Development and Yield of Jatropha curcas L. Under Weed Competition.

Jatropha is a promising plant for biodiesel production and it was recently  domesticated , also, short information were obtained about the effect of weed competition on Jatropha curcas development and Yield.  The  present study aimed to characterize the main weed species and their effect on growth and yield of Jatropha. This study was conducted out at the Experimental Farm of São Paulo State University, located at Selvíria, in the border of northwest of São Paulo State and southeastern of the Mato Grosso do Sul State.  The experimental design was a randomized completely blocks with four replications, consisting by seven periods of weed interference on the crop, performing 28 plots. Thus, after the end of each period, the  weed control was done by mechanical instruments in the corresponding plots, which were cleaned  until the harvest. The initial periods of competition were : 1 - Competition for 0 days (control); 2 - Competition for 15 days; 3 - Competition for 30 days; 4 - Competition for 60 days; 5 - Competition for 90 days; 6 - Competition for 120 days; 7 – without weed control. The experimental plots were composed by three rows with 5 plants each,  with 15 plants per plot arranged in with the row spacing of 3.0 m and 2.0 m between plants, with the total plot area of 90 m² (9.0 mx 10.0 m). It was found that Panicum maximum Jacq. was the predominant species in the experimental area. There was a reduction in growth variables plant height, stem diameter and number of stems until 60 days of competition. The Yield of jatropha was reduced from 15 days with competition. The period before the interference of weeds on Jatropha development was 21 days of competition.