Interferência de plantas daninhas e tolerância do pinhão-manso ao glyphosate

Abstract

Brazil stands out on the world stage in renewable energy. Among the various sources of raw material for the production of biodiesel, there is jatropha (Jatropha curcas L.). Technical Information management recommendations, chiefly concerning weeds are scarce for culture. The objective of this study was to evaluate the effect of glyphosate on early growth of plants jatropha and evaluate the effect of competition with weeds in the early development of jatropha. Two experiments were conducted under conditions of greenhouse and laboratory belonging to the Federal Rural University of Rio de Janeiro. In the first experiment was an increase in height, dry matter accumulation, increase in stem diameter and leaf area in plants jatropha after glyphosate application (180.0, 360.0, 720.0 and 1440.0 g ha-1) and a control application, in three positions application (whole plant "over the top", middle third and bottom third of the plants) in a completely randomized block design with four replications. In the second experiment, we evaluated increment in height, dry matter accumulation, increase in stem diameter and leaf area in plants of jatropha in competition with weed species. Five weed species (Bidens pilosa L., Mucuna aterrima Piper & Tracy, Urochloa decumbens Stapf, Panicum maximum Jacq. e Commelina benghaliensis L.) transplanted in each pot separately in five densities (1, 2, 3, 4 and 5 plants per pot) were used, containing a plant jatropha, with plus a control where the plant jatropha grown without the presence of competing species in a completely randomized block design with four replications. It was found in experiment 1, the jatropha plants showed more severe intoxication when herbicide application was performed on the whole plant, at a dose of 1,440 g ha-1 of glyphosate. A reduction in the height increment, the increase in stem diameter and leaf area of plants jatropha when applied to 1440 g ha-1 of glyphosate in the whole plant. For other doses and application site there were no significant effects. With the data it can be concluded that jatropha has high tolerance to glyphosate. It was found in experiment 2, the jatropha plants showed a reduction in dry matter accumulation in leaf area and increase in stem diameter, depending on the weed species competing and increasing densities. A reduction in height, stem diameter, leaf area and total dry mass of plants jatropha who knew the species Panicum maximum, the density of 5 plants. It is concluded that jatropha has reduced those parameters when in competition with weeds in early development.