Soil invertebrates in conventionally and organically farmed fields of winter wheat and winter oilseed rape in the Czech Republic

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1 Acta Soc. Zool. Bohem. 74: 85 89, 2010 ISSN X Soil invertebrates in conventionally and organically farmed fields of winter wheat and winter oilseed rape in the Czech Republic Jan MIKULA, Vratislav LAŠKA, Bořivoj ŠARAPATKA, Jana TUFOVÁ & Ivan H. TUF* Department of Ecology and Environmental Sciences, Faculty of Science, Palacky University, Třída Svobody 26, CZ Olomouc, Czech Republic * corresponding author: ivan.tuf@upol.cz Received 7 January 2010; accepted 9 December 2010 Published 20 December 2010 Abstract. This paper summarize the first results of a study aimed at evaluating soil and surface-dwelling invertebrate assemblages at an experimental field site in Praha-Uhříněves, where both organic and conventional farming have been practicised for 15 years. Analysis of the data on soil invertebrates confirms that agro-ecosystems are complex and underlines the importance of all the factors influencing biodiversity in both organic and conventional farming systems. Not only the application of insecticides/pesticides, covering the soil with the remains of plants, ploughing etc., but climatic conditions and type of crop can play an important role in determining the distribution and abundance of soil invertebrates. Organic farming favoured invertebrates like millipedes in dry more than wet years. The taxa most valuable for evaluating agrosystems seem to be mainly ground beetles (Carabidae), spiders (Araneae) and millipedes (Diplopoda). This study confirmed it is necessary to pay attention to the quality of soil and structure of the landscape, and use methods that are likely to enhance the diversity of organisms in the system. Key words. Soil zoology, ecology, biodiversity, soil fauna, sustainable agriculture, organic farming, conventional farming, Invertebrata, Diplopoda, Araneae, Carabidae, Chilopoda, Czech Republic. INTRODUCTION Intensification of agriculture had a remarkable effect on biodiversity and the quality of soil. At present, the effect of agricultural systems on biodiversity is intensely discussed and arthropods are frequently used as bioindicators for assessing the effect of landscape management and soil quality (Paoletti 1999). Soil organisms are assumed to be important in the soil ecosystem, especially in the decomposition of soil organic matter and nutrient cycling (Wardle & Giller 1997). Some studies indicate that there is a higher diversity of certain groups of invertebrates in organic than in conventional farmed areas, e.g. carabid beetles (Kromp 1999, Langmaack et al. 2001), spiders (Feber et al. 1998) and earthworms (Paoletti 1999). However, other studies indicate no difference in diversity in the two systems of farming, e.g. Berry et al. (1996) and Blackburn and Arthur (2001) for centipede communities. The population dynamics of soil organisms in agricultural systems depends on a range of different factors, such as soil characteristics, climate, type of farm management, crop, ploughing and use of pesticides (Debeljak et al. 2007). Physical disturbance of soil, such as tillage, is also has a detrimental effect on the diversity of the soil fauna (Altieri 1999). In this study the communities of soil-dwelling and surface-dwelling invertebrates in a conventional and an organic managed crop were compared. Presented at the 10 th Central European Workshop on Soil Zoology, České Budějovice, Czech Republic, April

2 MATERIALS AND METHODS This evaluation of invertebrate communities was carried out on an experimental site at a farm in Praha Uhříněves, where there is the longest-running trial comparing organic and conventional farming in the Czech Republic, and the conversion to organic farming began 15 years ago. In this study, sites used for growing winter wheat and winter oilseed rape under both organic and conventional farming conditions were compared. Each field (4 in total) was at least 2 hectares in area, the distances between fields were at least 20 metres. The fields did not differ in microclimatic conditions and basic soil parameters. Soil invertebrates were sampled in spring summer in 2007 and Five pitfall traps (plastic cup 7 cm in diameter with a metal cover and filled with a 4% water formaldehyde solution) were set in each field from April May in both years and were inspected monthly till June July, and the catches for each of the years in each of the fields were analysed. Five soil samples (area of each 1/30 m 2, 15 cm depth) were taken twice a year in spring (April and May in 2007, May and June in 2008) at each variant of field and crop. Samples were heat-extracted in modified Tullgren apparatus for 14 days. Animals were sorted into higher taxa: i.e. beetles and beetle larvae (Coleoptera), dipteran larvae (Diptera), millipedes (Diplopoda), centipedes (Chilopoda), spiders (Aranea) and harvestmen (Opiliones). The abundances of the soil invertebrates and activities of soil surface invertebrates were compared using Student t-test. RESULTS AND DISCUSSION In the two years, over 8,400 specimens of the above mentioned groups were recorded (Table 1). Beetles (Coleoptera) were the most dominant group (5,000 caught specimens). There were differences in the numbers of beetles in pitfall traps in the conventional and organic systems under winter wheat in both years, although in 2007 organic, and in 2008 conventional conditions, were more favourable for them. Similarly, in winter rape, larger densities were recorded in conventional fields (significant only in 2007). Like the beetles, beetle larvae were more abundant in conventionally managed winter oilseed rape in According to the results of a meta-analysis of the effect of organic farming on biodiversity, beetles are the most commonly used model group in agricultural research (Hole et al. 2005). Twelve of 16 evaluated studies recorded both a higher diversity and density of beetles in organically managed fields compared to conventional fields and 4 studies the opposite result. It is likely that conventional winter oilseed rape is a better habitat for carabids beetles. Results for fields of oilseed rape in 2007 confirm that reduced cultivation, which is less damaging to soil structure, has a positive effect on carabid beetles and their prey (Furnier et al.1998). Spiders (Aranea) were the second most dominant group of invertebrates with more than 2,000 individuals recorded. Although they did not differ in abundance in the organic and conventionally farmed winter wheat, they were significantly more abundant in organic winter rape than in the conventional crop in both years. The main difference between the fields of oilseed rape was in the density of plants, which was greater in the conventional than in the organic farmed field. Similarly, a lower number of spiders are recorded under dense than sparse plant-growth (Honěk 1988). It is generally known, that spiders are more diverse in organic fields, but differences in density are small (Basedow 1998). Hole et al. (2005) in their review of organic and conventional agriculture and found that 40% of studies report a positive effect of conventional farming on biodiversity, 40% a positive effect on the ecological system and 20% no difference between the two farming systems. There were no differences in the numbers of centipedes (Chilopoda) in the differently farmed fields. This accords with previously published findings that centipedes are relatively insensitive to how the fields are farmed (Blackburn & Arthur 2001, Berry et al. 1996). In contrast to centipedes, millipedes (Diplopoda) were more sensitive. They were more abundant in both organically farmed crops in 2007 but less so in Apparently, the difference in climatic conditions between the years was more important than field management. The first half of year 2007 (i.e. months I VII) was significantly warmer than in 2008 (p = , data from additionally April 86

3 Table 1. Activities (number of individuals per trap per 4 weeks) and abundances (ind./m 2 ) of soil invertebrates in conventionally and organically farmed fields of winter wheat and winter oilseed rape. Abbreviations: ORG organically farmed, CONV conventionally farmed, p probability of identical catches in organically and conventionally farmed systems. Significantly different values are in bold winter wheat winter oilseed rape ORG CONV p ORG CONV p ORG CONV p ORG CONV p activity Coleoptera (adults) Coleoptera (larvae) Diptera (larvae) Aranea Opiliones Chilopoda Diplopoda total abundance Coleoptera (adults) Coleoptera (larvae) Diptera (larvae) Aranea Chilopoda Diplopoda total

4 2007 was extremely dry. It is possible, that the greater number of hygrophilous millipedes in the organic plots in the dry hot year reflects the greater biomass plant remains on the soil there compared to open ground in the conventional plots. Similarly Klinger (1992) reports that millipedes are more abundant in ecological fields in which there is more food in the form of plant remains on the surface of the soil and no pesticides. In 2008 the more humid conditions in the conventional plots with dense tall crops favoured millipedes more than the drier conditions in the sparser organic crop. The distributions of the millipedes and dipterous larvae were similar in the organic and conventional crops. It is likely that these insects were more abundant in fields where the soils were more humid, because it is an important factor influencing their distribution (Frouz 1999). When the overall results are used to evaluate the different methods of farming the pattern was not stable between both crops and years. Organic management was only favourable for surface dwelling invertebrates in 2007 in winter wheat. In 2008 invertebrates were more abundant in conventionally farmed fields. In oilseed rape, the opposite results were obtained; in 2007, conventional fields were more favourable for soil invertebrates (in both soil samples and pitfall traps), while in 2008 the differences were not significant. This may be a result of not only the climatic differences mentioned above but of the type of crop. Crops of monocotyledonous plants like wheat protect the soil less than dicotyledonous oilseed rape. In dry seasons, the greater biomass of plant remains covering the soil surface in fields of oilseed rape provides a better shelter for invertebrates than the relatively bare ground in wheat fields. The results of this analysis of data on soil invertebrates confirms that agro-ecosystems are complex and underlines the importance of all the factors influencing biodiversity in both organic and conventional farming systems. Not only the application of insecticides/pesticides, covering the soil with the remains of plants, ploughing etc., but both climatic conditions and type of crop can play an important role in determining differences in the distribution and abundance of soil invertebrates. Organic management was more favourable for invertebrates like millipedes in dry than in wet years. The taxa most suitable for evaluating agrosystems seem to be mainly ground beetles, spiders and millipedes. In any case it is necessary to pay more attention to the quality of soil and structure of the landscape and use methods that are likely to enhance the diversity of organisms in the system. A c k n o w l e d g e m e n t s The authors wish to thank the Czech Ministry of Education (grant No. 2B06101) and the Czech Ministry of the Environment (grant VaV 1c/4/8/04) for funding this research. REFERENCES ALTIERI M. A. 1999: The ecological role of biodiversity in agroecosystems. Agriculture, Ecosystems & Environment 74: BASEDOW T. 1998: The species composition and frequency of spiders (Araneae) in fields of winter wheat grown under different conditions in Germany. Journal of Applied Entomology 122: BERRY N. A., WRATTEN S. D., MCERLICH A. & FRAMPTON C. 1996: Abundance and diversity of beneficial arthropods in conventional and organic carrot crops in New Zealand. New Zealand Journal of Crop and Horticultural Science 24: BLACKBURN J. & ARTHUR W. 2001: Comparative abundance of centipedes on organic and conventional farms, and its possible relation to declines in farmland bird populations. Basic and Applied Ecology 2: DEBELJAK M., CORTET J., DEMŠAR D., KROGH P. H. & DŽEROSKI S. 2007: Hierarchical classification of environmental factors and agricultural practices affecting soil fauna under cropping systems using Bt maize. Pedobiologia 51: FEBER R. E., BELL J., JOHNSON P. J., FIRBANK L.G. & MACDONALD D. W. 1998: The effects of organic farming on surfaceactive spider (Araneae) assemblages in wheat in southern England, UK. Journal of Arachnology 26:

5 FOURNIER E., LOREAU M. & HAVET P. 1998: Effects of new agricultural management practices on the structure and diversity of ground-beetle communities (Coleoptera, Carabidae). Gibier Faune Sauvage, Game Wildlife 15: FROUZ J. 1999: Use of soil dwelling Diptera (Insecta, Diptera) as bioindicators: a review of ecological requirements and response to disturbance. Agriculture, Ecosystems & Environment 74: HOLE D. G., PERKINS A. J., WILSON J. D., ALEXANDER I. H., GRICE P. V. & EVANS A. D. 2005: Does organic farming benefit biodiversity? Biological Conservation 122: HONĚK A. 1988: The effect of crop density and microclimate on pitfall trap catches of Carabidae, Staphylinidae (Coleoptera), and Lycosidae (Araneae) in cereal fields. Pedobiologia 32: KLINGER K. 1992: Diplopods and Chilopods of conventional and alternative (biodynamic) fields in Hesse (FRG). Berichte des Naturwissenschaftlich-medizinischen Vereins in Innsbruck Supplement 10: KROMP B. 1999: Carabid beetles in sustainable agriculture: a review on pest control efficacy, cultivation impacts and enhancement. Agriculture, Ecosystems & Environment 74: LANGMAACK M., LAND S. & BÜCHS W. 2001: Effects of different field management systems on the carabid coenosis in oil seed rape with special respect to ecology and nutritional status of predacious Poecilus cupreus L. (Col., Carabidae). Journal of Applied Entomology 125: PAOLETTI M. G. 1999: The role of earthworms for assessment of sustainability and as bioindicators. Agriculture, Ecosystems & Environment 74: PAOLETTI M. G. 1999: Using bioindicators based on biodiversity to assess landscape sustainability. Agriculture, Ecosystems & Environment 74: WARDLE D. A. & GILLER K. E. 1997: The quest for a contemporary ecological dimension to soil biology. Soil Biology and Biochemistry 8:

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