Within-furrow Erosion and Deposition of Sediment and Phosphorus

Sediment, an end product of soil erosion, hampers irrigation, pollutes rivers, and is an economic loss to farmers and a resource loss to the nations of the world. Slope, soil condition, stream-size, and the cropping system are important factors that govern both within-field erosion and sediment loss from a field. Under present management systems, irrigation drainage streams continually load sediment into streams and rivers. Technology needs to be developed to reduce or eliminate sediments and absorbed nutrients from surface irrigation return flows. Robbins and Carter (3) reported that small sediment retention ponds could remove 80 to 95 percent of the suspended sediments from surface drainage water. Soil erosion damages both the area from which the soil is eroded and the area where sediment is deposited. Large amounts of sediment may be carried from irrigation fields. Brown and associates (1) reported sediment concentrations in surface irrigation return flows ranging from 20 to 15,000 mg/l. Carter and associates (2) found that phosphorus (P) can be conserved by removing sediment from irrigation return flow. They found higher P concentrations on smaller particles and aggregates than on larger particles and aggregates. For example, 550, 1,150, and 1,285 mg/liter total P were attached to the sand, silt, and clay fraction, respectively