Effects of irrigation and fertilization coupling on protein and amino acids contents in grains of winter wheat

To evaluate effects of different water, nitrogen and phosphorus fertilizers and their interactions on grain quality of winter wheat in semiarid region, the experiment was carried out in rain-sheltered condition in Luoyang, west part of Henan Province during crop season of 2009~2010. Grain protein content and contents of amino acid components were tested. The results indicated that irrigation, application of nitrogen had significant effects on grain protein and amino acids contents (P≤0.01) of winter wheat. The interaction of irrigation and nitrogen fertilization also presented significant effects (P≤0.05 or ≤0.01). No significant effect of P fertilization on protein and amino acids contents was observed. Protein and amino acids contents in wheat grains increased with increasing nitrogen fertilization rate, but dropped with increasing of irrigation amount. However, as irrigation amount was above 282.0 mm, and nitrogen fertilization rate was above 179.2 kg·hm^-2, the changes became less obvious. Protein content decreased as the nitrogen fertilization rate above 179.2 kg·hm^-2. The trend of ETT/ATT (percent of essential amino acids to total amino acids) was contrary to that of amino acids contents. The contents of protein and amino acids in wheat grains reached the highest in treatment of N₁₀₅P₄₂W₁₂₇ with nitrogen fertilization rate of 105 kg(N)·hm^-2, phosphorus fertilization rate of 42 kg(P₂O₅)·hm^-2 and irrigation amount during growing season of 127 mm. While ETT/ATT reached the highest in treatment of N_30.8P₁₂₆W₂₈₂ with nitrogen fertilization rate of 30.8 kg(N)·hm^-2, phosphorus fertilization rate of 126 kg(P₂O₅)·hm^-2 and irrigation amount during growing season of 282 mm. The grain yield increased with the increasing of irrigation, and water use efficiency was higher with high yield. Overall, N_179.2P₁₂₆W₂₈₂ with nitrogen fertilization rate of 179.2 kg(N)·hm^-2, phosphorus fertilization rate of 126 kg(P₂O₅)·hm^-2 and irrigation amount during growing season of 282 mm was the best treatment.