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SOLUTION 7

Vegetatively established grasses

 

7.5  Establishment & Management of vegetatively established grasses

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Picking the right species and varieties

There is extensive diversity within these vegetatively established species – for example marine couch has from 10 to 30 chromosome pairs and its morphology ranges from short (<5 cm) mat-forming ecotypes to tall (~40 cm), erect ecotypes, with fine-textured to coarser leaves. Flowers vary from short compact ovoid panicles to longer narrower ones. This of course does not apply to the commercial Distichlis cultivar (NyPa Forage) which is a clone.

Given this level of genetic and morphological variation, similar variations in salt tolerance within species is to be expected. Success on the ground is likely to be highly dependent on genotype and therefore (if possible), vegetative material should be collected from sites that are similar to the intended establishment area, and that have the plant characteristics that are required.

In general, there has not been the consistency of demand to develop continuous, or commercial supplies of planting material. Many farmers have collected their own supplies from other saline environments and allowed stands to thicken up over time, though this can be a slow process. Distichlis is commercially available but if marine or saltwater couch are required, then the best place to start is with the turf-grass genotypes as these types will at least be readily accessible and have had some selection applied.

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Weed control

Despite the fact that these vegetatively established grasses are most suited to highly saline and waterlogged sites where few other species will grow well, weed control is still a major issue for establishment. Research with Distichlis showed that survival of planted material was very poor (about 30%) without weed control, but this rose to about 80% if a knockdown spray was used.

There are no specific herbicide recommendations but failure to control weeds greatly increases the risk of either failure or poor initial establishment.

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Establishment techniques and timing

Studies with Distichlis have used modified vegetable planters to ‘sow’ the harvested, vegetative material. For more information, see Rehabilitation of Highly Saline Areas for Forage Turf and Grain and Old and new plants underpin this system.  Trials of different planting systems were undertaken in South Australia and Western Australia and resulted in the adaptation of two broccoli vegetable planters to plant the rhizomes in previously ripped lines. This system was relatively labour intensive and occupied two people to dig and prepare rhizomes and to operate the tractor and planter. A rate of planting of about 2 hectares per day was achieved.

There are no reported results from timing of planting trials, but as these grasses do not grow at temperatures below about 15oC, it is not likely that late autumn or winter planting would be appropriate. Spring planting is more suitable, but can be problematic as sites suited to these grasses are likely to be heavily waterlogged (and therefore untrafficable) over winter and early spring. Late spring planting in many situations may not give the planted material sufficient time to establish before the sites dry off in summer.

Therefore, like many of the saltland solutions, the timing of establishment to take account of the site conditions and the plant requirements often means that the planting window can be very narrow and the risk of failure can be higher than for non-saline sites.

These grasses have to be propagated vegetatively and planted individually, making broadacre establishment costly and time consuming. However, as each of these plants spreads laterally by rhizomes and/or stolons, it should be possible to establish relatively continuous stands by planting vegetative material at relatively wide spacings, protecting the material from grazing and allowing the plants to “fill in” the bare patches. This is especially true where the site is not already supporting other grasses that will compete strongly with the sown species.

Research with Distichlis across southern Australia showed that a rate of spread of approximately one metre per year can be expected under suitable conditions, though this ‘rate’ tended to slow with time. Rates of spread were also very slow in heavy-textured highly saline soils. Experience has shown that in the Upper South East of SA, Distichlis Nypa has disappointing growth potential as it needs regular daily temeratures of > 30 degrees C for good growth.

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Grazing options and management

There is little or no research information regarding the grazing management of vegetatively established grasses. However, there is some anecdotal information and when combined with the general rules for grazing perennial grasses, we can reasonably conclude that:

  • Grazing over winter will be minimal due to both the slow growth of these warm season grasses, combined with the fact that most sites suited to these grasses will be heavily waterlogged and therefore highly susceptible to pugging damage

 

  • Rotational grazing will be better for the persistence of these grasses than continuous stocking.  
  • The vegetatively established grasses seem to be able to tolerate extremely heavy grazing, provided they are allowed time to recover. Research with Distichlis had one ‘plot’ that was not fenced off from the rest of the paddock, and so was heavily grazed each year to the point where the plants seemed to have vanished because it was the only green feed available. However, when the livestock were removed, the plants regrew each year without apparent harm and were still spreading slowly after six years of this ‘no care’ treatment.
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Animal nutrition issues

Both sheep and cattle will graze these vegetatively established grasses, which are often the only green material available on farms in southern Australia in summer and autumn. This production of out-of-season feed is one of the primary benefits saltland pastures provide to a grazing enterprise.

While there have been very few studies of nutritive value or animal performance associated with these grasses, the following, general conclusions can be drawn:

  • There are no known nutritional problems associated with grazing these vegetatively established grasses. They do not accumulate salt, but rather have glands on the leaves that exude salt. Plants that accumulate salt (such as saltbush) can be nutritionally challenging for livestock because of both the high salt content in the diet and the various compounds in the plant material that allow the plant cells to function in the presence of high internal salt concentrations;
     
  • As with all grasses, forage quality (both protein concentration and digestibility) decreases with increasing age of the plant material. A balance is required as long rests between grazings are best for the plants, but produce lower quality feed, while short rests are best for the animals but can reduce the persistence of the plants;
     
  • Forage quality will generally be improved by the use of fertiliser, but on highly saline, waterlogged and poorly productive land, such fertiliser applications may not be economic;
     
  • Summer growing grasses (whether salt-tolerant or not) are not as nutritious for livestock as cool season grasses. They tend to have higher fibre content (lower digestibility) and lower protein concentrations. There have been some recorded forage quality levels with Distichlis, which across a range of sites varied from 6 to 17% protein and from 45 to 60% digestibility - the higher nutritive values were associated with applications of N and K fertiliser.
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Integration into farming systems

There is no specific information available about integrating these vegetatively established grasses into farming systems in southern Australia. In addition, outside of Queensland, the areas revegetated with these grasses are small and they tend to make only a minor contribution to the feed supply on any particular farm.

However, as there are no particular nutritional limitations associated with the vegetatively established grasses, they will not be difficult to integrate into farming systems and will provide valuable green feed over summer when most other pastures will have hayed off.

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