Trials show yard sources significant pollution risk
How careful do you think you
are you when filling the
sprayer? Early results from a
detailed field study in Oxon
may make you think again
LATEST findings, from a two-year ADAS/HRI/Coventry University project funded by Rhône-Poulenc, confirm that point sources of pesticides, such as spillages, pose a significant threat to water quality.
A few drops splashed from an induction hopper could be as significant as losses from drift and drainage.
Herbicide from the yard where a sprayer was filled last autumn is even now still getting into the local river. And that follows what most farmers and the contractor involved would consider the use of good farm practice, say the researchers.
The study, automatically monitoring and sampling drainage water from 100ha (247 acres) of arable at the head of the Cherwell river, was set up to discover the precise fate of isoproturon (ipu) herbicide applied to winter cereals.
It comes against the background of the EUs Drinking Water Directive which imposes a 0.1parts per billion limit for pesticides on water companies, says R-Ps product stewardship manager, Steve Higginbotham.
Field drain monitoring in the dry autumns of 1995 and 1996 suggested that ipu, the active ingredient most often exceeding the limit, gets into watercourses mainly from point sources such as tank filling.
The new work, pinpointing what happened to four tank-mixes of 5litres/ha of ipu applied on Nov 17, shows that yard operations may be a bigger contamination culprit than previously thought.
"There is huge potential for improving current practice," says project co-ordinator Andrée Carter of ADAS. But both she and Mr Higginbotham stress that until now that message could not be quantified.
The contractors Frazier Stealth sprayer was in "pristine" condition when it arrived on the farm, says Dr Carter. Even so test swabs found it bore a considerable amount of ipu residues, particularly at the rear.
That reinforces advice that rained-off sprayers should be parked under cover, says Mr Higginbotham.
"Wide-necked containers do not necessarily eliminate glugging and splashing," says Dr Carter. The difficulty of handling foil seals and caps when wearing rubber gloves inevitably meant some drops of concentrate hit the concrete. "No farmer would consider them as spillage but they are a considerable source of contamination."
The key message is that as little as 0.0007% of the ipu applied to the field was responsible for the findings, she says. Ongoing work aims to determine the relative proportion of ipu lost from the yard as opposed to the field drains. *
Dont just tackle ipu contamination
Reducing contamination of water by all pesticides, not just ipu, is essential if growers are to retain as wide an armoury as possible, says Mr Higginbotham. "It is not just an ipu issue, it is a pesticide issue."
Relatively simple things like putting the sprayer under cover at night and avoiding over-filling, particularly when travelling bumpy tracks, can help, he says. Sprayer makers could also help through better-designed intake hoppers, adds Dr Carter.
"The results are a big eye-opener to me," says Jim Orson, Morley Research Centre director. With herbicide resistance in grass weeds a real threat to sustainable economic cropping, retaining ipu through proper stewardship is vital, he says.
"Ipu has a key role in anti-resistance strategies. There are strong practical arguments for its retention at the current approved doses. The challenge for the whole industry is to retain it while avoiding contamination of water."
A meeting this week between R-P, the Environment Agency, HSE, NFU, BAA and the NPTC is expected to discuss the findings and to work out practical solutions to the problems they highlight, says Mr Higginbotham.
SPRAY drift causes considerable concern to the HSE and others. Preventing it remains a key task for all sprayer operators.
"Avoiding drift is essential so that the public, surface water, neighbouring crops, wildlife, beneficial insects and the general environment are protected," says Chris Wise, crop science adviser for the NFU.
Lack of attention to the prevailing wind strength and direction and choosing an inappropriate spray quality lie behind many complaints.
In both situations a compromise is called for. Too coarse a spray quality may limit drift, but it can also reduce the efficacy of the product being applied.
Using a spray quality finer than necessary can greatly increase drift risk. Bear this in mind when increasing speed with pressure based rate compensation sprayers and balancing the airflow to target volume with air-sleeve booms.
While a gentle breeze away from vulnerable areas will usually give the best spraying result, it is vital to know when the wind starts to create a drift risk.
Check wind speed and direction before you start spraying, preferably using an impeller-driven hand-held wind meter, which is considered more accurate than the floating ball type, which can be affected by humidity.
If you dont have a meter watch the movement of twigs and leaves on nearby trees and shrubs. Full information on reading their movement can be found in MAFFs "Green Code".
Once you climb into the cab it can be difficult to monitor changes in wind speed and direction. A strip of plastic tied to a cane at each headland gives a useful check.
Lastly, select nozzles for optimum spray quality, do not set the boom too high and avoid excessive speed. *
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