[Weekly Times, September 7, 2011, by Keven Butler] -- With good spring rain and consequent prolific grass growth, the natural pastures on either side of the Great Dividing Range look better than previous years. However, a closer look will reveal that many of these lush paddocks are infested with Bent Grass or Brown-tops - a type of invasive couch which is summer active-winter dormant and has only a fraction of the nutritional value of healthy pastures.Bent grass gives the illusion of wonderfully productive pasture offering a mass of feed during mid-summer but becomes a horrible pest when grazing stock lose condition over winter. Not to be confused with kangaroo grass from a distance, which has a similar brown top, bent grass thrives from Kilmore to Ballarat to Hamilton, as well as around Bairnsdale. It is estimated that bent grass dominates up to two million hectares of Victoria, causing lost production in the hundreds of millions of dollars each year.
HOW DO I KNOW IF I HAVE IT?
Bent grass (Agrostis spp.) is a creeping, turf-forming couch with a dense mat of roots underneath. It can grow from root, stem or seed. It has a flat, prostrate habit in winter, grows lush during mid-spring, then sends up thin stems with flower heads in early summer. It favours wet and low-lying areas with clay soils with a pH of 4.3 to 6 in rainfall zones as low as 500mm per annum. It is rare in highly fertile, well-managed paddocks or hilly areas. Giant patches of the weed can dominate a paddock.
The basalt plains and some of the poorer sandstone or sedimentary country from Kilmore to Ballarat are often full of bent grass. This is especially so for those properties with little or no fertiliser history, no set stocking pattern, or which have only a few horses, cattle or sheep which selectively graze out other more-productive species of grass.
Bent grass will rear its ugly head, this year more so than any other, because we had good early summer rain. Many farmers mistakenly believe it is worth baling, which is true if you are trying to reduce the fire hazard.
When cut for hay, horses usually only eat it if they are extremely hungry. Cattle seem to handle it better, particularly when they need "packing" or roughage as the colder months come around. Sheep will often sniff it and walk away, especially if it has been rained on and bleached during the curing process and then baled without any green stems. Saturation with molasses will entice stock to eat it. BENT GRASS HABITS
Being an aggressive couch, bent grass grows on both poor and reasonably rich soils once given the chance. It grows a mat of grass and roots so thick that it is almost impossible to dig out with a shovel. A small snip of root or leaf will easily begin a new independent plant as many a gardener will testify.
The seeds spread easily in the wind, but this drought-tolerant perennial may not even seed if well grazed during dry seasons. It will rely on its root mass for survival and will re-establish when summer rain arrives.
It smothers more-desirable grasses and clovers and even oat crops find it difficult to establish once sown in cultivated ground.
THE COST OF BENT GRASS
A rule of thumb is that severely infested pastures will carry only a third of the stock of healthy balanced, natural pastures mainly because of the winter feed gap. Bent grass paddocks are either 'famine or feast': famine in winter, feast in late spring and ordinary in between.
During winter, when the green plant is dormant and the old plant material oxidises above and smothers clovers and other grasses from sunlight, bent grass can have less than 3 per cent protein and be of little more benefit than cardboard. Horses, cattle and sheep will most likely need supplementary feeding to stay alive.
During spring, when it is actively growing and the protein level may be up to 10 per cent, all animals will eat it but stock performance will be inferior to the weight gain of a mix of clovers and more-palatable grasses.
Where a healthy paddock next door can run 7.5 dry sheep equivalents per hectare, you will now battle to run 2.5DSE/ha.
Wool cuts and weaning weights can be as low as 50 per cent less than improved pastures.
Being quite rough and just barely palatable in summer and autumn as dry feed, cattle will readily graze bent grass but adult sheep will graze it as a last resort. Young stock such as Merino weaners up to five months of age will lose weight and may even die from grazing a paddock of dry bent grass. WHAT TO DO
1 Subdivide your farm into smaller paddocks and manage-rotate the animal impact and get an independent soil test done.
The only thing bent grass hates more than fertile soil is a mob of cattle or sheep grazing it down - defecating over it and using their hooves to grind the urine and pats into the roots. This practice also allows sunlight in so other grasses can have a chance.
To do this well, paddocks may need to be as small as half a hectare if you have only a few animals.
Stock should be rotated on and off and fed hay as often as desired. In fact, I set up the feed bins full of wheat seconds - right in the middle of the bent grass - so the sheep can unwittingly go to work. Remember that the hay and wheat seconds will introduce new seed and the most adaptable for your farm soil wins.
Recently, I bought a bag of balansa clover seed to scatter around where the hooves do their work. I would also like to experiment with modern types of phalaris and rye grass as well.
When the bent grass is eaten, trampled and defecated on to its roots, I move the feeders to a new patch and let nature do the rest. Lush grasses generally follow after the next rain.
If you don't have the numbers of stock nor big quantities of hay to feed to increase the fertility, arrange for an independent soil test, fertilise accordingly and monitor animal movements.
I have used this method on numerous paddocks and the only cost has been the recycled fencing. You just need to be able to concentrate stock numbers at will. I rehabilitate about five hectares of pasture a year with a mob of about 1000 sheep this way.
Never just spray out the bent grass, direct drill seed and fertilise and then hope for the best - if you don't use your animals to graze and recycle the nutrients, you will find within five years you will be back where you started - infested with bent grass.
2 Up the competition - direct drill better species
Not all landowners can keep subdividing land into smaller paddocks and using animals effectively as I do. An alternative is using glysophate at the manufacturer's recommendations on a sunny spring day to boomspray and ultimately kill the bent grass. Then, seven to 10 days later, direct drill better seeds into the root mass.
I favour direct drilling because while the soil structure and moisture is retained, a mulch and shade is provided for the young seedlings by the dying bent grass. Furthermore, it is a quicker and more reliable sowing strategy than cultivation with a plough, which simply chops up the bent grass roots into more pieces to regrow. Direct drilling could cost up to $500 a hectare including fertiliser, seed and contractor.
A fodder crop such as hunter or rape - alone or with a few grasses and clovers - is one of the best mixes. As long as there are good, early summer storms, the lambs can graze the fodder crop in six weeks and as long as you keep up the fertility and rotate the stock, say, two weeks on and six weeks off, you should have reasonable persistence.
In areas of heavy bent grass, you may have to glysophate spray and direct drill a fodder crop or oat crop the first year and then repeat the process the following year when you can sow a pasture mix.
It is hard to completely kill bent grass in the first year. You will find that two years of direct drill cropping will have the bent grass root mass well into decay and more conducive to seed establishment than one year alone.
I find that phalaris and rye grasses are persistent competitors with bent grass on our farm. Always put in clovers to build up nitrogen. Remember to rotate stock and keep fertilising, or the bent grass will take over again.
3 Spray topping can create more nutritious bent-grass feed this summer and set yourself up for a successful pasture establishment next spring.
Just 300ml of Roundup CT (glysophate) with a soil wetting agent for each hectare on a sunny, early November day may be enough to raise the sugars and protein levels in bent grass to prevent seeding and to fatten sheep over a wet summer.
This practice should thin out the bent grass and break its dominance while allowing other grass species and clover to grow. However, the practice depends on good late spring and summer rainfall - otherwise you will have less feed than if you had done nothing at all.
4 Harrow in chicken manure during late winter
I tried this years ago and fattened Merino wethers on bent grass over spring and early summer. By applying seven to 10 tonnes per hectare of chicken manure responsibly (far from waterways) and smudging it onto leaves and stems, you will boost the nitrogen levels and soil nutrition to achieve a few positive outcomes:
The other grass species will begin to outgrow the dormant bent grass and proliferate with more sunlight being available.
The bent grass will become particularly lush during spring and will have more protein-rich leaf and less stem.
There will be a longer lasting effect as long as you use adequate animals to keep it well grazed.
I would caution you on the possibility of bloat in cattle and prolapse in ewes whenever you use chicken manure. Cost would be about $200 a hectare (cost of the chicken manure delivered) and you do your own harrowing.
I suggest you experiment with all of these strategies on a small scale to see what suits you, your finances and your farm.