Earthworms as health indicators in no-tillage and no-tillage agroecosystems

A database was created from a systematic search in SciELO, Web of Science, Science Direct and Scopus using the following keywords in english and portuguese: ‘earthworm*’ OR ‘oligochaeta’ OR ‘minhoca*’ AND ‘no-tillage’ OR ‘no-tillage system*’ OR ‘conservation agriculture’ OR ‘plantio direto’ OR ‘semeadura direta’ OR ‘agricultura conservacionista’ OR ‘sistema conservacionista’ AND ‘Paraná’. For dissertations and theses that addressed the topic in the region of Paraná, we used the Brazilian Digital Library of Theses and Dissertations (Biblioteca Digital Brasileira de Teses e Dissertações -BDTD). The period evaluated was from sampling dates ranging from 1981 to 2020, being the published dates of the works from 1986 (Voss, 1986; Derpsch et al.1986) to 2023 (Bartz et al. 2023; Dudas et al. 2023). 

Data were extracted from 23 publications and compiled into an excel file. The database contains information on 29 municipalities, their geopolitical region (IBGE, 2010), and climate (Köppen, 1931). Paraná is divided into 10 geopolitical mesoregions - West (WE), Northwest (NW), Center West (CW), Center North (CN), North Pioneer (NP), Center East (CE), Metropolitan (MT), Center South (CS), Southeast (SE) and Southwest (SW) (IBGE, 2010). 

Earthworm data are presented as species found, their abundance (ind m-2), biomass (g m-2) and species richness (total number). The abundance and richness of earthworms can be used as an indicator of NT/NTS quality, and Bartz et al. (2013) proposed the following classification for the abundance data: poor quality <25 ind m-2, moderate 25 to 100 ind m-2, good 100 to 200 ind m-2 and excellent quality >200 ind m-2. For richness: poor 1 species, moderate 2-3 species, good 3-4 species and excellent >6 species. However, after analyzing the 181 sites included in this dataset together with the database by Nadolny et al. (2020), we proposed new values for each category and including a new one based on: mean, standard deviation, standard error and confidence intervals. The new classification for abundance and species richness is: <25 ind m-2 = poor, ≥25-<75 ind m-2 = moderate, ≥75-<125 ind m-2 = good, ≥125-<175 ind m-2 = very good and ≥175 ind m-2 = excellent. And for earthworm richness: <1 species = poor, 1- 3 species = moderate, 3-5 species = good, 5-7 species = very good and >7 species = excellent.

In the database, each class is represented by a different color, using a gradient for the worst to the best quality sites. Thus, red = poor, dark orange = moderate, yellow = good, light green = very good, and dark green = excellent.

For the earthworm species, the following information is provided: ecological category (anecic, epigeic, endogeic, polyhumic endogeic, mesohumic endogeic; according to Bouché, 1977), origin (native or exotic), author(s) and years of the species description, collection site, climate, region and the sampling method.

The methods considered were: Quantitative, including handsorting of soil using the standard Tropical Soil Biology and Fertility (identified as TSBF in the spreadsheet) method of monoliths 25 x 25 cm square at depths ranging from 10 to 40 cm (Anderson and Ingram, 1993), as well as other monolith dimensions like 20 x 20, 40 x 40 and 50 x 50 cm (identified as Handsorting in the spreadsheet). Qualitative method, including collecting in various niches like deeper soil layers, litter, under rocks, in and under rotting logs, next to water bodies like streams, lakes and swamps (Bartz et al. 2013) Finally, chemical extraction using a diluted formalin solution (usually over an area 50x50 cm) according to ISO 23611-1 (2017).

The sites were divided in No-tillage (NT), or No-tillage system (NTS) based on site history and soil management information.  For the areas under NTS, we classified the phases according to Sá et al. (2004; 2010), being the initial phase corresponding to the first five years of NTS, the transition phase from six to 10 years, consolidation from 11 to 20 years and older than 20 years as the maintenance phase.

The soil chemical and physical data were included in the database, when performed in the same site as the earthworm sampling. Chemical data included pH in water, CEC, P and C, and physical data included sand and clay.

All data are provided in excel format and include four tabs: Legend, Earthworms + environment, Species distribution and References. The Legend tab provides a description of the data presented in each of the other tabs. Earthworms + environment has information on earthworm abundance, biomass and richness in relation to the site location, quality, year, crop year, time and date of sampling, NT or NTS site and NTS phase. The Species distribution tab provides information on the species found, place of origin, author, year, ecological category and sampling method. And the References tab lists the studies/publications used to extract the data presented in the other tabs.