Crop Nutrition

Effects of P and K on Soybean Nodule and Seed Yield

eKonomics News Team

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The main goal of soil testing and having a nutrient management plan is to remove all limiting factors. Even research published back in the 1970s shows that potassium should be prioritized over phosphorus in soybean production when soil test show potassium and phosphorus are both deficient. When both potassium and phosphorus were applied together, pod formation and nodulation were increased – with more response from applications of potassium than phosphorus. So, specifically how was K and P fertilizer application found to affect soybean production?

Researchers at Virginia Tech found that potassium fertilizer applications increased the number of nodules – total and individual weight of nodules – which would increase the nitrogen fixation capability of the plant.1 Potassium applications also increased the number of pods per plant, and therefore yield. As for the nutrient interaction, increasing phosphorus rate did not result in additional yield, however, seed yield was increased as potassium rate increased when phosphorus was also applied. Subscribe here to get the full article.

For additional information, check out eKonomics videos and stories for potassium and phosphorus on soybean.

1 Jones, G. D., J. A. Lutz, Jr., and T. J. Smith. 1977. Effects of phosphorus and potassium on soybean nodules and see yield. Agron J. 69: 1003-1006.