A STATISTICAL-ANALYSIS OF THE INFLUENCE OF STRIGA-HERMONTHICA ON MAIZE YIELDS IN FERTILIZER TRIALS IN SOUTHWESTERN KENYA

The adverse effect of the parasitic weed Striga hermonthica on yield of maize was studied in a fertilizer trial in Southwestern Kenya. In two years of experimentation (1987 and 1988), the weed had a highly significant, negative impact on maize yields. The spotty incidence of Striga disturbed the fertilizer trials. Inclusion of the degree of Striga infestation in a regression model caused an increase in the fraction of experimental variation that could be explained by the model. Several methods were tested to combat Striga. Hand-pulling reduced Striga incidence and increased grain yields during the following growing season. No clear effect was obtained from the trap crop sunflower, although such an effect may have been concealed by the success of hand-pulling. Application of mineral fertilizers or farmyard manure did not significantly reduce Striga infestation.