Assessment of physico-chemical properties of soil under wheat (triticum aestivum) based cropping system in hetosa woreda, arsi zone, south east Ethiopia

Soil fertility plays a key role in crop production. However, due to intensive and continuous cultivation of agricultural land in Ethiopia, soil fertility has been decline. Therefore, the objective of this study was to assess the impact of wheat based cropping system on soil fertility in Hetosa Woreda. To achieve the objective a composite soil samples were collected from five cultivation fields, with three replication and two depths (0-15, 15-30cm). Totally, 30 soil samples were brought to laboratory from wheat rotated with legumes and cereals fields with simple random sampling system. The two-way ANOVA were used to compare the effects of wheat based cropping systems at different soil sampling depth with their interaction on selected soil physicochemical properties at P<0.05. There was a significantly (P<0.05) higher value of soil BD in wheat-wheat and wheat-barley than wheat-bean and wheat-pea cropping system. The wheat-wheat and wheat-barley cropping systems didn’t pose any changes in the values of pH, SOM, Av.P, CEC, PBS and basic cations. Similarly, mean comparison for wheat-bean and wheat-pea cropping system reveal that there were no significant changes in the value of pH, SOM, TN, Av.P, CEC, Ca2+, Mg2+, K+ , ex.Na+ and PBS while soil pH in wheat-maize was significantly different from the entire cropping systems. As compared to the adjacent continuous wheat cultivation, wheat-barley, wheat-bean, and wheat-maize cropping system increased SOM by 0.5%, 19.5%, and 3.7% and TN by 5%, 20% and 5%, respectively. Similarly, the value of Av.P, pH and CEC is increased by 39.6%, 12.3% and 19. 9% at the surface layer of wheat-bean while decreased by 15.4%, 0.9%, and 5.5% in the subsurface, respectively. The BD, sand and clay were significantly higher (P < 0.05) in wheat-maize cropping system at the subsurface whereas the pH, SOM, Av.P, ex.Ca2+, ex.Mg2+, CEC, and PBS were higher in wheat-bean cropping system at the surface. Generally, the cultivation of wheat-bean and wheat-pea cropping systems improve the selected properties of soil while wheat-barley and wheat-maize in comparison with continuous wheat cropping systems had adverse effects on the soil physicochemical properties of the study area. Therefore, it is recommended to include grain legume in wheat based cropping system for sustaining the soil fertility level. Key words: Cereal, Crop rotation Grain legume, Soil fertility, Soil properties.