Nitrogen sources and rates affect soybean seed composition in Mississippi

Authors: KAUR, GURPREET - Mississippi State University; SERSON, WILLIAM - Ave Maria University; ORLOWSKI, JOHN - Mississippi State University; MCCOY, JUSTIN - Mississippi State University; GOLDEN, BOBBY - Mississippi State University; Bellaloui, Nacer

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2017
Publication Date: 11/22/2017
Citation: Kaur, G., Serson, W.R., Orlowski, J.M., McCoy, J.M., Golden, B.R., Bellaloui, N. 2017. Nitrogen sources and rates affect soybean seed composition in Mississippi. Agronomy. 7(4):1-10. https://doi.org/10.3390/agronomy7040077.
DOI: https://doi.org/10.3390/agronomy7040077

Interpretive Summary: Soybean seed is a major source of protein, oil, carbohydrates and other nutrients that are important for human and animal nutrition. Producers have considered applying nitrogen (N) fertilizer to the soybean crop to maximize seed yield under nitrogen deficiency; however, its effect on seed composition (protein, oil, fatty acids, and sugars) is not well understood. Therefore, the objective of this research was to evaluate the effects of N fertilizer sources and application rates (45, 90, 135 and 179 kg N/ha) on soybean seed composition on two soil textures (clay and silt-loam) in Mississippi in 2015 and 2016. The three fertilizer sources included in this study were urea with N-(n butyl) thiophosphoric triamide (Urea+NBPT), polymer-coated urea (PCU), and ammonium sulfate (AMS). Results showed that nitrogen application at 179 kg/ha on clay soil reduced seed protein compared to unfertilized soybeans in 2016. However, N application at 179 kg/ha increased oil content on clay soil compared to the unfertilized soybeans only in 2016. Nitrogen application reduced the content of the sugar stachyose on both soil textures in 2015. The fatty acids showed variable response to N applications. This research demonstrated that nitrogen fertilizer can alter seed composition constituents, including oil and sugars. Because growers do not receive an economic incentive for higher seed composition nutritional quality at the moment, they are unlikely to adopt this practice for standard soybean production.

Technical Abstract: Soybean (Glycine max L.) seed is a major source of protein, oil, carbohydrates and other nutrients that are important for human and animal nutrition. Producers have considered applying nitrogen (N) fertilizer to soybean crop to maximize seed yield; however, its effect on seed composition is not well understood. The objective of this two-year (2015 and 2016) study was to evaluate the effects of N fertilizer sources and application rates (45, 90, 135 and 179 kg N ha-1) on soybean seed composition on two soil textures (clay and silt-loam) in Mississippi. The three fertilizer sources included in this study were urea with N-(n butyl) thiophosphoric triamide (Urea+NBPT), polymer-coated urea (PCU), and ammonium sulfate (AMS). Nitrogen application at 179 kg ha-1 on clay soil reduced seed protein by 1.05% compared to unfertilized soybeans in 2016. However, N application at 179 kg ha-1 increased oil content by 0.7% on clay soil compared to the unfertilized soybeans only in 2016. Nitrogen applications reduced stachyose content on both soil textures in 2015. The fatty acids showed variable response to N applications. Since, seed quality is not a trait from which growers receive an economic incentive, they are unlikely to adopt this practice for standard soybean production.