Effects of phosphorus and sulfur on yield and nutrient uptake of wheat ( L.) on Vertisols, North Central, Ethiopia.

Deficiency of phosphorus (P) and sulfur (S) is increasingly being reported in soils of Ethiopia. While some studies have shown significant response of wheat to P and S application, information on the response of wheat to P and S application interactively is conspicuously lacking. In this regard, we evaluated the response of wheat to P and S application interactively in the study area. A field experiment was conducted at two locations to determine the effects of P and S, on yield, uptake and P, S use efficiency of bread wheat. A factorial combination of four levels of P (0,11,22 and 44 kg h) and three levels S (0, 15 and 30 kg ha) laid out in Randomized Complete Block Design with three replications. Results revealed that interacted application of P and S at 22 and 15 kg ha respectively increased grain yield of wheat by 40.1 % over control. The corresponding increase with straw was 53.4 % over control. Wheat yield obtained with combined application of P and S greater than single application of P or S indicating synergistic between them. The maximum grain N (56.3 kg ha-1), P (12.8 kg ha-1) and S (4.2 kg ha-1) uptakes were obtained due to combined application of P and S at 22 P and 15 S kg ha-1. Agronomic efficiencies of P and S decreased as the rates of P and S application increased. Combined fertilization of S and P is necessary in the study district and 15 kg S combined with 22 kg P ha produced the highest yield. Thus, this treatment is found to be recommended for bread wheat production in Vertisols of the district. While, partial budget analysis result revealed that, combination of 22P and 15S kg ha produced the highest MMR (54.9 %) and thus, this treatment is found to be economically feasible treatment for bread wheat production in study area of the district. We recommend further experiments on different combination of P with S in different agro-ecologies and soil types are required for confirmation of results and the residual effect of P and S on the following crop is needed to study the long-term effect of P and S.