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Establishing and managing tall wheat grass in saline soils for productivity | AG0707 |
Chris Nichols, Hamilton
February, 2002 |  |
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This Agriculture Note describes the establishment and management of tall wheat grass on saline soils.
Background
Tall wheat grass (Thinopyrum ponticum) is an easy pasture to establish and manage if a few simple steps are followed. Grazing can commence within 12 months of sowing and has the capacity to increase stocking rates from 0.5 to 8 DSE/ha if managed like a good phalaris pasture. Species comparisons made in South America, USA and New Zealand indicate that tall wheat grass is one of the most productive species. Furthermore, silage comparisons between perennial ryegrass - sub clover pasture and tall wheat grass - legume pasture in the SW of Victoria, indicate that the two have very simular digestibility and crude protein levels. This is a far cry from the often perceived notion that it is a low producing grass that is difficult to establish, can not be grazed for at least 18 months after sowing and is difficult to manage over time.
Originating from the Balkans, Asia minor and Southern Russia, tall wheat grass is a drought tolerant, summer active, tussock-forming perennial that grows to a height of 2 metres. It grows particularly well in moderately saline areas that grow sea barley grass and buck's horn plantain with an ECe in top 10 cm of soil of less than 5 dS/m. It also establishes in areas where salinity levels are far more severe (ie ECe in top 10 cm of up to 40 dS/m). It persists in winter waterlogged soil that dry out in summer and grows equally well in acid and alkaline soil. It does not persist in soils that are waterlogged over spring and into summer. Under these conditions, Lotus pedunculatus may be a better option.
(ECe is the electrolyte conductivity measured on soil paste extracted from a saturated soil sample. The units used here are deciSiemen per metre.
The electrolyte conductivity may also be measured on a 1:5 soil:water sample, nominated as EC1:5. This alternative will give lower EC values.. See Agriculture Note Ag0284: Salinity and the growth of forage species).
Establishing tall wheat grass
Tall wheat grass is an improved pasture variety and must be established along the same lines as other types of improved pasture.
- The affected area must be fenced out and managed as a separate paddock.
- A soil test should be conducted to determine the fertiliser requirements and the ECe reading in the top 10 cm of soil (refer to Agriculture Note Ag0375: Sampling soils used for growing pasture, field and fodder crops).
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In most saline areas, phosphorous and nitrogen are limiting and sulphur is not required. For tall wheat grass to establish quickly in autumn, apply 100 kg/ha of a nitrogen based fertiliser such as M.A.P. at the time of sowing.
The ECe reading or salinity level of the soil will affect the sowing rate and pasture companion species. The higher the ECe, the higher the sowing rate for tall wheat grass and the fewer pasture companion species available.
Sites with low to moderate ECe readings can be sown with a pasture mix of 10-15 kg/ha tall wheat grass, 2 kg/ha phalaris (Phalaris aquatica), 1 kg/ha strawberry clover (Trifolium fragiferum) and 0.5 kg/ha balansa clover (Trifolium michelianum).
Sites with moderate to severe ECe readings can be sown with 15-20 kg/ha tall wheat grass, 2 kg/ha strawberry clover and 1kg/ha balansa clover.
Other companion species suited to saline areas are Persian clover (Trifolium resupinatum), Puccinellia (Puccinellia ciliata) and Tall Fescue (Festuca arundinacea).
It is essential that tall wheat grass seed is fresh. Germination percentages decline rapidly if the seed is more than two years old.
- While waiting for the results of the soil test, spraytop the pasture in spring and graze it over summer until it is bare by the end of March.
- Wherever possible, scarify the site to a depth of 10 cm before direct drilling in the pasture. This provides a soil tilth, leaches surface salt beyond the A1-A2 horizon after rain and creates an roughened soil surface for seed to settle into and establish.
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In some situations, scarifying may not be an option if the site is on a steep gradient or along a flowing drainage line. Under these circumstances, consult your local adviser for on-site advice.
- After scarifying, wait for the opening rains and weeds to germinate before doing a complete knockdown.
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Weed control before sowing is critical especially as tall wheat grass is an inherently weak seedling.
- Direct drill the pasture in with Baker Points or equivalent sowing implements in April or May after the opening rains.
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If the area is likely to get too wet after the opening rains, sow the seed in dry.
Autumn is the preferred sowing time due to most discharge sites being too wet to get machinery on to in spring. Likewise, if there is an early finish to the season, the newly sown tall wheat grass plants may struggle to germinate and grow in an environment where surface soil salinity increases in summer.
In an area where the ECe reading is moderate to severe, it may be necessary to cover the ground with a mulch of old hay or slashed tall wheat grass after the site has been scarified. This provides an initial vegetative cover to the site which will help conserve soil moisture and reduce the salinity concentration in the top 10 cm of soil through lower evaporation. It will also add vegetable matter to the soil which will help improve the soil structure.
Grazing management
The simplest and most effective strategy for grazing tall wheat grass is to observe the growth cycle of balansa clover - a companion species. Under this grazing regime,
- grazing stops at the first sign of balansa flowering (usually in September)
- grazing commences when balansa seed set is complete (usually in December)
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1st year of sowing
In spring, top-dress the pasture with 100-150 kg/ha urea followed by 100 kg/ha triple super in each of the ensuing years to maintain a highly productive pasture.
Sites sown to tall wheat grass in low to moderate ECe saline areas can be lightly grazed in early September before balansa starts to flower BUT only if the tall wheat grass plants are firmly anchored to the ground and the discharge site is not waterlogged. This can be tested by pulling at the base of the tall wheat grass plant with the thumb and forefinger. If the plant is easily removed, do not graze until after balansa seed set is complete by mid to late December.
At the first sign of balansa flowering, remove the stock. Once balansa seed set is complete, crash graze the pasture down to a uniform stubble of 10 cm. This removes excess growth, helps control weeds, encourages better leaf growth over summer and makes the grazing management over summer easier.
After the initial crash graze, lightly graze the pasture over summer and autumn to maintain a height of approximately 10 cm to encourage strong root development and water use. Give the pasture one last heavy graze at the autumn break to remove any excess trash. This provides a favourable environment for balansa to regenerate.
Over winter, do not graze the pasture if the site is waterlogged. If the site is not waterlogged or pugged by stock, graze it to utilise the balansa clover.
Sites with moderate to severe ECe readings may need to be spelled from grazing for up to 2 years after sowing. This will depend upon how successful the establishment was, how severe the site is scalded and how well the plants are growing.
2nd year after sowing
In the following spring, (18 months after sowing) graze the pasture hard to make use of the balansa clover. At the first sign of balansa flowering, shut the paddock up and allow the balansa to set seed. After balansa seed set is complete, crash graze the pasture hard to remove any excess growth and tall wheat grass stems.
To prevent the pasture from going clumpy and rank, graze it simular to a well-managed phalaris pasture. The pasture should be no more than 10 cm high over the summer months. If stock appear to be selectively grazing areas bare, crash graze it to a uniform height - (tall wheat grass handles hard grazing well). The pasture can be grazed through summer and into autumn until the paddock becomes too wet for stock to walk over.
To encourage balansa regeneration, give the pasture one last heavy graze at the autumn break to remove any excess growth.
Maintaining this simple but highly effective grazing pattern will result in a pasture that is easy to manage and highly productive. When managed correctly, tall wheat grass has the potential to cut high quality silage or hay. It is also a great fodder reserve in summer and is very effective in stabilising and rehabilitating soil in fragile, saline areas.
Cultivars
Tyrrell
Widely used in Australia. It has many varied agronomic traits. The new cultivar Dundas was developed from Tyrrell.
Dundas
A new cultivar selected to enhance leafiness and quality. Commercially available in 1999.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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