Abstract

LIETTI, Marcela et al. Effect of two tillage systems on the abundance of soil-dwelling arthropods. Ecol. austral [online]. 2008, vol.18, n.1, pp.71-87. ISSN 1667-782X.

Crop production by conservation tillage was readily adopted by farmers during the 1990's in Argentina. The type and degree of tillage cause modifications in the soil environment that affect the behavior, development and survival of soil-dwelling arthropods. The effect of conventional tillage (CT) and no tillage (NT) on density and activity of soil-inhabiting arthropods was evaluated on different dates, on two soybean crops (vegetative and reproductive stages), one maize crop (reproductive stage) and one soybean fallow. Two sampling methods, pitfall traps, with a preservative solution, for soil surface epigeous arthropods and quadrat samples for hypogeous arthropods, were used. In general, the density of phytophagous-detritivorous and predaceous arthropods, spiders and phitophagous-detritivorous larvae (Diptera, Coleoptera, Lepidoptera) was significantly higher in NT crops. The type of tillage did not affect the activity of most epigeous arthropods; but predator activity was generally higher in CT crops and spider frequency was superior in NT. Carabid density was not affected by the type of tillage, whereas their activity and particularly that of Calosoma spp. was greater under CT. Carabids species responded differently to both tillage systems. Pterostichini tribe (Carabidae) predominated in density in SD treatments, while its activity was low under both tillage systems. Argutoridius bonariensis Dejean (Carabidae: Ptrostichini) was only observed on NT soybean crops by quadrat samples. Selenophorus alternans Dejean (Carabidae: Harpalini) was more abundant under CT with both sampling methods. The different results obtained with different sampling methods, show the importance of using absolute and relative methods for assessing the effect of soil management in agroecosystems on arthropods populations. Relative abundance of carabids species in pitfall traps with respect to soil samples was explained by their sizes and circadian rhythms. The evaluation of all arthropods species of an ensemble and their classification in trophic groups provide unbiased, broad and functional information about the long time effects of soil management in agroecosystems.

Keywords : Agroecosystem; Soil arthropods; No tillage; Conventional tillage; Pitfall traps.

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