Winter wheat productivity under favorable and drought environments III. Effect of fertilization

A. Ivanova, N. Tsenov
Abstract. . Drought is a climatic specificity of the geography in Bulgaria. Under the effect of global climatic changes, drought becomes increasingly intense. A field trial investigated the effect of various mineral fertilization norms on the productivity of common wheat genotypes in two contrasting years. The investigated wheat cultivars were grown in two successive years: 2006 was favorable for wheat vegetation, and 2007 was the year with one of the most severe droughts affecting autumn crops ever registered in Bulgaria. The selected cultivars were studied within a scheme involving three levels of mineral fertilization and four previous crops. Fertilization was applied according to the type of predecessor: Т – check variants without fertilization, Т – N P after bean and N P after the 1 2 6 6 10 10 other predecessor, Т – N P after bean and N P after the other predecessor. Grain yield and the productivity components were investigated: 1000 kernel 3 10 10 14 14 weight, test weight, number of productive tillers, height of stem, number and weight of grains per spike. The correlations of grain yield with the related traits were analyzed at various mineral fertilization norms under the contrasting conditions of the above years. It was found out that the productivity of the investigated wheat genotypes decreased with about 13% under drought without applying mineral fertilizers. The use of mineral fertilization according to the type of predecessor under drought increased grain yield and the traits related to it, with the exception of 1000 kernel weight. Thousand kernel weight is an index which decreases with the higher mineral fertilization norms. The highest fertilization norm affected negatively wheat productivity under stress. The correlation of grain yield with height of stem, number and weight of grains per spike was highest under stress without fertilization and decreased with the higher fertilization rates.