The Effect of Furrow Irrigation Erosion on Crop Productivity

Furrow irrigation erosion redistributes topsoil by eroding upper ends of fields and depositing sediment on downslope portions causing a several fold topsoil depth difference on individual fields. This investigation was conducted to evaluate the effects of this erosion and deposition process on crop yield and to develop crop yield-topsoil depth relationships. Studies were conducted on 14 farmer-operated fields and on field plots with a continuous topsoil depth gradient from 10 to 66 cm. Severe erosion on the upper ends of fields combined with tillage has mixed light-colored subsoil with topsoil and caused these areas to become whitish in color. Crop yields have sharply decreased on these whitish areas compared to areas where the topsoil depth is 38 cm, or the original depth. Yields were increased, but less sharply, where sediment deposition has increased topsoil depth above 38 cm up to a depth of about 66 cm. Yield-topsoil depth relationships followed the equation Y = a+b 1nX with significant correlation coefficients for wheat (Triticum aestivum L.), sweet corn (Zea mays L.), barley (Hordeum vulgare L.), alfalfa (Medicago sativa L.), dry beans (Phaseolus sap.) and sugarbeets (Beta vulgaris L.). Yield decreases per unit loss of topsoil were greatest for wheat and sweet corn and least for sugarbeets. Yields on whitish soil areas could not be improved more than indicated by these relationships by adding additional fertilizer phosphorus or potassium