FURROW IRRIGATION EROSION LOWERS SOIL PRODUCTIVITY

Recent research efforts have shown that soil erosion decreases soil productivity. Erosion-caused crop production decreases of 15-40% are commonly reported with some values over 50%. Furrow erosion on irrigated land in Idaho decreases topsoil depth on the upslope approximately 33% of the field area and may increase topsoil depth on the downslope 50-55%. Crop yields are generally decreased where topsoil depths are decreased, but yields are not generally increased where topsoil depths are increased beyond a critical depth. Crops vary in their sensitivity to decreases in topsoil depth, but all crops studied exhibited lower yields on the eroded areas. Soil productivity potential of one area representing several million ha of furrow irrigated land was reduced at least 25% by furrow erosion over 80 irrigation seasons, Technology is not available to restore soil productivity potential to the level that would exist had there been no erosion except for returning topsoil to eroded areas. Research and technology applications are needed to reduce or eliminate topsoil loss and redistribution by irrigation erosion.