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In Japan, Sakanoue et al. (1995) used mixed grazing by goats and cows on a permanent pasture, and after 3 years reported effective control of R. obtusifolius by goats through a process of defoliation, suppression of propagation, and population decrease. SAC (1986) recommend, as a preventive measure, maintaining a dense, well-managed grassland sward, which can minimise infestation since seedlings of R. obtusifolius are poor competitors and seed germination is inhibited in the presence of a dense leaf canopy. The choice of high-tillering and persistent grasses further reduces competition from R. obtusifolius. Moreover, excessive treading and poaching in pastures should be avoided.
In a study carried out in Austria, Poetsch and Krautzer (2002) obtained a significant reduction of seed germination within three weeks of composting of farmyard manure, and they state that it can therefore be seen as an efficient tool to interrupt the R. obtusifolius seed cycle on grassland farms. Storage in silage significantly reduces the viability of mature seeds (Masuda et al., 1984). Humphreys et al. (1997) report that after being subjected to 100 days in silage, seeds were non-viable. Humphreys et al. (1999) discuss the possibility of limiting the abundance of R. obtusifolius in grassland by maintaining moderate soil K concentration. Balanced fertilizer use, especially N and K, may prevent its spread (SAC, 1986).
Hand-pulling is not normally practicable and usually does not result in the complete removal of the root (SAC, 1986). Plants which have been pulled out should be burned to prevent seed dispersal. Dierauer and Thomas (1994) state that the only effective method is the removal of the entire root or cutting the root to at least 10 cm below ground. In grassland, the cutting frequency of the sward affects abundance of the weed. Courtney (1985), Niggli et al. (1993) and Hopkins and Johnson (2002) showed that under frequent defoliation (every 3-4 weeks) dock plants were less competitive and their herbage production was considerably lower than when cut every 6-7 weeks. The height of cut had no consistent effect on R. obtusifolius yields. Cavers and Harper (1964) suggest that a series of rotary cultivations may be effective for the elimination of the weed, however, the timing of land management practices has to be taken into account, as cultivation in late summer may promote the spread of the weed by shortening the length of time between germination and seed production (Weaver and Cavers, 1979). Ploughing followed by fallowing and repeated cultivation during spring and early summer is recommended by the SAC (1986) to exhaust the root reserves and provide control of young seedlings.
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
R. obtusifolius is considered to be one of the most troublesome weeds in intensively managed permanent grassland (Holm et al., 1977; Jeangros and Nösberger, 1990; Niggli et al., 1993). It reduces production from grassland by reducing grass yields. Oswald and Haggar (1983) showed that densities of 5-10 plants/m² resulted in a reduction in total grass herbage of up to 30%. In infrequently cut swards the effect on grass yield is directly related to the percentage ground cover, with an approximately 1% decline in grass DM yield for each per cent ground cover of the weed (Courtney, 1985). Courtney and Johnston (1978) report that, on average, both the palatability and the digestibility are about 20% less for R. obtusifolius than for grasses. Therefore its feeding value for the grazing animal is only about 65% that of grasses. Digestibility of woody stems and inflorescences is only about 50% that of grass; intake by both cattle and sheep falls significantly after flowering (McGhie et al., 1983; Derrick et al., 1993).