I saw an earthworm a couple of months ago. It was visible for a few seconds; a red, ringed anterior end withdrawing into a burrow which had become exposed after I shifted a log. Quickly I replaced the log. Earthworms are very precious in this part of the country.
Charles Darwin published his book, On the Formation of Vegetable Mould Through the Action of Worms, in 1881. Struggling against ill health, he devoted his final years to writing about animals which most of us regard as insignificant. The book sold well, better than The Origin of Species. The literate public as well as scientists, not only in England, but much further afield, were interested in worms which were plentiful at that time. Darwin describes how, all around him, he observed an abundance of worms. When he went out at night he saw them ‘crawling about in large numbers.’ If he took a stroll after rain had interrupted a period when the weather was dry, he sometimes found an ‘astonishing number of dead worms.’ On his uncle’s farm he had found ‘a cake of dry earth, as large as my two open hands, which was penetrated by seven burrows, as large as goose quills’. However, although he is sometimes given credit for it, it was not Darwin but Professor Hensen in Germany who made the first estimate of a worm population. He calculated that a hectare of land was home to 133,000 worms. You could expect to find over 50,000 in an acre.
From childhood I remember hours spent in a walled garden. It produced apples and berries and a great variety of vegetables. There were shrubs bordering a lawn, scented roses rambling along wire and a succession of flowers to brighten our days from January until Hallowe’en. In the rich loamy soil worms burrowed, and every cart load of farmyard manure that arrived brought robust immigrants to swell their numbers. Land in the north of Ireland is said to be too acid and too rich in organic matter to sustain a high population of worms, but this is a generalisation.
As the nineteen fifties became the sixties and then the seventies we became aware that worms were becoming scarcer, and began to speculate about the cause. Was it the constant cultivation, the regular digging and weeding, which was disturbing them? Were they filling their gizzards with pellets of the artificial fertilizers we were using instead of manure because they were more convenient and didn’t bring with them troublesome weeds? Was it the herbicides we used to kill the weeds, or the copper sulphate that was put on the soil to prevent potato blight, or the other fungicides and insecticides we sprayed?
Answers to these questions can be found in the key text, Earthworm Ecology by Clive Edwards which is now in its second edition. In this book James P Curry from University College Dublin, has written an excellent chapter which is of great practical value to farmers and gardeners.
Not surprisingly, farmyard manure is an unfailing method of boosting the earthworm population. The plants which provide their food need to have sufficient nitrogen available for their optimum growth, and organic fertilizers are the most natural way of supplying this. Some farmers blame the disappearance of worms on the spreading of slurry on land, but slurry is only toxic if it contains high levels of ammonia and organic salts and is applied heavily. A moderate amount can have an adverse effect after it had been spread, but this effect is only temporary. The worm population recovers and even increases in the long term. To complicate the picture further, pig slurry, like landspread sewage, may contain copper and zinc which are poisonous to most species of worm.
What about mineral fertilizers? Again, moderation seems to be the key. The increased yield of plants is followed by a rise in the population of worms, provided the application of nitrogen is not too heavy and it is remembered that sulphate of ammonia and, to a lesser extent, sulphur coated urea make the soil more acid. Irish worms avoid acid soils and are found where the soil pH ranges between 5.0 and 7.4.
Weed killers? These do not appear to harm worms directly, but they can restrict their food supply, and by removing plant cover from the surface of the soil can make it more liable to dry out. Fungicides and insecticides can be even less innocuous. They vary in the effects they have on worms, but it is consoling to know that it is their repeated use over a long time that is really damaging, and not their occasional spraying.
To account for the almost total extinction of worms from gardens and garden centres in the north of Ireland we need to ask different questions. Have worms, perhaps been wiped out by a mystery ailment? Not much is known about the diseases from which these animals suffer, or the parasites which infect them, but although they play host to a variety of organisms, there is no evidence of a catastrophic epidemic.
There are, of course, animals and birds which feed on worms. Shrews, badgers and foxes include them in their diet, as do blackbirds, thrushes, starlings and magpies. Centipedes and ground beetles eat them too. Worms have co-existed with all of these for thousands, if not millions, of years and I very much doubt if any gardener or farmer considers any of these as a suspect. Sea gulls are also partial to worms. I have seen large flocks miraculously appear on fields over twenty miles inland, that have just been ploughed, but I can’t say I saw any recently. A gardener digging, if lucky, will be accompanied by a single robin.
Lurking in dark, damp places under flower pots, plastic sheets or logs is another predator, one that was first spotted in this country in 1963, after it arrived hidden in the roots of roses and in daffodil bulbs that we imported from New Zealand. It too is a worm, but of the flat variety, related to flukes and tapeworms and even more closely to the small black creatures that can be seen gliding up the glass of a jam jar in water fished out of a ditch. This New Zealand flatworm, Arthurdendyus triangulata, whose photograph and description are found on more than one website, feeds voraciously on earthworms but has been known to survive without food for over a year. So far no attempts to eradicate it have proved successful and it has spread to Scotland, the north of England and even the Faroe Islands. In Ireland it is widespread north of a line that stretches from Donegal Bay to Carlingford Lough. What limits its spread to other areas is the temperature of the soil. Soil temperatures above 23℃ are lethal to it. In its country of origin it is only found in South Island. The soils of North Island are too warm for it.
Today I walked past a grassy place and noticed an abundance of Lady’s smock where previously it was very rare. Lady’s smock is an attractive flower and provides food for Orange-tip butterflies, but it is a plant that thrives in marsh. It is unwise to jump to conclusions, but I can’t help wondering whether the absence of worms and their burrows is having an affect on the drainage and aeration of this soil. Darwin had a great appreciation of the part these animals, play in maintaining soil fertility. Although they are small, he noted, they ‘possess great muscular power.’ He wasn’t the person who first estimated the number of earthworms in soil, but he did measure the rate at which they added vegetable mould to its surface. His figures are just as astounding. ‘In many parts of England,’ he wrote, ‘a weight of more than ten tons of dry earth annually passes through their bodies and is brought to the surface on each acre of land.’ I saw an earthworm a couple of months ago. It was visible for a few seconds; a red, ringed anterior end withdrawing into a burrow which had become exposed after I shifted a log. Quickly I replaced the log. Earthworms are very precious in this part of the country.
Charles Darwin published his book, On the Formation of Vegetable Mould Through the Action of Worms, in 1881. Struggling against ill health, he devoted his final years to writing about animals which most of us regard as insignificant. The book sold well, better than The Origin of Species. The literate public as well as scientists, not only in England, but much further afield, were interested in worms which were plentiful at that time. Darwin describes how, all around him, he observed an abundance of worms. When he went out at night he saw them ‘crawling about in large numbers.’ If he took a stroll after rain had interrupted a period when the weather was dry, he sometimes found an ‘astonishing number of dead worms.’ On his uncle’s farm he had found ‘a cake of dry earth, as large as my two open hands, which was penetrated by seven burrows, as large as goose quills’. However, although he is sometimes given credit for it, it was not Darwin but Professor Hensen in Germany who made the first estimate of a worm population. He calculated that a hectare of land was home to 133,000 worms. You could expect to find over 50,000 in an acre.
From childhood I remember hours spent in a walled garden. It produced apples and berries and a great variety of vegetables. There were shrubs bordering a lawn, scented roses rambling along wire and a succession of flowers to brighten our days from January until Hallowe’en. In the rich loamy soil worms burrowed, and every cart load of farmyard manure that arrived brought robust immigrants to swell their numbers. Land in the north of Ireland is said to be too acid and too rich in organic matter to sustain a high population of worms, but this is a generalisation.
As the nineteen fifties became the sixties and then the seventies we became aware that worms were becoming scarcer, and began to speculate about the cause. Was it the constant cultivation, the regular digging and weeding, which was disturbing them? Were they filling their gizzards with pellets of the artificial fertilizers we were using instead of manure because they were more convenient and didn’t bring with them troublesome weeds? Was it the herbicides we used to kill the weeds, or the copper sulphate that was put on the soil to prevent potato blight, or the other fungicides and insecticides we sprayed?
Answers to these questions can be found in the key text, Earthworm Ecology by Clive Edwards which is now in its second edition. In this book James P Curry from University College Dublin, has written an excellent chapter which is of great practical value to farmers and gardeners.
Not surprisingly, farmyard manure is an unfailing method of boosting the earthworm population. The plants which provide their food need to have sufficient nitrogen available for their optimum growth, and organic fertilizers are the most natural way of supplying this. Some farmers blame the disappearance of worms on the spreading of slurry on land, but slurry is only toxic if it contains high levels of ammonia and organic salts and is applied heavily. A moderate amount can have an adverse effect after it had been spread, but this effect is only temporary. The worm population recovers and even increases in the long term. To complicate the picture further, pig slurry, like landspread sewage, may contain copper and zinc which are poisonous to most species of worm.
What about mineral fertilizers? Again, moderation seems to be the key. The increased yield of plants is followed by a rise in the population of worms, provided the application of nitrogen is not too heavy and it is remembered that sulphate of ammonia and, to a lesser extent, sulphur coated urea make the soil more acid. Irish worms avoid acid soils and are found where the soil pH ranges between 5.0 and 7.4.
Weed killers? These do not appear to harm worms directly, but they can restrict their food supply, and by removing plant cover from the surface of the soil can make it more liable to dry out. Fungicides and insecticides can be even less innocuous. They vary in the effects they have on worms, but it is consoling to know that it is their repeated use over a long time that is really damaging, and not their occasional spraying.
To account for the almost total extinction of worms from gardens and garden centres in the north of Ireland we need to ask different questions. Have worms, perhaps been wiped out by a mystery ailment? Not much is known about the diseases from which these animals suffer, or the parasites which infect them, but although they play host to a variety of organisms, there is no evidence of a catastrophic epidemic.
There are, of course, animals and birds which feed on worms. Shrews, badgers and foxes include them in their diet, as do blackbirds, thrushes, starlings and magpies. Centipedes and ground beetles eat them too. Worms have co-existed with all of these for thousands, if not millions, of years and I very much doubt if any gardener or farmer considers any of these as a suspect. Sea gulls are also partial to worms. I have seen large flocks miraculously appear on fields over twenty miles inland, that have just been ploughed, but I can’t say I saw any recently. A gardener digging, if lucky, will be accompanied by a single robin.
Lurking in dark, damp places under flower pots, plastic sheets or logs is another predator, one that was first spotted in this country in 1963, after it arrived hidden in the roots of roses and in daffodil bulbs that we imported from New Zealand. It too is a worm, but of the flat variety, related to flukes and tapeworms and even more closely to the small black creatures that can be seen gliding up the glass of a jam jar in water fished out of a ditch. This New Zealand flatworm, Arthurdendyus triangulata, whose photograph and description are found on more than one website, feeds voraciously on earthworms but has been known to survive without food for over a year. So far no attempts to eradicate it have proved successful and it has spread to Scotland, the north of England and even the Faroe Islands. In Ireland it is widespread north of a line that stretches from Donegal Bay to Carlingford Lough. What limits its spread to other areas is the temperature of the soil. Soil temperatures above 23℃ are lethal to it. In its country of origin it is only found in South Island. The soils of North Island are too warm for it.
Today I walked past a grassy place and noticed an abundance of Lady’s smock where previously it was very rare. Lady’s smock is an attractive flower and provides food for Orange-tip butterflies, but it is a plant that thrives in marsh. It is unwise to jump to conclusions, but I can’t help wondering whether the absence of worms and their burrows is having an affect on the drainage and aeration of this soil. Darwin had a great appreciation of the part these animals, play in maintaining soil fertility. Although they are small, he noted, they ‘possess great muscular power.’ He wasn’t the person who first estimated the number of earthworms in soil, but he did measure the rate at which they added vegetable mould to its surface. His figures are just as astounding. ‘In many parts of England,’ he wrote, ‘a weight of more than ten tons of dry earth annually passes through their bodies and is brought to the surface on each acre of land.’
