DISTRIBUTION AND SURVIVAL OF QUACKGRASS (ELYTRIGIA REPENS) RHIZOME BUDS

An experiment was established at three sites to determine the longevit y and distribution of rhizome buds of two quackgrass biotypes in the s oil profile under two tillage systems (no-till or fall-plow). The expe riments were established in May 1987 at sites initially free of quackg rass. Rhizome segments with three nodes were planted 2 to 5 cm deep to give an initial density of 21 buds m(-2), Production of new buds was prevented in subsequent years. Rhizome bud populations were sampled ev ery 6 mo between October 1987 and October 1989. Buds were produced unt il snow cover, indicating the need to control quackgrass until late fa ll to prevent a bud population increase. Under no-till conditions, 94% of quackgrass buds occurred in the top 10 cm of soil while 68 and 19% were found below 10 and 20 cm, respectively, in the fall-plow treatme nts. A control program against quackgrass should aim at keeping the ma jority of rhizomes in the top 10 cm in order to facilitate control by having most shoots emerging at the same time. There was no statistical ly significant difference in bud longevity between biotypes, sites, an d tillage systems. Viability of the rhizome buds declined rapidly duri ng the first year. In most cases it took 2 yr for the bud populations to reach extinction although 0.6% of buds of one biotype survived as l ong as 30 mo in one of the three sites. Therefore, a minimum of 2 yr o f total control would be required to eradicate quackgrass from most lo cations.