Root hairs and cortex contribute to soil loss due to root crop harvesting

Soil loss due to root crop harvesting (SLCH) has been increasingly recognized as an important soil degradation process. Root hairs can impact SLCH apart from playing nutrient uptake role in the soil. In order to better understand the role of root hairs in inducing SLCH, a two years field experiment was conducted in Nigeria to assess the impacts of root hairs on soil loss due to yam harvesting in response to organic fertilizer application. Two yam cultivars (Tropical Dioscorea alata 00/00194 - cultivar(A)) and (Tropical Dioscorea alata 00/00006 - cultivar(B)) were planted using three different fertilizer placements, i) ring placement, ii) side placement and iii) control (no fertilizer). SLCH was measured by removing the soil adhering to the harvested root crops. Then root hairs were trimmed and weighed to determine root hair density. Fertilizer application was found to significantly (p < 0.05) induce SLCH by increasing root yield and associated root hairs. Soil loss per unit root mass (SLCHspec) was by 70.8% and 68.7% higher in ring and side fertilized plots, respectively than unfertilized plots. Changes in SLCH vary mainly with yam cultivar due to differences in root hair density per unit crop yield. Soil loss due to crop harvest (SLCHcrop) from cultivar(A) was significantly (p < 0.05) higher compared to cultivar(B) by 11.2% and 36.3%, respectively for years 1 and 2. Root hair density, root cortex, clay and organic matter significantly (p < 0.0001) contributed 97% of SLCHspec variation. The contribution of the determining factors decreases in the order of root hair density (40%) > clay (28%) > organic matter (18%) > root cortex (14%). Our results suggest that root hair density and root cortex as well as soil factors should be considered together in evaluating SLCH induced land degradation and associated influencing mechanism.