Stopping the set of seeds
Preventing seeds from setting is an important step for weed control
I AM still on weeds this week, even though it is very dry throughout much of eastern Australia.
I would like you to look at this photo taken earlier this year, after some significant rain. How many species of weeds can you count here next to this block of cotton? Let me list the ones I can see – urochloa grass, caltrop with the yellow flower, turnip weed with the big broad leaves, fleabane with the white fluffy flower tops and bladder ketmia with the white cup-shaped flower and round seed pods.
Now, on their own these are weeds that can compete very much with any of our summer crops. By the looks of it, these plants had gone to mature seed status on my next trip past. So with urochloa grass plants dropping up to 3000 seeds per plant, caltrop extending many feet in any direction with its 10,000 to 20,000 seeds being produced, turnip weed having similar seeds per plant numbers, fleabane in the 100,000-plus mark and bladder ketmia 5000 to 10,000 seeds per plant, is it any wonder that one key fact in good future weed control is stopping these annual plants from setting seed. It is what my learned colleagues at Weedsmart base in WA and I call stopping seed set as one of the big six in weed control.
Calculate the total count of those numbers of weed seeds produced along this fenceline. Is it any wonder our paddocks and watercourses get infested by weeds of all species.
Fencelines are tricky aren’t they? If you spray fencelines with a glyphosate based product, as it is the most practical and safe herbicide, you will control most green plants including these weeds. You will control them, that is, until they obtain glyphosate-resistant status and two of these above species may have that herbicide resistance already, peculiarity in eastern Australia.
What is your weed control plan then, when it becomes impossible to add any other herbicide product due to any number of reasons, like a cotton crop one metre away from your spray pattern as above?
This fenceline has been previously sprayed many times with a glyphosate product and that has killed all the desirable plants on the fenceline, as well as the bad ones probably.
So these previous spray operations with a robust rate of gly herbicide have killed all the pioneer rhodes grass as well, shall we say.
Never the most fashionable or edible livestock fodder, pioneer rhodes, however, ever since its introduction into Australia in the early 1900s, has held watercourses together and much reduced our soil erosion by wind and overland flow. It has also fed quite a few animals over the dry years. Unfortunately for pioneer rhodes it does take some effort in reseeding it successfully to an area.
Not so for our above weed seeds with big seed bank numbers and their seed size giving no chance of re-establishment for our more preferable and competitive fenceline species of pioneer rhodes grass.
So as one of the big six diversity tactics, you must stop weed seed set on your area of land management or property. Take no prisoners when it comes to these weed seed operations. Clean up your future weed population by reducing the viable seed numbers reaching the soil surface.
The actual mechanics of this operation I will leave to you, however whether it is a chip hoe or fire or hand pulling, the objective is the same for a weed free zone eventually and to still be able to use judiciously our current suite of herbicides.