Nutrients in runoff from a clay loam soil protected by narrow grass strips

Nutrient loss from water erosion is a major contributor to negative nutrient balance in most sub-Saharan African countries. Due to their low-cost, narrow grass strips are becoming popular as means of controlling soil erosion. There is a need to study the effectiveness of narrow grass strips in controlling nutrient loss due to water erosion. Performance of narrow strips of Vetiver (Vetiveria zizanioides) and Napier (Pennisetum purpureum) grass in controlling nutrient loss and runoff was determined on a clay loam soil in Kenya. Grass strips were planted in March 2000, and nutrient loss and runoff measurements were carried out from June 2000 to August 2001 (15 months). Compared with the control, Napier grass reduced PO4-P, NO2-N, NO3-N and NH4-N by 55, 70, 45 and 47%, respectively, while Vetiver grass reduced them by 11, 35, 11 and 0%, respectively. Napier grass and Vetiver grass reduced runoff by an average of 54 and 12%, respectively. Napier grass was more effective, since it formed a barrier faster than Vetiver grass.