Nutrient and Sediment Discharge from Southern Plains Grasslands

Abstract

Amounts of nitrogen, phosphorus, and sediment were measured in runoff from grassland watersheds in the Blackland Prairies, High Plains, Reddish Prairies, and Rolling Red Plains land resource areas of Oklahoma and Texas. Periods of study were 3 to 5 years and included treatments involving fertilization, cultivation, and burning. Overall nutrient concentrations generally ranged from 2 to 10 mg/l for nitrogen and 0.3 to 2 mg/l for phosphorus. In most cases, less than half the nutrients existed as soluble forms in the runoff water. Typically, annual sediment losses were less than 0.5 metric tons/ha. Corresponding losses for nitrogen and phosphorus were less than 5 and 2 kg/ha, respectively. In the case of nitrate, more was received in precipitation than was lost in runoff. Total nitrogen and phosphorus losses were strongly correlated with sediment losses. Preliminary results using predictive techniques to estimate nutrient and sediment discharge from the watersheds were encouraging. With proper management, the likelihood of any adverse environmental effects due to nutrient and sediment discharge from Southern Plains grasslands appears slight.