Effect of nitrogen fertilizer strategies on rice bran yield and protein composition in YRL39 rice

Abstract

Rice bran, a byproduct of the milling process, is a valuable source of protein with potential applications in food and feed industries. While nitrogen (N) fertilization is known to influence grain protein content, its effect on rice bran protein composition remains poorly characterized. This study aimed to evaluate the effects of thirteen nitrogen fertilizer treatments, including conventional, stabilized, and controlled-release formulations, on bran yield, protein concentration, and amino acid composition in Oryza sativa cv. YRL39. Field trials were conducted during the 2018–2019 dry season at the Walkamin Research Facility, North Queensland, Australia, using a randomized complete block design with three replicates per treatment. Nitrogen treatments significantly affected rice bran yield (F (12,38) = 13.459, p < 0.001) and soluble protein extractability (F (12,38) = 37.534, p < 0.001), but not total protein concentration in the bran (p > 0.05). Nitrogen treatments significantly influenced bran yield (F(12,38) = 13.459, p < 0.001) and soluble protein extractability (F(12,38) = 37.534, p < 0.001), but not total protein concentration (p > 0.05). The highest yields were recorded for Entec 100 % (a stabilized nitrogen fertilizer containing the nitrification inhibitor 3 (14.6 % ± 0.60) and N80 CRU + foliar (13.9 % ± 0.35), compared to the control (10.9 % ± 0.45). Soluble protein was markedly greater in the 90-day controlled-release urea with foliar application (42.08 % ± 1.6) and grower-standard urea (40.34 % ± 1.4), relative to the control (25.45 % ± 1.2). Amino acid profiling revealed enrichment of essential and hydrophilic amino acids in bran protein from 90-day CRU + foliar treatments. These results demonstrate that optimized N fertilization, particularly controlled-release formulations with foliar supplementation, can enhance rice bran protein functionality without altering total protein content.