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

Abstract

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.