论文部分内容阅读
The term rainfastness refers to the time needed between application and rainfall event to avoid significant reduction in efficacy.In order to evaluate the influence of drying time and rain quantity on rainfastness of natural pre-emergence herbicide from the leaf of Aglaia odorata Lour.(NHA) on emergence of large crabgrass (Digitaria adscendens) and horse purslane (Trianthema portulacastrum) was studies.In the first experiment, rainfall of 1, 10 and 20 mm events was simulated using a sprayer rain simulator after applied NHA at the rate of 20 kg ai/ha for 1 h.The results showed that, application of NHA at the rate of 20 kg ai/ha as surface soil pre-emergence herbicide inhibited emergence of D.adscendens and T.portulacastrum 69.8% and 23.1% compared with control (untreated).A heavy rain of 20 mm simulation after drying time of 1 h reduced efficacy of NHA, emergence inhibition percentage of both weed species decreased to 14.36% and 6.63% of control, respectively.At lower volume of rain (1 and 10 mm) showed no significant effect on NHA efficiency impact on emergence of both weeds.In the second experiment, drying time of 1, 3, 6 and 12 h before 20 mm of rainfall simulation was evaluated.Herbicidal effect of NHA on emergence of D.adscendens losses after 20ram rain reached about 18% of the initial deposit after a drying time of 12 h, and 13%, 26% and 43% after drying times of 6, 3 and 1 h, respectively.Our data show clearly that herbicidal potential of NHA is influenced by both rain volume and drying time.