Earthworms in Brazilian no-tillage agriculture: Current status and future challenges

No-tillage (NT) agriculture represents a great advance in soil conservation in tropical and subtropical zones, occupying more than 32 million ha in Brazil in 2017. No-tillage systems can promote earthworm populations, which can improve soil physical and chemical properties, thus enhancing the benefits of NT for soil conservation and ecosystem services. Furthermore, earthworms can be used as indicators of the quality of NT systems. Here, we summarize the studies that evaluated earthworm populations in NT systems between 1986 and 2016 in Brazil, highlighting important gaps in knowledge. The studies were highly skewed geographically, with most data from southern and south-eastern Brazil, and had very little information from the two states with the greatest NT area (Mato Grosso and Rio Grande do Sul) which together represent 43% of Brazilʼs NT area. Abundance values ranged from 0 to 660 ind. m⁻², with a mean of 91 ± 129 ind. m⁻² (±SD), and at least 33 species were identified in NT systems. However, 73% of sites were considered to have poor and moderate soil quality based on their earthworm populations, raising concern regarding soil quality levels in Brazilian NT systems. Climate, soil and management conditions are important drivers of earthworm populations in Brazilian NT systems and future earthworm surveys in NT systems should provide ample data on these attributes, as well as on earthworm species, in order to improve their use as soil quality bioindicators. Highlights: Mean earthworm abundance in Brazilian NT is 91 ± 129 ind. m⁻² (range 0–660 ind. m⁻²) 33 species were identified in NT, most endogeic and epi-endogeic (0 anecics, 1 epigeic) Around 75% of NT sites sampled in Brazil had moderate to poor earthworm populations Soil management practices need improvement in many NT systems to increase earthworm populations.