Nutrient Uptake, Concentration and Protein Content of Bread Wheat as Affected by Nitrogen, Sulfur and Phosphorus Interactions

Abstract

Field experiments were conducted in six sites to investigate the concentrations of nitrogen (N), sulfur (S), and phosphorus (P); their uptake; and the grain protein-contents including the grain yield (GY) of bread-wheat in central Ethiopia. The experiments were laid-out in RCBD in triplicate. The mean values of these elements in wheat grain responded significantly to their respective nutrient applications. In total, there were (n=144) entries across locations. Nutrient-concentrations varied spatially ranging between 1.10–2.35% (N); 0.06–0.21% (S); and 0.01–0.16% (P). Similarly, their respective nutrient-uptakes ranged between 7.42–137.55 kg/ha; 0.38–11.87 kg/ha; and 0.08–9.88 kg/ha. But, the protein-concentrations in wheat-flour varied between 6.44–13.71%. At the specific sites, the mean N-concentration in wheat-grain and its uptake were responded significantly to the N supply (***P≤ .001). Meanwhile, the S concentration and uptake were responded to both N and S supplies (**P≤ .01). But the P concentration and its uptake were responded mainly to the interaction-effects N×S×P; N×P; and to a lesser extent to the sole-P application (*P≥ .05). Similarly, the grain protein-concentration was influenced by the interaction-effects N×S×P, N×S, N×P; and by the sole-N and sole-S applications, in a decreasing order of significance. In this analysis, it is noted that the N-concentration and its uptake in the grain were considerably higher than those of S and P. It was furthermore noted that the wheat grain-protein content was strongly correlated with the native-soil N (r= +0.99); S (r= +0.81); and P (r= +0.37), suggesting their degree of significance in protein-synthesis. Under external-supply conditions, the treatment-effects also followed clear gradations in the plant-components formation with the CK≤ S≤ P≤ SP< N< NS< NP≤ NPS. However, the observed changes in the overall plant-variables are likely to be influenced not only by the soil-conditions, but also by plant-factors, environmental-factors and the farming-practices among others, necessitating their further investigations even at the partial-factor level. Especially, the effects of N, S, and P; and even other-nutrients on the true-protein composition and other quality attributes merit further study.