Abstract
Effect of fertilizer management, seeding density and irrigation on yield, protein content and grain yield-grain protein relationship in wheat were studied in six experiments involving i) variety and irrigation, ii) variety and split application of nitrogen, iii) seeding density, nitrogen and sulphur, iv) cowdung, nitrogen and boron, v) cowdung, rate and time of nitrogen application, and vi) seeding density, sulphur and boron. Varietal differences were observed for grain yield, grain protein content and protein yield. Higher grain yield, biological yield, grain protein content, protein content grain⁻¹ and grain protein yield were obtained from Kanchan. The varieties Aghrani and Kanchan produced higher nitrogen harvest index than Akbar. The effect of variety on relationship between grain yield and grain protein content was not significant but that between grain yield and grain protein yield was significant and positive. Three time irrigation resulted in higher grain yield and biological yield, but higher 1000-grain weight and harvest index were observed in zero irrigation. Grain protein content and grain protein yield were increased and nitrogen harvest index decreased by irrigation. Effect of irrigation on relationships of grain yield with grain protein content and grain protein yield were significantly positive. Grain yield and biological yield were not influenced by seeding densities ranging from 120 to 220 kg ha⁻¹. At higher seeding density, higher number of ears m⁻² was compensated adequately by additional grains ear⁻¹ at lower seeding density to produce similar yields. Plant nitrogen content at anthesis was higher at lower seeding density. The effect of seeding density was not significant for grain protein content and grain protein yield. Application of cowdung increased 1000-grain weight and number of ears m⁻² and finally grain yield and biological yield. Grain yields and biological yields from 10 and 15 t cowdung ha⁻¹ were identical, however, addition of cowdung increased grain yield, delayed maturity and prolonged grain filling duration. An increase in the rate of cowdung increased plant nitrogen content at anthesis, grain protein content and grain protein yield, but decreased nitrogen harvest index. Correlation coefficients between grain yield and grain protein content and between grain yield and grain protein yield were significantly positive as influenced by cowdung. Application of nitrogen increased grain yield due to higher number of ears m⁻² and grains ear⁻¹. For highest grain yield, a nitrogen rate of 100 kg ha⁻¹ was optimum in experiments with cowdung but it was 150 kg N ha⁻¹ in experiment without cowdung. Plant nitrogen content at anthesis, grain protein content, grain protein yield, grain sulphur content and grain boron content at maturity increased and nitrogen harvest index decreased due to increasing levels of nitrogen. Grain yield was significantly and positively correlated with grain protein yield and negatively with nitrogen harvest index as influenced by the level of nitrogen. Highest grain yield, biological yield, grain protein content, grain protein yield and nitrogen harvest index were produced by three split applications of nitrogen. Effect of split application of nitrogen on correlation coefficient of grain yield with grain protein content was not significant but that with grain protein yield and nitrogen harvest index was positive and significant. Application of 20 kg S ha⁻¹ produced higher grain yield and biological yield. Plant nitrogen content at anthesis, grain protein content, grain sulphur content and grain protein yield were increased with sulphur application. Grain yield was significantly and positively correlated with grain protein yield due to sulphur application. Application of 2 kg B ha⁻¹ produced higher plant height, grains ear⁻¹, grain yield, biological yield, plant nitrogen content at anthesis, grain protein content, grain boron content and grain protein yield. Effect of boron on correlation coefficient of grain yield vs. grain protein yield was significant. A significant linear relationship was observed between plant nitrogen content at anthesis and grain yield and grain protein content at maturity. On the other hand, the relationship of grain yield with grain protein content and grain protein yield was quadratic.