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In-Season Nitrogen Fertilization of Soybean
Iowa State Research Farm Progress Reports
  • John E. Sawyer, Iowa State University
  • Daniel W. Barker, Iowa State University
Rhodes Research and Demonstration Farm
Publication Date
Nitrogen (N) fertilization is not a traditional nutrient management practice for soybean production in Iowa. Soybean is a legume plant and is assumed to adequately obtain needed N through symbiotic fixation. However, there is interest in using N fertilization to increase yield and grain protein due to the recognition of the large N requirement associated with high yields. Despite the fact that soybean is a legume, it readily utilizes soil inorganic N and will do so preferentially to symbiotic N2 fixation. Depending on the residual inorganic N level and soil N mineralization characteristics, approximately 40 to 75% of the N in a mature soybean plant is derived from the soil. Also, soybean seems to require this soil derived N for high yield. The overall objectives of this research were to determine the impact of soil applied N fertilizer at the beginning pod stage (R3) of soybean growth on grain yield and quality components. Additional objectives were to study response to N fertilizer placement, material (N release characteristic), and rate.
Copyright Owner
Iowa State University
File Format
Citation Information
John E. Sawyer and Daniel W. Barker. "In-Season Nitrogen Fertilization of Soybean" (2001)
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