Lucerne leaves grow from the tip of the stem. When these growing points are removed during cutting or grazing, growth of that stem stops and subsequent crop growth is solely from new stems growing from the crown (base of plant). These shoots/new stems must be allowed enough time to grow before further grazing/cutting, so that they return carbohydrates to the roots, which drive the subsequent growth of the next wave of shoots. Cutting or grazing too early will reduce regrowth and if repeated, can allow weeds a competitive advantage and weaken the lucerne plant.
The ideal length of time between grazings ranges between 35-42 days, depending on the time of year. Leaving lucerne too long between cuttings will reduce the digestibility of the crop. Where stock is to be continually rotated, at least six paddocks/breaks are needed. When starting a rotation, the first paddock will need to be grazed at a shorter height than ideal (for a short duration) so that the last paddock in the rotation is not too rank.
It is not necessary to allow lucerne to flower before each cutting/grazing. The only exceptions to this are the first grazing after establishment and once every autumn. A more useful decision tool is to ensure that basal shoots have formed on the crown of the plant.
Grazing duration of less than 7-10 days is advised as this is the time it takes for new growth to appear; so any longer than that and the stock may graze the new growth. Set stocking is never advisable.
The key is to start grazing the first paddock when the crop is 15-20 cm tall, which will be before any new shoots are visible on the crown. If cutting the crop, the crop should be cut late morning to mid afternoon once the dew has lifted, as this is the time when the plant has the most sugars. However, during very hot and dry weather, it may be best to cut early in the morning to reduce loss of leaf at mowing and then also rake early in the morning. The first fertiliser application for the season should be applied after the first cut/graze.
Growth is increasing at this time of year with increased daylight and temperatures meaning grazing frequencies can drop to 30 days. The best indicator for when to graze/cut is the initiation of new shoots at the base of the lucerne plant (“crown”). As soon as these are seen, the crop should be harvested, as these new shoots are important for fast recovery. This is similar, but more precise, than the old rule of grazing/cutting when about 10% of the paddock is flowering.
Management of lucerne at this time has a direct influence on the following season’s production. Crops should be spelled until 50% of the crop is flowering. This will encourage significant build up of root reserves for winter and leads to increased growth and plant survival in the following spring.
A final clean up of the paddock should be done after the first frost, as lucerne stops growing at this time. The removal of the crop, particularly by grazing, will decrease the potential disease and aphid infestations and allow for more effective herbicide use in winter.
A herbicide should be applied to most stands from the second winter onwards, during winter whilst the crop is dormant. This is best done in early winter (e.g. June) shortly after the autumn spelled crop has been grazed off (all green material removed). Spraying must be done before late winter due to the chance that new shoots can be damaged by the herbicide, resulting in decreased spring production. Once grazed in late autumn, stock must be removed until the crop is ready for grazing in spring.