Maintaining productive pasture
Benefits of clover rich grass swards compared with all grass swards:
- Maintains high digestibility over longer period leading to improved intakes.
- Up to 10 percent higher liveweight gain in cattle, 20 perccent more from dairy cows and 25 percent higher liveweight gain in sheep.
- Enhances lean meat gain and milk protein content.
- Contains more minerals, in particular magnesium, thereby reducing the risk of animal health problems associated with mineral deficiency.
- Can result in substantial savings in fertiliser costs. A grass/clover sward containing 30-40 percent clover in the dry matter can yield as much as a grass sward receiving 200 KG of fertiliser nitrogen per hectare (six bags of 27 percent N per acre).
- Saves on energy usage thereby indirectly reducing environmental pollution.
- Evidence of reduced nitrogen loss to the environment.
Clover rich swards on beef/sheep farms
Clover based swards are particularly suitable for grazing on Northern Ireland beef/sheep farms. Currently these farms use relatively low rates of fertiliser nitrogen (on average approximately 120 KG nitrogen per hectare; 96 units per acre). At these low rates, switching part of the farm to productive clover-based swards can allow an increase in stock carrying capacity on the grazing areas, thereby releasing land either for a lower nitrogen input silage system or an alternative use. Sheep grazing in the same area as cattle (mixed grazing) improves pasture utilisation, and in particular, using sheep to graze pasture in early winter improves clover contribution. In addition, mixed grazing dilutes worm burdens and reduces the risk of bloat in cattle. Consequently mixed grazing should be adopted where possible.
Over the years research and development work has shown that clover has an invaluable contribution to make in improving margins on beef and sheep farms.
Over the years research and development work has shown that clover has an invaluable contribution to make in improving margins on beef and sheep farms.
Establishing clover
Choice of clover variety
White clovers are classified according to leaf size:- small, medium, large or very large.
- Small leaved varieties survive best under intensive sheep grazing as they have a creeping growth habit, but they can be expensive and some varieties can, at times be in short supply.
- Medium leaved varieties are generally tolerant of a wide range of conditions and should always be included in mixtures intended for all general grazing use. Menna tends to be more winter hardy than Grasslands Huia.
- Large leaved varieties are best suited to rotational grazing by cattle or sheep where some fertiliser nitrogen is applied and where silage cuts are frequently taken.
- Very large leaved varieties are high yielding but are least persistent under grazing and are best confined to hay or silage swards with only limited grazing use.
The best compromise is to use a mixture of clover varieties, half of which should be medium leaved and the remainder either small, medium or large leaved varieties depending on the intended sward use.
The following are more readily available recommended varieties in Northern Ireland.
| Small Leaved | Medium Leaved | Large Leaved | Very Large Leaved |
|---|---|---|---|
| Kent Wild White | Menna | Alice | Aran |
| Aberystwyth | Avoca | Milkanova | |
| Tara | Grasslands Huia | Sterling | |
| Gwenda | Aberhald | ||
| Grasslands Demand |
Choice of companion grass for clover
Intermediate heading perennial ryegrasses, particularly some tetraploid varieties, are the best companion grasses for clover but, select varieties with care.
- Select erect, less aggressive types such as Aberelan, Merbo and Portstewart, which develop a sward structure which will encourage the spread of clover.
- Avoid dense growing varieties such as Moy, Glen and Veritas as they are highly competitive and may restrict clover spread.
- Tetraploid varieties such as Bastion/Labrador, Rosalin/Fetione and Tivoli/Elgon may assist in maintaining an open sward which should help to promote a higher clover content.
Seeding methods
There are several ways of achieving clover-rich swards:
- Direct reseeding.
- Undersowing.
- Strip or slot seeding.
- Minimal cultivation.
Direct reseeding before the end of August is the most reliable method of establishing grass/clover swards. To ensure a good establishment of clover be generous with the clover seed and economise on the grass seed.
The best compromise is about 25 KG of perennial ryegrass with 4-5 KG of clover seed, sown at 29-30 KG per hectare. The seedbag should be firm and fine and should be rolled prior to sowing the grass/clover mixture. Undersowing can be useful for spring reseeds, using early maturing spring cereal varieties as the cover crop. Existing swards can be upgraded using specialist drills but the technique has given variable results under local conditions. Minimal cultivation represents an alternative to strip or slot seeding in that the technique does not involve ploughing.
Low cost methods of introducing clover
For successful clover establishment, by any method, there are some principles which must be adhered to:
- Correct Timing
Late summer (August) is best for seed germination and full plant development before winter.
- Good seed/soil contact
Seeds need to be placed into a shallow (1-2 cm) seedbed.
- Control grass competition
Existing grass sward must be checked before and after seed sowing otherwise young seedlings will not survive.
All the other basic principles for any reseeding operation must also be considered as part of the overall sward improvement, for example adequate drainage, pH, fertility, weed and pest control.
There are a range of methods available for placing seed into the sward such as discing/broadcasting, Moore Unidrill and the Vertikator.
Discing and Broadcasting
The first step is to reduce grass cover by grazing the sward tightly (4-5 cm; 1.5-2 inches) in late July. Alternatively follow in immediately after a silage cut taken mid July to late August. When soil conditions are dry, set the disc with minimum cut (coulters running straight) and add weight. Disc the field in several directions to open up slits in the ground. Mix 5 KG of recommended varieties of clover seed with 250 KG of 0:20:20 fertilser and broadcast.
Afterwards the ground should be rolled before rain to achieve good seed to soil contact, conserve moisture and ensure rapid germination. The cost of seed and fertiliser is approximately £60 per hectare (£24 per acre). This is 40 percent of the cost of these same inputs when used at normal rates in a conventional reseed.
The technique has worked well for introducing clover into an existing sward. It would not be recommended for the introduction of grass seed. Where pasture consists of weed grasses a direct reseed to grass/clover is recommended.
Hatzenbichler Vertikator - this uses a bank of 100 spring tines to tear the existing grass and loosen surface soil. Seed is distributed between the tines and incorporated into the disturbed surface.
Managing clover
- Early season - Set stocking with the use of buffer grazing to control grass.
- Mid season - Rotational grazing or light silage cut.
- Late season - Avoid poaching. Tight autumn/winter grazing (3-5 cm; 1-2 inches).
- Control weeds using clover safe herbicide
Overcoming problems
Poor growth early in season
Use slurry and limited early nitrogen to boost grass growth in spring.
Not enough clover in sward
- Preferably use less than 70 KG of nitrogen per hectare (two bags 27 percent N/acre) over the whole season. Using no nitrogen will significantly boost clover levels however a good distribution of clover must be present (one plant per 3-4 m2 ) before pursuing this option.
- Minimal cultivation techniques increase clover at low cost.
- Rest swards mid-season.
- Tight autumn/winter grazing.
Bloat
- Sheep selectively graze clover and are not prone to bloat. Grazing sheep ahead of cattle reduces the risk.
- Never allow hungry cattle to gorge themselves on clover-rich pasture.
- Always move cattle onto dry clover pasture, particularly if they are coming off grass.
- Feed roughage, such as straw or hay, before turning out and of necessary during grazing.
- Anti-foaming agents may be added to the water or feed, or used in free access blocks.
- Affected animals may be treated with anti-foaming agents. In severe cases remove animals from clover swards and seek veterinary advice.
Note: No cases of bloat have occured to date on clover development farms.
Clover Development Farms
There are six development beef/sheep farms operating across the province. These farms now have over 50 percent of their grazing areas managed successfully under a grass/clover system. The saving on fertilser, through the use of clover, has made a significant contribution to the gross margin on all farms.