Effects of soil physical properties on soil loss due to manual yam harvesting under a sandy loam environment

Soil degradation is a growing problem worldwide because it reduces the fertile top layer of the soil available for food production and one such degradative action is soil erosion due to the harvesting of crops. Soil loss due to crop harvesting with particular reference to yam tubers has not been quantified globally despite the fact that yam is a major staple food consumed worldwide and it is prevalent in many parts of Nigeria. Harvesting yams in our environment is usually done with the soil attached to the yams due to the fact that farmers do not want additional work of removing soil attached to the yams. This study investigates the soil physical properties that influence soil loss due to yam harvesting in Abeokuta, South-Western Nigeria and to assess the quantity of soil loss due to yam harvesting. Based on representative sampling area per location, yam tubers were harvested manually within the entire yam farmland from October to December 2012. Gross weight, net weight and the amount of soil adhering to the yams were measured. Effects of soil physical properties such as soil moisture content, heap bulk density, inter-heap bulk density and soil texture were investigated with respect to soil losses. The results showed that moisture content ranged from 4% to 15%, heap bulk density ranged from 0.93 to 1.29gcm−3 and inter-heap bulk density ranged from 1.03 to 1.50gcm−3. They all had a positive correlation with soil loss. Soil particle size analysis for Federal University of Agricultural, Abeokuta (FUNAAB) and Alabata revealed that sand content was (86.78% and 88.32%), clay content (10.69% and 7.6%) and silt content, (2.53% and 4.08%) respectively. Study also revealed that clay content of the soil positively influenced the total soil loss during the yam harvesting. The mean soil losses in Federal University of Agriculture, Abeokuta (FUNAAB) and Alabata village yam farms were 4303 and 2125kg/ha/harvest respectively. The study also revealed that soil moisture content at harvesting time and clay content are the key factors affecting soil loss due to yam harvesting. Consequently, soil loss due to crop harvesting should be considered in soil erosion control strategies, sediment budget and for better post harvest procedures.