Tolerância de mamoneira ao herbicida pendimethalin em solos com diferentes capacidades de adsorção

The castor bean is a species of slow initial growth. The absence of registered herbicides for this crop is still a limiting factor for its expansion. The aim of this study was to evaluate the castor bean tolerance to the herbicide pendimethalin in soils with different adsorption capacities. The experiment was conducted under greenhouse conditions in a completely randomized design with five replications and consisted of a factorial combination of eight doses of the herbicide pendimethalin applied as pre-emergence (0; 187,5; 375; 750; 1500; 3000; 6000 and 12000 g ha-1 i.a.), and four types of substrate (clay loam, sandy clay loam, sandy loam and sandy soil). At 22 days after sowing the variables: plant height, leaf area, fresh and dry mass of shoots, root system volume and dry weight were determined. It was concluded that the dose of the herbicide pendimethalin tolerated by the castor bean is influenced by the adsorption capacity of the soil. The herbicide was found to be very selective to this crop, not causing significant reduction of plant growth at the doses indicated to be used for weed control.