Selected physical and chemical characteristics of soils of the middle awash irrigated farm lands, Ethiopia

The irrigation based cotton production system in the Middle Awash basin has got progressive productivity decline in the present times. A study was made to provide basic information with regard to the present fertility status and physical characteristics on the soils of the basin. Based on soil color, texture, and land use, 12 pedons were opened in Melka-Sedi farm and Werer Agricultural Research Center and studied for their physical and chemical characteristic. Results showed that the main soil types were Salic Fluvisos, Eutric Fluvisols and Eutric Vertisols. Among these soil types, Eutric Flvisoils occupies the largest portion of the cultivated land of the basin. Salic and Eutic Fluvisols show stratification with weak horizon differentiation with alternating silt and clay particle size dominance within profile depth, while the Eutric Vertisols have homogenous solum overlaying stratified subsoil. Eutric and Salic Fluvisols have 1.2 -1.3 g cm-3 bulk density, pH values ranging from 7.0 - 8.4 and high ECe (37 dS m-1). The bulk density, pH and the average ECe of the Eutric Vertisol ranges from 1.3-1.6 g cm-3 , 8.1- 8.4 and 0.5 dS m-1, respectively. Total nitrogen in all soil types is low to medium, while available phosphorous and CEC is high. The fertility status of the irrigated soils of the middle Awash as observed from this work is medium to high except the toxic concentration of Mn and deficiency of Zn. Undesirable salt accumulation commonly aggravates salinity and sodicity in the area.Keywords: Alluvials, Horizon, Pedons, Salinity, Sodicity, and Vertisol