Kvickrotens reaktion på klippning och konkurrens i rajgräs- och vitklöverbestånd

Abstract: Couch grass (Elymus repens (L.) Gould) is a severe weed in Sweden, and since both the use of herbicides and cultivation should be decreased, it will become increasingly problematic to control couch. The present work is meant to, by literature studies and an experiment, give some answers to the question if cutting and competition can depress the growth of couch. The experiment was carried out in the growing season 2001 at Ultuna, Uppsala, in plastic boxes. The design was three-factorial randomised complete blocks. The factors were plant combination, nitrogen level and cutting strategy. The plant combinations were couch, couch + ryegrass (Lolium perenne L.), couch + white clover (Trifolium repens L.). Nitrogen levels were 64 and 193 kg N/ha. Cutting carried out at hights of 4 cm above ground, 12 cm above ground and no cutting. After the plants in all boxes had been cut at 8 cm 10 weeks after sowing, cuttings were made twice at 4 and 12 cm respectively, 14 and 17 weeks after sowing. All cut material was sorted and measured by weight and at the end of the experiment, 21 weeks after sowing and planting, all rhizomes were measured by weight. The amount of rhizomes produced when couch growed without competition and with low cutting was 47% of the amount without cutting. In competition with ryegrass and white clover the amount with low cutting was 72 and 55%, respectively, of the amount without cutting. In competition with ryegrass without cutting, the amount of rhizomes was 20% of the amount without competition. In competition with white clover the amount was 46% of the amount without competition. The total regrowth after the first cutting of couch above ground with low cutting and in competition with ryegrass and white clover was 91 and 87%, respectively, of the total regrowth without cutting. The regrowth of ryegrass and white clover was 85 and 64%, respectively, of the regrowth without cutting. The proportion between couch growth above and below ground differed at different situations of competition and cutting. Uncut couch with no competition showed to have a larger part below ground than other combinations. In competition with ryegrass or white clover, the part below ground was lower than without competition. Where cutting was carried out, the part of couch biomass below ground was smaller than without cutting. The proportion between couch growth above and below ground was lower at high nitrogen level. The difference between nitrogen levels was smaller in competition with ryegrass and still smaller in competition with white clover. The most important conclusions of the project is that cutting and competition depress the below ground growth of couch. Three cuttings at the 4-cm level halved the amount of rhizomes produced without competition. Competition from ryegrass reduced the amount rhizomes to 20% of the amount without competition. Agrovoc: Elymus repens, Lolium perenne, Trifolium repens, plant competition, cutting, weed control