Do no-tillage and biochar management practices decrease soil CO2 emissions? – A case study from a sugar beet (Beta vulgaris) plantation.

Agriculture, Ecosystems and Environment Do no-tillage and biochar management practices decrease soil CO2 emissions? – A case study from a sugar beet (Beta vulgaris) plantation. --Manuscript Draft-- Manuscript Number: Article Type: Research Paper Keywords: Conventional tillage; Soil temperature; Soil water content; Chamber technique. Corresponding Author: MANUEL ACOSTA Global Change Research Institute CAS Brno, The Czech Republic, CZECH REPUBLIC First Author: Manuel Acosta Order of Authors: Manuel Acosta Lukáš Kokrda Peter Hlavinka Marian Pavelka Manuscript Region of Origin: CZECH REPUBLIC Abstract: In agricultural cropping systems, the larger part of the carbon is stored in the soil. Improving agricultural practices has great potential to increase the amount of carbon sequestered in cropland soil. Promising approaches in recent years are changes in management practices and biochar application. We conducted soil CO2 emissions (SCO2) measurements on four identical plots with different management practices (tillage, no-tillage, biochar, no-biochar) on a sugar beet plantation during a vegetation season. In all the investigated management, SCO2 showed a good correlation with soil temperature but not with soil water content. The highest SCO2 (5.5 μmolCO2m-2s-1) was measured at the conventional tillage without biochar application management while the lowest measured SCO2 (1.4 μmolCO2m-2s-1) was at the no-tillage without biochar application management. The variances of the random effects determined by our model showed that there was more variance among positions than between measurement campaigns. Furthermore, the Kruskal-Wallis test did not reveal a statistically significant difference between managements. Nevertheless, in our study, the highest calculated SCO2 (up to 19 tha-1) in our sugar beet plantation during the investigated period was obtained in the conventional tillage without biochar application management, indicating that this kind of soil agricultural management is not appropriate when SCO2 is taking into account. Suggested Reviewers: Christine Moureaux Faculté Universitaire des Sciences Agronomiques de Gembloux [email protected] her expertise. Jeffrey Smith Washington State University [email protected] his expertise. Xiaoyu Liu Nanjing Agricultural University [email protected] his expertise. Bruno De Oliveira Silva Universidade de São Paulo [email protected] His expertise. Dalia Feiziene Lithuanian Research Centre for Agriculture and Forestry Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation [email protected] her expertise Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Dear Madam/Sir, We would like to submit the manuscript titled: “Do no-tillage and biochar management practices decrease soil CO2 emissions? – A case study from a sugar beet (Beta vulgaris) plantation.” by Manuel Acosta et al. In agricultural cropping systems, the larger part of the carbon is stored in the soil. Improving agricultural practices has great potential to increase the amount of carbon sequestered in cropland soil. In our manuscript, we present soil CO2 emissions measurements on four identical plots with different management practices (tillage, no-tillage, biochar, no-biochar) on a sugar beet plantation during a vegetation season. Thanks to this study, we determined and clarified the dynamics of soil CO2 emissions from the investigated agricultural management practices. We consider that our study and findings are of interest to the research community and the international readership of the journal Agriculture, Ecosystems and Environment. Thank you in advance for your consideration Best regards Manuel Acosta – corresponding author On behalf of the authors Cover Letter Highlights (maximum 85 characters, including spaces, per bullet point) • No relationship between soil CO2 emissions (SCO2) and soil water content was found. • Soil temperature was the most significant factor influencing SCO2. • A mixed-effect model was used to assess the SCO2 driving ecosystem factors. • Biochar application has a decreasing effect on SCO2. • Conventional tillage and no-biochar have an increased effect on SCO2. Highlights 1 Do no-tillage and biochar management practices decrease soil CO2 emissions? – A case study from a sugar beet (Beta vulgaris) plantation. Manuel Acosta1,*, Lukáš Kokrda1, Peter Hlavinka1,2, Marian Pavelka1 Affiliation: 1Global Change Research Institute, Czech Academy of Sciences, Bělidla 986/4a 603 00 Brno, the Czech Republic. 2Institute of Agriculture Systems and Bioclimatology, Mendel University in Brno, Zemedelska 1, 613 00, Brno, the Czech Republic *Corresponding author: Manuel Acosta - [email protected] Lukáš Kokrda - [email protected] Peter Hlavinka - [email protected] Marian Pavelka - pave[email protected] Manuscript File Click here to view linked References 2 Highlights (maximum 85 characters, including spaces, per bullet point)  No relationship between soil CO2 emissions (SCO2) and soil water content was found.  Soil temperature was the most significant factor influencing SCO2.  A mixed-effect model was used to assess the SCO2 driving ecosystem factors.  Biochar application has a decreasing effect on SCO2.  Conventional tillage and no-biochar have an increased effect on SCO2. Keywords: Conventional tillage; Soil temperature; Soil water content; Precipitation; Soil respiration; Chamber technique; Central Europe. Abstract: In agricultural cropping systems, the larger part of the carbon is stored in the soil. Improving agricultural practices has great potential to increase the amount of carbon sequestered in cropland soil. Promising approaches in recent years are changes in management practices and biochar application. We conducted soil CO2 emissions (SCO2) measurements on four identical plots with different management practices (tillage, no-tillage, biochar, no-biochar) on a sugar beet plantation during a vegetation season. In all the investigated management, SCO2 showed a good correlation with soil temperature but not with soil water content. The highest SCO2 (5.5 molCO2m-2s-1) was measured at the conventional tillage without biochar application management while the lowest measured SCO2 (1.4 molCO2m-2s-1) was at the no-tillage without biochar application management. The variances of the random effects determined by our model showed that there was more variance among positions than between measurement campaigns. Furthermore, the Kruskal-Wallis test did not reveal a statistically significant difference between managements. Nevertheless, in our study, the highest calculated SCO2 (up to 19 tha-1) in our sugar beet plantation during the investigated period was obtained in the conventional tillage without biochar application management, indicating that this kind of soil agricultural management is not appropriate when SCO2 is taking into account. 3 1. Introduction Carbon dioxide (CO2) emissions from soils (i.e., soil respiration - CO2 efflux) exceed all other terrestrial-atmospheric carbon exchanges with the exception of gross photosynthesis; Almost 10% of the atmosphere’s CO2 passes through soils each year (Raich & Potter 1995). Any increases in soil CO2 emissions in response to environmental change have the potential to exacerbate increasing atmospheric CO2 levels and provide positive feedback to global warming (Raich & Schlesinger 1992, Kutsch et al., 2009). Various biotic and abiotic factors influence soil CO2 production. These include soil temperature and moisture (Keith et al., 1997; Pavelka et al., 2007), root density or biomass (Fang et al., 1998; Moyano et al., 2008), as well as quantity and quality of organic matter and microbial biomass (Rayment and Jarvis, 2000; Kuzyakov, 2006; Fekete et al., 2014) and vegetation characteristics (Law et al., 2001; Acosta et al., 2013). Vegetation affects soil CO2 emissions by influencing soil microclimate and structure, the quantity of detritus supplied to the soil, the quality of that detritus, and the overall rate of root respiration (Raich and Tufekciogul, 2000). When soils are disturbed through cultivation, their content of organic matter declines. The decline is seen because the conditions for decomposition, soil aeration and moisture content, are often improved when soils are disturbed, leading to greater rates of soil CO2 emissions (Paustian et al., 2000). The impact of cultivated land on climate change is multiple and significant. Compared with forested land, agricultural lands are characterised by a greater albedo, lower soil roughness and soil humidity variation that influence soil CO2 gas exchange (Bonan, 2002). Whether agricultural soils are a sink or source of carbon depends on the actual organic matter content in the soil (Vleeshouwers and Verhagen, 2002). The climate mitigation potentials from increased carbon sequestration and decreased greenhouse gas emissions in the agricultural system alone are in the order of 1.7-6.7 GtCO2-eq yr-1 (Nabuurs et al., 2022). In agricultural cropping systems, the larger part of the carbon is stored in the soil. The input of carbon to soil is determined by the net primary production and the fraction of it remaining on the field. Loss of carbon is determined by decomposition and loss of topsoil by erosion. In general, low crop yields, high soil carbon contents and high soil organic matter decomposition rates enhance the loss of carbon from agricultural soils (Freibauer et al., 2004). Agricultural soils are estimated to potentially sequester 0.4–0.8 Pg C per year by adopting conservation agricultural practices, which represent 33.3–100% of the total potential of C sequestration in world soils (Lal, 2004). In a study realized by Chen et al. (2010) applying a model describing the dependence of annual soil CO2 emissions on climate and soil properties using 20 experimental cropland sites across the world, they determined that the annual soil CO2 emissions rate in croplands was relatively lower, the average being 0.52 kg C m2 yr1, as compared to an average of 0.84 kg C m2 yr1 in grasslands and 0.99 kg C m2 yr1 in forests. Soil organic carbon storage was, on average, estimated to be 3.18 kg C m2 in croplands, which is about half of that in forests. Overall, the proportion of mean annual soil CO2 emissions to soil carbon storage (turnover rate) was comparable among the ecosystems, equivalent to 15–16% of topsoil carbon released as C. Crop management techniques might also influence the local and regional climate. Irrigation contributes to increased air humidity, cloud density and precipitation, on the other hand, overgrazing, land use and deforestation contribute to lower rainfall (Aubinet et al., 2009, Darenova et al., 2023). Improved agricultural practices have a great potential to increase the amount of 4 carbon sequestration in cropland soils. Frant et al. (2015) pointed out that the European cropland has the potential to mitigate about 40 Mt CO2 eq. By the adoption of recommended management practices, agriculture contributes not only to soil conservation and water quality but also to enhance the amount of soil organic carbon in the soil and to mitigating CO2 emissions effects on climate change (Follett, 2001, Darenova et al., 2022). Conservative tillage management affects the distribution and transformation of soil organic carbon content by opening or closing new paths to air and water exchanges between the surface and the atmosphere. Moreover, tillage practices affect aggregate stability, water holding capacity and soil temperature, in turn altering the dynamic of organic matter decomposition by soil microbial communities (Lu et al., 2015; Lal 2004) and increasing soil CO2 emissions (Paustian et al., 2000; Abdalla et al., 2016). Tillage methods vary widely depending on climate and soil type, crop management objectives, availability of technology, tradition and the personal preference of farmers. The conversion from conventional tillage to no-tillage is considered to be one of the potentially efficient strategies to decrease soil CO2 emissions (La Scala et al., 2006; Luo et al., 2010). Abdalla et al. (2015) in a meta-analysis to identify the impact of tillage management on soil found that tilled soils emitted 21% more CO2 than untilled soils. Adopting no-tillage in agro-ecosystems has been widely recommended as a means of enhancing carbon sequestration in soils. However, study results are inconsistent and vary from significant increase to significant decrease. It is unclear whether this variability is caused by environmental, or management factors or by sampling errors and analysis methodology (Paustian et al., 2000; Luo et al, 2010). In recent years, there has been a significant interest in biochar use in agricultural management for various environmental applications, e.g., pollutants removal, carbon sequestration, and soil amelioration. Biochar has several unique properties, which makes it an efficient, cost-effective and environmentally friendly material for diverse contaminants removal (Oliveira, et al., 2017). Applications of biochar in soil not only improve the soil properties but also remediate the pollutants from the soil. Biochar improves biological (e.g., microbial abundance, diversity and activity), chemical (e.g., pollutants immobilization and carbon sequestration) and physical (e.g., water holding capacity, O2 content and moisture level) properties of the soils (Gul et al., 2015). These biochar characteristics contribute to greenhouse gases (GHGs) emission reduction (Stewart et al.,2013) and soil carbon sequestration (Smith, 2016). Therefore, biochar production and its land application have been proposed as a possible strategy for climate change mitigation. The carbon present in the biomass is transformed into a more stable form of biochar and remains in soils for thousands of years or more (Lehmann, 2007). Liu et al. (2015) estimated that storing carbon in biochar could prevent the emission of 0.1–0.3 billion tons of CO2 yr−1. In the Czech Republic agricultural area represents 53% of the land surface, which is used for agricultural activity, i.e. activity on arable land, orchards, hop farms, vineyards and permanent grasslands. Arable land occupies 37.5% of the total land. The sugar beet crop (Beta vulgaris L.) covered more than 60 Kha in the Czech Republic (ca 1.4% of the crop area in 2021) (Kotyza et al., 2019; Smutka et al., 2020). The Czech Republic has a long tradition of sugar beet cultivation and sugar production within Europe, that being from the very start of sugar beet cultivation and the sugar industry. Sugar production started in the Czech Republic 230 years ago. These results rank the Czech Republic among the most productive Member States of the European Union; it is fully self-sufficient in sugar production and a net exporter of sugar. Considering the above-mentioned statements we conducted soil CO2 emissions measurements on a sugar beet plantation during a vegetation season with the objectives i) to determine the 5 influence of soil temperature, soil water content and precipitation on soil CO2 emissions in different agricultural management practices, ii) to assess the influence (decrease or increase) of no-tillage management and biochar application on soil CO2 emissions, and iii) to quantify the soil CO2 emission from different management practices (tillage, no-tillage, biochar, nobiochar). 2. Materials and Methods 2.1 Site description The experimental site is located in Polkovice (49°23′42.8″N, 17°14′47.3″E, altitude 200 m) in the Central Moravia region of the Czech Republic. The total area of the field is 24 ha and it is a typical agricultural area in a flat terrain. The long-term average precipitation is 553 mm and the mean annual temperature is 8.3 °C (Pozníková et al., 2018). The overall climate of the area is influenced by the penetration and mingling of ocean and continental effects. The soil is a Luvic Chernozem with a silt-clay texture (26% clay, 68% loam, 6% sand) on the bedrock material loess (Hlaváčová et al., 2018). Most crops in the investigated region are managed following a 4-year rotation scheme with alternation between cereals (mainly winter wheat) and crops such as sugar beet, winter rapeseed and silage maize. 2.2 Experimental design The investigated field of a rectangular shape with a length of 504 m and width of 300 m was divided into four equal plots with dimensions 252 m by 150 m each. At each plot, different agricultural management practices were applied (see Fig. 1). In the first plot, a conventional tillage practice was done within the top 20-25 cm of the soil profile and biochar application (CTB). In the second plot, a conventional tillage practice was done within the top 20-25 cm of the soil profile but not biochar application (CTN). In the third plot, no-tillage practice was done and no biochar application was realised (NTN). In the fourth plot, no-tillage practice was done but biochar application was realised (NTB). Both NT plots had crop residues of the former crop left in the soil. The biochar (Agrouhel®, CZ) application was done in September 2018 by the fraction of 2 tons of dry matter per ha for 3 years. During the investigated growing season in 2021, the plots were covered with sugar beet (Beta vulgaris L. var. Yucatan). The sowing of the sugar beet was done on 23 March 2021 in the prepared plots and the harvest was between 13-15 November 2021. 2.3 Soil CO2 emissions measurements Measurements of soil CO2 emission (SCO2) were carried out during the growth period 2021 (June till October) in all investigated plots. The closed dynamic chamber system (non-steady state flow-through system) was used to determine soil CO2 emission, it was composed of a portable infrared gas analyzer Li-8100 (Li-Cor, Inc., Lincoln, NE, USA) connected to a custommade opaque cylinder shape PVC soil chamber (9,5 cm in diameter and 12 cm height), following the recommendation by Pavelka et al., (2018). At each investigated plot five collars (10 cm in diameter and 5 cm in height) were inserted into the soil to protrude 2.5 cm above the soil, and a total of 20 positions were investigated. The collars were installed between crop rows (45 cm row width) in the middle of each plot in line with the approximate 5 m spacing between 12 application was done two and a half years before the SCO2 measurements. On the other hand, Šlapáková et al. (2018) in a study of the biochar effect on two different soils, did not register higher CO2 efflux in the soil after biochar application. Liu et al., (2013) reported that biochar has no effect on SCO2 across Chinese agricultural soils, biochar addition did not alter the carbon use efficiency by soil microbes and biochar types and the amendment rate did not affect soil respiration. Nevertheless, in our study, the plots with biochar application in both managements (NTB and CTB) showed similar mean SCO2 values (about 3 molCO2m-2s-1) (Fig. 5). While plots without biochar application (CTN and NTN) showed the highest and the lowest mean SCO2 values (3.27 and 2.87 molCO2m-2s-1, respectively). The difference between plots with and without biochar application can be explained by the main reason why biochar is added to soil, as an option to enhance soil carbon sequestration by introducing recalcitrant organic matter; Moreover, carbon dioxide evolution from SOM decomposition is regulated by the size and composition of microbial communities and by the available carbon substrates under a certain vegetation (Liu et al., 2016). In our study, the conventional tillage plot without biochar (CTN) showed the highest SCO2 rates compared to the other managements (Fig. 4). This can be attributed to soil conventional tillage, tillage practices affect aggregate stability, soil temperature and water holding capacity, in turn altering the dynamic of organic matter decomposition by soil microbial communities and increasing soil CO2 emissions (Paustian et al., 2000; Lu et al., 2015). Notwithstanding, the overall results in our study indicated lower SCO2 when biochar application is used. The time since the establishment of an experiment and the transition time (conventional to notill management or vice versa) also influence soil processes and microorganisms. A difference in management practices often results in differences in the biological, chemical and physical properties of soil which in turn, result in changes in the functional quality of soil (Aziz et al., 2013, Stubbs et al., 2004). In our experiment, the biochar application and soil management practices (conversion from conventional to no-till) were done 3 years before our soil CO2 measurements. Therefore, we consider that a possible effect after these practices did not have any legacy effect on our results. Another interesting issue regarding SCO2 and agriculture management practices is soil heterogeneity (variation). The emission of CO2 from the soil is typically characterized by a large temporal and spatial variability, and a high heterogeneity introduces uncertainty in the estimations (Rayment and Jarvis 2000). Rochette et al., (1991) pointed out that spatial heterogeneity in SCO2 in croplands occurs at a scale smaller than 15 cm. The authors also reported that SCO2 in the row was significantly higher than in the interrow when the soil surface was dry, but under wet soil conditions, no significant difference was found between rows and interrows. The temporal heterogeneity of SCO2 is more related to the soil temperature and state of the plant growth. In our study, SCO2 showed larger spatial heterogeneity than temporal heterogeneity at the beginning of our study (early summer 16.6.2021 – 12.7.2021) (Tables 1 and 2). These differences were attributed to the contribution of plant roots to SCO2 in dry conditions and the role of microbial activity in wetter soil. During the period of middle summer till early autumn (28.7.2021 – 5.10.2021), these differences between spatial and temporal heterogeneity of SCO2 were less significant. This was attributed to the rapid vegetation growth of the crop in this period, followed by a gradual decrease as the crop matured and the abundant leaf cover of the sugar beet covering the soil surface from direct sun radiation and precipitation. 13 5. Conclusions This study highlights the importance of agricultural soil management and its effect on SCO2. While soil temperature was identified to be the most important factor influencing SCO2 in our sugar beet plantation in all four soil management practices, no relationship between soil water content and soil CO2 emissions was determined. A possible explanation for the lack of correlation between SWC and SCO2 is connected to the dense canopy layer of the sugar beet (abundance of leaves biomass) that creates a barrier for precipitation to reach the soil surface. Nonetheless, in all four plots, an increase in soil CO2 emissions was registered after precipitation events. SCO2 increases within some minutes or hours after the onset of precipitation and returns to background levels. Regarding soil management practices, in our study, the highest SCO2 were measured at the conventional tillage plot without biochar (CTN). We consider that one of the reasons for these results is that conventional tillage influences soil aggregate turnover, improves soil aeration, infiltration, and increases the contact between soil and crop residues, which results in increased SCO2 compared to no-tillage. Plots with biochar application in both managements, no-tillage (NTB) and conventional tillage (CTB), showed more constant SCO2 rates compared to plots without biochar application, and to some extent indicated lower SCO2 when biochar application is used. A possible explanation for these results could be related to the low carbon turnover activity when biochar is added to soils. Another possible factor that could influence the response of soil CO2 emissions to biochar can be connected to the biochar application rate (the amount of biochar used), but this factor was not studied in our case. Nevertheless, in our study, the highest calculated SCO2 (up to 19 tha-1) in our sugar beet plantation during the investigated period (June – October) was obtained in the conventional tillage without biochar application plot (CTN), indicating that this kind of soil agricultural management is not appropriate when SCO2 is taking into account. In other words, based on our results the combination of no-tillage and biochar management practices decreases soil CO2 emissions in sugar beet crops. However, it is necessary to point out that soil CO2 emission of sugar beet crops also depends on many other factors such as soil types, fertilizer applications, controls of weeds and disease that must be considered when interpreting data. On the other hand, more research for a longer period is needed to provide a better knowledge and understanding of biochar application and its effects on soil CO2 emissions. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data Availability Data will be made available on request. 14 Acknowledgements: We acknowledge support from AdAgriF - Advanced methods of greenhouse gases emission reduction and sequestration in agriculture and forest landscape for climate change mitigation (CZ.02.01.01/00/22_008/0004635). This work is based on use of Large Research Infrastructure CzeCOS supported by the Ministry of Education, Youth and Sports of CR within the CzeCOS program, grant number LM2023048. References Abdalla, K., Chivenge, P., Ciais, P., Chaplot, V., 2016. No-tillage lessens soil CO2 emissions the most under arid and sandy soil conditions: results from a meta-analysis. Biogeosciences, 13(12), 3619-3633. 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Forest Ecology and Management, 192, 297-311. Variable Fixed Effect Variance of random effects P value Position Date Intercept 1.4582 0.9707 0.4370 0.5738 Treatment NTB 0.4316 0.6056 CTN -2.1252 0.0321 CTB -1.3934 0.1422 𝑇𝑆𝑚 0.0403 0.6409 𝑆𝑊𝐶𝑚 0.0924 0.0244 Residual ------------------------------- 1.3535 ---------- Table 1. Results of the mixed-effect model (LMM) used to assess the driving ecosystem factors of soil CO2 emissions during the period: 16.6.2021 – 12.7.2021. WhereTSm is soil temperature at 2 cm, SWCm is soil moisture in the 0-6 cm profile, both measured manually during campaign measurement, NTB is no-tillage with biochar application, CTN is conventional tillage without biochar application and CTB is conventional tillage with biochar application. NTN is no-tillage without biochar application. Variable Fixed Effect Variance of random effects P value Position Date Intercept -0.3190 0.05094 0.04082 0.4649 Treatment NTB 0.0925 0.5745 CTN 0.4369 0.0172 CTB 0.1550 0.3607 𝑇𝑆𝑚 0.0589 0.0277 𝑆𝑊𝐶𝑚 0.0072 0.3023 Residual ------------------------------- 0.08154 ---------- Table 2. Results of the mixed-effect model (LMM) used to assess the driving ecosystem factors of soil CO2 emissions during the period: 28.7.2021 – 5.10.2021. WhereTSm is soil temperature at 2 cm, SWCm is soil moisture in the 0-6 cm profile, both measured manually during campaign measurement, NTB is no-tillage with biochar application, CTN is conventional tillage without biochar application and CTB is conventional tillage with biochar application. NTN is no-tillage without biochar application. Table (Editable version) Click here to access/download;Table (Editable version);Table_soil CO2 emissions_Sugar.docx Conventional Tillage with Biochar (CTB) No-Tillage without Biochar (NTN) Conventional Tillage without Biochar (CTN) No-Tillage with Biochar (NTB) Fig. 1 252 m 150 m Figure Click here to access/download;Figure;Figures_ soil CO2 emissions.docx Figure captions. Fig. 1 Schema of the experiment set up in Polkovice field station (the Czech Republic). The investigated sugar beet field was divided into four identical plots. At each plot an agricultural management practice was applied, Soil CO2 emissions were measured at five positions per plot from July to October 2021. Fig.2 Daily mean soil temperature (a) at 5 cm depth, daily mean soil water content (b) at the profile 030 cm depth and daily sum of precipitation (c) at the investigated sugar beet plantation in Polkovice during the growing season 2021. Measurements were carried out at the conventional (CTN) and notillage (NTN) plots, both without biochar application. Due to a malfunction of the rain gauge precipitation data was recorded from 21 March 2021. Fig. 3 Mean soil temperature (a) at 2 cm depth and mean soil water content (b) at the profile 0-6 cm at sugar beet plantation, measured during soil CO2 emissions campaigns. Measurements were carried out from June to October 2021 in the four investigated agricultural management practices. Where NTB is no-tillage with biochar application, NTN is no-tillage without biochar application, CTB is conventional tillage with biochar application and CTN is conventional tillage without biochar application. Fig. 4 Dynamics of mean soil CO2 emissions (SCO2) in sugar beet plantation. Measurements were carried out from June to October 2021 at the four investigated agricultural management practices. Where NTB is no-tillage with biochar application, NTN is no-tillage without biochar application, CTB is conventional tillage with biochar application and CTN is conventional tillage without biochar application. Fig. 5 Soil CO2 emissions (SCO2) in a sugar beet plantation with four different agricultural management practices. Measurements were carried out from June to October 2021. Boxplot with center lines shows the medians, box limits indicate the 25th and 75th percentiles, sample means (indicated by crosses) and whiskers extend to minimum and maximum values of SCO2 at individual management practices. Fig. 6 Total calculated soil CO2 emissions (SCO2) in a sugar beet plantation with four different agricultural management practices, from June to October 2021. Where CTN is conventional tillage without biochar application, CTB is conventional tillage with biochar application, NTN is no-tillage without biochar application and NTB is no-tillage with biochar application. Fig. 7 Relationship between soil CO2 emissions (SCO2) in a sugar beet plantation and soil temperature (measured at 2 cm depth) in the four investigated agricultural management practices. Measurements were carried out from June to October 2021. Where NTB (a) is no-tillage with biochar application, NTN (b) is no-tillage without biochar application, CTB (c) is conventional tillage with biochar application and CTN (d) is conventional tillage without biochar application. Figure captions Click here to access/download;Figure;Figure captions_Soil_CO2.docx Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Declaration of Interest Statement