Soil Fertility Assessment and Mapping at Kofele District, West Arsi Zone, Oromia Ethiopia

Soil fertility assessment and mapping is the way of assessing soil nutrients on the basis of soil samples test results and preparing maps at required scale. The study tried to map selected plant nutrients phosphorous, potassium, organic carbon and other soil fertility indicators (pH. EC, CEC) for Kofele district, Oromia, Ethiopia. About 161 soil samples were collected across the district and used to map the whole area. Standard laboratory analyses were followed for every soil parameters. In order to predict values for not sampled locations the Ordinary Kriging interpolation was used by ArcGIS10.1 software. The potassium level in the study site has two classes’ medium and high which covers 79.98% and 20.02%, respectively. The district has four categories of soilpH but the majority of the area falls in strongly acidic. Generally, the pH of the study were very strongly acidic (5.63% of the area, strongly acidic (63.85% of the area), extremely acidic (0.35% of the area) and moderately acidic (30.16% of the area). The available phosphorus level is categorized as low, medium and high which is 0.71%, 98.36%, and 0.93%, respectively. The dominating class is medium. Cation Exchange Capacity can also be categorized in three classes namely low (9.14%), moderate (90.84%) and high (0.016%) in soils of the area. Soil Electrical Conductivity is ranged from 0.085 to 0.383 mmhos/cm at 25oCi.e, are salt free. Soil Organic Matter content ranged from 1.10% to 4.79%namely from low to moderate in rating classes. The organic matter content of soils of the study area are dominated by moderate and low with percent share of 79.73%, 20.27%, respectively. Exchangeable potassium (K) can also be categorized in two classes namely medium 79.98% and high 20.02% in soil of the area.