Responses of Amino Acid Composition to Nitrogen Application in High‐ and Low‐Protein Wheat Cultivars at Two Planting Environments

Abstract

Amino acid content and composition are important nutritional components of wheat (Triticum aestivum L.) grain. Field experiments were conducted with six high‐protein and four low‐protein cultivars (HPCs and LPCs), grown under four N application rates (0, 120, 225, and 330 kg ha−1) at two sites to understand the variations of amino acid composition in wheat grain and its responses to N fertilizer management. Amino acid composition was significantly influenced by site, cultivar, N rates, and their interactions. Planting site had the greatest effects on lysine, threonine, isoleucine, histidine, and total essential amino acids (EAA), while N fertilizer had the greatest effects on leucine, phenylalanine, total amino acid (TAA) and essential amino acids index (EAAI). In contrast, cultivars displayed relative low but stable effects on amino acid composition. High‐protein cultivars always obtained greater content of EAA compositions, while LPCs had higher N use efficiencies for EAA and lysine contents. Applied N significantly increased grain yield and contents of protein, EAA, TAA, and lysine at both sites, while it significantly decreased EAAI and protein digestibility‐corrected amino acid score (PDCAAS) at Xinyang. The greater yield and lysine, EAA, and TAA content were optimized with the application of N rates of 225 kg ha−1 at Nanyang (wheat–maize [Zea mays L.] rotation system) and 120 to 225 kg ha−1 at Xinyang (wheat–rice [Oryza sativa L.] rotation system). It indicated that under rainfed and temperate environmental conditions, improving lysine, EAA, and TAA in wheat production could be achieved through combinations of cultivar selection and adoption of site‐specific nutrient management practices.