Soil earthworm activity

Particulate organic matter LF — 2-18% of organic C, 1-16% of total N SSF - 20 45% of organic C and 13-40% of total N Partially decomposed plant litter isolated by density fractionation (LF) or sieving (SSF). Substrate and centre for soil microbial activity, short-term reservoir of nutrients, food source for earthworms and other soil fauna and focci for formation of water stable aggregates. 

Fig. 2.13. Earthworm activity - evidence of intact soil life.

Lavelle P. (1988) Earthworm activities and the soil system. Biol. Fertility Soils 6(3), 237-251. 

In studies of earthworm activity in forest soils of Wisconsin, Nielsen and Hole (1964) estimated that the total live weight of earthworms per acre was 1,980 lb., more than half of which was the imported L. terrestris. They state that this species is changing the process of incorporation of organic matter into the soil with accompanying changes in soil microclimate, erosion, condition of seedbed, rate of nutrient cycling, and depth of A-horizon. ... 

Drilosphere All soils affected by earthworm activities, including external structures (middens, burrows, diapause chambers, surface and belowground casts) and the earthworm s gut. 

Ma, W.C. 1984. Sublethal toxic effects of copper on growth, reproduction and litter breakdown activity in the earthworm Lumbricus rubellus, with observations on the influence of temperature, and soil pH. Environ. Pollut. 33A 207-219. 

Soil teems with many different kinds of life— from microscopic bacteria and fungi to more noticeable creatures such as earthworms, beetles, slugs, and insect larvae. Many of these creatures are responsible for recycling organic matter (see below), breaking it down so that the nutrients it contains are once again available to plants. Their activities also build soil structure. 

Biological activity is an important indicator of the decomposition of soil organic matter within the soil. High biological activity promotes metabolism between soil and plants and is an essential part of sustainable plant production and fertiliser management. Earthworms, as a key species for soil macro-fauna, are an appropriate indicator of soil s biological activities due to their sensitivity to any kind of soil disturbance. Microbial activity of soils is an indicator of soil micro-fauna. Both indicators are reviewed below. 

Compared to the conventional treatment, the organic treatment showed higher microbial biomass C and N, mycorrhizal colonisation, enzyme activities (FlieDbach and Mader 2000), earthworm biomass and density (Siegrist et al. 1998) and microbial, faunal and plant diversity (Mader et al. 2002). In the laboratory, there was over 10% greater organic matter decomposition in the biodynamic soil than in the conventional soils (Flielibach et al. 2000). 

Some studies, including more prominent ones (Reganold et al. 1993, Mader et al. 2002), have repeatedly shown a clearly positive impact of the biodynamic method on soil structure, enzyme activities, CO2 exchange and earthworm populations (Koepf 1993, Goldstein 2000). However, there are also studies that were not able to show such results (Carpenter-Boggs ef al. 

Poor maintenance of topsoil is also a major concern. Synthetic fertilizers have no organic bulk and do not provide a food source for soil microorganisms and earthworms. Over time, a soil treated with only these fertilizers loses biological activity, which diminishes the soil s fertility. Soils void of organic bulk become chalky and susceptible to wind erosion. Chalky soils lose their capacity to hold water, which means that more applied fertilizer is leached away. Ever-increasing amounts of fertilizer are thus needed. 

There are many examples of decomposition being slower in acidic compared with near neutral soils (e.g., Jenkinson 1971). This is in part because of the reduced overall microbial activity in acidic soils. As already mentioned, the absence of earthworms from low pH soils also indirectly affects the decomposition rate as well as the accumulation of partially decomposed organic matter in the upper part of the profile (Hopkins, Shiel, and O Donnell 1988). 

To a large degree, decomposers in the soil and litter beneath a community are affected by the species of plants shedding the litter and penetrating the soil with roots. As Eyre (4) has pointed out, soils beneath northern conifer forests are acidic because conifer litter is acidic and its decomposition influences soil pH. Fungi, as a result, dominate the soil microflora while bacteria dominate more neutral soil beneath deciduous forests. There are also differences even within one conifer forest pine needles are much more acidic than spruce, and the soil beneath most pine species has less decomposer activity and is almost devoid of earthworms, in comparison with soil beneath spruce species. 

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