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Common agricultural practices, e.g. soil tillage and organic amendment, may affect field earthworm communities considerably. However, there is little data to show how long the changes persist after a certain action. The effect of peat, commonly used in Finland to improve the horticultural soil structure, on key soil organisms is also largely unknown. Earthworm abundance and microbial biomass were studied in a strawberry field experiment (soil type silty clay) with a history of different crops (strawberry, timothy, caraway, rye, turnip rape, fiddleneck, onion and buckwheat) and peat treatments. Sampling was carried out after three years of perennial cropping of strawberry. Half of the area was peat-amended twice three years apart. The earthworm community consisted mainly of Aporrectodea caliginosa and Lumbricus terrestris. Soil peat amendment almost doubled the number of endogeic A. caliginosa, but had no effect on the anecic L. terrestris. The effect of cropping history on earthworms diminished after three years of strawberry cropping. Only the positive effect of caraway on juvenile Lumbricus spp. was detectable three years after its cropping had been finished. However, some crops had secondary effects on the earthworm distribution without significant influence on their numbers while they were grown, e.g. high numbers of A. caliginosa were recorded from soil with a history of timothy ley. The effect of strawberry cropping was contradictory: six years of continuous strawberry cropping decreased the number of the anecic L. terrestris, but during the last three years on strawberry, the proportion of L. terrestris increased from 6% to 40% in the experimental area with a concomitant great drop in the number of A. caliginosa. The role of different agricultural practices (no tillage, mulching, inter-row grass cover and pesticides) is discussed. The crop-induced changes persisted in the microbial biomass for three years (onion cropping reduced microbial biomass C), but soil amendment had no effect on microbes. The abundance of A. caliginosa was associated with soil organic C, but not with soil microbial biomass. 相似文献
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A field experiment was conducted to study the effects of peat amendment and crop production system on earthworms. The experiment was established on a field previously cultivated with oats and with silt as the main soil type. Perennial crops strawberry, timothy and caraway, and annual crops rye, turnip rape, buckwheat, onion and fiddleneck were cultivated with conventional methods. All the crops were grown with and without soil amendment with peat. Earthworms were sampled twice: 4 and 28 months after establishment of the experiment. In the former case part of the experimental plots were soil sampled and hand sorted for estimation of earthworms. In the latter case all experimental plots were sampled and both soil sampling and mustard extraction was carried out. Soil organic carbon and microbial biomass was measured at 14 and 28 months. Peat increased the abundance of juvenile Aporrectodea caliginosa by 74% in three growing seasons, but had no effect on adult numbers. Lumbricus terrestris numbers were not increased by peat treatment. Three season cultivation of caraway favoured both A. caliginosa and L. terrestris. An equal abundance of A. caliginosa was also found in plots cultivated with turnip rape and fiddleneck. Total earthworm and especially A. caliginosa numbers were very small in plastic-mulched strawberry beds. This was mainly attributed to repeated use of the insecticide endosulfan. With the strawberry plots omitted there was a significant correlation between soil microbial N measured at 14 months and juvenile Aporrectodea spp. and Lumbricus spp. numbers measured at 28 months. Adult earthworm numbers were not associated with either soil organic C or microbial biomass. 相似文献
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Seppo AM Saari Kirsi H Juuti Joanna H Paloj?rvi Kirsi M V?is?nen Riitta-Liisa Rajaniemi Leena E Saijonmaa-Koulumies 《Acta veterinaria Scandinavica》2009,51(1):40
Background
Demodex gatoi is unique among demodectic mites. It possesses a distinct stubby appearance, and, instead of residing in the hair follicles, it dwells in the keratin layer of the epidermis, causing a pruritic and contagious skin disease in cats. Little is known of the occurrence of D. gatoi in Europe or control of D. gatoi infestation.Case presentation
We describe D. gatoi in 10 cats, including five Cornish Rex, two Burmese, one Exotic, one Persian and one Siamese, living in six multi-cat households in different locations in Finland containing 21 cats in total. Intense pruritus was the main clinical sign. Scaling, broken hairs, alopecia and self-inflicted excoriations were also observed.Diagnosis was based on finding typical short-bodied demodectic mites in skin scrapings, skin biopsies or on tape strips. Other pruritic skin diseases, such as allergies and dermatophytoses, were ruled out. In one household, despite finding several mites on one cat, all six cats of the household remained symptomless.Amitraz used weekly at a concentration of 125-250 ppm for 2-3 months, proved successful in three households, 2% lime sulphur weekly dips applied for six weeks in one household and peroral ivermectin (1 mg every other day for 10 weeks) in one household. Previous trials in four households with imidacloprid-moxidectin, selamectin or injected ivermectin given once or twice a month appeared ineffective.Conclusion
D. gatoi-associated dermatitis is an emerging contagious skin disease in cats in Finland. Although pruritus is common, some cats may harbour the mites without clinical signs. In addition, due to translucency of the mites and fastidious feline grooming habits, the diagnosis may be challenging. An effective and convenient way to treat D. gatoi infestations has yet to emerge. 相似文献
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