Earthworm services for cropping systems. A review

Intensive agriculture is often criticized for negative impacts on environment and human health. This issue may be solved by a better management of organisms living in crop fields. Here, we review the benefits of earthworms for crops, and we present techniques to increase earthworm abundance. The major points are the following: (1) Earthworms usually improve soil structural stability and soil porosity and reduce runoff. (2) Earthworms modify soil organic matter (SOM) and nutrient cycling. Specifically, earthworms stabilize SOM fractions within their casts, and they also increase the mineralization of organic matter in the short term by altering physical protection within aggregates and enhancing microbial activity. (3) The positive correlation between earthworm abundance and crop production is not systematic, and contrasting effects on yields have been observed. Earthworms induce the production of hormone-like substances that improve plant growth and health. (4) Direct drilling increases earthworm abundance and species diversity, but the beneficial effect of reduced tillage depends upon the species present and tillage intensity. (5) Organic amendments enhance earthworm abundance. (6) Earthworms feeding at soil surface are the most exposed to pesticides and other agrochemicals. Finally, we discuss how to combine management practices, including inoculation, to increase the earthworm services. We conclude that using earthworm services in cropping systems has potential to boost agricultural sustainability.