BIOLOGICAL-CONTROL OF RUMEX-OBTUSIFOLIUS L BY GOAT GRAZING

Effect of goat grazing on the growth, propagation and survival of a do ck, Rumex obtusifolius L. was investigated during a period of 3 years in a permanent pasture divided into 2 parts. Three cows were grazed on one part (namely, cow-grazing plot) and 3 cows plus 4 goats were graz ed on the other part (mixed-grazing plot). In both plots, 3 belt trans ects were set up to determine the degree of defoliation, plant height, maximum leaf length and the number of bolting stalks of adult docks. Apart from the transects, typical adults were collected to determine t he dry weight of seeds in both plots in late July. Five permanent quad rats were set up to take a census of the seedlings of the dock. The ad ult docks were defoliated more severely up to August in the mixed-graz ing plot than in the cow-grazing plot. In the former plot, the leaf le ngth was shortened to 67%, the plant height was lowered to 26% and the number of bolting stalks was reduced to 41% of the respective ones in the latter plot in July. Moreover, the adults formed shorter bolting stalks in the mixed-grazing plot. This suppression of reproduction of the dock led to a decrease in the number of seedlings. In the mixed-gr azing plot, the seedlings emerged at a rate of 18% of that in the cow- grazing plot in the autumn of the first grazing year and 30% in the sp ring of the second year. There were few differences between the surviv orship curves of the dock in the two plots. A low percentage of seedli ngs survived during one year, although with a slightly higher rate in the mixed-grazing plot than in the cow-grazing plot. The established i ndividuals could set numerous seeds in the latter plots. It was conclu ded that goats controlled Rumex obtusifolius effectively through a pro cess of defoliation, suppression of the propagation and decline of the population of the dock. Mixed-grazing could afford both weed control and improvement of pasture production.