Nutrient Uptake, Concentration and Protein Content of Bread Wheat as Affected by Nitrogen, Sulfur and Phosphorus Interactions
Assefa Menna *
Ethiopian Institute of Agricultural Research (EIAR), Soil and Water Management Research, Bishoftu Research Center, P.O. Box – 2003, Addis Ababa, Ethiopia.
*Author to whom correspondence should be addressed.
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.
Keywords: Yield, nutrient-concentrations, nutrients-uptake, bread-wheat, nutritional-quality