Ronald J Yates

There are currently two ways of establishing chenopod shrubs: sowing from seed using a niche seeder, or planting nursery-raised seedlings with a tree planter. Planting seedlings is the more reliable method, but is relatively expensive (in excess of $450 per hectare). On the other hand, direct seeding using the specialised “niche seeder” is much less expensive ($100-150 per hectare), but is also less reliable. This project aimed to investigate alternative methods of direct seeding chenopod shrubs for saltland and rangeland areas by developing a greater understanding of their seed biology and agronomic requirements. Our aspiration was that shrubs should be established using more conventional farm machinery. This bulletin reports on a combination of seed biology and agronomic research to develop reliable, low-cost direct seeding options for chenopod shrubs. Experiments into the impact of changing environmental conditions on seeds were studied in the laboratory, and field experiments were conducted to test the applicability of these insights in the field using conventional modified farm seeding machinery. As a result of this work, a successful direct seeding package using farm seeding equipment (modified for wide row spacings and depth control) was developed for Atriplex nummularia (old man saltbush), the most widely planted saltbush species across southern Australia. The nine key elements of the package are: 1. Select suitable paddocks for introduction of new shrubs 2. Prepare a weed-free seedbed using two knockdown herbicide applications (4-6 weeks and 1-2 weeks before seeding) and commence control of rabbits and kangaroos 3. Sow the best seed, by ensuring: a. Large fruits, with a high proportion of viable seeds, have been selected b. Seed is of subspecies nummularia (not subsp. spathulata) c. Fruits have been harvested within the previous six months and stored in a cool, dry environment d. Bracts are retained around the seeds 4. Sow into moisture in late winter - early spring (depending on district) a. If the area to be sown is waterlogged, defer sowing until later in spring b. If insufficient soil moisture, defer sowing until the following year 5. Use a sowing rate of ~10 fruits/m (if germination rate is 15%) to provide at least one plant for every 2 m of row; use higher rates for seed of lower germination 6. Set the seeder up to sow into furrows with trailing press wheels 7. Sow to a depth of 5-10 mm (very critical) 8. Control weeds and pests (insects, mites, kangaroos and rabbits) 9. Defer grazing until seedlings are well established This establishment method has also been shown to work for Rhagodia preissii (mallee saltbush). This project was not able to develop reliable direct seeding packages for other Atriplex species, including A. amnicola and A. undulata. Further work is needed to understand the triggers for their germination, before these species can be direct-seeded with conventional machinery. Direct sowing of M. brevifolia and M. pyramidata appears to be problematic in much of southern Australia, due to their requirement for temperatures >30°C for germination, which do not occur within the normal winter growing season. An exception to this would be areas with more reliable summer rainfall, such as northern New South Wales, where sowing could be deferred until late spring-early summer. An alternative strategy for establishing M. brevifolia, is to encourage natural recruitment of seedlings from seed produced on surrounding bushes (if it is already present in the area), or to transplant a low density of nursery-raised seedlings, which could then act as a seed source for natural recruitment (if it is not already present).

Sub-tropical grasses are showing excellent potential in the Northern Agricultural Region (NAR) of Western Australia in areas with mild winters and where the rainfall is greater than 300 mm. They have also been widely used on the south coast of WA, where kikuyu, in particular, has been sown over an estimated area of 120,000 ha. Five years ago seeding failures of sub-tropical perennial grasses in Western Australia were common, with patchy establishment and densities of less than 1 plant/m2. Greater understanding of their seed biology and agronomic requirements has led to the development of a reliable establishment package for warm-season perennial grasses. Rapid adoption of the key elements of the package has resulted in the bar being raised considerably throughout the industry and farmers now expect a much higher and more even plant establishment. The ten key elements of the package are: 1. Plan a year ahead and reduce weed seed-set, commence control of rabbits and kangaroos and consider sowing a cereal to provide stubble for reduced erosion risk 2. Purchase good quality seed of appropriate species and varieties 3. Control weeds and insects prior to sowing 4. Sow into moisture in late winter-early spring (depending on district) - if soil moisture is limiting defer sowing until the following year 5. Set up the seeder to sow into furrows with trailing press wheels and a row spacing of 50−60 cm 6. Sow 2−5 kg/ha of seed, depending on seed quality and whether coated or uncoated 7. Sow at a depth of 5−10 mm 8. Don’t sow too fast 9. Control weeds and pests (insects, kangaroos and rabbits) post-sowing 10. Defer grazing until grasses are well established This bulletin provides information that provides an understanding of the key factors for successful establishment of sub-tropical perennial grasses. It is primarily aimed at establishment of sub-tropical grasses in south-western Australia, but the principles are also applicable to other areas with similar climates and soils.