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Regulating the content of white clover in mixed swards using grass‐suppressing herbicides
Author(s) -
HAGGAR R. J.,
BASTIAN C. J.
Publication year - 1980
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1980.tb01502.x
Subject(s) - legume , agronomy , growing season , paraquat , stolon , litter , dry matter , zoology , biology , biochemistry
A preliminary investigation evaluated six grass‐suppressing herbicides applied on two occasions in late winter to a predominantly ryegrass ley containing only 15% ground cover of white clover. Substantial increases in clover growth, estimated visually, and flower head numbers per unit area were recorded in the first summer after treatment with 2·8 kg ha ‐1 carbetamide, 0·8 kg ha ‐1 propyzamide and 0·6 kg ha ‐1 paraquat. To achieve these increases, visual estimates suggested that spring growth of grass was reduced by 40–80%. However, grass growth recovered fully by mid‐summer on the majority of the treatments. The following year five of the herbicides were compared in a field experiment. Dry matter (DM) and nitrogen (N) assessments of the grass and legume components were made at three harvests in the first growing season and a single harvest in the second year. Carbetamide, paraquat and, especially, propyzamide increased the proportion of clover in the DM (to 89% in the case of 1·2 kg ha ‐1 propyzamide); in general, using herbicides to raise clover contents above 20% lead to reductions in spring grass growth of about 70%. However, such reduction was offset by subsequent increased growth so that total annual yields were largely unaffected. The increased legume content resulted in an increased N concentration in both grass and legume components, measured in the second summer. At this time, the greatest increase in total N yield (up to 35%) was recorded from 0·6 kg ha ‐1 propyzamide. Potential uses to achieve legume dominance by grass‐suppression are suggested and the needs for further research are outlined.