On-farm Integrated soil fertility managment in wheat on nitisols of centreal Ethiopian highlands.

Soil acidity and associated low nutrient availability are constraints to wheat (Triticum aestivum L.) production on Nitisols of central Ethiopian highlands. On-farm integrated nutrient management trials were conducted in highland Nitisols areas of Ethiopia during the 2003 and 2004 cropping seasons. The objective of the study was to investigate the ameliorating effects of the combined application of inorganic N and P fertilizers and farmyard manure (FYM) on wheat yield and yield components. The treatments consisted of five combinations of N/P/FYM (9/10/0, 9/10/8000 32/10/40000, 32/10/8000 and 64/20/0 kg ha-1, respectively). These were arranged in a randomized complete block design with three replications. Results revealed that grain yield, Total biomass yield, plant height, spike length and number of kernels per spike were significantly affected by N/P/FYM applications. The application of N/P/FYM at the rates of 9/10/8000, 32/10/4000, 32/10/8000 and 64/20/0 kg ha-1 incresed mean grain yield of wheat by 16, 24, 31 and 32%, respectively. On dila (medium fertility) and 32, 41. 59 and 71%, respectively, on dimile (low fertility) soils compared to the farmers' check (9/10/0 kg N/P/FYM ha-1). The grain yield of wheat was significantly correlated with total biomass yield, plant height, number of spikelet per spike and spike length (r = 0.89*** 0.67***, 0.42* and 0.45*, respectively) on dila and (r = 0.90*** 0.65***, 0.54** and 0.61***, respectively) on dimile soils. Though the application of FYM with 50% of the recommended rate of N/P fertilizers resulted in a comparable output as that of the full rate of N/P fertilizers, in terms of economic return, the highest marginal rate of return was obtained from the application of 64/20/0 kg N/P/FYM ha-1 for both soils. Hence, the economic fertilizer rate for wheat production was found to be 64/20/0 kg N/P/FYM ha-1. Despite the highest net benefit from the application of 64/20/0 kg N/P/FYM ha-1, nonetheless, application of 32/10/4000 kg N/P/FYM ha-1 is above the minimum acceptable rate of return and it could be considered as an alternative rate in situation, where the cost of inorganic fertilizer is expensive and limited in availability.