Spatial Distribution of Organic Carbon and Nutrients under Farmers’ Crop Residue Management Practices in Eastern Ethiopia

Understanding the distribution and transport of organic carbon and nutrients under any management in a farming system is vital for predicting the sustainability of a farming system. This study was conducted to characterize the spatial distribution and transport of organic carbon and nutrients under farmer’s crop residues management involving complete removal of the residues and to identify which nutrients are highly affected by such management practices. Two farms, representing the major farming systems of the study areas, were selected from Adele and Bala Langey villages in Haramaya and Kersa districts, respectively in Eastern Ethiopia. Soil samples were collected along the slope gradient from the crop fields and at a given distance from home in homesteads of each farm at a depth of 0 – 30 cm. The samples were analyzed following standard methods for soil organic carbon and nutrient contents. Results indicated that distributions of organic carbon and nutrients were affected by slope gradients in crop fields and by distances in homesteads at both farms. Results showed that 2.95 and 2.15% OC, 0.52 and 0.25% N, 100.15 and 41.23 mgkg-1 available P, and 25.05 and 1.65 mgkg-1 extractable S were accumulated near homes of the households at Adele and Bala Langey farms, respectively. Quantities of OC, N, P, and S were less than 2%, 0.15%, 25 mgkg-1 and 2 mgkg-1, respectively in the crop fields at both farms. Amounts of N transported from Adele and Bala Langey crop fields through haricot bean residue were 4.70 and 5.60 g/kg dry matter, respectively. The extent of crop residue removal management effects on the distribution of the nutrients, from the most to the least affected, follows the order P > OC > S > N > exchangeable bases > micronutrients at both farms. Intervention management should focus on reversing the flow of organic carbon and nutrients from crop fields to the homesteads and minimizing unequal distribution of organic carbon and nutrients in the farming system at both farms.