The main factor in prolonging the life of a red clover sward is the initial plant population. For a specialist red clover sward the aim is to have a red clover population of 200 red clover plants/sq/metre in the October of the sowing year. This should be achieved by sowing a least 8-10kg per ha of red clover seeds.
Plants can be lost by diseases such as clover rot (Sclerotinia trifoliorum) and pest such as stem eelworm (Ditylenchus dipsaci). Clover rot usually appears in the autumn, encouraged by wet weather, and causes rotting of the leaves, with patches of black rotting foliage appearing over winter. In north Britain and Scotland Clover rot is less of a problem.
Stem eelworm invades the plant and multiplies at the base of the clover stems, causing swelling and eventually killing the plant. In the field this shows as patches which increase in size, eventually merging to cover the whole field. It is because of these pathogens, it is advisable to a a break from red clover for at least five to eight years. The longer period if stem eelworm was present.
When selecting a red clover variety, look for good disease resistance and proven persistence. Current varieties have been bred for better persistence and, with proper management, you can expect two to three good harvest years after the year of establishment.
Another factor affecting red clover loss is the physical damage caused by machines and grazing cattle, which then leads to secondary infection of the root and crown by fungal infection. This damage can be minimised by reducing machinery traffic and not cutting below the top of the growing crown. Cutting height should be no lower than 7-8cm and aftermaths should not be grazed lower than 4-6cm in autumn and early winter.
It is best to delay autumn grazing until growth has stopped. If grazing is earlier it affects the following year’s crop yield and especially the first cut yield.
As for soil fertility aim for a pH of 6.0 (and above) and soil indices for P and K of 2 (and above).
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