Effect of Vermicompost on Soil Fertility and Crop Productivity in the Drylands of Ethiopia

The nutrient type and amount contributed from vermicompost varies depending on the source material, earthworm type used, agro-ecology and farmers' management. These call for crop, soil and site specific study. This study, therefore, aimed at determining: (i) the optimal vermicompost application rate/s for wheat and maize production; and (ii) the role of vermicompost on soil fertility improvements. Field experiments in three agro-climatic zones (highland, midland and lowlands) were established on wheat and maize crops following a randomized complete block design. The treatments were vermicompost (2.5, 5.0, 7.5 and 10 t ha-1), conventional compost (10 t ha-1), and recommended rates of Nitrogen and Phosphorus (NP = 100 kg DAP and 50 kg Urea) fertilizers. Our results revealed that the studied soil chemical properties, primarily, organic carbon (OC %), N (%) and available P (mg kg-1) increased with increasing vermicompost rate. The 10 t ha-1 vermicompost treated plots had 157-210%, 64-81% and 100-242% higher soil total nitrogen content as compared to the control, 10 t ha-1 conventional compost and NP fertilizer treatments, respectively. Application of 10 t ha-1 vermicompost also resulted in a 1.5-fold and 43-63% grain yield increment of both tested crops compared to the control and NP treated plots, respectively. However, the highest net benefit was obtained from 5 t ha-1 vermicompost for maize (86% increase) and 10 t ha-1 of vermicompost for wheat (152% increase compared to the control). In conclusion, vermicompost at 5 t ha-1 for maize and 10 t ha-1 for wheat can be recommended to sustainably manage farm productivity.