Nitrogen, phosphorus and potassium effects on the incidence of Striga asiatica (L.) Kuntze in maize

Summary This work was conducted in an attempt to elucidate some of the effects of nutrition on the incidence of witchweed (Striga asiatica (L.) Kuntze) in maize (Zeu mays L.). In an N, P, K field trial N applications resulted in up to 93% reduction in the incidence of witchweed. Maize height was unaffected by N and decreases in the incidence of Striga could not be attributed to the effects of host‐parasite competition. Although plant height was 10% lower on zero‐P plots, P did not have a significant effect on Striga and the beneficial effects of N were equally evident on both high and low‐P plots. Potassium applications had the opposite effect to N. While the main effect of K was not quite significant at the 5% level of probability, an N × K interaction was evident, and in the absence of applied N, K applications led to a more than 4‐fold increase in the incidence of Striga. As with N, K did not influence plant height and it seems unlikely that competition effects were responsible.