Implications of Manuring and Crop Rotation on Crop Productivity and Soil Properties in the Highlands of Ethiopia, Edition 1

Soil nutrient depletion has been the greatest concern for decades for Ethiopian agriculture. The most important soil physico-chemical properties are below the critical level to support crop growth. Inappropriate crop and soil management practices are the causes of soil depletion. Overlaying of synthetic fertilizer, removal of crop residue, continuous cropping and low levels of organic manure use are the deep-rooted challenges of the agro-ecosystem of the highlands of Ethiopia. Hence experiments were initiated with the aim of investigation of the effect of long-term organic fertilizer application and sound rotation pattern on the productivity of crops and soil quality parameters. Four levels of organic treatments and five levels of crop rotations were arranged factorially and laid out in Randomized Complete Block Design (RCBD) with four replications. The organic treatments include V1 = 0 t/ha farmyard manure (FYM); V2 = 2.5 t/ha fresh sesbania biomass (FSB); V3 = 5 t/ha FYM and V4 = 5 t/ha FYM + 2.5 t/ha FSB. Whereas the crop rotations were R1 = wheat-clover-potato; R2 = clover-wheat under sown lupine-potato; R3 = potato-clover-wheat; R4 = wheat under sown lupine-potato under sown lupine-wheat and R5 = lupine-potato under sown lupine-wheat. The rotation pattern of wheat-faba bean-potato and 1 t/ha FYM was also used as farmers' practice without the factorial combination. Data of plant height and grain yield of wheat; marketable and unmarketable yield of potato and fresh and dry biomass yield of clover were recorded to measure the agronomic performance of each crop. In addition, the cation exchange capacity (CEC), soil reaction (pH), total nitrogen (N), available phosphorus (P), soil organic carbon (SOC) and bulk density of experimental soil were analyzed and recorded following the standard methods before commencing and at the end of the experiment. The data were subjected to analysis of variance (ANOVA) using General Linear Model (GLM) procedures. The experimental results showed that the types of preceding crops and the levels of organic treatments greatly influenced the performance of each crop and physico-chemical properties of experimental soil. The productivity of potato, wheat and clover showed incredible variation in response to the variation of the organic treatments and crop rotation patterns. The yields of potato, wheat, and clover increased three to four times in response to effective crop rotation patterns and organic treatments compared to their respective untreated controls. Similarly, the organic carbon, cation exchange capacity, total nitrogen, phosphorus, potassium, pH, and bulk density of the experimental soil showed significant improvements with organic matter application and crop rotation. In general, maximum crop yield and soil quality improvement are obtained at the maximum level of organic treatments and sound rotation patterns. Hence it could be concluded that organic matter applications of 5 t/ha FYM + 2.5 t/ha FSB and the respective sound rotation pattern of each crop be viewed as alternative soil fertility management options at Awi climatic and soil conditions.