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SOLUTION 5

Tall wheatgrass

 

5.3  What are the benefits from tall wheatgrass pastures?

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Production

In an experiment at Dunkeld, western Victoria, the productivity of tall wheatgrass was affected by soil salinity. Yields of 7t/ha/yr occurred in soils of moderate subsoil salinity, but these increased to 13t/ha/yr in soils of low subsoil salinity. At an SGSL Producer Network site near Kingston in SA tall wheatgrass maintained a 20 dse/ha over the life of the project.

Previously, enquiries from producers in Victoria prompted a pilot feed quality study of 84 samples of tall wheatgrass from 9 different locations across the southwest to test feed quality at various times of the year. The sites included newly renovated and established pastures including both Tyrell and Dundas cultivars. Old established sites that had been mismanaged for years and allowed to go rank were included to see if they could be brought back to productivity by grazing or other management.

The results clearly indicated that removing the rank grass and allowing new green growth to regenerate significantly improved pasture quality (digestibility, crude protein and metabolisable energy). While the data were insufficient to show a direct link between the different management techniques and feed value, they strongly indicated that effectively managed tall wheatgrass pastures are more than capable of filling the summer/autumn feed gap, whilst most other pastures are dormant or dead.

The best managed tall wheatgrass sites had crude protein and energy levels similar to perennial ryegrass and tall fescue but quality declined rapidly as tall wheatgrass grew rank and went to head.

Table 5.1: Mean feed quality results for Spring 2002.

Species 

CP (Protein) %

Digestibility %

ME (Energy MJ/kg)

Tall fescue

20.0 

74.5 

11.2 

Perennial ryegrass

21.2

77.3 

11.3 

Annual ryegrass

13.2 

70.6 

10.3 

Phalaris  

14.3 

74.9 

11.0 

Mixed pasture 

19.3 

72.7 

10.6 

Tall wheatgrass (< 20cm)

18.9 

75.3 

11.0 

Tall wheatgrass (>20cm)

15.2 

66.4 

9.6 

Tall wheatgrass (>1m) 

7.6 

52.4 

7.4 


The tall wheatgrass declined in quality over late summer even when kept short and green, however by then it was the only green pasture available on farm. The researchers concluded that, for the region studied, tall wheatgrass is the most successful perennial grass species that can be grown in moderately saline soils. It offers the added potential benefit of being an alternative pasture in areas where ryegrass staggers and phalaris toxicity are problems in early autumn. For more information, see Dundas Tall Wheatgrass, Our Number One Saline Agronomy Species for the High Rainfall Zone.

A clear message from all the work on wheatgrass pastures is that they must be kept short and vegetative. This management rule also assists with the persistence of any complementary legumes in the pasture.

How the short pasture is achieved is not really important, although clearly hard grazing is the best use of the resource. Old rank tall wheatgrass also responds to slashing, burning or mulching of old growth, however working in old neglected wheatgrass paddocks can be hard on machinery.

The ability of tall wheatgrass to locally lower the saline watertable can provide a more hospitable environment for companion legumes such as balansa or strawberry clover. When effectively managed, tall wheatgrass pastures sown with a companion legume are capable of increasing stocking rates from 0.5 DSE/ha to 12 DSE/ha or higher (Kingston SE of SA where 20 dse/ha was achieved).

Research at four non-saline sites in the upper south-east of SA from 2002 to 2005 compared the herbage produced by 17 different perennial grasses including tall wheatgrass. Despite displaying good persistence throughout the trial period, Dundas tall wheatgrass was consistently outperformed by other species. In addition, the spring crude protein and energy content of Dundas was lower than that of all other grasses. This appears to suggest that this cultivar is best suited to environments where its relative ability to tolerate moderate soil salinity and moderate waterlogging can be exploited.  

Farmer case studies indicate that tall wheatgrass pastures can be used to make good silage, although the rapid decline in pasture quality with plant maturity suggests that it is more difficult to produce good hay.

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Water use

Tall wheatgrass can reduce topsoil salinity in local ground water flow system catchments, firstly by preventing the capillary rise of salts to the surface, and secondly by drying out the soil which then allows rainfall to wash salts deeper into the profile.

The ability of tall wheatgrass to use soil water throughout summer means that the soil will be drier in autumn and will need more rainfall to become saturated following the autumn break. This delays the onset of winter waterlogging under tall wheatgrass pastures (which may include other species such as balansa clover or puccinellia). Monitoring of a site in the Great Southern Region, WA, showed that winter waterlogging occurred a month later on tall wheatgrass-balansa pasture compared to balansa-only pasture. The duration of waterlogging on tall wheatgrass-balansa pastures was also reduced to a third of the time of the balansa-only pasture during a growing season (May - October).

Pasture production is generally reduced under waterlogged conditions, so the summer water use by tall wheatgrass has a further benefit beyond its own direct contribution to productivity, by providing a more suitable environment for less waterlogging tolerant pasture species. For more information, see ‘Tall wheatgrass and balansa clover: a beneficial partnership for waterlogged, mildly saline soils growth and productivity’.

In 2001 the Esperance Downs Research Station, reporting on a 7 year pasture rehabilitation program to research and demonstrate economic methods of obtaining production from land affected by salinity, waterlogging and wind erosion, noted that compared to annual pastures the perennials, particularly tall wheatgrass, provided a buffer that delayed waterlogging. Similar observations have been reported elsewhere.

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Amenity & environmental

Improved visual amenity is a strong motivator for many farmers revegetating saltland. Under suitable conditions (moderate salinity and waterlogging), tall wheatgrass can transform a salt affected site otherwise supporting only sparse sea barleygrass. 

Geoff Kroemer of Tumby Bay (SA) spoke of his experience: “Five years ago I would never have dreamed that we could turn such apparently useless land into something so good. I just wish we had started this 20 years ago, but I am pleased to be doing it now for the next generation.”

In 1920 there were approximately 20 Australians for every farm in the country. Today the ratio is about 175:1. There is a growing expectation that land be managed sustainably. Bare scalds do not support this perception. 

Tall wheatgrass should not be used where grazing pressure is insufficient to control its spread by seed into non-target areas.

In terms of biodiversity value, the SGSL initiative showed that tall wheatgrass-based pastures are intermediate between bare salt scalds and remnant native vegetation as measured by Landscape Functional Analysis. They represent better production and environmental outcomes than untreated saline areas.

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How do the $$$s stack up?

Farmer experiences

The widespread use of tall wheatgrass throughout south-west Victoria and the upper south-east of SA does not give a strong indication of the profitability of this pasture. For many graziers the main issue has become how to get rid of poorly managed wheatgrass (usually Tyrell) rather than how to encourage it to persist. The value of tall wheatgrass, particularly its economic value, is critically dependent on the management practices that support it.

As a rule, the grazing benefit from tall wheatgrass is principally that it allows graziers to maintain more stock per hectare rather than to finish stock for market.

Three case studies illustrate the potential for profitable use of tall wheatgrass on salt-affected land.

  1. Charlie Bruce produces prime lambs, wool and cattle near Kingston in the Upper South East of SA (annual average rainfall 525mm). He has about 600ha of inter-dunal flats affected by waterlogging and salinity resulting from a watertable that sits about 1m below the soil surface.

    Typical costs and benefits expected from pasture establishment were fed into a profitability calculator. The boost in production on Charlie’s saline flats following development was estimated to represent an increase in stocking rates from around 2.5 to 5dse/ha/yr based on the established practice of applying minimal N inputs. Greater production (up to 10dse/ha/yr) could be expected with greater N fertiliser inputs.

    Assuming that a gross margin of $25/dse for the extra 2.5 dse/ha is maintained over the 20 year life of the pasture, the total future profit arising from pasture development in today’s dollars (assuming a discounting rate of 10%) would be around $158/ha. The payback time for the initial investment would be at least 7 years.

    In this scenario, minimal inputs and a long pasture life contribute to the profitability of this system, despite only modest gains in production. Profits would improve if higher stocking rates can be supported, however this is likely to require greater use of fertiliser which could impose too high a cost. For more information, see Case Study of Success with Saltland Pastures #7.
     
  2. Sheep grazier Michael Blake,Hamilton, Victoria (690 mm annual average rainfall) sowed 90ha of salt affected land to Dundas at 7kg/ha through an air seeder along with balansa and strawberry clover.

    The benefits of a tall wheatgrass pasture were modelled with an annualised stocking rate of 15.5 dse/ha with a provision for supplementary feeding on alternative pastures in winter. The investment in pasture establishment was analysed on a gross margin basis for a self-replacing Merino wool flock and accounting for the extra costs of grazing management labour and fertiliser to maintain the pastures. This modelling showed that gains in carrying capacity resulted in annual increases in gross margin per hectare of up to $162/ha by year 3. 

    The Blakes’ tall wheatgrass pastures were analysed over 10 and 20 years to determine the net present value (NPV) and internal rate of return on investment (IRR) in pasture establishment. The results indicate that the tall wheatgrass and clover pasture may well be a highly profitable investment for unproductive saline areas, even if the pasture is only maintained for 10 years.
     
  3. Craig Bignell, Broomehill, WA (annual average rainfall 432mm) established 49ha of tall wheatgrass and saltbush in 2004. Overall, the tall wheatgrass was the most successful component of the mix. During dry conditions in 2006 it supported 1600 young Merino ewes for six weeks from 24 May with only 150g/hd/day of supplementary feed. An economic analysis showed that at this rate the cost of establishing the paddock would be recouped in 4 years, despite the fact that it had been kept out of production for 2 years during establishment.

    An added benefit from this pasture, not accounted for in the economic analysis, was the opportunity to harvest 1.2 tonnes of viable tall wheatgrass seed. This became a very marketable commodity given the acute shortage of seed in the eastern states. This story was reported in MLA’s farm magazine, Prograzier in autumn 2008

 

Research results

The economics theme in the SGSL program used whole farm modelling to determine the economic value of forage produced from salt-tolerant perennial pastures at each of the SGSL research sites. MIDAS is a suite of models that have been developed for a number of different regions of Western Australia, south-west Victoria and the slopes of New South Wales and was used in the SGSL site analyses.

There were 4 study regions as part of this project, based on the location of research sites of the SGSL program. These were south west Victoria, upper south east of South Australia, the central wheatbelt of Western Australia and the Central West Slopes of NSW. The analyses for each region examined the benefits of introducing improved pasture species and applying different management treatments to saltland.

The Victorian site examined the role of tall wheatgrass-based pastures, sown into saltland with differing levels of salinity. The analysis for this site was aimed at estimated the profitability of tall wheatgrass pasture on land with low (Class 1) and moderate (Class 2) salinity.

In south west Victoria the very high benefit ($265/ha) of improving production on Class 1 land resulted from an increase in the stocking rate by almost 1dse across the whole farm. Supplementary grain feeding was also reduced, as well managed tall wheatgrass pasture provides good quality feed over the summer-autumn period, with around 140mm of rain falling during the dry periods. In total around 700dse are added to the flock, resulting in a total net benefit of over $13,000 to the whole farm or $19/dse.

Class 2 saltland, has a higher level of salinity and therefore is less productive and has a lower profitability ($158/ha). Moreover the relative increase in feed value of improved species on this land unit is less compared to Class 1. The digestibility of volunteer pasture on the Class 2 land unit is 1-2% higher in the growing season compared to tall wheatgrass, and up to 6% higher during the summer and autumn months. However, there is a net benefit to establishing tall wheatgrass on Class 2 land because the much improved growth rate more than compensates for its lower quality.

Despite the lower feed value the net benefits of establishing tall wheatgrass on Class 2 land is substantial. The increase in profit is achieved by increasing the stocking rate (whole farm), however the level of supplementary feed is not reduced to the same extent as it is when tall wheatgrass is established on Class 1 land.

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