Abstract
The effect of soil application of the fungicide PCNB (quintozen, pentachloronitrobenzene) on weed growth was evaluated as follows.
1. In the transplanter experiments, it was shown that the application of PCNB (20% dust formulation) at the rate of 15kg/10a resulted in a considerable reduction in the fresh weight of the following 6 species of weeds: Chenopodium album, Polygonum longisetum, Portulaca oleracea, Amaranthus lividus, Stellaria media and Digitaria ciliaris.
2. In field experiments the following 11 species of weeds, D. ciliaris, Cardamine flexuosa, Eclipta prostrata, Cyperus microiria, P. longisetum, S. media, Alopecurus aequalis var. amurensis, Poa annua, Echinochloa crus-galli var. crus-galli, Echinochloa oryzicola and Oenanthe javanica were found in untreated plots, plots with PCNB applied at the rate of 30 and 60kg/10a respectively. In the plot where PCNB had been applied at the rate of 30kg/10a and 60kg/10a, the fresh weight of weeds decreased by 67% and 36% respectively.
3. Although experiments conducted to evaluate the effect of the application of PCNB, PCA, PCTA and HCB on germination of seeds of weeds failed to reveal any difference in the germination rate among these chemicals, there was a high percentage of growth inhibitory activity in the plot where PCNB had been applied.
