Another Life: The rose some Connacht people call The Rambling Rector has now climbed half-way up our ESB pole, enveloping both it and a neighbouring spruce tree. At the end of June it unfurls cascades of creamy blossom with a honeyed perfume that is the very scent of summer. So long as the breeze comes straight off the sea, we dwell for a while in Arcadia, writes Michael Viney.
Around the hill, however, we meet the truer odour of Ireland's mid-summer countryside: shocking as a gas attack, the ammoniac stench of slurry. No sooner have the silage machines departed than the mown fields, lemon-bright, are sprayed with the fermenting manure from beef cattle and sheep.
An e-mail from Co Waterford protests the horrors of the slurry season, when "this evil, invisible cloud spreads over the countryside" and windows must be shut at meal-times or for hours before going to bed. "Do you consider slurry to be necessary?" demands the reader. "Am I being hard and ignorant in detesting it and feeling that, in reality, it has absolutely no value? Are farmers blatantly flouting the rules for the spreading of this foul liquid?" A great many people harbour a similar wrath; in Northern Ireland, slurry-spreading accounts for more than 80 per cent of odour complaints to local authorities. "Avoid spreading slurry in the evenings, at weekends or on public holidays," farmers are advised, "and ensure the wind is blowing away from dwelling houses". Ah yes.
In Germany, where landspreading accounts for half of all ammonia emissions, wind-tunnels have been used to find the right kind of weather for spreading. The cooler, calmer and wetter it gets, the less ammonia is given off. But then, spreading too close to heavy rain risks polluting run-off into rivers and lakes. Irish farmers can't win.
"The silage process is not complete," Teagasc says, "until slurry has been recycled to where the nutrients were removed." Slurry spread in summer provides little available nitrogen, but 1,000 gallons equals a bag of artificial fertilizer rich in phosphorus and potash, both valuable plant nutrients. Overall, the slurry from 100 beef animals kept on slats for the winter can save the farmer about €1,750.
Recycling organic nutrients sounds fine ecologically, and when slurry is injected into bare soil rather than being spread on the surface of grass stubble, the nuisance is considerably less. Ironically, what seems a more "natural" and relatively odour-free way of distributing dung - in cow-pats dropped by grazing cattle - has its own ecological hazards. The pats can be laced with the residue of veterinary insecticides, used in summer to rid young grazing cattle of intestinal worm parasites picked up from the grass.
When avermectins - in particular, ivermectin - are administered in long-acting form, as much as 90 per cent can end up on the ground, there to kill or damage the insects that arrive almost at once to colonise the cow-pat. Studies in Britain and Denmark, in particular, have found pats made "insect-sterile" by residue of the chemical and, consequently, are slow to decompose.
A letter from the Dublin Trout Anglers' Association reports on the anxiety of fishermen over the apparent disappearance of fly life from many riverside pastures; it speculates on the link with cattle pesticides. One British study has, indeed, found that half of a population of the common yellow dung fly were killed in the laboratory within 48 hours of exposure to ivermectin concentrations of 36 parts per billion - a microscopic measure compared with typical slow-release levels. Other insects are rendered infertile or produce malformed larvae.
A cow-pat is colonised by four successive waves of insects: first the flies, laying their eggs before the cow-pat crusts over; then an army of dung-beetles, whose larvae develop within the pat, breaking it up as they grow and mixing it with the surface of the soil. The beetles also bring their passengers, mites and nematodes. And finally, after 20 days or so, comes an upward invasion by the earthworms and other soil species, such as springtails. Their tunnelling opens up the pat to yet more beetles and lets in the air that hastens decay. In Ireland's moist climate, earthworms do most of the "processing", but all the insects play some part.
Even this complex ecosystem has links beyond itself - to freshwater fish, bats and swallows skimming cattle pastures, to the choughs of coastal dunes, rifling cow-pats for beetles and grubs. Research at Teagasc and UCC has concentrated so far on the ecology of untainted cow-pat communities. In Scotland, the RSPB is funding university research into the impact of avermectins on insects needed by breeding birds. Can dosing cattle be better timed, better administered, or kept to young cattle that really need it? Little by little, the "collateral damage" of farming must be contained.