Also known as alfalfa, Medicago sativa is an upright legume grown for grazing or haymaking. It is commonly used in dryland pastures, as its taproots can extract water from deep in the soil, making it more tolerant to drought than other pasture plants.
Lucerne is best grown on fertile, well-drained soils. It does not reseed easily, but can survive for about eight years when managed well. It is best left to flower during the first summer, as this allows carbohydrate reserves to build up for regrowth and persistence. Lucerne should then be rotationally grazed or cut every four to six weeks.
Types of lucerne are now available with resistance to bacterial wilt, Phytophthora root rot, stem nematodes (worms) and aphids. Before sowing, the seed must be inoculated with the bacteria that enables it to fix nitrogen.
Subterranean clover (Trifolium subterraneum) is an annual that germinates in autumn and reseeds in late winter and spring. After flowering, it stops growing and pushes its seed heads into the soil, surviving over summer as dormant seeds, which germinate in autumn.
Subterrranean clover is useful in east coast regions on soils too dry for white clover, where it can contribute more than 20% of winter pasture. It needs minimal grazing during spring flowering so it can reseed. Types that don’t flower until late spring appear best suited to New Zealand, as they stay in a vegetative state for longer before going to seed.
Lotus major (Lotus uliginosus) a perennial legume, grows well in wet, acidic, infertile soils where grazing pressure is light. Lotus has also been widely sown in agroforestry situations (where forestry and agriculture are combined) because it tolerates shade and needle litter better than clovers.
Lotus spreads by rhizome growth and can grow up steep banks. Lotus contains chemicals (condensed tannins) that prevent it causing bloat in cows – as may occur with some clovers – and that also reduce the effects of internal parasites in sheep and cattle. Resistant to some serious pasture pests, such as grass grub and porina, it is valuable for extensive farms where intensive chemical pesticides are not used.
Lotus normally takes a year to become established, though it is faster when soil temperatures are over 15°C. Light grazing is essential, as regrowth comes from lateral buds on the shoot stubble left behind after grazing. Grazing closer than 7–10 centimetres above the soil will slow down regrowth.