It is important to understand the growth pattern of lucerne to know how it fits into the annual feed budget of your farm. Below is a diagram comparing the growth rates of winter dormant and winter active lucerne against two grasses and an annual pasture legume.
All lucerne varieties provide a broad distribution of growth, and summer feed with or without irrigation (however the diagram is yield potential so it assumes irrigation). This enables producers to finish off prime lambs, maintain liveweight of breeders over summer months, and improve sheep fleece staple strength. The graph also shows that whilst lucerne differs in its level of winter production, summer activity is the same in all lucerne varieties.
Winter activity is measured using regrowth height in winter to give a rating between 1 and 11.
The picture (right) was taken at Dooki Victoria, in August 2004. What is remarkable is that it was only 4 weeks after the opening break to the season, following the driest spring to autumn on record. The variety, SARDI Ten, is a very highly winter active class ‘10’ lucerne. Because lucerne is a perennial and over-summers with a large crown, it responds much quicker to opening rains than sub clover or annual medics germinating from seed. This can provide valuable early feed, filling the feed gap. It can also mean that stock can be taken from the annual pastures and put onto the lucerne, allowing the annual pastures to get away much quicker.
The winter production of lucerne is of varying degrees of importance depending on your farming system. In the example above, a cropping rotation at Dooki, SARDI Ten was chosen because the farmer required the maximum level of winter production achievable in a lucerne stand that was to live for 3–5 years. Dooki has a winter dominant annual rainfall of ~350mm; so the most efficient use of the rainfall is made by choosing a highly winter active lucerne variety. Contributing to the decision to grow SARDI Ten was the fact that it was being grown as a monoculture (so that grass weeds can be cleaned up outside of the cereal phase) and winter active grasses were not contributing to total winter production of the pasture.
SARDI Seven was chosen for this paddock near Cootamundra, southern NSW as multipurpose long-term lucerne. The paddock is grazed with ‘flexible grazing management’ that involves 4–8 weeks of grazing followed by a similar period of rest. The recovery period is very important because it allows the lucerne plant to recharge the energy level in its root system. The paddock is too large to graze down in a week or two with the number of sheep available, but the flexibility and improved grazing tolerance of SARDI Seven makes it easy to fit into the grazing management of nearby paddocks. SARDI Seven also has a high level of disease and aphid resistance, so it is reliable in areas with a high disease pressure developed from a long history of growing lucerne.
This farm at Balmoral, south-western Victoria is on a heavy clay-gravel soil that receives some mild waterlogging in winter each year. The paddock is used for grazing throughout the year, and volunteer grasses and sub-clover are utilised to help fill the winter feed-gap. The annual pasture is cleaned up each spring, and the lucerne uses stored soil moisture to provide feed throughout the
summer months. A semi-winter active lucerne is grown because it can handle to cold, wet conditions in winter, and the set stocking that is used during the winter months to graze what is predominantly annual grasses and clover. The lucerne is given several rest periods from late spring
to autumn and is used to finish off prime lambs for market. The photograph shows a highly winter active plot that has died out (the lucerne paddock is now 9 years old), whilst the SARDI Five parent lines look like they will keep going for another 9 years.
SARDI Five is also an excellent variety for hay production. It was selected specifically for fine stems and an attractive dark green colour. SARDI Five replaces Prime in PL55 that are no longer available from 2006.
• Strict rotational management
– ½ day grazing, 3–7 weeks recovery
– 1–2 weeks grazing, 3–7 weeks recovery
• Flexible grazing management
– 1 month grazing, wait for regrowth
– 2 months grazing, six weeks recovery (not for highly winter active lucerne).
• Continuous grazing
– Not currently recommended
Strict rotational grazing is the most production option, but requires intensive management and infrastructure, common to dairy farms. Flexible grazing management is required on most broad-acre farms, where it may take 1–2 months to graze a 50 ha paddock. This grazing management makes it easier for a farmer to incorporate one or two lucerne paddocks into the whole farm grazing management.
The list of traits for improvement in a lucerne-breeding program is extensive. Selection for resistance to insect pests and diseases occurs in the SARDI glasshouses at the Waite Institute. World-class facilities allow us to create the perfect conditions for the insect pests and diseases, so we can evaluate our new lines under the toughest conditions.
The only way to breed for adaptation to the Australian environment and the farming systems that land managers use is to test the performance of our lines across a large number of trials in different regions of Australia. Locations can be seen on map of SARDI lucerne field trial locations.
The SARDI lucerne-breeding program has been breeding lucerne with improved tolerance to grazing since the late 1970s through a series of continuous grazing experiments. In recent years, the Grains Research Development Corporation (GRDC) funded project (DAS347) has had grazing trials at Roseworthy (1998–2002), Turretfield (2003–ongoing) in South Australia and Katanning in Western Australia (2003–ongoing).
The trials are established with conventional rotational grazing for 6–9 months and then continuously grazed with sheep for one year. A recovery period is allowed to assess regrowth vigour (an indication of the level of energy reserves left in each plant) and the persistence of each line before continuous grazing is initiated again for another year.
After two years of continuous grazing plants are selected for their ability to survive and regrow. This length of continuous grazing is not recommended for graziers but is useful to us as plant breeders because we want to kill as many plants with grazing as we can in a short amount of time. The extreme grazing pressure allows us to select tolerant plants in three years, which would take 7-10 years through conventional management.
We also compare the persistence of the continuously grazed lucerne lines with a second trial containing the same entries that has been managed with strict rotational grazing. The ratio of rotational grazing/ continuously grazing is used to give us a figure of grazing tolerance for each cultivar.
Pictures from our grazing tolerance experiment at Turretfield