Recovery of Soil Health and Crop Productivity of Degraded Cultivated Land of Northwest Ethiopian Highlands

Severe soil degradation and fertility depletion have resulted in poor soil health and low crop productivity in the cultivated land of most Ethiopian highlands. Thus, a three-year experiment from 2013 to 2015 was conducted to assess the potential of crop rotation and organic matter application for recovery of the soil health and crop productivity of cultivated land in northwest Ethiopian highlands. Factorial combinations of five crop rotations [bread wheat–clover–potato (R1+); clover–bread wheat undersowing lupine– potato (R2+); potato–clover–bread wheat (R3+); bread wheat undersowing lupine–potato undersowing lupine–bread wheat (R4+); and lupine–potato undersowing lupine–bread wheat (R5+)] and four manure application rates [control without manure (M1); 2.5 t ha-1 sesbania green manure SGM (M2); 5 t ha-1 fresh cattle manure FCM (M3); and 2.5 t ha-1 SGM + 5 t ha-1 FCM (M4)] were laid out in randomized complete block design with four replications at on-station and on-farm testing sites. Interaction of crop rotation and manure application significantly improved the soil properties and crop productivity of the experimental plots. Combined applications of crop rotation and manure in a three-year period resulted in the improvement of crop productivity up to 13 folds, as well as of bulk density, pH, CEC, and contents of organic carbon, total nitrogen, available phosphorous, and exchangeable potassium of the experimental soils up to 25, 20, 67, 92, 154, 96 and 54 percent, respectively, compared to their baseline records. These highest improvements of physicochemical soil properties and crop productivity were mainly recorded from the interaction of R1+ and M4. The results clearly showed that long-term sound crop rotation and organic matter application have a great potential for recovering the soil health and crop productivity of degraded cultivated land in Ethiopian highlands.

埃塞俄比亚大部分高地耕地均面临严重土壤退化与肥力耗竭问题，导致土壤健康状况不佳、作物生产力低下。为此，本研究于2013—2015年实施了一项为期三年的田间试验，旨在评估作物轮作与有机质施用对埃塞俄比亚西北部高地耕地土壤健康及作物生产力的恢复潜力。试验采用随机完全区组设计，设置5种作物轮作与4种有机肥施用量的因子组合，共设4次重复，分别在定位试验站与农户田间试验点开展。其中，5组作物轮作处理为：面包小麦-三叶草-马铃薯（R1+）、三叶草-面包小麦套播羽扇豆-马铃薯（R2+）、马铃薯-三叶草-面包小麦（R3+）、面包小麦套播羽扇豆-马铃薯套播羽扇豆-面包小麦（R4+）、羽扇豆-马铃薯套播羽扇豆-面包小麦（R5+）；4组有机肥施用量处理为：无有机肥对照（M1）、2.5 t ha⁻¹田菁绿肥（SGM）（M2）、5 t ha⁻¹鲜牛粪（FCM）（M3）、2.5 t ha⁻¹ SGM + 5 t ha⁻¹ FCM（M4）。作物轮作与有机肥施用的交互作用可显著改善试验田块的土壤性状与作物生产力。与初始基准值相比，三年间联合实施作物轮作与有机肥施用可使作物生产力最高提升13倍，同时可使试验土壤的容重、pH值、阳离子交换量（CEC）、有机碳含量、全氮含量、有效磷含量及交换性钾含量分别最高提升25%、20%、67%、92%、154%、96%及54%。其中，土壤理化性状与作物生产力的最优提升效果均来自R1+与M4的交互处理。研究结果清晰表明，长期合理的作物轮作与有机质施用方案，对埃塞俄比亚高地退化耕地的土壤健康恢复与作物生产力提升具有极大潜力。