Making the most of clover

Making the most of clover

Maintaining a level of white clover in swards that will have a significant impact on both the quality of grazing and nitrogen fixation is a sensible target for all grazing systems. If clover averages around 30% of the sward then it should produce over 100kgN/ha/yr; about £90 worth, and with no spreading cost!

Through the summer white clover will tend to have greater nutritional quality than ryegrass, with D values around 80 and proteins above 25%. Research has shown dry matter intakes increase with clover swards as it requires less chewing and less rumination.

Higher intake and increased quality means more milk; research from both the UK and New Zealand has recorded an extra litre per cow/day where there is a significant clover component in the sward.

Ideally the cover content should peak in late summer at around 50% of the sward dry matter, dropping to nearer 20% in spring and autumn. The greatest problem in most grazing systems is getting the balance of white clover right. Too often clover can start to dominate a sward, reducing yields and ultimately leading to open and weedy leys, particularly in late season.

This can often be triggered by surface soil compaction. White clover has the capacity to move away from the severely compacted areas of a hoof print, to re-root its stolons in a more favourable location. Ryegrass can't relocate so has to struggle with poor rooting conditions. It is possible to reduce the clover content in the sward either by physical damage, such as raking - or even slurry injection which will cut the stolons into smaller lengths.

Conversely many can struggle to keep white clover in the sward at all. Stocking pressures, high levels of nitrogen and strong covers, particularly in early season, will all put clover under pressure, as of course will a decent dock control programme. Clover is particularly sensitive to poor soil chemistry, keeping pH levels between 6 and 6.5 and phosphate indexes at 2 is crucial to its survival.

Often below par performance of clover can be due to poor variety selection. In a rotational grazing system a medium to large leaved white clover will tend to fair well, but can easily disappear if there are over wintered sheep. Using a clover blend that includes a mix of medium and smaller leaved varieties will normally give a better chance of success. In a silage system the large and very large leaved varieties such as Aran, Alice and Barblanca will be the best choice, but beware taking very late silage cuts in late September/October as this can seriously shorten the lifespan of the clover.

Strategies to build clover content this summer

Hold off on nitrogen inputs (either slurry or bag) to slow grass growth - slower growth will extend the grazing rotation, giving clover a chance to grow stolons and spread. Ideally 28 days+ before grazing, but if covers go above 3000kgDM get in and graze.

Introduce new seed - oversowing can be very effective but success relies on having enough soil/seed contact when seed is introduced and on managing swards after sowing to prevent seedlings being outcompeted. Several passes with grassland harrows is a relatively quick and cheap way to generate a tilth in a ley - but is less successful in tight swards where a drill can be far more effective. 

Seriously consider slug pellets to protect seedlings, apply no nitrogen for the remainder of the summer and don't let covers creep above 2500kgDM or seedlings can be shaded out.

Managing the sward to protect the young clover plants has to continue to a certain degree right through the winter and into next spring. Avoid grazing in wet conditions when treading can damage the plants and make sure they are grazed in early season before covers build too high.