Title: Weeds will suck soil dry

[Weekly Times 22 September 2010, p. 117: By Fiona Myers] -- GETTING your weeds under control may mean more than keeping your paddocks pretty. And not spraying could be the difference between a good crop or a poor one next year.
Industry and Investment NSW Parkes agronomist Col McMaster told farmers at a field day at Merriwagga recently that fallow efficiency was greatly effected by weeds.

Fallow efficiency is the amount of moisture retained in the soil over summer, from harvest until sowing the following year. It takes into consideration summer rain, and can be as high as 40 per cent. So if 300mm of rain falls during summer, a fallow efficiency of 40 per cent means 120mm is available to the coming crop. But poor weed control can bring fallow efficiency back down to as little as 0-2 per cent.

Trials have been set up near Parkes, NSW, to establish how spraying and the timing of sprays affects fallow efficiency, with results expected in January. But Mr McMaster is confident that spray fallow is the way to go if farmers want to maximisc soil moisture profiles.

"We know that weeds rob moisture from the soil, but they also rob nutrients and this is what you are trying to stop," he said. "A better fallow efficiency means there is more stored moisture in the soil, and this can decrease the risks of growing the next crop if the in-crop rainfall in the coming year is not as good as it should be," he said.

"We all need to be reminded that we should try to capture as much of that summer rainfall as possible so that we can rely on some of the stored moisture for the next crop. "It is a matter of making sure the weeds don’t get away." For some farmers, this may be a case of getting off theis headers and back on to the spray rigs if rain keeps up.

Mr McMaster said chemical fallow on stubble paddocks could also increase fallow efficiency, rather than ploughed up country. "The retained stubble can help water infiltration, especially if there is a big summer storm," he said. "This is in contrast to worked up country, which can form a crust and this reduces the ability to capture the rainfall, and it decreases the fallow efficiency."



Caption Text: In a hole: Col McMaster tells NSW farmers poor weed control can have a detrimental effect on soil moisture over summer.



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Article: WeedsNews1032 (permalink)
Categories: :WeedsNews:agricultural weed, :WeedsNews:herbicides, :WeedsNews:weed control, :WeedsNews:tillage, :WeedsNews:soil research
Date: 22 September 2010; 10:46:28 AM AEST

Author Name: David Low
Author ID: adminDavid