Lucerne Seed Production In South Australia
Lucerne (Medicago sativa) is a perennial legume pasture that fixes nitrogen and has deep-rooted capacity (>two meters in length in favourable soils) found in mixed farming systems. An established stand can assist in addressing rising water tables and salinity.
There is a lot of lucerne grown for grazing and hay production, however, seed production is quite concentrated with about 83% in the south east of South Australia, specifically around Keith, Tintinara and Bordertown.
Lucerne seed cycle/ pollination
Lucerne is a summer dominant plant where production occurs quite quickly from vegetative, flowering, budding to seed set over around four months. Pollination is key in seed production and getting the optimal stress level (OSL), where the plant “trips” easiest occurs from water stress. However, this can be quite difficult to achieve but with improved technology, i.e. moisture probes assist growers in obtaining that OSL. If the plant gets too stressed pollination can stop and “stripping” of flowers can occur, where the flower is aborted and that area on the stem can no longer achieve a viable bud. Honeybees are the main lucerne pollinator in Australia. The introduction of bees into the crop assists native bees and other pollinators in ‘tripping’ flowers to allow the crop to proceed from flowering to bud formation.
Most of lucerne seed produced in Australia is either certified seed under protocols: OECD (Organisation for Economic Cooperation and Development), AOSCA (Association of Official Seed Certifying Agencies); or uncertified/out of certification. Seed must be bought by OECD to be eligible to be certified and varieties are decided by contractual and current market demand.
Similarly, in broadacre cropping, seed lucerne has similar problems in terms of insect pests which in peak season are monitored regularly to reduce pest impact on yield. Heliothis (H. punctiger) grubs and mirids can be a problem in early foliage up until pod formation but are biggest problem at flowering, with consequently damaged flowers not setting seed. Seed wasp is another pest with crops at most risk at pod formation where adults lay eggs into developing seed, resulting in damaged or half formed seed and therefore destroying it. Uncommonly, aphids can become a problem but rarely are they solely sprayed for. Once populations reach threshold which generally occurs between 10-14 days depending on the season an insecticide is recommended.
Lucerne requires a desiccation at approximately 90% black/brown pod, before harvesting to reduce the moisture, even up the uniformity and percentage of black/brown pod. Within 5-10 days of desiccation harvest goes ahead with about 14% seed moisture. Seed must be cleaned before it is sold to produce “cleaned seed weight” which is what the grower gets paid on compared to straight off the header.
Article produced by - Clare Svilans, Western AG Kaniva