Nitrogen and phosphorus supply strongly reduced the control efficacy of maize against sunflower broomrape

Heavy infestation by the root parasitic sunflower broomrape over wide regions constitutes a major biological constraint to sunflower production. The use of maize as a trap crop to induce sunflower broomrape germination is considered a cost-effective method for controlling sunflower broomrape. This study was designed to examine the activity of maize to induce sunflower broomrape seeds germination under varying levels of nitrogen (N) and phosphorus (P) fertilization. Orthogonal experiments were conducted during two cropping seasons with four maize cultivars under four levels of N and P application. A significant reduction in sunflower broomrape germination induced by maize root and rhizosphere soil extracts upon N and P application was observed in both 2014 and 2015, with P having the strongest effect on the broomrape germination inducing activity of maize root extracts. Structural equation modelling analysis revealed that N and P supplementation not only directly affected the germination-inducing capacity towards sunflower broomrape of maize root extracts but also had an indirect effect through the impact on abscisic acid contents. This study may contribute to a better understanding of the connection between soil fertility and the production and release of germination stimulants in maize and that can lead to improved control strategies.