Response of earthworms, soil biota, and soil structure to agricultural practices in corn, soybean ad cereal rotations

Abstract

Conventional cropping systems require substantial herbicide input for weed control, and reduced or zero-till methods use herbicides to prepare the seed-bed for direct drilling. The comparative effects of herbicide treatments, crop rotations and weed control practice on soil fauna, microflora, and soil microfabric features (eg. soil particle size and shape) were measured in a multifactorial experimental design. The effects of organic insecticides and fungicides on earthworms and other soil fauna have been widely reported in the literature, but effects of herbicides on soil fauna are rarely studied because destruction of vegetation by the herbicide reduces soil faunal populations inhabiting the soil beneath the vegetation, thus masking herbicide toxicity. Generally, soil fauna responds to less intensive tillage methods by increasing in abundance, biomass and diversity, and this has been clearly demonstrated for earthworms. Increases in earthworm abundance and biomass under low or zero tillage are usually accompanied by increased soil macroporosity and increased water infiltration rates into soil. Because of the extensive availability of nutrients in earthworm casts both at the surface and within the burrows, agronomic techniques enhancing or reducing earthworm populations have significant consequences for processes involving soil microflora and soil microfauna colonizing the burrows. We have been able to develop methods of measuring the effects of agronomic practices on microfabric soil physical features (eg. soil aggregates and voids) using image analysis techniques. We now more clearly understand how the abiotic physical environment of soil interacts with agronomic practices. We can use the same image analysis techniques at microfabric scale to trace the impact of biotic contributions to soil microfabric and structure. This is a real advance because most soil biological processes are poorly understood. These tools will allow us to construct a more complete picture of soil processes and soil ecosystem function.