Grain protein and amino acid dynamics in sorghum with in-season split-nitrogen application

Authors: OSTMEYER, TROY - Texas Tech University; SOMAYANDA, IMPA - Texas Tech University; Peiris, Kamaranga; Bean, Scott; RITCHIE, GLEN - Texas Tech University; JAGADISH, KRISHNA - Texas Tech University

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2024
Publication Date: 3/25/2024
Citation: Ostmeyer, T.J., Somayanda, I.S., Peiris, K.H., Bean, S.R., Ritchie, G., Jagadish, K. 2024. Grain protein and amino acid dynamics in sorghum with in-season split-nitrogen application. Cereal Chemistry. https://doi.org/10.1002/cche.10783
DOI: https://doi.org/10.1002/cche.10783

Interpretive Summary: Interest in the development of high protein sorghum varieties has increased recently. Many factors ultimately contribute to the final protein content of sorghum grain. To determine how application of nitrogen fertilization influences sorghum grain protein traits, field experiments were done to assess the influence of in-season-split application of nitrogen (N) on total grain protein, protein composition, protein digestibility and amino acid content in grain sorghum, in three different environments. High nitrogen fertilization resulted in increased protein levels, increased levels of 15 out of 22 amino acids measured and resulted in harder grain. Timing of nitrogen fertilization was also found to be important, with fertilization applied when the sorghum plant starts to produce the head of grain having the most impact. This research demonstrated that nitrogen fertilization can positively impact sorghum protein content and the nutritional quality of sorghum grain.

Technical Abstract: A global increase in demand for gluten-free and antioxidant rich sorghum-based food, improving grain quality parameters especially protein-content and -digestibility of sorghum is critical. Field experiments were conducted to assess the influence of in-season-split application of nitrogen (N) on total grain protein, protein classes, protein digestibility and amino acid dynamics in grain sorghum, in three different environments. The nine N treatments imposed included a zero check, where no N was applied (N0) and eight treatments with varying N application timings and amount. The five N treatments with the greatest amount of total N applied ranging between 92 and 170 kg N ha-1 had significantly greater grain protein content than that of the lower four N treatments. As the total protein increased, the kafirin portion of the protein increased, whereas the albumin-globulin levels decreased. Treatments with high N application recorded 19% increase in vitreousity compared to N0. Nitrogen treatment had a significant effect on 15 of the 22 amino acids. High N applications significantly increased amino acids on a protein basis including alanine, glutamic acid, leucine, proline and phenyl alanine. Treatment N92 with N applied @ 92 kg N ha-1 as split application at three different growth stages including planting, panicle initiation and booting emerged as the optimum N treatment for increasing protein and amino acid concentration in grain sorghum.