Running weeds down with pasture

Running weeds down with pasture

Cropping
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A pasture phase can help run down weed seed banks and increase soil fertility.

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Tim Condon, Delta Agribusiness, says mixed farmers can unleash serious benefits across their entire farm enterprise through incorporating pasture phases into their cropping rotation.

Tim Condon, Delta Agribusiness, says mixed farmers can unleash serious benefits across their entire farm enterprise through incorporating pasture phases into their cropping rotation.

A NSW-based agronomist has talked up the nutritional and weed management benefits of a pasture phase in cropping rotations.

Tim Condon, Delta Agribusiness, Harden, told the crowd at last month's Grains Research and Development Corporation (GRDC) update for advisors that continuous cropping had placed pressure on organic nitrogen (N) levels and led to a rise in problem weeds.

He said the boom in the livestock sector meant mixed farmers had the perfect opportunity to rectify these issues with a pasture phase.

"Pastures can help rebuild organic carbon and replenish soil N reserves while also allowing opportunities to reduce the weed seed bank," Mr Condon said.

However, he said it was not a simple matter of scratching in a bit of clover and hoping for the best.

"To achieve the full benefits you really need a thick and productive pasture, and if you're going with a pasture legume you need to ensure there are the rhizobia helping fix that N."

Mr Condon said there was no one size fits all approach to successfully integrating pasture.

"It can go from a small percentage of your farm if you are in a low rainfall zone to a much larger proportion in a high rainfall zone."

Just as the percentage of pasture varied, so too did the preferred species.

"In the drier areas, medics and vetch are a good fit, as you head east you will see more perennial grasses and more long-term pasture phases."

The weed seed management advantage is a critical part of maximising the value of the pasture phase.

Mr Condon said farmers could make fodder, spray top and fallow or graze among other options.

He said the aim was to have a competitive pasture mix that could outcompete weed species early on keeping numbers down and then to consolidate this run-down of weed numbers by stopping weed seed set.

"A typical strategy to really reduce weed numbers could be a crash grazing, fodder making or spray topping in year one, reducing weed seed set by 70-80 per cent followed by a winter clean (heavy grazing followed by a spray, typically a gramoxone / simazine mix) in year two then an early fallow in year three."

Mr Condon said where possible farmers should look at deep-rooted pastures for their soil amelioration benefits.

"Species such as lucerne and chicory have the ability to improve macroporosity well into the subsoil which in turn gives greater access to deeper water and nutrients for following crops."

He said well managed pastures would be an important tool for mixed farmers to combat problems such as limited nutrition and rising weed numbers.

"Well managed productive pastures will provide significant synergies for a mixed farm, firstly the fodder for livestock and secondly the advantages for the cropping phases to follow."

The story Running weeds down with pasture first appeared on Farm Online.

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