Quantification of Soil and Nutrient Loss Due to Yam Harvesting: a Case Study in Two Local Government Areas in Benue State, Nigeria.

Soil loss due to crop harvesting is a recognized erosion process which has significantly contributed to soil degradation. Despite its significance, soil loss due to crop harvesting has been given little attention in Benue state and Nigeria at large. This is evident in the paucity of information on soil loss due to crop harvesting in Nigeria. Therefore a field experiment was conducted to quantify soil and nutrient loss due to yam harvesting in two local government areas (Kwande and Ushongo) of Benue state and to identify factors which could contribute to soil loss in these areas. Data collected on soil loss were subjected to t-test at α = 0.05. Average crop yield in Kwande was 18.9 t ha-1 and 16.3 t ha-1in Ushongo with corresponding soil loss of 3.26 t ha-1 harvest-1 and 1.97 t ha-1harvest-1 respectively. Higher soil loss observed in Kwande compared to Ushongo can be attributed to higher crop yield and clay content of the soil. Crop yield, clay content and soil organic matter correlated positively with soil loss in Kwande (r = 0.75, r = 0.58, r = 0.65) while in addition to crop yield and clay content sand correlated negatively with soil loss in Ushongo (r = 0.77, r = 0.60, r = -0.60). Soil nutrient losses for nitrogen, phosphorus and potassium were significantly higher in Kwande compared to Ushongo by 2.71, 2.67 and 2.02 times respectively. The findings suggest that soil loss in these areas could degrade the land within a short time, especially where mono-cropping of yam is practiced. Farmers are therefore advised to hand-rub yam tubers while harvesting on the field and practice crop rotation.