Sowing salt tolerant pastures is often a successful way to treat saline and waterlogged sites. They are easy to establish, provide early economic returns and protect the soil from further degradation. Salt tolerant pastures add organic matter to the soil and improve soil structure. They can also be sown in between rows of saltbush or other edible shrubs.
The preparation for pasture establishment needs to begin a year before the growing season, especially with regard to weed control. Good grazing management is important for the long-term persistence and productivity of pastures. The main steps in establishing salt tolerant pastures are outlined here.
Selecting Salt Tolerant Pasture Species
The article Salt tolerant pasture species recommends salt tolerant species for different classes of saline soil. The table can best be used to develop a mix of salt tolerant pasture species for southern, central and northern NSW but is applicable elsewhere.
It is best to select a combination of grasses and clovers based on rainfall (amount and the season), degree and season of waterlogging, soil pH and soil fertility. It is important to consider these factors when selecting a pasture mix. For example:
- a low to moderate salinity site in a moderate rainfall (approximately 550-600mm) area in southern NSW (eg Young) may use Phalaris, Tall Wheat Grass, Fescue, Sub and Balansa clovers;
- a moderate to high salinity site in a moderate rainfall (approximately 550-600mm) area in northern NSW (eg Narrabri) may use Rhodes Grass, Tall Wheat Grass, and Pucinnella and Lotus clovers if the site is waterlogged;
Although seeding rates are high in saline areas because salinity reduces emergence, the total seed rate should not exceed 12 kg/ha. Rates listed in the article Salt tolerant pasture species are a guide and may be adjusted to suit the 12 kg limit. Always seek advice from your local agronomist before making saline pasture decisions.
Steps to Establish Salt Tolerant Pasture
Step 1 - Planning and long term weed control
- Record the period of waterlogging. This will give an indication of the best time to sow the area while the area is still trafficable.
- Soil test the area to determine what ameliorants, for example, phosphorous, gypsum or lime, need to be added to ensure optimal growth.
As with all new pastures, areas to be sown should have a weed control plan that is commenced at least one year prior to sowing. Most species on saline sites are annuals and will need to have their seed set reduced in the year prior to sowing. This can be done with either knock down or selective herbicides depending on the species condition of the site. It is important to talk to an agronomist when planning your weed control program.
Step 2 - Pre-sowing works
You may need to divert water away from the area to prevent erosion. This will depend on the site slope and soil type. Seek advice before undertaking any earthworks on these sites as incorrect work can exacerbate the problems.
Fence the area to allow control of future grazing.
Step 3 - Pre sowing weed control
Winter/Spring: Graze the area heavily in early spring to reduce the bulk of material. This will also ensure even growth of annual grass species which is important for effective herbicide control.
Spring: Spray fallow in late spring/early summer when trafficable and at the emergence of seed heads of annuals such as Sea Barley Grass. A knock down herbicide can be used to do this. It is also possible to include an insecticide to control earth mites.
Summer: On sites with large amounts of Couch an extra summer spray may be needed.
Autumn: Use a knockdown spray in autumn after the break. If the site becomes very wet in early autumn, it may be necessary to sow as soon as it rains; however, this will result in more competition for the newly sown pasture.
Step 4 - Sowing
It is important to sow in autumn, before it becomes too wet. However, in some areas, it is possible to sow in spring and get a good result providing usual summer rainfall occurs.
Optimum sowing techniques will vary from site to site. For example:
- Flatter sites - use a conventional combine without harrows. Drop the seed on top to avoid burial.
- Highly saline - working with a scarifier just prior to sowing may assist, then proceed as above.
- Sloping sites - direct drill seeding will minimise the erosion hazard. Sow the seed as shallow as possible to avoid water lying in the slots during winter.
- Extremely wet sites - if the area is not accessible most of the year, hand broadcasting seed may be the only way to establish pasture species.
It is very important to obtain a current soil test of the area to help make sensible fertiliser and ameliorant (lime or gypsum) decisions. Also be aware that, on saline sites, soil pH can be unpredictable. In many cases they have a high pH and can occasionally be very acidic.
On acid soils, an application of lime at 2.5 t/ha will aid pasture establishment. Lime should be applied as early as possible prior to sowing, particularly if it is not incorporated. Applications of gypsum of 1.5 - 2.5 t/ha can aid establishment on saline/sodic soils by improving soil structure and reducing soil crusting. The gypsum will also help rectify sulphur deficiencies in the soil.
At sowing use a fertiliser containing phosphorous, nitrogen and sulphur. “Starter” type fertilisers, such a MAP, DAP, Granulok can be used at rates of 125 – 250 kg/ha. The adding of nutrients should be done in conjunction with a soil test. Seed should be treated with an insecticide to prevent ant theft. Legume seed should be lime coated and can also be treated with molybdenum.
Step 5 - Post emergence
To ensure the successful establishment of the new pasture, delay grazing for at least twelve months. Use the paddock as a feed gap reserve, that is, graze for a short period in late summer/early autumn each year.
Step 6 - Ongoing management
The following principles should be employed to ensure the survival and productivity of your new pasture into the future:
- allow perennials to set seed in the first year and then every 2-3 years after;
- do not allow pastures to become rank, only growing leaves use water
- do not graze if the site is waterlogged, too dry or bare areas are present.
- Fertilise regularly. An application of Molybdenum fortified superphosphate every 4-5 years aids legume persistence, particularly if the site is acid.
