by Robert L. Bugg
Adapted from "Ecological Soil Management and Soil Fauna: Best Practices in California Vineyards." Presentation at 1997 Viticulture Seminar, Australian Society for Viticulture and Oenology.
Soil animals may play a range of roles in vineyards. Decomposers (some of which are opportunistic herbivores) are important in nutrient dynamics, because by reducing organic matter to its constituents, they liberate nutrients usable by grapevines. Decomposers of interest in California include various species of peregrine earthworms (Lee, 1987), such as green worm (Allolobophora chlorotica), southern worm (Aporrectodea trapezoides), red wriggler (Lumbricus rubellus), nightcrawler (Lumbricus terrestris), crazy worm (Amynthas corticis), and Microscolex dubius (see Appendix 5). Several of these have been studied in various agricultural systems. Other less well understood groups of decomposers include field crickets (Gryllus spp.), European earwig (Forficula auricularia), springtails (Collembola), pillbugs and sowbugs (Crustacea: Isopoda), and miscellaneous slugs (Mollusca).
Several species of epigeic earthworms, e.g., Eisenia foetida, Lumbricus rubellus, and Amynthas gracilis, are currently being used to compost animal wastes in California (e.g., in Humboldt County). The resulting vermicomposts have yet to be formally compared to the more widely available thermic composts. Systematic comparisons could aid in determining the possible need for hybrid composting systems that make use of thermophilic microorganisms and epigeic earthworms in sequence, e.g., to reduce the incidence of pathogens of vertebrates.
Various burrowing animals improve soil structure and permeability to water through their creation of biopores (macropores) that conduct water deep into the soil (Lee and Foster, 1991; Lee and Smettem, 1995). These animals include several invertebrates mentioned above as well as various mammals, notably moles, voles, and pocket gophers. The latter two types can be damaging to grapevines and may be exacerbated by some cover cropping regimes (Smallwood, 1996). Earthworms (Annelida: Oligochaeta) and some other decomposers coat soil particles with gummy polysaccharidic exudates, improving soil aggregate stability (Lee and Foster, 1991; Zhang and Schrader, 1993; Lee and Smettem, 1995).
A limited number of studies have concerned the effects of various vineyard management techniques on soil fauna; Californian studies of this type are virtually lacking. Unfortunately, some studies of vineyard soil ecology suffer from lack of the replication or randomization that would justify the use of inferential statistics. For example, Lüftenegger and Foissner (1989) reported a study in two vineyards, comparing plots under minimal, conventional, Biodynamic, organic, and semibiological management. The latter three management systems received high inputs of green manures and composts. In general, testate amoebae, nematodes, and earthworms (Lumbricidae) appeared more abundant in plots under the latter three regimes. However, due to lack of randomization and insufficient replication, clear inferences were not possible.
In another unreplicated study, Cluzeau et al. (1987) reported that the leveling operations incurred prior to vineyard establishment severely reduced earthworm densities. Subsequent use of copper-based fungicides and heavy application of organic materials without tillage appeared to have virtually eliminated epigeic species, greatly reduced the endogeic types, and led to dominance by the anecic nightcrawler earthworm (Lumbricus terrestris).
Lee and Smettem (1995) recommend the establishment on farmlands of deep-burrowing anecic earthworm species, to enhance water infiltration. Such species, including L. terrestris, are typically scarce in California orchards and vineyards, yet have been successfully established in apple orchards. Once established, L. terrestris substantially enhances the disappearance of leaf litter (Werner, 1996). The species is also believed important in increasing decomposition of cover-crop residues left on the surface, and the liberation of soil nitrogen (Binet and Trehen, 1992). No related studies of inoculative release have been conducted in California vineyards, which receive much less irrigation than do most orchard crops, and may not be hospitable to this species. Perhaps more drought-tolerant surface feeding earthworms (e.g., A. corticis) will prove more appropriate in California vineyards.
The profiles on the following pages summarize the key characteristics of eight earthworm species found in California orchards and vineyards, based on accounts in Gates (1972) and Reynolds (1977).
Allolobophora chlorotica (Savigny) (Lumbricidae)
Amynthas corticis (Kinberg, 1867) (Megascolecidae)
Aporrectodea trapezoides (Dugés) (Lumbricidae)
Aporrectodea tuberculata (Eisen) (Lumbricidae)
Eisenia fetida (Savigny) (Lumbricidae)
Lumbricus terrestris L. (Lumbricidae)
Lumbricus rubellus Hoffmeister, 1843 (Lumbricidae)
Microscolex dubius (Fletcher) (Megascolecidae)
Binet, F., and P. Trehen. 1992. Experimental microcosm study of the role of Lumbricus terrestris (Oligochaeta: Lumbricidae) on nitrogen dynamics in cultivated soils. Soil Biology and Biochemistry 24:1501-1506.
Cluzeau, D., M. Lebouvier, P. Trahen, M.B. Bouché, C. Badour and A. Perraud. 1987. Relations between earthworms and agricultural practices in the vineyards of Champagne: preliminary results. Pp. 465-484 in: A.M. Bonvicini Pagliai and P. Omodeo (eds.). On Earthworms. Selected Symposia and Monographs, 2 Collani U.Z.I. Mucchi Editore, Modena, Italy.
Gates, G.E. 1972. Burmese Earthworms: An Introduction to the Systematics and Biology of Megadrile Oligochaetes with Special Reference to Southeast Asia. Transactions of the American Philosophical Society 62(7): 1-326.
Lee, K.E. 1987. Peregrine species of earthworms. Pp. 315-327 in: A.M. Bonvicini Pagliai and P. Omodeo (eds.). On Earthworms. Selected Symposia and Monographs, 2 Collani U.Z.I. Mucchi Editore, Modena, Italy.
Lee, K.E., and R.C. Foster. 1991. Soil fauna and soil structure. Australian Journal of Soil Research 29:745-775.
Lee, K.E., and K.R.J. Smettem. 1995. Identification and manipulation of soil biopores for the management of subsoil problems. Pp. 211-244 in: Jayawardane, N.S., and B.A. Stewart (eds.). Advances in Soil Science. Lewis Publishers, Boca Raton, Florida.
Lüftenegger, G., and W. Foissner. 1989. Bodenzoologishe Untersuchungen an ökologisch un konventionell bewirtschafteten Weinbergen. Landwirtschaftliche Forschung 42, 105-113.
Reynolds, J.W. 1977. The Earthworms (Lumbricidae and Sparganophilidae) of Ontario. Life Science Miscellaneous Publications, Royal Ontario Museum, Toronto, Canada.
Smallwood, K.S. 1996. Managing vertebrates in cover crops: a first study. American Journal of Alternative Agriculture 11, 155-160.
Werner, M.R. 1996. Inoculative release of anecic earthworms in a California orchard. American Journal of Alternative Agriculture 11, 176-181.
Zhang, H., and S. Schrader. 1993. Earthworm effects on selected physical and chemical properties of soil aggregates. Biology and Fertility of Soils 15, 229-234.
Edwards, C.A. (editor). 1996. Earthworm Ecology. St. Lucie Press, Delray Beach, Florida.
Edwards, C.A., and P.J., Bohlen. 1996. Biology and Ecology of Earthworms. Chapman and Hall, London.
Hendriksen, N.B. 1990. Leaf litter selection by detritivore and geophagous earthworms. Biology and Fertility of Soils 10:17-21.
Hendrix, P.F. 1995. Earthworm Ecology and Biogeography in North America. Lewis Publishers, Boca Raton, Florida.
Jerez, B.E.R., P.R. Ball, and R.W. Tillman. 1988. The role of earthworms in nitrogen release from herbage residues. Pp. 355-370 in: Jenkinson, D.S., and K.A. Smith (eds.). Nitrogen Efficiency in Agricultural Soils. Elsevier Applied Science, London.
Lee, K.E. 1985. Earthworms: Their Ecology and Relationships with Soil and Land Use. Academic Press, New York.
Lee, K.E. 1985. Peregrine species of earthworms. Pp. 315-327 in: A.M. Bonvicini Pagliai and P. Omodeo (eds.). On Earthworms. Selected Symposia and Monographs, 2 Collani U.Z.I. Mucchi Editore, Modena, Italy.
Ma, W.-C., L. Brussard, and J.A. De Ridder. 1990. Long-term effects of nitrogenous fertilizers on grassland earthworms (Oligochaeta: Lumbricidae): Their relation to soil acidification. Agriculture, Ecosystems and Environment 30:71-80.
Marinissen, J.C.Y., and P.C. de Ruiter. 1993. Contribution of earthworms to carbon and nitrogen cycling in agro-ecosystems. Agriculture, Ecosystems and Environment 47:59-74.
Scheu, S. 1987. The influence of earthworms (Lumbricidae) on the nitrogen dynamics in the soil litter system of a deciduous forest. Oecologia 72:197-201.
Springett, J.A., R.A.J. Gray, and J.B. Reid. 1992. Effect of introducing earthworms into horticultural land previously denuded of earthworms. Soil Biology and Biochemistry 24:1615-1622.