Earthworms offset straw-induced increase of greenhouse gas emission in upland rice production

Journal Pre-proof Earthworms offset straw-induced increase of greenhouse gas emission in upland rice production

Katharina John, Baldur Janz, Ralf Kiese, Reiner Wassmann, Andrey S. Zaitsev, Volkmar Wolters PII:

S0048-9697(19)36348-X

DOI:

https://doi.org/10.1016/j.scitotenv.2019.136352

Reference:

STOTEN 136352

To appear in:

Science of the Total Environment

Received date:

7 August 2019

Revised date:

20 December 2019

Accepted date:

24 December 2019

Please cite this article as: K. John, B. Janz, R. Kiese, et al., Earthworms offset strawinduced increase of greenhouse gas emission in upland rice production, Science of the Total Environment (2018), https://doi.org/10.1016/j.scitotenv.2019.136352

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2018 Published by Elsevier.

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TITLE: “Earthworms offset straw-induced increase of greenhouse gas emission in upland rice production” (Primary research article)

Katharina John*1a, Baldur Janz1b, Ralf Kieseb, Reiner Wassmannb,c, Andrey S. Zaitseva,

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Volkmar Woltersa

Katharina John and Baldur Janz contributed equally to the manuscript and should be

Justus-Liebig-University, Department of Animal Ecology, Heinrich-Buff-Ring 26-32, 35392

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considered joint first author.

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Giessen, Germany

Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research (IMK-

International Rice Research Institute (IRRI), Crop and Environmental Sciences Division

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IFU), Kreuzeckbahnstraße 19, 82467 Garmisch-Partenkirchen, Germany

(CESD), Los Baños, Philippines

*corresponding author: +49 641 9935713, [email protected]

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Abstract

Increasing water scarcity and rapid socio-economic development are driving farmers in Asia to transform traditionally flooded rice cropping systems into non-flooded crop production. The management of earthworms in non-flooded rice fields appears to be a promising strategy to support residue recycling and mitigate greenhouse gas (GHG) emissions triggered by

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residue amendment. We conducted a field experiment on non-flooded rainfed rice fields, with

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and without residue amendment. In-situ mesocosms were inoculated with endogeic earthworms (Metaphire sp.), with either low (ET1: 150 individuals m-2), or high density (ET2:

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450 individuals m-2), and a control (ET0: no earthworms). We measured GHG emissions

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(methane (CH4); nitrous oxide (N2O); carbon dioxide (CO2)) twice a week during the

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cropping season with static chambers. Effects of earthworms on yield and root growth were additionally assessed. Earthworms offset the enormous increase of CH4 emissions induced by

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straw amendment (from 4.6 ± 5 to 75.3 ± 46 kg CH4-C ha-1 in ET0). Earthworm activity

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significantly reduced CH4 release, particularly at ET2, by more than one-third (to 22 ± 15 kg CH4-C ha-1). In contrast, earthworm inoculation did not affect N2O emission. Straw amendment more than doubled the global warming potential (GWP). Earthworms reduced GWP by 39 % at low (ET1) and 55 % at high densities (ET2). Earthworm activity reduced root mass density under conditions of straw amendment but did not affect yield. Earthworms can significantly reduce detrimental effects of rice crop residue amendment on GHG release under upland rice production. Organic carbon (C) might be preserved in earthworm casts and thereby limit C availability for CH4 production. At the same time, earthworm activity might increase methanotrophic CH4 consumption, due to improved soil aeration or less root exudates. Consequently, earthworms have a strong potential for regulating ecosystem functions related to rice straw decomposition, nutrient allocation and thus GHG reduction. 2

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Keywords: Aerobic rice, soil fauna, residue decomposition, bioturbation, ecosystem services, global

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warming potential

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1 Introduction

The mitigation of greenhouse gas (GHG) emission, rice straw residue recycling and management adaptations towards more sustainable rice production are among the major challenges for agriculture in Southeast Asia. Rice (Oryza sativa L.) is the main staple food for more than half of the world’s population (Khush, 2005). At the same time, global rice

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production contributes about 16 % to anthropogenic methane (CH4) emission and, although

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CH4’s atmospheric concentration is much lower than that of carbon dioxide (CO2), its global warming potential (GWP) on a 100 year time span is approximately 28 times larger (IPCC,

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2014). Increasing water scarcity and Asia’s rapid socio-economic development are driving

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farmers to transform their traditionally flooded double rice cropping systems into diversified

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rice crop rotations, including non-flooded crops such as upland (aerobic) rice or maize (Timsina et al., 2010; Wassmann et al., 2000, Belder et al., 2005). This, along with the need

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for feasible and sustainable adaptation strategies in rice production, may create some

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synergies in terms of CH4 emission. Recent studies have reported a reduction of CH4 emissions of up to 84 % in a crop rotation of flooded rice and non-flooded upland rice as compared to continuously flooded rice cultivation (Cha-un et al. ,2017), however, accompanied by an increase in nitrous oxide (N2O) emissions (Wassmann et al., 2000; Weller et al., 2016). The latter gas is also known for an extremely high GWP. The introduction of upland crops into paddy rice systems goes along with a drastically altered water regime, leading not only to changes in the soil microbial community and its activity (Breidenbach et al., 2015; Breidenbach et al., 2017), but also in soil physicochemical properties. This creates the possibility of establishing a more diverse soil fauna by promoting less flood-resistant species like earthworms (Schmidt et al., 2016).

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Earthworms and their effect on CH4 emissions are the subject of controversial debate, since the results of recent investigations range from a considerable reduction (Moon et al., 2010; Park et al., 2008) to an acceleration of methanogenic activity (Depkat-Jakob et al., 2012), with the latter being attributed to the stimulating effect of substrates from earthworm guts and in fresh casts. Generally, earthworms are considered to protect soil organic carbon (C) in their cast aggregates (Wolters, 2000). Elevated microbial activity in earthworm casts

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and burrow walls, however, may increase soil respiration rates (Kizilkaya and Hepşen, 2004;

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Parkin and Berry, 1999; Tiunov and Dobrovolskaya, 2002; Tiunov and Scheu, 1999). And also elevated N2O emissions due to earthworm activity as reported by Lubbers et al. (2013)

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may be mainly caused by microorganisms benefitting from improved metabolic conditions in

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both intestines and casts of earthworms (Horn et al., 2003). Enhanced denitrification from the

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latter leads to increased N2O emissions (Majeed et al., 2013). In contrast, several studies have shown that earthworms increase CO2 but not N2O fluxes (Chapuis-Lardy et al., 2010; Speratti

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and Whalen, 2008) and even considerable reductions of N2O emission (Chen et al., 2014).

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Due to these partially contradictory results reported from various agroecosystems, there is still some uncertainty regarding the interplay of earthworm-induced soil organic matter stabilization and mobilization, as well as resulting GHG emissions. Consequently, it is important to measure all three GHGs from certain land use systems and management practices to be able to assess the contribution of earthworm activity to the net GHG balance over time. Additional challenges for a comprehensive assessment of the role of earthworms in maintaining C-storage and affecting GHG emissions from soils are associated with the effects of crop residue return. Rice straw incorporation is becoming increasingly popular for nutrient return in rice agroecosystems (Janz et al., 2019) as an environmentally-friendly alternative to straw burning (Huang et al., 2013). Rice straw open-field burning is still a widely practiced 5

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residue disposal practice in the Philippines (Gadde et al., 2009). Despite the intuitively positive effects of straw burning associated with the rapid return of nutrients into the soil in ash, those are outweigh by the negative influence of the organic matter combustion on climate, air quality and public health (Huang et al., 2013; Streets et al., 2003; Tipayarom and Oanh, 2007). Thus farmers have been encouraged to adopt alternative strategies for the disposal of the relatively poor-quality rice straw residue material (Jiang et al., 2018). Rice

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straw application has been reported to stabilize soil moisture and to improve soil fertility

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(Devêvre and Horwath, 2000; Xia et al., 2014). At the same time, however, it may entail the risks of reducing rice production efficiencies (Mandal et al., 2004; Yadvinder-Singh et al.,

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2005) and increasing GHG emissions (Janz et al., 2019; Pandey et al., 2014; Sander and

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Wassmann, 2014). The input of organic matter, such as rice residues, to rice soil promotes

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CH4 emissions (Bronson et al.,1997; Wassmann et al., 2000) as it provides additional substrate for methanogenic microorganisms (Le Mer and Roger, 2001). In non-flooded rice

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ecosystems, however, rice residue amendment might be especially promising if accompanied

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by natural colonization by earthworms or active soil fauna management. The presence of earthworms may increase the benefits of straw amendment, as they can accelerate the initial degradation of residue material (Lubbers et al., 2017), and thus positively affect plant growth (Fonte and Six, 2010; Noguera et al., 2010). Positive feedbacks of earthworms to nutrient decomposition, nutrient cycling, and plant growth have long been recognized and are wellestablished (e.g. Brown et al., 1999; Darwin, 1881; Scheu, 2003; Wolters and Stickan, 1991; Xiao et al., 2018). This is mainly achieved by releasing nitrogen from the residue material and soil organic matter (see e.g. van Groenigen et al., 2014). Brown et al. (1999) observed an average increase in plant growth of more than 50 % due to the presence of earthworms in tropical soils, especially if accompanied by the application of additional organic C sources (Blouin et al., 2013; van Groenigen et al., 2014). 6

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Evidence from various agroecosystems suggests that the introduction of earthworms into paddy soils may considerably contribute to the regulation and stimulation of microbial crop residue decomposition as well as to the improvement of nutrient availability for plants, while it may simultaneously mitigate GHG emissions (e.g. John et al., 2015; van Groenigen et al., 2014; Xiao et al., 2018). Before recommending earthworm addition or active promotion of local earthworm populations as a convenient measure for increasing the sustainable

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management of upland rice soils amended with crop residues, however, it will be crucial to

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fully understand both the potential and the risks associated with earthworm effects on GHG emissions and crop productivity. Yet, to the best of our knowledge, the pros and cons of these

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effects have never been experimentally quantified in the field. To fill this gap, we conducted a

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full-factorial experiment at non-flooded rainfed rice fields of the IRRI experimental farm (Los

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Baños, Philippines). The experiment was carried out in contained mesocosms with three different levels of earthworm density (ET0: no earthworms, ET1: 150 ind. m-2, ET2: 450 ind.

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m-2) as well as with and without rice straw amendment. The impact of these treatments on

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GHG release and on the GWP was quantified by means of closed chamber measurements. We measured both gas fluxes from bare soil and from soil with rice plants to better understand the potential GHG mitigation by earthworm presence. We hypothesized that earthworm addition reduces the GWP after rice straw amendment by supressing the stimulation of CH4 emissions without boosting N2O and CO2 release. In addition, we determined treatment-specific differences in rice yield, shoot biomass and root mass density. The underlying hypothesis was that earthworm-induced physicochemical changes alter both growth and productivity of rice plants.

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2 Materials and Methods

2.1 Field Site Description The field experiment was established at the experimental farm of the International Rice Research Institute (IRRI), Los Baños, Philippines (60 km south of Manila). The site is located at 14°09′45″ N, 121°15′35″ E, at an elevation of 21 m above sea level. The cropping year is

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determined by a dry season (DS) and wet season (WS) as rainfall is unevenly distributed over

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the year. 15 % of annual rainfall fells from Jan-May (DS) and 85 % fells in the period Jun-

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Dec (WS). The experiment was conducted during the rice cropping phase of the wet season

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2016 (July-October). The mean temperature during the cropping season was 28.9 °C, with a total rainfall of 1004 mm (IRRI Climate Unit 2016). The highest rainfall was recorded in

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September 2016 (32.4 % of total seasonal precipitation), due to a tropical storm at the end of

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the month. The soil had a clay-dominated texture (54.2 % clay, 32.8 % silt, 13 % sand) and a pH of 6.6. It was classified as “Andaqueptic Haplaquoll” (USDA classification) or

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“Anthraquic Gleysol” according to the World Reference Base for Soil Resources. Field management was in accordance with the existing crop rotation scheme, alternating between maize in the dry season and non-flooded upland rice in the wet season for four years before the start of the experiment.

2.2 Set-Up of Contained Soil Mesocosms and Agronomic Practice A total of 24 containments (“soil-plant mesocosms”) were installed at two adjacent 14 m x 20 m fields (12 each) to confine earthworms to the enclosed soil. Containment structures for the in-situ mesocosm experiment were made of plastic buckets with 60 cm diameter (= 0.28 m² surface area) and 70 cm height. Each was evenly perforated with 120 holes (5 cm diameter)

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that were manually drilled in the side walls and the bottom of the buckets (Supplementary material Figure S.2-A). 500 μm nylon mesh fabric layered to the inside of the mesocosms ensured permeability for soil water, nutrients, microorganisms and soil mesofauna but prevented both escape of inoculated earthworms and invasion of local soil macrofauna (see e.g. Setälä et al., 1996). Mesocosms were installed as soon as the usual land preparation practice for upland rice cultivation had been carried out (see below). They were located at a

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maximum distance to the field boundaries (min. 3 m) and at a distance of 2.5 m between the

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external borders of adjacent mesocosms, to avoid edge effects and mutual interference. The mesocosms were buried in the ground to a depth of 60 cm (i.e. 10 cm still protruded above

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ground) and filled with the original excavated soil. The soil was compacted to the surface

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level of the surrounding field. When filling the mesocosms, care was taken to ensure that no

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cavities were created between the soil inside and outside of the containers to ensure maximum coalescence. The soil used for the experiment was not defaunated, since earthworms were

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absent from the experimental fields after field preparation. Other soil macrofauna groups (e.g.

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gastropods or mole crickets) were manually removed. For land preparation, the fields were soaked for about one week before ploughing and harrowing until July 15, 2016 (see Supplementary material Table S.1 for the schedule of field activities). The fields and contained mesocosms were manually levelled and mesocosm soil was left undisturbed to settle for a few days before the transplanting of rice seedlings on July 21, 2016 (Supplementary material Table S.1). Three-week-old dry-bed grown seedlings of aerobic rice (NSIC Rc192) were manually transplanted in straight rows with equal distances of 20 cm x 20 cm spacing between hills and one to two seedlings per hill. Each mesocosm was planted with 7 hills in an identical pattern (see Supplementary material Figure S.2-B). A basal fertilization of 30 kg ha-1 K (as potash) and 30 kg ha-1 P (as solophos) was conducted shortly after transplanting. Nitrogen (N) fertilizer application occurred in three splits and 9

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quantities of 30, 50, and 50 kg urea-N ha-1 at 8, 26 and 34 days after transplanting (DAT; Supplementary material Table S.1). Wooden planks were installed on July 25, 2016 (4 DAT) to reach the mesocosms while minimizing disturbance to surrounding rice plants. The fields were irrigated if necessary in case of drought, and drainage channels were opened in case of heavy rainfall and subsequent flooding. Rice was harvested by hand on October 19, 2016 (90

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DAT).

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2.3 Straw and Earthworm Treatments

The experiment followed a full-factorial design of two different straw residue treatments and

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three levels of earthworm densities in four replicates each. We established the field

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experiment with 2 x 12 mesocosms in two bunded fields. One of the two fields received no

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rice straw (‘Without Straw’), while the other field received 6 Mg ha-1 air dried rice straw (‘With Straw’), partly incorporated during field-preparation (3 Mg ha-1) and applied as mulch

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after rice seedling transplanting (3 Mg ha-1) to preserve soil moisture and avoid crack

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formation (Mousavi et al., 2012). Mesocosms in both fields were subject to three earthworm treatments with zero (ET0), 150 (ET1) and 450 individuals (ind.) m-² (ET2), relating to 42 and 126 mature individuals of the earthworm genus Metaphire sp. per mesocosm, respectively. Earthworms were collected from grasslands in close vicinity to the experimental sites. The ET1 earthworm density equals the natural abundance of the earthworm species in the original habitat, while ET2 represents a three-fold increased density treatment. To adapt to field soil conditions, earthworms were incubated in a styrofoam box filled with soil from the experimental field for five days prior to mesocosm inoculation. After rice transplanting, earthworms were transferred to the respective mesocosms on August 1, 2016 (11 DAT). See Supplementary material Figure S.1 for a dimensionally accurate schematic overview of the

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field experimental design and Supplementary material Table S.1 for the field activity schedule. After harvest, all mesocosm containers were removed from the fields and the soil was manually examined to count for earthworms. We recovered an average of 27 ± 5 and 61 ± 22 individuals for the ET1 and ET2 treatments, respectively. Despite the apparently low recovery, the difference between the two earthworm treatments was still significant (P <

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0.001). Moreover, the recovery rate was not affected by the initial earthworm density (ET1:

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64.6 ± 11.8 %; ET2: 48.5 ± 16.0 %; P = 0.452) and is within the usual range reported for this type of experiment (Lubbers and van Groenigen, 2013; Paul et al., 2012; van Groenigen et al.,

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2014). Straw application did not affect the recovery rate either (P = 0.755).

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Bulk soil and rhizosphere soil (0-10 cm & 10-20 cm depth) were manually collected

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with soil corers (3 cm in diameter) at the beginning (10 DAT) and after the experiment (2 DAH) within each confinement for analyses of the soil C and N amount using a CN elemental

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analyser (Vario Max, Hanau, Germany).

2.4 Greenhouse Gas Measurements Soil CH4, CO2 and N2O gas fluxes were measured using manually operated static closed chambers consisting of a permanent frame installed in the field and mobile measurement chambers. Two chamber frames were installed at each of the 24 mesocosms, one covering bare soil without plants (N-frames) and one covering the middle hill including the rice plants (P-frames), and remained installed for the duration of the experiment (see Supplementary material Figure S.2-B). While P-chamber measurements captured emissions from soil, roots, and rice plants, N-chamber measurements were not directly affected by plants. However, as N-chamber fluxes are also influenced by roots and associated rhizosphere processes that

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extend over the entire soil matrix, we were aware that they do not only measure bare soil emissions. N-frames consisted of a circular plastic (PVC) base frame (25 cm length, 15 cm in diameter), inserted 10 cm into the soil of each mesocosm between hills, covering bare soil with no plant inside. The respective N-chambers were made of non-transparent PVC piping material with a fixed height of 11.5 cm (6.5 cm overlap, 15 cm in diameter), resulting in a

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total height of 20 cm when attached to the base frame.

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P-frames consisted of a larger circular base frame (25 cm in diameter, 20cm length), inserted about 10 cm into the soil, covering the middle hill of rice plants in each mesocosm,

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with an above-ground frame height of another 10 cm. The respective P-chambers were

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constructed from semi-transparent, plastic water gallons with a diameter of 25.5 cm and used

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in variable chamber heights (35, 65, 95, 120 cm), depending on the height of the plant inside

forming an airtight seal.

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the chamber. The overlap of frame and chamber was covered with a 3.5 cm rubber band,

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Both chamber types were equipped with ports for gas sampling, a thermometer and a vent for pressure equilibration. Gas samples were collected from inside the chambers using a 60 mL syringe at 0, 10, 20, and 30 min time points after chamber closure. A battery-powered fan was installed inside the P-chambers to ensure a well-mixed air sample, particularly with increasing chamber size. The air inside the N-chambers was thoroughly mixed by flushing three times with the 60 mL volume of the sampling syringe right before each sampling. A 10 mL glass vial with butyl rubber septum was flushed (30 mL) with sample air before it was filled and over pressurized with 15 mL of the same sample. Sampling took place twice a week during the entire rice growing season (11-88 DAT; 23 measurement days in total) between 8:30 and 10:30 a.m. to capture the mean of diurnal variabilities, according to protocol settings (e.g. Butterbach-Bahl et al., 2016, Sander and Wassmann, 2014). Soil temperature and water 12

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filled pore space (WFPS) were monitored during each measurement occasion (see Supplementary material Figure S.3). The gas samples were transported to Germany and analysed with a gas chromatograph (GC; 8610C SRI Instruments) equipped with an 63Ni electron capture detector (ECD) for analysis of N2O, and a flame ionization detector (FID) and methanizer for analysis of CH4 and CO2. Hourly flux rates were calculated by linear regression of the four measurement points,

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based on the ideal gas law, and corrected by chamber air temperature and air pressure

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(Minamikawa et al., 2015). The daily gas flux was calculated by multiplying the mean hourly gas flux by 24. Cumulative seasonal CH4 and N2O emissions were calculated from the daily

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emissions between every two consecutive measurements from the P- and N-chamber average

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using linear interpolation. Interpolated daily gas fluxes were summed up to calculate the

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emissions for vegetative (0-25 DAT), reproductive (26-55 DAT), and ripening (56-90 DAT) growth stages as well as total seasonal emissions. The GWP (CH4 and N2O) was estimated

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using the radiative forcing potentials (relative to CO2, for a 100-year time horizon without the

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inclusion of climate-C feedback), i.e. 265 and 28 for N2O and CH4, respectively (Myhre et al., 2013). GWP was averaged across P- and N-chambers. CO2 fluxes were only used to analyse the relative changes of treatment effects from chambers without plants (N), but not included in the calculations of seasonal emissions and GWP, because they were affected by plant photosynthesis in P-chambers.

2.5 Rice Yield, Shoot Biomass and Root Mass Density Assessment Above-ground biomass was harvested from the mesocosms on October 19, 2016 (90 DAT) and analysed for rice grain yield (corrected to 14 % moisture content), dry weight of straw and harvest index, following the ORYZA 2000 crop data collection protocol (IRRI, 2009).

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Root mass density was determined as described by Henry et al. (2012) as a proxy for root production under field conditions. The respective soil cores (60 cm in depth, 3 cm in diameter) were sampled two days after harvest (Supplementary material Table S.1) within the mesocosms in between two hills. Each soil core was cut into four pieces, which were separately placed on sieves (355 μm) and washed under running water to separate soil particles from the rice roots. The roots were dried for 48 hours at 63°C before weighing. Total

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root mass density per mesocosm was calculated by summing up the resulting root weights of

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the four pieces of the respective soil cores. Root mass values were converted to g (dry weight)

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cm-3 according to the soil core volume.

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2.6 Statistical Analysis

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GHG fluxes (CH4, N2O, and CO2) were analysed using the general linear model procedure in R (version 3.4.3) with forward and backward stepwise inclusion of variables. Independent

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categorical predictors were “earthworm” (three levels), “straw application” (two levels),

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“chamber type” (two levels), “growth stage” (three levels of rice growth: the vegetative growth stage, the reproductive and the ripening stage, to examine inter-seasonal dynamics of the earthworm treatments on GHG release during the cropping season) as well as their interactions. Dependent variables were checked for normal distribution and homogeneity of variance and adjusted by logarithmic transformation if they did not meet the criteria. Seasonal cumulative GHG emissions were analysed for the impact of earthworm and straw residue treatment as well as of chamber type (P- and N-chambers) by means of multiple factorial analyses of variance (ANOVA, R package “agricolae” v. 1.2-8). Hence, seasonal cumulative GHG emission was analysed for each growth stage with chamber type as fixed effect, while replication was the random effect.

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GWP as well as plant parameters (rice yield, shoot biomass, root mass density) were compared across earthworm and straw residue treatments. Multiple comparisons among treatment means were performed using the Tukey-Kramer HSD (honestly significant

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difference) test on a probability level of 5 % or lower (R package “agricolae” v. 1.2-8).

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3 Results

3.1 Greenhouse Gas Emissions 3.1.1 Methane Flux Earthworm density and straw application significantly affected the magnitude of CH4 fluxes during aerobic rice cultivation (Table 1). Earthworms significantly decreased seasonal

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cumulative emissions in the treatment with straw application by 43 and 71 % under ET1 and

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ET2, respectively (Table 2). Significant interactions between straw and earthworm treatment thus suggest a strong modulation of earthworm effects by the addition of rice straw as an

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additional C source (Table 1). On average, rice straw application increased CH4 emissions by

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a factor of 10 (Table 2). Only in the field without straw amendment were occasional increases

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in CH4 flux observed when earthworms were present during the vegetative or reproductive growth stage (Figure 1). However, the magnitude of CH4 emission was on a very low level

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compared to the field receiving rice straw (Table 2).

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CH4 emissions were increased by rice plants inside the measurement chambers (Pchambers compared to N-chambers; Table 1). Total seasonal emissions accumulated to 19.8 ± 9.5 kg CH4-C ha-1 in chambers without and to 31.4 ± 8.7 kg CH4-C ha-1 with rice plants. Most of the CH4 (80-99 %) was emitted during vegetative and reproductive growth stages, irrespective of plants and straw residues (Figure 1). During these earlier growth stages, significantly larger amounts of CH4 were detected in mesocosms without earthworm inoculation compared to mesocosms with ET2 earthworm inoculation under conditions of rice straw residue amendment (Table 2). ET1 significantly reduced cumulative CH4 emissions as well, but only in N-chambers (Table 2). This effect was negligible in P-chambers. Peak emissions in chambers with and without plants were reached at 28 DAT. After that, magnitude and variation of flux measurements gradually decreased during the 16

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reproductive growth stage until 43 DAT and remained low for the rest of the season (Figure 1). The ripening stage did not significantly contribute to total seasonal CH4 emissions. However, seasonal emissions decreased with increasing earthworm density in all chambers when straw was applied (Table 2).

Table 1: Response of CH4, N2O and CO2 flux rates on rice Straw residue amendment (S),

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Earthworm treatments (W), Growth stage (G), Chamber type (C), and their first-order

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interactions (Sum of Squares and their significance levels). Treatment effects without explanatory power where excluded from the model (GLM analysis, stepwise backward and

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0.05 0.08 5.94 *** 0.35 *** 0.41 ***

CO2 -C 0.33 0.16 4.62 23.926 2.05

** *** *** ***

1.159 *

7.788 ***

CxW CxS WxS Residual Error R2

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GxS

11.095 0.94 11.816 2.559

N2O -N

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Straw (S) Earthworm (W) Growth stage (G) Chamber type (C) GxC GxW

CH4 -C

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Predictor variable

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forward selection).

0.638 * 0.931 ** 1.272 ** 108.983

21.3

Model 0.2479 *** 0.24 *** Significance level: ***P < 0.001, **P < 0.01, *P < 0.05

51.92 0.37 ***

Table 2: Cumulative CH4 emissions during three rice growth stages and seasonal cumulative CH4 emissions as affected by rice straw residue amendment and earthworm treatment (ET0, ET1, and ET2) in chambers without (N) and with rice plants (P) (means ± S.E.). Means followed by a different letter are significantly different between the three earthworm

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treatments within the respective growth stage and chamber type according to Tukey’s HSD test at P ≤ 0.05.

Without Straw ET0 ET1 ET2 With Straw ET0 ET1 ET2

vegetative

reproductive (N) without Plants

ripening

0.4 ± 0.3 b 0.3 ± 0.1 b 1.1 ± 0.3 a

0.5 ± 0.8 b 1.6 ± 1.6 ab 3.0 ± 5.0 a

0.2 ± 0.4 0.1 ± 0.1 n.s. 0.1 ± 0.1

50.7 ± 11 a 7.1 ± 1.7 b 9.7 ± 1.5 b

23.8 ± 32 a 9.6 ± 11 ab 8.0 ± 9.9 b (P) with Plants

0.8 ± 1.0 0.5 ± 0.5 n.s. 0.9 ± 1.7

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CH4 emission [kg C ha-1] ± SE

0.9 ± 0.6 1.0 ± 0.7 n.s. 1.0 ± 0.4 4.6 ± 1.4 7.3 ± 3.8 n.s. 3.9 ± 1.6

1.2 ± 1.0 2.0 ± 1.6 4.2 ± 5.0

b ab a

75.4 ± 34.2 a 17.2 ± 10.9 b 18.6 ± 10.2 b

8.0 ± 5.0 4.7 ± 1.7 6.8 ± 2.1

a b a

75.3 ± 30.8 a 68.4 ± 22.2 a 25.3 ± 10.4 b

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Without Straw ET0 2.9 ± 0.5 a 4.2 ± 5.0 ET1 1.4 ± 0.2 b 2.4 ± 1.6 n.s. ET2 2.2 ± 0.3 ab 3.6 ± 2.0 With Straw ET0 38.2 ± 6.2 a 32.5 ± 30 a ET1 34.2 ± 4.1 a 26.9 ± 22 a ET2 8.3 ± 1.2 b 13.1 ± 10 b different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

total season

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Figure 1: CH4 flux dynamics during the upland rice growing season as affected by straw

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residue amendment and earthworm treatment in chambers without (N) and with rice plants

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(P). Vertical dashed lines separate vegetative, reproductive, and ripening plant growth stage. Error bars correspond to standard error.

3.1.2 Nitrous Oxide Fluxes

N2O fluxes were generally low with occasional peak emissions during the upland rice growing season (Supplementary material Figure S.4). Neither earthworm nor rice straw residue treatment had a significant effect on N2O fluxes (Table 1). Only seasonal cumulative N2O emissions from the field without rice straw residue amendment were significantly lower in mesocosms without earthworms (ET0) ( Table 3). Averaged across both chamber types with and without plants, emissions increased by about 50 % from 2.1 ± 1.4 kg N2O-N ha-1 (ET0) to 3.0 ± 1.8 and 3.2 ± 1.7 kg N2O-N ha-1 19

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under ET1 and ET2 earthworm density, respectively, when no straw was amended. Peak emissions were measured particularly after urea-N fertilization during the reproductive growth phase under earthworm presence in ET1 (P-chambers) and ET2 both with and without plants (Supplementary material Figure S.4). However, no such effect was observed when rice straw was applied to the field.

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Table 3: Cumulative N2O emissions during three rice growth stages and seasonal cumulative

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N2O emissions as affected by rice straw residue amendment and earthworm treatment (ET0, ET1, and ET2) in chambers without (N) and with rice plants (P) (means ± S.E.). Means

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followed by a different letter are significantly different between the three earthworm

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treatments within the respective growth stage and chamber type according to Tukey’s HSD

reproductive (N) without Plants

ripening

total season

0.2 ± 0.1 b 0.2 ± 0.0 b 0.4 ± 0.1 a

2.2 ± 1.1 b 2.2 ± 1.2 b 3.0 ± 1.2 a

0.2 ± 0.3 b 0.2 ± 0.3 b 0.5 ± 0.5 a

2.7 ± 1.2 2.7 ± 1.2 4.0 ± 1.3

b b a

0.4 ± 0.1 0.2 ± 0.1 n.s. 0.4 ± 0.1

2.4 ± 1.2 2.5 ± 1.3 n.s. 2.6 ± 1.5 (P) with Plants

0.2 ± 0.2 0.2 ± 0.2 n.s. 0.2 ± 0.2

3.0 ± 1.2 2.9 ± 1.4 3.2 ± 1.5

n.s.

0.0 ± 0.1 0.1 ± 0.2 n.s. 0.1 ± 0.3

1.4 ± 0.8 3.3 ± 1.4 2.5 ± 1.2

b a ab

0.0 ± 0.2 0.0 ± 0.1 n.s. 0.1 ± 0.1

3.1 ± 3.8 1.5 ± 1.1 2.1 ± 1.3

n.s.

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Without Straw ET0 ET1 ET2 With Straw ET0 ET1 ET2

vegetative

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N2O emission [kg N ha-1] ± SE

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test at P ≤ 0.05.

Without Straw ET0 0.4 ± 0.1 1.0 ± 0.8 c ET1 0.5 ± 0.1 n.s. 2.7 ± 1.4 a ET2 0.6 ± 0.1 1.8 ± 1.1 b With Straw ET0 0.5 ± 0.1 2.6 ± 3.8 ET1 0.2 ± 0.0 n.s. 1.2 ± 1.0 n.s. ET2 0.5 ± 0.1 1.5 ± 1.3 different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

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3.1.3 Carbon Dioxide Flux Soil CO2 fluxes from in between plants increased significantly due to the amendment of rice straw, but they were not affected by earthworm treatment (Table 1; Supplementary material Figure S.5). Seasonal cumulative CO2 emission increased by 36 % with rice straw residue amendment (from 694 to 947 kg CO2-C ha-1 season-1). Comparisons within the growth stages and straw treatments revealed an earthworm effect on CO2 emissions (Table 4). During the

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vegetative and reproductive growth stage, CO2 release was significantly increased by ET2,

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but only in the field without rice straw residue amendment. No clear pattern of earthworms affecting CO2 emissions was observed in the field amended with rice straw residue. Overall,

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CO2 emission was lowest under ET1 compared to ET0 and ET2 during the vegetative and

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ripening stage.

Table 4: Cumulative CO2 emissions during three rice growth stages and seasonal cumulative

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CO2 emissions as affected by earthworm (ET0, ET1, and ET2) and residue treatment for

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chambers without plants (means ± S.E.). Means followed by a different letter are significantly different within growth stage and chamber type according to Tukey’s HSD test at P ≤ 0.05. CO2 emission [kg C ha -1] ± SE

vegetative

reproductive (N) without Plants

ripening

Without Straw ET0 84 ± 15 b 328 ± 114 b 183 ET1 93 ± 15 b 350 ± 97 b 203 ET2 167 ± 20 a 466 ± 140 a 207 With Straw ET0 250 ± 37 ab 496 ± 203 278 ET1 169 ± 30 b 426 ± 150 n.s. 212 ET2 272 ± 37 a 495 ± 146 242 different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

total season

± 44 ± 49 n.s. ± 54

595 ± 123 b 646 ± 110 b 840 ± 151 a

± 82 a ± 48 b ± 73 ab

1024 ± 222 a 807 ± 160 b 1009 ± 167 a

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3.2 Global Warming Potential (CH4 + N2O) Without straw addition, N2O emissions accounted for the largest share of GWP (approx. 90 %), whereas up to 72 % of total GWP resulted from CH4 emissions in the rice straw treatment. The strongly elevated CH4 emissions under rice straw application significantly increased the GWP (P < 0.001; Figure 2). Average emissions, equal to 2007 kg CO2-C ha-1 season-1, occurred when straw was amended, which is more than twice as high as compared to

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the field without residue input (854.6 kg CO2-C eq. ha-1 season-1).

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Earthworm presence significantly supressed the stimulating effect of straw amendment on CH4 production and thereby reduced the GWP during upland rice cultivation (Figure 2). A

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strong modulation of straw-induced CH4 emissions by earthworm presence and density was

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suggested by the significant interaction effect (P < 0.05). The highest seasonal peak in GWP

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occurred shortly after rice straw residue amendment (ET0: 2927.9 kg CO2-C eq. ha-1 season-1; Figure 2). ET1 and ET2 supressed that instant stimulating effect of straw amendment on CH4

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production (Table 2) and consequently reduced the GWP by 39 % and 55 %, respectively

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(Figure 2), mainly caused by differences during vegetative and reproductive growth stages. No earthworm effect on GWP was observed in mesocosms without rice straw residue amendment.

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Figure 2: Seasonal global warming potential (GWP; CH4 + N2O) of upland rice cropping as affected by three earthworm (ET0, ET1 and ET2) and two rice straw residue (“Without

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Straw” and “With Straw”) treatments. Error bars correspond to standard error with negative

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values for different gas species and positive values for total GWP. Bars marked with same letters are not significantly different at P = 0.05 (Tukey’s HSD test).

3.3 Rice Yield, Shoot Biomass, Root Mass Density, and Soil Parameters Neither the dry mass of the harvested rice straw from the mesocosms nor the harvest index were affected by different earthworm densities or rice straw residue management (Supplementary material Table S.2; Table 5). Grain yield, in contrast, though not affected by earthworms, was significantly reduced by straw amendment (Supplementary material Table S.2; Table 5). Average rice yields declined from 7.4 ± 1.7 Mg ha-1 without straw amendment

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to 6.0 ± 1 Mg ha-1 with straw. Only under earthworm density ET1 were rice yields practically identical with and without straw residue amendment (Table 5). Root mass density was significantly reduced by earthworm activity in fields with rice straw residue amendment (Supplementary material Table S.2; Table 5). Particularly the ET1 earthworm density resulted in the lowest root mass density (21.1 ± 2.5 g cm-3; Supplementary material Table S.2), significantly different from mesocosms without earthworms (ET0: 49.7 ±

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7.6 g cm-3; Table 5).

Table 5: Effect of earthworm density and rice straw residue amendment on mean (± SE) Root

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mass density, Straw dry mass, Grain yield, and Harvest Index. Means marked with different

Straw treatment

Earthworm abundance ET0 ET1 ET2

Root mass density cm-3]

Straw dry mass ha-1]

Grain yield

ET0 50 ± 8 a 6.8 ± 0.6 ET1 21 ± 3 b 8.5 ± 0.8 n.s. ET2 30 ± 1 b 8 ± 1 different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

5.3 ± 0.5 6.5 ± 0.9 6.2 ± 0.3

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With Straw

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[Mg 8.7 ± 1.5 6.2 ± 0.5 7.4 ± 0.6

n.s.

Harvest

ha-1]

[Mg 10.3 ± 1.9 6.3 ± 0.3 n.s. 8.5 ± 0.9

Without Straw

[g 46 ± 5 42 ± 5 36 ± 4

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letters within a column are significantly different according to Tukey’s HSD test at P ≤ 0.05.

n.s.

n.s.

Index 0.46 ± 0.1 0.50 ± 0.1 n.s. 0.46 ± 0.1 0.44 ± 0.0 0.43 ± 0.1 n.s. 0.43 ± 0.1

Average soil organic C concentration remained stable during the cropping season (from 1.140 % to 1.210 %) while average N concentration decreased (from 1.42 % to 0.14 %). C/N ratio thus increased from 4.4 to 11.1. No treatment-related significant differences were observed for the concentration change of C or N, and C/N ratio between any of the straw residue or earthworm treatments (see Supplementary material Table S.3).

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Discussion

The experiment reported here demonstrates a considerable potential of native earthworms to mitigate increased CH4 emissions and GWP (CH4 and N2O) induced by rice straw addition to non-flooded paddy soils. This is supported by earlier findings implicating that earthworms increase the sustainability of agricultural systems as they modify nutrient allocation, GHG

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emission, and plant productivity by affecting soil conditions, microbial community

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composition and crop residue decomposition (Byers et al., 2006; Huang et al., 2015; Lavelle et al., 2016). The promotion of local earthworm populations thus seems to provide a feasible

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management option for increasing the sustainability of upland rice production.

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Rice straw amendment per se detrimentally affected crop yield, strongly increased

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CO2 emissions and CH4 release, and ultimately raised GWP (CH4 and N2O) by more than 400 %. This was accompanied by a shift from N2O to CH4 as the major contributor to total GWP.

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The effect of crop residues on CH4 and CO2 production was earlier explained by a number of

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mechanisms (e.g. microbial activity stimulation) (Conrad, 2002; Glissmann and Conrad, 2006; Kimura et al., 2004), but based on the set of parameters that we measured, we can only speculate which mechanisms were realistic in our experimental fields. Our experiment was conducted under well-drained, aerobic soil conditions. However, wet season rainfall events (Supplementary material Figure S.3) coupled with straw addition may have occasionally led to anaerobic decomposition of organic matter (Janz et al. 2019). According to Rath et al. (2005), CH4 emissions from non-flooded rice fields amended with rice straw can be almost as high as those from flooded fields without residue addition. CH4 emission was highest shortly after straw addition and gradually decreased during the cropping season to zero at ripening. This further demonstrates that CH4 release strongly depends on the availability of nonmetabolized crop residues and fades with progressing state of decomposition. 25

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The potential of earthworms to mitigate CH4 emission has been shown by several authors for various soil types and environmental conditions (e.g. Kernecker et al., 2014; Moon et al., 2010; Park et al., 2008). Our results suggest, however, that this effect is particularly pronounced when the proportion of undecomposed organic material is high. Earthworm-induced reductions of CH4 release after rice straw addition to non-saturated paddy soils may be the result of a variety of processes. First, earthworm activity may limit C

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availability for methanogenic archaea by stabilizing and physically protecting straw-derived C

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sources in soil macro- and microaggregates (Bossuyt et al., 2005; Chen et al., 2017). Then, earthworms may stimulate the growth and activity of methanotrophic bacteria (Kim et al.,

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2011; Moon et al., 2010; Park et al., 2008). And finally, by increasing the diffusion rate of

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oxygen into the soil profile, earthworms may decrease the availability of favourable anoxic

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microsites for methanogens (Kernecker et al., 2014; Lin et al., 2016). In our study, earthworm-related mitigation of CH4 emission was particularly strong at the beginning of the

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cropping season, and lasted until approx. 40 DAT, when most of the straw was decomposed.

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Even the sharp increase in CH4 release caused by heavy rains and the associated increase of water saturation at 20-30 DAT (Neue et al., 1996) was significantly buffered in the earthworm treatments. Thus, in contrast to a microcosm experiment with the earthworm Pheretima sp. (John et al., 2015), the addition of Metaphire sp. does not seem to increase the risk of CH4 emissions under conditions of high inflow of water in the field. These seemingly contradictory results can most probably be explained by the fact that endogeic earthworms increased the porosity of soils and, thus, promoted the accumulation of backwater in the bottom layers of soil-filled microcosms but increased water outflow under field conditions (Trojan and Linden, 1992). The strong increase of CH4 emissions (factor ≥ 2.6) in measurement chambers with rice plants compared to those without plants is in accordance with Butterbach-Bahl et al. (1997), who reported that a high proportion of CH4 is transported 26

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through rice plants’ aerenchymatous stem tissue. Earthworms were most effective in mitigating bare soil-derived CH4 emission between rice plants (N), but only reduced CH4 release in plant covered areas (P) at high density (ET2). With increasing earthworm density, more individuals probably entered the root zone, where they altered rhizodeposited C resources (Shao et al., 2019) and thus affected CH4 emission. Interestingly, such effects are visible only after straw amendment.

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Earthworm effects on N2O emission were limited to treatments without rice straw

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amendment. The significant, yet short-term increase in N2O emissions after fertilizer application during the reproductive growth stage observed at ET1 and ET2 partly supports the

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findings of other authors (Borken et al., 2000; Lubbers et al., 2011; Lubbers et al., 2013;

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Marhan et al., 2010; Rizhiya et al., 2007). However, it contradicts the earthworm-induced

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reduction of net N2O release from rice soil reported by Chen et al. (2014). Plant N uptake and the diffusion of N2O to the atmosphere may both be increased by improved soil aeration and

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porosity as a result of high earthworm activity (ET2). The increase of N2O emissions

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nevertheless was much lower in our study than postulated in other studies (Borken et al., 2000; Lubbers et al., 2013; Lubbers et al., 2011), particularly after residue amendment (Giannopoulos et al., 2010; Rizhiya et al., 2007). One explanation might be that different functional groups of earthworms can have quite contrasting effects on GHG emissions (see e.g. Majeed et al., 2013; Zhang et al., 2013). For example, denitrifying microorganisms do not seem to be affected in the same way in the gut of Metaphire sp. as has been reported for other earthworm species (Horn et al., 2003). The cyclic increase of N2O release in our experiment can partly be explained by the obvious association between N2O evolution and N fertilizer application (Bouwman et al., 2002). Additionally, N2O emission peaks might have been triggered by dry-wet alternations resulting from heavy rainfall events between two dry periods (11-18 DAT and 35-54 DAT) (Zou et al., 2005). Whether the improvement of soil aeration by 27

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earthworm activity contributes to the buffering of such dry-wet cycle induced peaks of N2O emission has to be tested in the future. We did not detect any effect of straw amendment on N2O flux at any time of the cropping season, although rice residue addition is thought to increase N uptake by plants (Verma and Bhagat, 1992). Yao et al. (2017) recently described strongly diminished N2O emissions after straw amendment, with improved N use efficiency by plants and hence

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increased yields from wheat-based crop rotations in China. However, this did not occur in our

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experiment carried out under conditions of aerobic upland rice cropping. Rice straw is a residue with relatively poor-quality, due to low N content, a high C/N ratio as well as high

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lignin and polyphenol contents (Jiang et al., 2018). Therefore, its decomposition bears the risk

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of microbial immobilization of N (Yadvinder-Singh et al., 2005), which can lead to negative

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short-term effects on crop production. However, proper N-fertilization management (e.g. 130 kg N in three splits as in this experiment) can reduce N immobilization after straw

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amendment (Eagle et al., 2000; Mandal et al., 2004), but can also allow N2O emissions.

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Several studies carried out in a variety of rice-cropping systems reported an initial decrease of rice yields after residue incorporation (Azam et al., 1991; Rao and Mikkelsen, 1976; Verma and Bhagat, 1992). However, residue amendment may increase soil N supply after several cropping seasons and thus does not adversely affect yield (Eagle et al., 2000). An obvious benefit of residue amendment is the reduction of the still widely practised open-field burning of rice straw in Southeast Asia, which is environmentally harmful and damaging to human health (Gadde et al., 2009; Huang et al., 2013; Streets et al., 2003; Tipayarom and Oanh, 2007). In the longer run, straw amendment is also preferable to straw burning in terms of nutrient return (Kimura et al., 1992). CO2 emission from upland rice soil is mainly determined by soil moisture (DossouYovo et al., 2016). It was thus relatively high in the study reported here, as the experiment 28

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was conducted during the wet season. Cyclic increases in CO2 emissions clearly resulted from increased soil respiration after urea application (Tisdale et al., 1985). Rice straw residue amendment tremendously increased the CO2 released from soil, which confirms the results of previous studies (Bhattacharyya et al., 2012; Dossou-Yovo et al., 2016). Earthworms increased CO2 emission in the treatments without straw addition, significantly reduced it after rice straw amendment under conditions of low earthworm density (ET1), and did not cause a

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significant reduction of CO2 emission after rice straw amendment under higher earthworm

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density (ET2). This can probably be explained by the fact that the net effect of earthworms on the amount of CO2 released from soil results from two opposing processes: the stimulation of

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microbial metabolic activity by bioturbation (e.g. Lubbers et al., 2013; Parkin and Berry,

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1999; Tiunov and Dobrovolskaya, 2002) and the physical protection of organic C in casts and

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soil aggregates (Bossuyt et al., 2005; Pulleman and Marinissen, 2004). We hypothesize that straw addition shifts the balance between these two processes from dominance of the former

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to dominance of the latter at low earthworm densities. On the other hand, adding straw to soils

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with high earthworm density may cause the two processes to mutually compensate each other. Lubbers et al. (2017) reported a simultaneous increase of both, CO2 emission by stimulated microbial activity and C stabilization in macro-aggregates under conditions of permanent maize residue C availability by earthworm activity, however with a higher fraction of mineralized than stabilized residue-derived C in the long run. The discrepancy between those reported and the results which we obtained might be attributed to the fact that residue-derived C was limited in our experimental system. Evidence thus suggests that the protection of organic C in soil aggregates and earthworm casts may increase the sustainability of nonflooded rice production systems in the long run by promoting C sequestration (Scheu and Wolters, 1991; Wolters, 2000; Zhang et al., 2013).

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In contrast to the usual view (e.g. Fonte and Six, 2010; Noguera et al., 2010; Xiao et al., 2018), earthworm activity did not beneficially affect plant biomass and crop yield in our experiment. The results nevertheless indicate that earthworms may at least partially compensate for the yield loss induced by straw amendment (ET1). Van Groenigen et al. (2014) found that the positive effects of earthworms on plant growth increased with increasing amounts of crop residue return to the soil, but that this effect may disappear under

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conditions of high soil N availability. The latter most probably applies to our experiment

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conducted under conventional high fertilizer inputs. Depending on their lifeform, some earthworm species can also have negative effects on plant growth and yields, e.g. by

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increasing soil water loss (Edwards et al., 1992; Tomlin et al., 1995) and nutrient leaching

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(Domínguez et al., 2004) as well as by feeding on plant roots (Curry and Schmidt, 2007;

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Gunn and Cherrett, 1993). While no detrimental effects of Metaphire sp. on shoot biomass and yield occurred in our experiment, we observed a decrease of root mass density in the

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rhizosphere when earthworms were present under conditions of straw amendment. Since this

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had no negative effect on crop production, however, reduced root mass density most probably mainly reflects a plant response to improved soil conditions and nutrient availability in the earthworm treatments (Chapuis-Lardy et al., 2011; Laossi et al., 2010). This may have additionally contributed to the earthworm-induced reductions of CH4 release, as root exudates act as substrates for methanogenesis (Lu et al., 2000; Wassmann and Aulakh, 2000).

Conclusion

To conclude, earthworms have a remarkable potential for providing ecosystem functions for the sustainable cultivation of upland crops in non-flooded tropical paddy soils, such as rice residue decomposition, nutrient allocation and the reduction of crop residue 30

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amendment-related increase of GHG release confined to CH4 without affecting N2O and CO2 emissions substantially, and neither crop productivity. Active earthworm management thus can be an attractive and easy to implement strategy to promote alternative crop residue disposal management following the ban on open field burning and to reduce straw-induced CH4 emission. The actual mechanisms behind the presented results require further studies including environmental and microbiological factors to be measured and long-term

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observations would be helpful for both validating the findings of our study and investigating

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the development of earthworm populations under field conditions.

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Acknowledgements

This work was funded by the German Research Foundation (DFG) as part of the Research Group FOR 1701 ICON (“Introducing Non‐Flooded Crops in Rice‐Dominated Landscapes: Impacts on Carbon, Nitrogen and Water Cycles” (BU1173/13-2) subprojects: “Influence of trophic interactions in soil on carbon and nitrogen turnover” (WO670/15-1) and “Greenhouse

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gas emission of different crop rotations of rice (flooded and non-flooded) and maize”

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(KI1431/3-2). The students Mr. Michael Christian Kratz and Mr. Mathias Rzytki from Justus Liebig University Gießen greatly supported earthworm sampling, experimental set-up,

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greenhouse gas measurements and technical assistance during the whole experiment. Their

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stay in the Philippines was supported by a scholarship within the PROMOS Programme of the

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German Academic Exchange Service (DAAD). We gratefully acknowledge the International Rice Research Institute (IRRI), especially Mr. Jericho Bigornia and Mrs. Mary L. Mendoza

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from Crop and Environmental Sciences Division (CESD) for providing facilities, supporting

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with logistics, field activities, and sampling.

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References

Azam, F., Lodhi, A., Ashraf, M. (1991). Availability of soil and fertilizer nitrogen to wetland rice following wheat straw amendment. Biology and Fertility of Soils, 11(2), 97–100. https://doi.org/10.1007/BF00336371 Bhattacharyya, P., Roy, K. S., Neogi, S., Adhya, T. K., Rao, K. S., Manna, M. C. (2012).

of

Effects of rice straw and nitrogen fertilization on greenhouse gas emissions and carbon

ro

storage in tropical flooded soil planted with rice. Soil and Tillage Research, 124, 119– 130. https://doi.org/10.1016/j.still.2012.05.015

-p

Blouin, M., Hodson, M. E., Delgado, E. A., Baker, G., Brussard, L., Butt, K. R., … Brun, J.-J.

re

(2013). A review of earthworm impact on soil function and ecosystem services.

lP

European Journal of Soil Science, 64(2), 161–182. https://doi.org/10.1111/ejss/12025 Borken, W., Gründel, S., Beese, F. (2000). Potential contribution of Lumbricus terrestris L. to

na

carbon dioxide, methane and nitrous oxide fluxes from a forest soil. Biology and

Jo ur

Fertility of Soils, 32(2), 142–148. https://doi.org/10.1007/s003740000228 Bossuyt, H., Six, J., Hendrix, P. F. (2005). Protection of soil carbon by microaggregates within earthworm casts. Soil Biology and Biochemistry, 37(2), 251–258. https://doi.org/10.1016/j.soilbio.2004.07.035 Bouwman, A. F., Boumans, L. J. M., Batjes, N. H. (2002). Modeling global annual N2O and NO emissions from fertilized fields. Global Biogeochemical Cycles, 16(4), 28-1–28-9. https://doi.org/10.1029/2001GB001812 Breidenbach, B., Blaser, M. B., Klose, M., Conrad, R. (2015). Crop rotation of flooded rice with upland maize impacts the resident and active methanogenic microbial community. Environmental Microbiology, 18(9), 2868–85. https://doi.org/10.1111/1462-2920.13041 Breidenbach, B., Brenzinger, K., Brandt, F. B., Blaser, M. B., Conrad, R. (2017). The effect 33

Journal Pre-proof

of crop rotation between wetland rice and upland maize on the microbial communities associated with roots. Plant and Soil, 419(1-2), 435–445. https://doi.org/10.1007/s11104-017-3351-5 Bronson, K. F., Neue, H.-U., Singh, U., Abac Jr., E. B. (1997). Automated Chamber Measurements of Methane and Nitrous Oxide Flux in a Flooded Rice Soil: I. Residue, Nitrogen, and Water Management. Soil Science Society of America Journal, 61(3), 981–

of

987. https://doi.org/10.2136/sssaj1997.03615995006100030038x

ro

Brown, G., Pashanasi, B., Villenave, C., Patron, J. C., Senapati, B., Giri, S., … Boyer, J. (1999). Effects of earthworms on plant production in the tropics. In P. Lavelle, L.

re

87–146). Wallingford: CABI.

-p

Brussaard, P. Hendrix (Eds.), Earthworm management in tropical agroecosystems (pp.

lP

Butterbach-Bahl, K., Papen, H., Rennenberg, H. (1997). Impact of gas transport through rice cultivars on methane emission from rice paddy fields. Plant, Cell and Environment,

na

20(9), 1175–1183. https://doi.org/10.1046/j.1365-3040.1997.d01-142.x

Jo ur

Butterbach-Bahl, K., Sander, B. O., Pelster, D., Díaz-Pinés, E. (2016). Quantifying Greenhouse Gas Emissions from Managed and Natural Soils. In T. S. Rosenstock, M. C. Rufino, K. Butterbach-Bahl, E. Wollenberg, M. Richards (Eds.), Methods for Measuring Greenhouse Gas Balances and Evaluating Mitigation Options in Smallholder Agriculture (pp. 71–96). Cham: Springer. https://doi.org/10.1007/978-3319-29794-1 Byers, J. E., Cuddington, K., Jones, C. G., Talley, T. S., Hastings, A., Lambrinos, J. G., … Wilson, W. G. (2006). Using ecosystem engineers to restore ecological systems. Trends in Ecology and Evolution, 21(9), 493–500. https://doi.org/10.1016/j.tree.2006.06.002 Devêvre, O. C., Horwath, W. (2000). Decomposition of rice straw and microbial carbon use efficiency under different soil temperatures and moistures. Soil Biology and 34

Journal Pre-proof

Biochemistry, 32(11-12), 1773–1785. https://doi.org/10.1016/S0038-0717(00)00096-1 Cha-un, N., Chidthaisong, A., Yagi, K., Sudo, S., Towprayoon, S. (2017). Greenhouse gas emissions, soil carbon sequestration and crop yields in a rain-fed rice field with crop rotation management. Agriculture, Ecosystems & Environment, 237, 109–120. https://doi.org/10.1016/j.agee.2016.12.025 Chapuis-Lardy, L., Brauman, A., Bernard, L., Pablo, A. L., Toucet, J., Mano, M. J., …

of

Blanchart, E. (2010). Effect of the endogeic earthworm Pontoscolex corethrurus on the

ro

microbial structure and activity related to CO2 and N2O fluxes from a tropical soil (Madagascar). Applied Soil Ecology, 45(3), 201–208.

-p

https://doi.org/10.1016/j.apsoil.2010.04.006

re

Chapuis-Lardy, L., Le Bayon, R. C., Brossard, M., López-Hernández, D., Blanchart, E.

lP

(2011). Role of Soil Macrofauna in Phosphorus Cycling. In E. Bünemann, A. Oberson, E. Frossard (Eds.), Phosphorus in Action. Soil Biology, vol 26 (pp. 199–213). Berlin,

na

Heidelberg: Springer. https://doi.org/10.1007/978-3-642-15271-9_8

Jo ur

Chen, C., Whalen, J. K., Guo, X. (2014). Earthworms reduce soil nitrous oxide emissions during drying and rewetting cycles. Soil Biology and Biochemistry, 68, 117–124. https://doi.org/10.1016/j.soilbio.2013.09.020 Chen, Z., Wang, H., Liu, X., Zhao, X., Lu, D., Zhou, J., Li, C. (2017). Changes in soil microbial community and organic carbon fractions under short-term straw return in a rice–wheat cropping system. Soil and Tillage Research, 165, 121–127. https://doi.org/10.1016/j.still.2016.07.018 Conrad, R. (2002). Control of microbial methane production in wetland rice fields. Nutrient Cycling in Agroecosystems, 64(1-2), 59–69. https://doi.org/10.1023/A:1021178713988 Curry, J. P., Schmidt, O. (2007). The feeding ecology of earthworms – A review. Pedobiologia, 50(6), 463–477. https://doi.org/10.1016/J.PEDOBI.2006.09.001 35

Journal Pre-proof

Darwin, C. (1881). The formation of vegetable mould, through the action of worms, with observations on their habits (1st ed.). London: John Murray. Depkat-Jakob, P. S., Hunger, S., Schulz, K., Brown, G. G., Tsai, S. M., Drake, H. L. (2012). Emission of methane by Eudrilus eugeniae and other earthworms from Brazil. Applied and Environmental Microbiology, 78(8), 3014–9. https://doi.org/10.1128/AEM.0794911

of

Domínguez, J., Bohlen, P. J., Parmelee, R. W. (2004). Earthworms increase nitrogen leaching

https://doi.org/10.1007/s10021-004-0150-7

ro

to greater soil depths in row crop agroecosystems. Ecosystems, 7(6), 672–685.

-p

Dossou-Yovo, E. R., Brüggemann, N., Jesse, N., Huat, J., Ago, E. E., Agbossou, E. K. (2016).

re

Reducing soil CO2 emission and improving upland rice yield with no-tillage, straw

lP

mulch and nitrogen fertilization in northern Benin. Soil and Tillage Research, 156, 44– 53. https://doi.org/10.1016/J.STILL.2015.10.001

na

Eagle, A. J., Bird, J. A., Horwath, W. R., Linquist, B. A., Brouder, S. M., Hill, J. E., van

Jo ur

Kessel, C. (2000). Rice yield and nitrogen utilization efficiency under alternative straw management practices. Agronomy Journal, 92(6), 1093–1103. https://doi.org/10.2134/agronj2000.9261096x Edwards, W. M., Shipitalo, M. J., Traina, S. J., Edwards, C. A., Owens, L. B. (1992). Role of Lumbricus terrestris (L.) burrows on quality of infiltrating water. Soil Biology and Biochemistry, 24(12), 1555–1561. https://doi.org/10.1016/0038-0717(92)90150-V Fonte, S. J., Six, J. (2010). Earthworms and litter management contributions to ecosystem services in a tropical agroforestry system. Ecological Applications, 20(4), 1061–73. https://doi.org/10.1890/09-0795.1 Gadde, B., Bonnet, S., Menke, C., Garivait, S. (2009). Air pollutant emissions from rice straw open field burning in India, Thailand and the Philippines. Environmental Pollution, 36

Journal Pre-proof

157(5), 1554–1558. https://doi.org/10.1016/j.envpol.2009.01.004 Giannopoulos, G., Pulleman, M. M., van Groenigen, J. W. (2010). Interactions between residue placement and earthworm ecological strategy affect aggregate turnover and N2O dynamics in agricultural soil. Soil Biology and Biochemistry, 42(4), 618–625. https://doi.org/10.1016/J.SOILBIO.2009.12.015 Glissmann, K., Conrad, R. (2006). Fermentation pattern of methanogenic degradation of rice

of

straw in anoxic paddy soil. FEMS Microbiology Ecology, 31(2), 117–126.

ro

https://doi.org/doi:10.1111/j.1574-6941.2000.tb00677.x

Gunn, A., Cherrett, J. M. (1993). The exploitation of food resources by soil meso- and

-p

macroinvertebrates. Pedobiologia, 37, 303–320.

re

Henry, A., Torres, R., Holongbayan, L. (2012). Root sampling in the field with soil cores and

lP

monoliths. In H. E. Shashidhar, A. Henry, B. Hardy (Eds.), Methodologies for root

Research Institute.

na

drought studies in rice (pp. 52–61). Los Baños, Philippines,: International Rice

Jo ur

Horn, M. A., Schramm, A., Drake, H. L. (2003). The earthworm gut: An ideal habitat for ingested N2O-producing microorganisms. Applied and Environmental Microbiology, 69(3), 1662–1669. https://doi.org/10.1128/AEM.69.3.1662-1669.2003 Huang, J., Zhang, W., Liu, M., Briones, M. J. I., Eisenhauer, N., Shao, Y., … Xia, H. (2015). Different impacts of native and exotic earthworms on rhizodeposit carbon sequestration in a subtropical soil. Soil Biology and Biochemistry, 90, 152–160. https://doi.org/10.1016/j.soilbio.2015.08.011 Huang, T., Gao, B., Christie, P., Ju, X. (2013). Net global warming potential and greenhouse gas intensity in a double-cropping cereal rotation as affected by nitrogen and straw management. Biogeosciences, 10, 7897–7911. https://doi.org/10.5194/bg-10-7897-2013 IPCC. (2014). Summary for Policymakers. In: O. Edenhofer., R. Pichs-Madruga, Y. Sokona, 37

Journal Pre-proof

E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel, J.C. Minx (Eds.), Climate Change 2014, Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. https://doi.org/10.1017/CBO9781107415324

of

IRRI, 2009. ORYZA2000: Experimental data collection and analysis. Retrieved from

ro

https://sites.google.com/a/irri.org/oryza2000/calibration-and-validation/experimentaldata-collection-and-analysis. Accessed: 5 July 2018 11:24 am

-p

Janz, B., Weller, S., Kraus, D., Racela, H. S., Wassmann, R., Butterbach-Bahl, K., Kiese, R.

re

(2019). Greenhouse gas footprint of diversifying rice cropping systems: Impacts of

lP

water regime and organic amendments. Agriculture, Ecosystems & Environment, 270– 271, 41–54. https://doi.org/10.1016/j.agee.2018.10.011

na

Jiang, Y., Wang, J., Muhammad, S., Zhou, A., Hao, R., Wu, Y. (2018). How do earthworms

Jo ur

affect decomposition of residues with different quality apart from fragmentation and incorporation? Geoderma, 326, 68–75. https://doi.org/10.1016/j.geoderma.2018.04.013 John, K., Jauker, F., Marxsen, J., Zaitsev, A. S., Wolters, V. (2015). Earthworm bioturbation stabilizes carbon in non-flooded paddy soil at the risk of increasing methane emissions under wet soil conditions. Soil Biology and Biochemistry, 91, 127–132. https://doi.org/10.1016/j.soilbio.2015.08.033 Kernecker, M., Whalen, J. K., Bradley, R. L. (2014). Endogeic earthworms lower net methane production in saturated riparian soils. Biology and Fertility of Soils, 51(2), 271–275. https://doi.org/10.1007/s00374-014-0965-0 Khush, G. S. (2005). What it will take to Feed 5.0 Billion Rice consumers in 2030. Plant Molecular Biology, 59(1), 1–6. https://doi.org/10.1007/s11103-005-2159-5 38

Journal Pre-proof

Kim, T. G., Moon, K.-E., Lee, E.-H., Choi, S.-A., Cho, K.-S. (2011). Assessing effects of earthworm cast on methanotrophic community in a soil biocover by concurrent use of microarray and quantitative real-time PCR. Applied Soil Ecology, 50, 52–55. https://doi.org/10.1016/J.APSOIL.2011.07.011 Kimura, M., Miura, Y., Watanabe, A., Murase, J., Kuwatsuka, S., Miura, Y. (1992). Methane production and its fate in paddy fields: I. Effects of rice straw application and

ro

Soil Science and Plant Nutrition, 38(4), 665–672.

of

percolation rate on the leaching of methane and other soil components into the subsoil.

https://doi.org/10.1080/00380768.1992.10416696

-p

Kimura, M., Murase, J., Lu, Y. (2004). Carbon cycling in rice field ecosystems in the context

re

of input, decomposition and translocation of organic materials and the fates of their end

lP

products (CO2and CH4). Soil Biology and Biochemistry, 36(9), 1399–1416. https://doi.org/10.1016/j.soilbio.2004.03.006

na

Kizilkaya, R., Hepşen, Ş. (2004). Effect of biosolid amendment on enzyme activities in

Jo ur

earthworm (Lumbricus terrestris) casts. Journal of Plant Nutrition and Soil Science, 167(2), 202–208. https://doi.org/10.1002/jpln.200321263 Laossi, K. R., Ginot, A., Noguera, D. C., Blouin, M., Barot, S. (2010). Earthworm effects on plant growth do not necessarily decrease with soil fertility. Plant and Soil, 328(1-2), 109–118. https://doi.org/10.1007/s11104-009-0086-y Lavelle, Patrick, Spain, A., Blouin, M., Brown, G., Decaëns, T., Grimaldi, M., … Zangerlé, A. (2016). Ecosystem engineers in a self-organized soil: A review of concepts and future research questions. Soil Science, 181, 91–109. https://doi.org/10.1097/SS.0000000000000155 Le Mer, J., Roger, P. (2001). Production, oxidation, emission and consumption of methane by soils : A review. European Journal of Soil Biology, 37(1), 25–50. 39

Journal Pre-proof

https://doi.org/http://dx.doi.org/10.1016/S1164-5563(01)01067-6 Lin, Z., Zhen, Z., Wu, Z., Yang, J., Zhong, L., Hu, H., … Zhang, D. (2016). The impact on the soil microbial community and enzyme activity of two earthworm species during the bioremediation of pentachlorophenol-contaminated soils. Journal of Hazardous Materials, 301, 35–45. https://doi.org/10.1016/j.jhazmat.2015.08.034 Lu, Y., Wassmann, R., Neue, H. U., Huang, C., Bueno, C. S. (2000). Methanogenic responses

of

to exogenous substrates in anaerobic rice soils. Soil Biology and Biochemistry, 32, 11–

ro

12. https://doi.org/10.1016/S0038-0717(00)00085-7

Lubbers, I. M., Brussaard, L., Otten, W., van Groenigen, J. W. (2011). Earthworm-induced N

-p

mineralization in fertilized grassland increases both N2O emission and crop-N uptake.

re

European Journal of Soil Science, 62, 152–161. https://doi.org/10.1111/j.1365-

lP

2389.2010.01313.x

Lubbers, I. M., López González, E., Hummelink, E. W. J., van Groenigen, J. W. (2013).

na

Earthworms can increase nitrous oxide emissions from managed grassland: A field

Jo ur

study. Agriculture, Ecosystems & Environment, 174, 40–48. https://doi.org/10.1016/J.AGEE.2013.05.001 Lubbers, I. M., Pulleman, M. M., van Groenigen, J. W. (2017). Can earthworms simultaneously enhance decomposition and stabilization of plant residue carbon? Soil Biology and Biochemistry, 105, 15–24. https://doi.org/10.1016/j.soilbio.2016.11.008 Lubbers, I. M., van Groenigen, J. W. (2013). A simple and effective method to keep earthworms confined to open-top mesocosms. Applied Soil Ecology, 64, 190–193. https://doi.org/10.1016/j.apsoil.2012.12.008 Lubbers, I. M., van Groenigen, K. J., Fonte, S. J., Six, J., Brussaard, L., van Groenigen, J. W. (2013). Greenhouse-gas emissions from soils increased by earthworms. Nature Climate Change, 3(3), 187–194. https://doi.org/10.1038/nclimate1692 40

Journal Pre-proof

Majeed, M. Z., Miambi, E., Barois, I., Blanchart, E., Brauman, A. (2013). Emissions of nitrous oxide from casts of tropical earthworms belonging to different ecological categories. Pedobiologia, 56(1), 49–58. https://doi.org/10.1016/j.pedobi.2012.10.003 Mandal, K. G., Misra, A. K., Hati, K. M., Bandyopadhyay, K. K., Ghosh, P. K. (2004). Rice residue- management options and effects on soil properties and crop productivity. Food, Agriculture & Environment, 2(1), 224–231. https://doi.org/10.1234/4.2004.127

of

Marhan, S., Rempt, F., Högy, P., Fangmeier, A., Kandeler, E. (2010). Effects of Aporrectodea

ro

caliginosa (Savigny) on nitrogen mobilization and decomposition of elevated‐CO2

https://doi.org/10.1002/jpln.201000092

-p

Charlock mustard litter. Journal of Plant Nutrition and Soil Science, 173(6), 861–868.

re

Minamikawa, K., Tokida, T., Sudo, S., Padre, A., Yagi, K. (2015). Guidelines for Measuring

lP

CH4 and N2O Emissions from Rice Paddies by a Manually Operated Closed Chamber Method. Tsukuba, Japan: National Institute for Agro-Environmental Science.

na

https://doi.org/10.1016/j.agee.2016.10.011

Jo ur

Moon, K. E., Lee, S. Y., Lee, S. H., Ryu, H. W., Cho, K. S. (2010). Earthworm cast as a promising filter bed material and its methanotrophic contribution to methane removal. Journal of Hazardous Materials, 176(1–3), 131–138. https://doi.org/10.1016/j.jhazmat.2009.11.007 Mousavi, S. F., Moazzeni, M., Mostafazadeh-Fard, B., Yazdani, M. R. (2012). Effects of rice straw incorporation on some physical characteristics of paddy soils. Journal of Agricultural Science and Technology, 14(5), 1173–1183. Myhre, G., Shindell, D., Bréon, F.-M., Collins, W., Fuglestvedt, J., Huang, J., … Zhang, H. (2013). Anthropogenic and Natural Radiative Forcing. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. 41

Journal Pre-proof

https://doi.org/10.1017/CBO9781107415324.018 Neue, H. U., Wassmann, R., Lantin, R. S., Alberto, M. C. R., Aduna, J. B., Javellana, a. M. (1996). Factors affecting methane emission from rice fields. Atmospheric Environment, 30(10-11), 1751–1754. https://doi.org/10.1016/1352-2310(95)00375-4 Noguera, D., Rondón, M., Laossi, K. R., Hoyos, V., Lavelle, P., Cruz de Carvalho, M. H., Barot, S. (2010). Contrasted effect of biochar and earthworms on rice growth and

of

resource allocation in different soils. Soil Biology and Biochemistry, 42(7), 1017–1027.

ro

https://doi.org/10.1016/j.soilbio.2010.03.001

Pandey, A., Mai, V. T., Vu, D. Q., Bui, T. P. L., Mai, T. L. A., Jensen, L. S., de Neergaard, A.

-p

(2014). Organic matter and water management strategies to reduce methane and nitrous

re

oxide emissions from rice paddies in Vietnam. Agriculture, Ecosystems & Environment,

lP

196, 137–146. https://doi.org/10.1016/j.agee.2014.06.010 Park, S., Lee, I., Cho, C., Sung, K. (2008). Effects of earthworm cast and powdered activated

na

carbon on methane removal capacity of landfill cover soils. Chemosphere, 70(6), 1117–

Jo ur

23. https://doi.org/10.1016/j.chemosphere.2007.07.034 Parkin, T. B., Berry, E. C. (1994). Nitrogen transformations in earthworm casts. Soil Biology and Biochemistry, 26(9), 1233–1238. https://doi.org/10.1016/0038-0717(94)90148-1 Paul, B. K., Lubbers, I. M., van Groenigen, J. W. (2012). Residue incorporation depth is a controlling factor of earthworm-induced nitrous oxide emissions. Global Change Biology, 18(3), 1141–1151. https://doi.org/10.1111/j.1365-2486.2011.02525.x Pulleman, M. M., Marinissen, J. C. Y. (2004). Physical protection of mineralizable C in aggregates from long-term pasture and arable soil. Geoderma, 120(3–4), 273–282. https://doi.org/10.1016/j.geoderma.2003.09.009 Rao, D. N., Mikkelsen, D. S. (1976). Effect of Rice Straw Incorporation on Rice Plant Growth and Nutrition. Agronomy Journal, 68(5), 752–755. 42

Journal Pre-proof

https://doi.org/10.2134/agronj1976.00021962006800050017x Rath, A. K., Ramakrishnan, B., Rao, V. R., Sethunathan, N. (2005). Effects of rice-straw and phosphorus application on production and emission of methane from tropical rice soil. Journal of Plant Nutrition and Soil Science, 168(2), 248–254. https://doi.org/10.1002/jpln.200421604 Rizhiya, E., Bertora, C., van Vliet, P. C. J., Kuikman, P. J., Faber, J. H., van Groenigen, J. W.

of

(2007). Earthworm activity as a determinant for N2O emission from crop residue. Soil

ro

Biology and Biochemistry, 39(8), 2058–2069. https://doi.org/10.1016/J.SOILBIO.2007.03.008

-p

Sander, B. O., Wassmann, R. (2014). Common practices for manual greenhouse gas sampling

re

in rice production: a literature study on sampling modalities of the closed chamber

lP

method. Greenhouse Gas Measurement and Management, 4(1), 1–13. https://doi.org/10.1080/20430779.2014.892807

na

Scheu, S. (2003). Effects of earthworms on plant growth: patterns and perspectives – The 7th

Jo ur

international symposium on earthworm ecology Cardiff Wales 2002. Pedobiologia, 47(5-6), 846–856. https://doi.org/10.1016/S0031-4056(04)70279-6 Scheu, S., Wolters, V. (1991). Influence of fragmentation and bioturbation on the decomposition of 14C-labelled beech leaf litter. Soil Biology and Biochemistry, 23(11), 1029–1034. https://doi.org/10.1016/0038-0717(91)90039-M Schmidt, A., John, K., Auge, H., Brandl, R., Horgan, F. G., Settele, J., … Schädler, M. (2016). Compensatory mechanisms of litter decomposition under alternating moisture regimes in tropical rice fields. Applied Soil Ecology, 107, 79–90. https://doi.org/10.1016/j.apsoil.2016.05.014 Setälä, H., Marshall, V. G., Trofymow, J. A. (1996). Influence of body size of soil fauna on litter decomposition and 15N uptake by poplar in a pot trial. Soil Biology and 43

Journal Pre-proof

Biochemistry, 28(12), 1661–1675. https://doi.org/10.1016/S0038-0717(96)00252-0 Shao, Y., Zhang, W., Eisenhauer, N., Liu, T., Ferlian, O., Wang, X., … Fu, S. (2019). Exotic earthworms maintain soil biodiversity by altering bottom-up effects of plants on the composition of soil microbial groups and nematode communities. Biology and Fertility of Soils, 55(3), 213–227. https://doi.org/10.1007/s00374-019-01343-0 Speratti, A. B., Whalen, J. K. (2008). Carbon dioxide and nitrous oxide fluxes from soil as

of

influenced by anecic and endogeic earthworms. Applied Soil Ecology, 38(1), 27–33.

ro

https://doi.org/10.1016/j.apsoil.2007.08.009

Streets, D. G., Yarber, K. F., Woo, J.-H., Carmichael, G. R. (2003). Biomass burning in Asia:

-p

Annual and seasonal estimates and atmospheric emissions. Global Biogeochemical

re

Cycles, 17(4), 10-1–12-20. https://doi.org/10.1029/2003GB002040

lP

Timsina, J., Jat, M. L., Majumdar, K. (2010). Rice-maize systems of South Asia: Current status, future prospects and research priorities for nutrient management. Plant and Soil,

na

335(1), 65–82. https://doi.org/10.1007/s11104-010-0418-y

Jo ur

Tipayarom, D., Oanh, N. T. K. (2007). Effects from open rice straw burning emission on air quality in the Bangkok metropolitan region. ScienceAsia, 33, 339–345. https://doi.org/10.2306/scienceasia1513-1874.2007.33.339 Tisdale, S. L., Nelson, W. L., Beaton, J. D. (1985). Soil fertility and fertilizers. London: Collier Macmillan Publishers. Tiunov, A. V., Dobrovolskaya, T. G. (2002). Fungal and bacterial communities in Lumbricus terrestris burrow walls: A laboratory experiment. Pedobiologia, 46(6), 595–605. https://doi.org/10.1078/0031-4056-00162 Tiunov, A. V., Scheu, S. (1999). Microbial respiration, biomass, biovolume and nutrient status in burrow walls of Lumbricus terrestris L. (Lumbricidae). Soil Biology and Biochemistry, 31(14), 2039–2048. https://doi.org/10.1016/S0038-0717(99)00127-3 44

Journal Pre-proof

Tomlin, A. ., Shipitalo, M. J., Edwards, W. M., Protz, R. (1995). Earthworms and their influence on soil structure and infiltration. In P. F. Hendrix (Ed.), Earthworm Ecology and Biogeography in North America. (pp. 159–183). Boca Raton, Fla, USA: CRC Press. Trojan, M. D., Linden, D. R. (1992). Microrelief and Rainfall Effects on Water and Solute Movement in Earthworm Burrows. Soil Science Society of America Journal, 56(3),

of

727–733. https://doi.org/10.2136/sssaj1992.03615995005600030009x

ro

van Groenigen, J. W., Lubbers, I. M., Vos, H. M. J., Brown, G. G., De Deyn, G. B., van Groenigen, K. J. (2014). Earthworms increase plant production: a meta-analysis.

-p

Scientific Reports, 4, 6365. https://doi.org/10.1038/srep06365

re

Verma, T. S., Bhagat, R. M. (1992). Impact of rice straw management practices on yield,

lP

nitrogen uptake and soil properties in a wheat-rice rotation in northern India. Fertilizer Research, 33(2), 97–106. https://doi.org/10.1007/BF01051164

na

Wassmann, R, Aulakh, M. S. (2000). The role of rice plants in regulating mechanisms of

Jo ur

methane missions. Biology and Fertility of Soils, 31(1), 20–29. https://doi.org/10.1007/s003740050619 Wassmann, Reiner, Buendia, L. V, Lantin, R. S., Bueno, C. S., Lubigan, L. A., Umali, A., … Neue, H. U. (2000). Mechanisms of crop management impact on methane emissions from rice fields in Los Banos, Philippines. Nutrient Cycling in Agroecosystems, 58(1– 3), 107–119. https://doi.org/10.1023/A:1009838401699 Weller, S., Janz, B., Jörg, L., Kraus, D., Racela, H. S. U., Wassmann, R., … Kiese, R. (2016). Greenhouse gas emissions and global warming potential of traditional and diversified tropical rice rotation systems. Global Change Biology, 22(1), 432–448. https://doi.org/10.1111/gcb.13099 Wolters, V. (2000). Invertebrate control of soil organic matter stability. Biology and Fertility 45

Journal Pre-proof

of Soils, 31(1), 1–19. https://doi.org/10.1007/s003740050618 Wolters, V., Stickan, W. (1991). Resource allocation of beech seedlings (Fagus sylvatica L.) relationship to earthworm activity and soil conditions. Oecologia, 88(1), 125–131. https://doi.org/10.1007/BF00328412 Xia, L., Wang, S., Yan, X. (2014). Effects of long-term straw incorporation on the net global warming potential and the net economic benefit in a rice-wheat cropping system in

of

China. Agriculture, Ecosystems & Environment, 197, 118–127.

ro

https://doi.org/10.1016/j.agee.2014.08.001

Xiao, Z., Wang, X., Koricheva, J., Kergunteuil, A., Le Bayon, R. C., Liu, M., … Rasmann, S.

-p

(2018). Earthworms affect plant growth and resistance against herbivores: A meta-

re

analysis. Functional Ecology, 32(1), 150–160. https://doi.org/10.1111/1365-2435.12969

lP

Yadvinder-Singh, Bijay-Singh, Timsina, J. (2005). Crop Residue Management for Nutrient Cycling and Improving Soil Productivity in Rice-Based Cropping Systems in the

Jo ur

2113(04)85006-5

na

Tropics. Advances in Agronomy, 85, 269–407. https://doi.org/10.1016/S0065-

Yao, Z., Yan, G., Zheng, X., Wang, R., Liu, C., Butterbach-Bahl, K. (2017). Straw return reduces yield-scaled N2O plus NO emissions from annual winter wheat-based cropping systems in the North China Plain. Science of The Total Environment, 590-591, 174–185. https://doi.org/10.1016/j.scitotenv.2017.02.194 Zhang, W., Hendrix, P. F., Dame, L. E., Burke, R. A., Wu, J., Neher, D. A., … Fu, S. (2013). Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization. Nature Communications, 4, 2576. https://doi.org/10.1038/ncomms3576 Zou, J., Huang, Y., Jiang, J., Zheng, X., Sass, R. L. (2005). A 3-year field measurement of methane and nitrous oxide emissions from rice paddies in China: Effects of water 46

Jo ur

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of

Journal Pre-proof

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regime, crop residue, and fertilizer application. Global Biogeochemical Cycles, 19(2), 1–9. https://doi.org/10.1029/2004GB002401 Table 1: Response of CH4, N2O and CO2 flux rates on rice Straw residue amendment (S), Earthworm treatments (W), Growth stage (G), Chamber type (C), and their first-order interactions (Sum of Squares and their significance levels). Treatment effects without explanatory power where excluded from the model (GLM analysis, stepwise backward and

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1.159 *

CxW CxS WxS Residual Error 2

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0.638 * 0.931 ** 1.272 ** 108.983

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GxS

11.095 0.94 11.816 2.559

N2O -N

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Straw (S) Earthworm (W) Growth stage (G) Chamber type (C) GxC GxW

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forward selection).

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Model R 0.2479 *** 0.24 *** Significance level: ***P < 0.001, **P < 0.01, *P < 0.05

51.92 0.37 ***

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Journal Pre-proof Table 2: Cumulative CH4 emissions during three rice growth stages and seasonal cumulative CH4 emissions as affected by rice straw residue amendment and earthworm treatment (ET0, ET1, and ET2) in chambers without (N) and with rice plants (P) (means ± S.E.). Means followed by a different letter are significantly different between the three earthworm treatments within the respective growth stage and chamber type according to Tukey’s HSD test at P ≤ 0.05. CH4 emission [kg C ha-1] ± SE Without Straw ET0 ET1 ET2 With Straw ET0 ET1 ET2

vegetative

reproductive (N) without Plants

0.4 ± 0.3 b 0.3 ± 0.1 b 1.1 ± 0.3 a

0.5 ± 0.8 b 1.6 ± 1.6 ab 3.0 ± 5.0 a

50.7 ± 11 a 7.1 ± 1.7 b 9.7 ± 1.5 b

23.8 ± 32 a 9.6 ± 11 ab 8.0 ± 9.9 b (P) with Plants

n r u

l a

f o

o r p

0.2 ± 0.4 0.1 ± 0.1 n.s. 0.1 ± 0.1

e

r P

Without Straw ET0 2.9 ± 0.5 a 4.2 ± 5.0 ET1 1.4 ± 0.2 b 2.4 ± 1.6 n.s. ET2 2.2 ± 0.3 ab 3.6 ± 2.0 With Straw ET0 38.2 ± 6.2 a 32.5 ± 30 a ET1 34.2 ± 4.1 a 26.9 ± 22 a ET2 8.3 ± 1.2 b 13.1 ± 10 b different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

o J

ripening

0.8 ± 1.0 0.5 ± 0.5 n.s. 0.9 ± 1.7

0.9 ± 0.6 1.0 ± 0.7 n.s. 1.0 ± 0.4 4.6 ± 1.4 7.3 ± 3.8 n.s. 3.9 ± 1.6

total season

1.2 ± 1.0 2.0 ± 1.6 4.2 ± 5.0

b ab a

75.4 ± 34.2 a 17.2 ± 10.9 b 18.6 ± 10.2 b

8.0 ± 5.0 4.7 ± 1.7 6.8 ± 2.1

a b a

75.3 ± 30.8 a 68.4 ± 22.2 a 25.3 ± 10.4 b

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Table 3: Cumulative N2O emissions during three rice growth stages and seasonal cumulative N2O emissions as affected by rice straw residue amendment and earthworm treatment (ET0, ET1, and ET2) in chambers without (N) and with rice plants (P) (means ± S.E.). Means followed

f o

by a different letter are significantly different between the three earthworm treatments within the respective growth stage and chamber type according to Tukey’s HSD test at P ≤ 0.05. N2O emission [kg N ha-1] ± SE Without Straw ET0 ET1 ET2 With Straw ET0 ET1 ET2 Without Straw ET0 ET1 ET2 With Straw ET0 ET1

vegetative

reproductive (N) without Plants

0.2 ± 0.1 b 0.2 ± 0.0 b 0.4 ± 0.1 a

2.2 ± 1.1 b 2.2 ± 1.2 b 3.0 ± 1.2 a

o r p

e

ripening

r P

total season

0.2 ± 0.3 b 0.2 ± 0.3 b 0.5 ± 0.5 a

2.7 ± 1.2 2.7 ± 1.2 4.0 ± 1.3

b b a

2.4 ± 1.2 2.5 ± 1.3 n.s. 2.6 ± 1.5 (P) with Plants

0.2 ± 0.2 0.2 ± 0.2 n.s. 0.2 ± 0.2

3.0 ± 1.2 2.9 ± 1.4 3.2 ± 1.5

n.s.

0.4 ± 0.1 0.5 ± 0.1 n.s. 0.6 ± 0.1

1.0 ± 0.8 c 2.7 ± 1.4 a 1.8 ± 1.1 b

0.0 ± 0.1 0.1 ± 0.2 n.s. 0.1 ± 0.3

1.4 ± 0.8 3.3 ± 1.4 2.5 ± 1.2

b a ab

0.5 ± 0.1 0.2 ± 0.0 n.s.

2.6 ± 3.8 1.2 ± 1.0 n.s.

0.0 ± 0.2 0.0 ± 0.1 n.s.

3.1 ± 3.8 1.5 ± 1.1

n.s.

0.4 ± 0.1 0.2 ± 0.1 n.s. 0.4 ± 0.1

l a

o J

n r u

50

Journal Pre-proof ET2 0.5 ± 0.1 1.5 ± 1.3 0.1 ± 0.1 different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

2.1 ± 1.3

f o

l a

o r p

r P

e

n r u

o J

51

Journal Pre-proof Table 4: Cumulative CO2 emissions during three rice growth stages and seasonal cumulative CO2 emissions as affected by earthworm (ET0, ET1, and ET2) and residue treatment for chambers without plants (means ± S.E.). Means followed by a different letter are significantly different within growth stage and chamber type according to Tukey’s HSD test at P ≤ 0.05.

CO2 emission [kg N ha-1] ± SE

vegetative

reproductive (N) without Plants

Without Straw ET0 84 ± 15 b 328 ± 114 b ET1 93 ± 15 b 350 ± 97 b ET2 167 ± 20 a 466 ± 140 a With Straw ET0 250 ± 37 ab 496 ± 203 ET1 169 ± 30 b 426 ± 150 n.s. ET2 272 ± 37 a 495 ± 146 different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

l a

n r u

ripening

o r p

f o

e

total season

183 ± 44 203 ± 49 n.s. 207 ± 54

595 ± 123 b 646 ± 110 b 840 ± 151 a

278 ± 82 212 ± 48 n.s. 242 ± 73

1024 ± 222 a 807 ± 160 b 1009 ± 167 a

r P

o J

52

Journal Pre-proof Table 5: Effect of earthworm density and rice straw residue amendment on mean (± SE) Root mass density, Straw dry mass, Grain yield, and Harvest Index. Means marked with different letters within a column are significantly different according to Tukey’s HSD test at P ≤ 0.05.

Straw treatment Without Straw

Earthworm abundance ET0 ET1 ET2

Root mass density -3

[g cm ] 46 ± 5 42 ± 5 n.s. 36 ± 4

Straw dry mass

Grain yield

-1

[Mg ha ] 10.3 ± 1.9 6.3 ± 0.3 n.s. 8.5 ± 0.9

r P

l a

Harvest

[Mg ha ] 8.7 ± 1.5 6.2 ± 0.5 n.s. 7.4 ± 0.6

Index 0.46 ± 0.1 0.50 ± 0.1 n.s. 0.46 ± 0.1

5.3 ± 0.5 6.5 ± 0.9 6.2 ± 0.3

0.44 ± 0.0 0.43 ± 0.1 n.s. 0.43 ± 0.1

o r p

e

ET0 50 ± 8 a 6.8 ± 0.6 With ET1 21 ± 3 b 8.5 ± 0.8 n.s. Straw ET2 30 ± 1 b 8 ± 1 different letters indicate sig. differences between earthworm treatments n.s. = not significant at P ≤ 0.05

f o

-1

n.s.

n r u

o J

53

Journal Pre-proof

Jo ur

na

lP

re

-p

ro

of

Graphical abstract

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Journal Pre-proof

John & Janz et al. “Earthworms offset straw-induced increase of greenhouse gas emission in upland rice production”

Highlights

of

ro

-p re lP na

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We tested if earthworms can mitigate residue-induced GHG emission in non-flooded rice. Earthworms offset the enormous increase of CH4 induced by rice straw amendment. Rice straw amendment more than doubled the global warming potential (GWP; CH4 & N2O). Earthworms reduced the GWP by 39 % at low and 55 % at high densities. Earthworms did neither affect N2O emission, nor yield but reduced root mass density.

Jo ur

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