Período de interferência de plantas daninhas e seletividade a herbicidas na cultura do crambe (Crambe abyssinica Hoechst)

Abstract

The crambe (Crambe abyssinica Hoechst) has shown a promising oil crop for the production of raw material for the production of biodiesel, because it contains a percentage between 26 and 38% grain oil and high erucic acid, a fatty acid long chain that has a high industrial value. Originally from Ethiopia and domesticated in the Mediterranean, the crambe belongs to the family Brassicaceae, is a rustic plant, with good tolerance to variations in climate, low cost production and precocity, one of the main advantages of culture that flowers at 35 days and can be harvested at days 85-90. Because it is a new culture in the country and have a market still very expressive, does not have a production system established and are almost nonexistent information about the cultivation, especially on weed interference imposed culture and use of chemical herbicides to control them. Therefore, the aim with this work to determine the periods of weed interference and to study the effect of competition on productivity, but also to evaluate the selectivity of doses and herbicides applied in the crambe crop. Two experiments were conducted under field conditions in the years 2010 and 2011 at the Experimental Farm of Agricultural Sciences University of Grande Dourados, located in Dourados, MS. In the first experiment was studied the initial periods of control and coping after crop emergence in the periods 0-10, 0-20, 0-30, 0-40 and 0-50 days after emergence (DAE), and the witness was represented by the coexistence periods (dirty) and control (clean) from 0 to 90 DAE, performing at the end of this period, the harvest. For the determination of periods of weed interference, the data yields obtained in different periods, in both models of interference were fitted to a nonlinear regression model, assuming 5% reduction in yield. The second experiment studied the selectivity of the herbicides applied in the crambe crop, the treatments were used: in preemergence S-Metolachlor (0, 600, 1200 g ha-1) and post-emergence Fomesafen (0, 112, 225 g ha-1), Fomesafen + Fluazifop-P-Butyl (0, 112 + 100, was 225 + 200 g ha-1), Bentazon (0, 350, 700 g ha-1) and Bentazon + Imazomox (0, 300 14 +, 600 + 28 g ha-1), applied when plants had between four and six leaves. Was used a sprayer system, pressurized CO2 to solution volume of 150 L ha-1. The visual phytotoxicity assessments were performed at 7, 14, and 21 days after application (DAA). The visual grades followed a percentage scale, where 0 (zero) corresponds to no injury demonstrated by plants and 100 (one hundred) plant death. The results were analyzed statistically by analysis of variance, as selective herbicides that had no significant effect on the 5% level for the F test in relation to witnesses. In conditions where the experiments were performed it was concluded that the weed community identified in the crambe crop was composed of 21 species, verifying losses of up to 80% in the weeds along the development cycle of culture. The interference imposed by living with weeds reflected negatively on all parameters of development of crambe plants, revealing that the period previous to interference (PPI) tolerated after crambe plant emergence was 10 DAE and the total period of interference prevention (TPIP) of 40 DAE, resulting in a critical period of interference prevention (CPIP), 10 to 40 DAE. The herbicides applied were not selective the crambe crop