Soil Test Crop Response Based NPS Fertilizer Rates Determination for Maize (Zea mays L.) Production at Sibu Sire District, Western Oromia Region

The use of improper fertilizer type and amount, the cultivation of unimproved, low-yielding varieties and poor soil fertility are among the main obstacles limiting the productivity of maize in Ethiopia in general and in the study area in particular. A field trial was therefore initiated to identify economically justifiable amount of NPS fertilizer in Sibu Sire district. The treatments consist of 100% Pc from TSP and 100, 75, 50, 25% Pc from NPS fertilizer with all recommended N fertilizer and control (no fertilizer application). The experimental design was a randomized complete block design (RCBD) with three replications. Limu seed variety was used for the trial. The results of soil samples collected before sowing showed a deficiency in soil chemical properties. Results of agronomic data showed that all Pc rates significantly increased the plant height, cob length, Seeds per cob and grain yield over control. Phosphorus critical level rate of 100% Pc from NPS gave grain yield (7057 kg ha<sup>-1</sup>), which is not statistically not different from the application of 50, 75 and 100 % Pc from NPS and also 100% Pc from TSP. The application rate of 75% Pc from NPS offered net return of 130045 ETB ha<sup>-1</sup> which was substantially greater than the rest of the fertilizer application. Hence, fertilizer application rate of 75% Pc from NPS is more economically beneficial and recommended for maize production in Sibu Sire district. It is important to deal with further awareness creation and demonstrating of the technology for wider popularization.