Effects of farmyard manure and combined N and P fertilizer on sorghum and soil characteristics in northeastern Ethiopia

The soils of the semi-arid areas of northeastern Ethiopia are poor in Soil nutrients owing to intensive soil erosion, continuous cereal growing, and age-old Cultivation. Consequently, low soil fertility is the most severe constraint to small holder crop production and to sustainable food security. Farmers in northeastern Ethiopia are also very poor in resource endowment and are incapable Of Supplying the nutrient requirements of crops through commercial fertilizers. Therefore, integrated nutrient management through the combined use of mineral and organic fertilizer Sources is of great importance for the Sustainable improvement of soil productivity in intensive cropping systems. This study evaluated the integrated use of mineral fertilizers at the rates of 0%, 50% and 100% of the recommended rates and the organic fertilizer source (farmyard manure, FYM) at the rates of 0, 5, 10, and 15 t ha(-1). The results indicated that the highest significant grain yield increases were obtained when 15 t ha(-1) FYM was applied with 50% and 100% of the recommended levels of mineral fertilizers followed by application of 10 t ha(-1) FYM alone. These yield increments gave yield benefits of 50%, 51% and 47% over the control. In addition both FYM and mineral fertilizer application positively influenced stover yield and panicle weight. Four years' application of FYM at the rates of 10 and 15 t ha(-1) increased the soil total N content by 17 to 24%, organic carbon by 13 to 26%, available P by 67 to 85%, K by 42 to 79% and Mg by 6 to 30% compared to the plot lacking FYM application in the 0-20 cm soil depth.