THE EFFECT OF JULY APPLICATIONS OF DALAPON ON THE GROWTH AND BOTANICAL COMPOSITION OF AN AGROSTIS/LOLIUM PASTURE

Summary. Dalapon–sodium at 3.3–7.5 Ib ac/a.e. was applied in early, mid– and late July 1964 to an Agrostis/Lolium pasture for selective control of the weed grasses Agrostis stolonifera, Poa trivialis and Holcus lanatus. These species were significantly more susceptible than Lolium perenne to dalapon at all doses regardless of the time of spraying. The most promising treatment was 33 lb/ac applied on 4th July, which increased the ground cover of L. perenne and substantially reduced Agrostis stolonifera and Poa trivialis. The total yield of herbage 12 weeks after spraying was only 50% of that from the unsprayed control, but the yield of Lolium perenne was not affected. When cut on 21st May and 5th August 1965, total yield was only slightly reduced and that of L. perenne was increased by 60–90%. The successful practical utilization of this selectivity is likely to depend largely on the spacing of the plants of L. perenne in the pasture. Simazine at 0.75 Ib/ac applied to half of each plot 3–4 weeks alter dalapon treatment had no lasting beneficial effect on the composition of the sward.