| Summary: | <p>This thesis contains a literature review of <em>Holcus lanatus</em> and records studies on both the growth and spread of the species and the response of it and of <em>Lolium perenne</em> to several management and edaphic factors. <em>Holcus lanatus</em> is an adaptable, competitive species with ecotypes growing in a wide range of environments. It is valuable on hill land, acid, low nutrient soils and to prevent erosion. Beef cattle grazing it have made greater liveweight gains than on <em>L. perenne</em>.</p> <p>Experiments used plants growing in pots and small field plots. A growth study of spaced <em>H. lanatus</em> plants showed they can produce up to 240,000 seeds, most of which germinated shortly after being shed onto moist soil. Seedlings established poorly in a closed sward. Spaced plants produced runners in autumn whose plantlets established better when plants were cut regularly in spring. <em>Holcus lanatus</em> plants needed vernalization in order to flower. This was enhanced by and to a small extent replaced by short days. When <em>H. lanatus</em> plants in bud were cut, useful summer vegetative regrowth resulted. The New Zealand cultivar Massey Basyn was more productive than Oxfordshire <em>H. lanatus</em> in a pot trial.</p> <p><em>Holcus lanatus</em> dominated a mixture with <em>L. perenne</em> in a glasshouse experiment, especially under high or infrequent cutting, but it was not so dominant in a field experiment. Cattle treading damaged <em>H. lanatus</em> more than it did <em>L. perenne</em>. <em>Holcus lanatus</em> responded to a high water table by producing adventitious and surface roots. Propyzamide at 2.24 and linuron at 1.12 kg a.i./ha in early summer and asulam at 1.12 or 2.24 kg a.i./ha in early September gave good control of established <em>H. lanatus</em> in <em>L. perenne</em> in preliminary trials. The agricultural significance of these results is discussed.</p>
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