Avoid grazing during establishment. Graze first when in full flower. Earlier grazing or mowing may be necessary if weed competition has been severe or if a dry spell sets in.
It may also be necessary to graze undersown lucerne in winter/spring if the cereal crop is dense and early sown. This allows light to reach lucerne seedlings and promote development.
After harvest, a brief grazing (10 days, or less if the stocking rate is high) will help to disperse crop stubble. Grazing promotes new stems and makes use of grain lost from the header. Allow the lucerne to flower, then graze as outlined below.
Lucerne needs a period of spelling or recovery alternated with a period of grazing. The spelling period is the key to lucerne management. Recent research indicates that essential root energy reserves are at their lowest about 2–3 weeks after grazing and at their best at full flower. If cut or grazed at 10% flower, it takes about 35 days in the warmer months to replenish root reserves to the level prior to grazing. High temperatures and moisture stress can reduce accumulation of root reserves and shorten the period to reach flowering.
Continuous stocking can cause rapid decline in plant numbers. The heavier the stocking rate, the more rapid plant death, as constant removal of new shoots depletes root reserves, especially if growing conditions are unfavourable.
When grazing, aim to preserve basal buds and preferably some leaf. This allows rapid regrowth. As a general rule, remove stock when lucerne is 5 cm high.
When most of the leaf has been eaten and stems remain, livestock production can be reduced.
As far as is practicable, spell paddocks for five to six weeks (i.e. to about the ten per cent flowering stage) before returning stock to the paddock. The spelling period can be extended in winter. Grazing periods should be in the range of l–3 weeks.
Subdivide large paddocks. The degree of subdivision needed will vary according to the production targets, the required life of the lucerne stand, the growing conditions, the class of stock and the likely availability of other feed and the needs of other enterprises (e.g. cropping) on the property. Subdivision is expensive and rotational grazing requires extra management. The need for subdivision is greatest where maximum production is required, where stocking rates are high, and where rainfall is low or erratic.
Inflexible rotations have a range of problems. Be prepared to adapt your system to fit your enterprise and lucerne growing conditions.
Under dry conditions for example, lucerne can drop leaf. If stock are available, the paddocks are best grazed before leaf is lost, rather than wasting feed.
Stock may have to be moved to prevent a weight loss or to lessen adverse effects on reproduction. When grazing two classes of stock with different feed requirements (for example, weaners and dry ewes), give the class with the higher requirement (the weaners) access to the paddock until the bulk of the leaf has been eaten; then move them to the next paddock and put the dry ewes into the partly grazed paddock. Similarly, graze cattle before wethers.
Rotational grazing of lambing flocks can lead to mismothering and reduced lamb survival. If lambing must occur on lucerne, spread the flock over as large an area as possible to minimise damage to the lucerne.
When the rotation is relaxed in this way, it can be difficult to return to the rotation, as the pattern of feed supply has been disrupted.
Grazing lucerne during winter can decrease spring and summer production.
Excess production during the warmer months can be conserved as hay and fed back over winter.
When spelling paddocks during the winter, sub clover pastures or oats can effectively fill the winter feed gap.
Optimum stocking rates will vary with climate, enterprise, management and attitude to risk. Stocking rates that have been carried successfully under rigid rotational systems in trials have ranged from l2.5 wethers per hectare at Trangie on the plains, through l5 dry sheep per hectare on the slopes at Wagga and Tamworth, to 20 breeding Merino ewes per hectare at Canberra on the tablelands. These rates should be regarded as maximum potential rates and may involve feeding back excess production (hay). Rates will not be realised where lucerne management is less than ideal for the conditions.
Where long-term persistence is not essential, (e.g. up to 4 years) a more relaxed system, but using the same principles will often suffice.
On the slopes for example, with low stocking rates, and where other species are sown with the lucerne, good production and adequate persistence have been achieved using rest periods of at least five weeks and grazing periods of up to three weeks.
The full benefits of a rigid rotation (i.e. high production, persistence, nitrogen input, weed control etc.) may not be achieved. These systems are more successful with cattle than sheep, and where growing conditions are favourable.
Use a variety well adapted to the area and resistant to the major pests and diseases. Varieties of all dormancy groups will usually survive 3–4 years given reasonable management. If the pasture may be required for a longer period, semi dormant and some selected proven winter active varieties have demonstrated better persistence over highly winter active varieties.
If spelling is not routine, aim to spell as often as the system will allow, especially if it can be timed to reduce the effects of stress periods.
The following management practices may improve productivity and persistence:
Persistence will generally be better where cattle are grazed in preference to sheep and where stocking pressure is low to moderate as opposed to high.
Note: Grazing management should also consider the requirements for livestock health, especially in relation to bloat, redgut and infertility etc.
More details should be obtained from NSW Agriculture livestock and veterinary officers. Further information - Lucerne for Pasture & Fodder Agfact P2.5.25.