Soil Nutrient Status of Smallholder Cassava Farms in Southern Ethiopia

This study investigates the soil nutrient status of cassava farms in Wolaita, Southern Ethiopia. Soil samples were randomly collected form 12 cassava farms and soil management practices on the farm were also recorded. The samples were analyzed for physical and chemical properties. The result reveled that cassava in the study sites was cultivated under low to no fertilizer application in which farmers applied phosphorous (P) and nitrogen(N) fertilizer ranging from nil to 32.2 kg/ha P2O5 and nil to 19.2 kg/ha, respectively. Non- use of organic fertilizer and complete removal of crop residues from the field were also common farm practices. The physico-chemical properties of cassava farms revealed clay textural class with an ideal bulk density (1.06 to1.35 gcm-3). The soil pH was strong to moderate acidity (pH 5.0–6.1). The farms were very low to low in their organic carbon (1.2–2.5%) and total N content was low (< 0.2%). The soil available P was below the critical level (< 30 mg kg-1) in 100% of the cassava farms, while 92% of the studied soils showed sulfur (S) deficiency (< 20 mg kg-1). Exchangeable calcium (Ca) on 83% of farms was low (< 5 Cmol (+) kg-1), while magnesium (Mg) was under medium category. Potassium (K) to Mg varied from 0.4:1 to 0.9:1. Thus, Mg induced K deficiency was speculated on 75% of cassava farms. The result regarding micronutrient status indicated that boron (B) and copper (Cu) in 100% of the cassava farms were deficient. Lower content of iron (Fe) on 33% and zinc (Zn) on 17% farms was also recorded. All soil samples were adequate in manganese. Regardless of their share, about 57% essential elements derived from soil (N, P, K, S, B, Cu, Fe and Zn) were found limiting nutrients to cassava production in the study area. Thus, correcting the limitation through balanced fertilizer application is needed. Further study is suggested in order to have firm conclusion. Keywords: Cassava, Ethiopia, Nutrient, Soil, Wolait