Poor soil fertility is one of the bottlenecks for sustaining maize production and productivity in Ethiopia in general and in western Oromia in particular (Tolessa et al., 2002). In most regions of Ethiopia, soils are deficient in nitrogen (N) and phosphorus (P). In some places of western Ethiopia, adverse soil conditions prevail, and frequently a combination of these limit crop production. The situation has been further aggravated by the long history of cultivation without any NP replenishment, which led to low soil fertility and low crop yields.