THE INFLUENCE OF NITROGEN ON A PASTURE TREATED WITH DALAPON FOR THE SELECTIVE SUPPRESSION OF AGROSTIS STOLONIFERA AND HOLCUS LANATUS IN PERENNIAL RYEGRASS

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Abstract
This experiment confirmed earlier experience that dalapon applied at doses between 2 and 5 lb a.e./ac (2.242 and 5.605 kg/ha) in early July can suppress Agrostis stolonifera and Holcus lanatus growing in perennial ryegrass pasture. The long‐term control of Poa trivialis was not achieved, partly because of a widespread emergence of seedlings shortly after spraying. Dalapon caused a reduction in the total herbage harvested diuring the 14 weeks after spraying, but the yield subsequently increased above that of the unsprayed sward. A substantial increase in the yield of ryegrass occurred. Nitrogen caused a general increase in the yield of herbage and the proportion of ryegrass, but neither N nor dalapon used alone was as efficient in improving yield as their use in combination. Treatment with dalapon resulted in an increase in the number of ryegrass tillers per unit area in the April following spraying, as well as in the yield and ground cover of this species.
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