Lucerne
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Lucerne is a perennial legume with a deep taproot, allowing it to tolerate moisture stress more than most pasture species. In NZ, most cultivars are winter dormant, but some newer ones grow earlier in spring and later in autumn. Lucerne's warm season growth outperforms ryegrass, making it a valuable addition to farm systems. It yields up to 21 t DM/ha/year under irrigation and often becomes high-quality hay or a protein supplement for dairy cows. Lucerne lasts 5-8 years, with proper management. When growing it, choose well-drained paddocks, control weeds, maintain high soil fertility, and manage initial grazing. Select cultivars resistant to local pests and diseases.
Lucerne is an erect growing, perennial legume. It has a deep taproot that allows it to extract water from deeper soil layers and consequently has greater tolerance to moisture stress than most pasture species.
Most cultivars in NZ are winter dormant. Recently more winter active cultivars have been sold, however, while they can start growing a week or two earlier into spring and later into autumn, in general, their persistence has been poorer than winter dormant types.
Lucerne in farm systems
Cool season growth is significantly less than ryegrass, but warm season growth is significantly better, as is its feed quality through late spring and summer. Because of this Lucerne can be used to complement other pastures within a farm system.
Under irrigation, pure swards of Lucerne can grow 21 t DM/ha/year, although yields are most often less because the species is sown in summer-dry areas where growth is limited by rainfall.
Lucerne is also often made into high-quality hay, to be used in dry summer and cold winter regions. It is increasingly ensiled to produce a protein-rich supplement for dairy cows.
Lucerne persistence
The species does not reseed itself easily and can persist from 5-8 years or more, depending on grazing management and climate.
In general, a period of prolonged growth and potential flowering (6-8 weeks or up to 50% of stems with flowers) during February/March each year encourages the build-up of root reserves for the following spring and improves stand persistence.
Flat weeds, such as dandelions and annual grasses, tend to invade older, thinning stands and need to be controlled to help stands persist.
Growing Lucerne
Lucerne establishes best when spring-sown, using inoculated seed at 3-7 kg/ha, although rates used can be as high as 8-10 kg/ha.
Paddock selection
Select well-drained paddocks, soils that waterlog at any time in the year create conditions for fungal diseases, and avoid paddocks with more than 4 ppm aluminium in the subsoil. Soil test 6 months prior to sowing as pH may need to be addressed.
Weed control
Control perennial weeds prior to planting either through spraying or crop rotations. Herbicides at sowing can be necessary to control fast establishing annual weeds. Inoculate the seed with rhizobia type AL just before sowing.
Fertility
For optimum production, Lucerne requires high soil fertility and a pH greater than 6.0. This encourages early growth and increases stand tolerance to insects and disease. It can take 6 months from the time of lime application to achieve the pH drop required.
Grazing/harvesting
Newly sown Lucerne tends to develop roots more than shoots so the longer it is left before the first grazing the greater the root development. This allows the plant to build up carbohydrate reserves for spring re-growth and improved stand persistence. The first grazing/harvesting should remove only the top of the plant and leave the crowns untouched.
Lucerne pests and diseases
It is best to sow cultivars with resistance to bacterial wilt, root rot, stem nematode, and aphids as these pests are present in NZ and can reduce performance and persistence.