NUTRIENT LOSSES FROM CROPLAND IN THE CENTRAL HIGHLANDS OF KENYA DUE TO SURFACE RUNOFF AND SOIL-EROSION

Soil loss, runoff and nutrient losses were measured on runoff plots du ring the rainy season from November 1992 to January 1993. Crops grown were maize (Zea mays L.), beans (Phaseolus, vulgaris L.) and an interc rop of maize and beans. The control treatment was bare fallow. The tot al loss of C, N, P, K and plant-available P and K in the eroded soil a s well as P and K dissolved in the surface runoff water were not depen dent on the nutrient concentration of the eroded soil and water, but r ather on the total amount of runoff and eroded soil. Compared to bare fallow, P (and K) losses under maize were reduced to 24.2% (28.3%), un der beans to 15.3% (15.4%) and under intercrop to 9.3% (10.7%).