Nutrient contents and yield of lupin as influenced by splitting NPK.fertilizers in a clay soil.

Two field experiments were conducted in Assiut Univ. Exp. Farm during 1997/98 and 1998<S/1999 seasons to study the influence of splitting N, P and K fertilizers on concentration and uptake of N, P, K, Ca and Mg, as well as yield and yield components of lupine (Lupinus termis, L.) grown on a clay soil. The results could be summarized as follows: - The tallest plants were obtained by applying three splitted doses of N, P and K fertilizers. However, the highest values of total number of branches and pods per plant, 100-seed weight, seed yield/fed., and protein percentage in seeds were resulted from two splitted doses of N, P and K fertilizers. The highest straw yield/fed, was obtained at one time full dose. The split application had significant effect on N, P, K, Ca and Mg concentration over all growth stages. Partitioning the full dose of the fertilizer in 2 equal increments gave the highest concentration of N, P, K and Ca in lupine seeds. Splitting the full dose of NPK fertilizers into two equal doses increased the amount of N, P, K, Ca and Mg accumulated in lupine seeds by 27.64, 37.31, 34.33 30.37 and 23.45 respectively. - The tallest plants and the highest protein content were obtained by applying N fertilizer alone or in combination with P and K fertilizers. The highest values of total number of branches and pods per plant, 100-seed weight and seed yield/fed, were resulted from using NPK fertilizers. However, applying N or P fertilizer alone produced the heaviest straw yield/fed. The highest concentration and uptake of N by shoots and seeds of lupine were obtained when the NPK fertilizers were used in combinations. Applying PK fertilizers produced the highest concentrations of P and K in shoots and seeds as well as the highest accumulated amount of K in both straw and seeds of lupine. Adding the N fertilizer alone gave the lowest levels of N, P and K in both shoots and seeds. The highest concentration and uptake of Ca and Mg in shoots and seeds of lupine were recorded when P fertilizer was used alone. On other hand, the lowest concentration and uptake of these nutrients were resulted from the application of K fertilizer. - The highest values of seed yield and yield components were resulted from applying two splitted doses of a mixture of NPK fertilizers. The application of one time full dose of N fertilizer produced the highest straw yield and protein content in seeds- Using of NPK fertilizers in two and three splitted doses resulted in the highest uptake and concentration of N In seeds, respectively. Two doses of PK fertilizers gave the highest concentration and uptake of P and K in shoots and seeds. Both straw and seed yields were highly significantly correlated with the uptake of each of N, P, K, Ca and Mg by straw and seeds, respectively.