LIKE most properties, we have a number of weed issues on our mixed grazing cropping farm.
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By and large we cope with these by trying to eliminate some but in the main living with most in a containment strategy.
Our weeds include low palatability perennial summer growing grasses Coolatai and African lovegrass.
These are widespread on roadsides in our area and can gradually creep into light soil areas adjoining public roads.
They can then spread via stock.
Other weed issues include Nut grass, which probably arrived by machinery many decades ago, spiny burr grass, fleabane, khaki weed, cathead, saffron thistle, Bathurst burrs, melons, wattle regrowth, pine regrowth, Charlies weed, capeweed, Paterson's curse and various winter grass weeds, such as barley grass and vulpia.
Weeds such as St John's wort and blue heliotrope have been eliminated but can reappear if not watched.
Perennial summer growing grass weeds are managed on two fronts.
Success has been achieved by winter cropping for three years with paddocks fallowed through summer using glyphosate any time rain results in germination of annual or perennial weeds and regrowth of only partially killed perennial weeds.
Over three summers the perennials are well and truly killed out and seed reserves virtually eliminated.
At the end of the cropping phase the paddocks are sown down to tropical grasses.
These compete aggressively with any future perennial grass weed invasions and can greatly slow, if not prevent, their reinvasion.
In native grass paddocks with these perennial grass weeds but not designated for cropping in the near future, paddocks are managed to contain their spread with pretty good success.
Fertiliser to correct phosphorus and sulphur deficiency, winter legumes such as sub clover, biserrula and serradella to improve palatability of all grasses and flexible rotational grazing all play a part in having a strong perennial native grass base to restrict the spread of weeds.
In a dry summer like the one just past, African lovegrass and Coolatai, because of good soil fertility, were actually well utilised by stock and commonly provided quality green feed when none or little else was available.
They are more a problem and less used in good seasons when there is plenty of more palatable feed available.
The myriad of summer annual weeds such as spiny burr grass, cathead, Charlie weed, fleabane burrs and melons are nearly always outcompeted with good quality tropical grass based pastures, and to a large degree by strong native perennial grass pastures.
Again soil fertility, winter legumes and grazing management are critical.
Summer annual weeds are more a problem in establishment of tropical pastures and therefore the need for their elimination as far as possible in the fallow periods leading up to their sowing.
Unfortunately if you miss a fallow weed kill, you are quickly back to high soil weed seed levels and have to begin a weed seed reduction strategy again.
Winter weeds like Paterson's curse and saffron thistle are to a large degree contained by strong winter and spring growing pastures and so far we have avoided the need to use herbicides, other than in-crop or fallow periods for their control.
Some farmers attack many of these weeds before they develop into a problem by spraying infestation entry points, for example around gates or on a boundary, preventing seed set and thus their spread across the farm.
Next week: Assessing role of new barley varieties.
Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
