Data/hora: 02/06/2024 17:22:55

Biblioteca(s): 	Embrapa Florestas.	
Data corrente: 	03/10/2008	
Data da última atualização: 	10/10/2008	
Autoria: 	VALCKX, J.; GOVERS, G.; HERMY, M.; MUYS, B.	
Título: 	Manipulated earthworm populations affect runoff generation and erosion rates in cropland with distinct soil tillage treatments.	
Ano de publicação: 	2008	
Fonte/Imprenta: 	In: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.	
Idioma: 	Inglês	
Conteúdo: 	Earthworms are considered beneficial soil organisms in agro-ecosystems as they have positive
effects on soil structure, aeration, drainage and nutrient dynamics making them potential
promoters of plant growth. However, previous studies gave inconclusive results about the role
that earthworms play in soil erosion processes. Soil erosion can lead to denudation of the soil
profile, exposing less fertile soil, washing away soil organic carbon and nutrients, with a
decreased soil quality and a lowered productivity as consequences. Earthworm activities can
both have erosive effects (e.g. casting) and erosion reducing effects (e.g. gallery network). This
study considered the net effects of earthworm activities on runoff generation and erosion rates
in an erosion-prone agricultural setting comparing different tillage systems.
A field experiment was carried out on a sandy loam soil in a moderately sloping (~8%) arable
parcel in a maize-beet-wheat rotation in central Belgium. In 2004 the parcel was divided in three
parallel strips receiving different tillage regimes: conventional (inversion) tillage, reduced (noninversion)
tillage and direct drilling. In each strip nine manipulated earthworm plots were installed
of which three served as controls. In three plots earthworm populations were reduced by means
of electro-shocking and removal of surfacing individuals. In the three remaining plots commercially
purchased earthworms (Lumbricus terrestris L.) were added in quantities between 400 and
800 kg per ha. Earthworm populations were manipulated at six occasions during the period
2005-2008. In spring 2007 and 2008 erosion rates and runoff generation were measured through
rainfall simulations (plot area: 0.85 × 0.85 m²) and runoff discharge experiments (slope length: 7
m), together with soil bulk density, texture, moisture and organic carbon content.
Over the years earthworm populations varied considerably as a consequence of crop rotation
and weather conditions, irrespective of tillage or manipulation treatments. However, less disturbing
tillage regimes clearly promoted more diverse earthworm communities with higher biomasses.
In the tilled strip biomass of unmanipulated populations fluctuated around 200 kg per ha, while it
was respectively two and around three times higher in the reduced tilled and direct drilled parts
of the field.
Earthworm biomass and numbers correlated significantly negative both with sediment load and
runoff generated from rainfall simulations. Higher earthworm biomass and numbers reduced
also downslope runoff distance and speed when a known water volume was applied at a constant
discharge rate across the plot length. These correlations were more pronounced if only biomass
of deep-burrowing species was considered.
These results clearly indicate that earthworms contribute in a significant way to reduction of
runoff and soil loss in arable land in the studied agro-ecosystem. Our experiment demonstrates
that the erosive effects of earthworms by removal of surface crop residues and fresh surface
cast deposition are outweighed by an increased infiltration capacity due to maintenance of a
gallery network by deep-burrowing species. This study underlines the importance of good soil
ecosystem management by the farmer and the need for the promotion of agricultural practices
supporting populations of deep-burrowing earthworm species (non-inversion tillage, direct
drilling).	
Categoria do assunto: 	--	
Registro original: 	Embrapa Florestas (CNPF)	
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