[ASC-media] DRAIN WITH SUMMER RAIN: Crop Doctor
brendon at iinet.net.au
Wed Mar 22 11:36:12 EST 2006
DRAIN WITH SUMMER RAIN 22.3.06<?xml:namespace prefix = o ns =
Heavy summer weed activity can hamper wheat emergence in the following
season and also drain soil nutrients to offset the benefits of residual soil
When the Grains Research and Development Corporation (GRDC) supported CRC
for Australian Weed Management monitored summer weeds for three years, they
were found to chew through up to 66 per cent of available soil nitrogen,
cutting yields in two seasons and persistently diminishing protein.
When harvesting weeds after a wet summer, simulated with irrigation at
Merredin, Department of Agriculture researchers, Dr Abul Hashem, Dr Shahab
Pathan and Catherine Borger found that their biomass contained up to 15kg/ha
of robbed soil nitrogen.
This is half of the nitrogen a grower might expect to have added by running
a pulse rotation the previous year.
Apart from sucking up soil nutrients, certain weeds are also suspected of
chemical warfare on subsequent crops, lacing the soil with allelochemicals
that inhibit wheat emergence.
When the dominant summer weed was caltrop, wheat emergence slumped 22 per
cent in the following season, with yield plummeting 40 per cent and grain
protein dropping from 9.2 to 7.5 per cent.
While the research investigated the difference between weedy and weed
controlled plots in dry and wet summer conditions, it was predictably under
moist conditions that weeds really burgled the soils.
With a bit of moisture to fuel growth, the weeds appetites grew and they
dipped roots into the ground to suck up more of the available nitrogen. Wet
weedy plots demonstrated a substantially greater drain on nutrients than wet
clean ones, making it clear that weeds were doing the damage and not
As if disease and pests were not enough reason to manage green bridges, this
research has added a new incentive to control summer weeds.
The Crop Doctor is GRDC Managing Director, Peter Reading, Tel 02 6272 5525
Further Information: Dr Abul Hashem, Tel 08 9690 2000
Brendon Cant & Associates
Public Relations & Marketing
4 Gugeri St
Claremont WA 6010
Tel 08 9384 1122
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