# Effects of biochar and its co-application with inorganic and organic fertilizers on soil microbial respiration and temperature sensitivity of carbon mineralization

Maria José Carpio Espinosa, Clément Bonnefoy-Claudet, Mathieu Thevenot, Olivier Mathieu, Iria Benavente-Ferraces, Juan Carlos García-Gil, César Plaza, Marco Panettieri

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Maria José Carpio Espinosa, Clément Bonnefoy-Claudet, Mathieu Thevenot, Olivier Mathieu, Iria Benavente-Ferraces, et al.. Effects of biochar and its co-application with inorganic and organic fertilizers on soil microbial respiration and temperature sensitivity of carbon mineralization. Congrès EGU 2024 (European Geoscience Union), Apr 2024, Vienne, Austria., 10.5194/egusphere-egu24-2795. hal-05406060

HAL Id: hal-05406060

https://hal.science/hal-05406060v1

Submitted on 9 Dec 2025

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Distributed under a Creative Commons Attribution 4.0 International License
M.J. Carpio Espinosa<fnref n="1" />, C. Bonnefoy-Claudet<fnref n="2" />, M. Thevenot<fnref n="2" />, O. Mathieu<fnref n="2" />, I. Benavente<fnref n="1" />, J.C. García-Gil<fnref n="1" />, C. Plaza<fnref n="1" />, M. Panettieri<fnref n="1" />

## INTRODUCTION AND OBJECTIVE

Biochar application to agricultural soils represents a strategy for carbon sequestration and soil quality enhancement. However, long-term field studies on the interactive effects of co-application of biochar and fertilizers on soil respiration and its temperature sensitivity (namely Q₁₀) are still scarce. Biochar addition could increase Q₁₀ by creating niches and enhancing microbial activities and abundance (Chen et al., 2021), or Q₁₀ could be reduced due to the physical protection of organic-mineral interactions or the shifts of microbial community (Zhang et al., 2021). Therefore, this study aimed to investigate the effects of combined application of biochar and inorganic or organic fertilizers on soil respiration (SR), mineralization quotient (qM) and its temperature sensitivity (Q₁₀) within a long-term field experiment in a semiarid agricultural soil in Central Spain.

## MATERIALS AND METHODS

### RAINFED FIELD EXPERIMENT

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* Study site located in the experimental farm "La Poveda" (Spanish National Research Council, CSIC), Madrid, Spain.

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* Experiment set up in 2012 as a RCBD under barley-camelina-fallow rotation including 32 plots with 8 treatments and 4 plot replicates/treatment (1 in each block) (Figure 1).

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* Treatments studied: unfertilized control, biochar applied at a rate of 20 t ha⁻<fnref n="1" /> year⁻<fnref n="1" />, mineral fertilizer, municipal compost and sewage sludge applied at a rate of potentially available N contents based on crops N needs and each fertilizer combined with biochar (at the same rates used for the single treatments).

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* Soil samples taken post-harvest of 2023, 8 months after the latest soil fertilization.

<figure><img src="image_6.png" /><figcaption>Figure 1. Randomized complete block design (RCBD) established in the experimental farm "La Poveda"</figcaption></figure>

### SOIL RESPIRATION MEASUREMENTS

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* A 30 g dry-soil was placed into plastic vessels, water content was kept at 40% of the WHC and soils were pre-incubated for 7 days at 15 °C (Figure 2).

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* Soil C mineralization measured at 5, 10, 15, 20, 25, 30 and 35°C with a Respicond respirometer (Figure 3) during 24 h of soil incubation per temperature.

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* Mineralization quotient (qM) calculated as the ratio between SR and total organic carbon content of the soil: $qM = \frac{C_{mineralization}}{TOC}$

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* Exponential equation used to calculate the relationship between temperature (t) and SR: $SR_t = a * \exp^{bxt}$

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* Q₁₀ value (increase of SR by a 10°C increase in temperature) calculated by inserting the parameter b: $Q_{10} = \exp^{10xb}$

<figure><img src="image_12.png" /><figcaption>Figure 2. Preincubation of soil samples (at 40% WHC)</figcaption></figure>

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<figure><img src="image_14.png" /><figcaption>Figure 3. CO₂ analyzer (Respicond)</figcaption></figure>

## RESULTS

1. Biochar co-application did not affect SOC mineralization. Total CO₂ emissions increased among treatments by increasing temperature (Figure 4).

<figure><img src="image_15.png" /><figcaption>Figure 4. Soil C mineralization</figcaption></figure>

2. Biochar co-application with organic fertilizers significantly decreased the qM at all temperatures by ~23-34% for B+MC and ~18-44% for B+SS. Co-application of biochar with the inorganic fertilizer did not showed significant differences, although it tended to decreased the qM (Figure 5).

<figure><img src="image_16.png" /><figcaption>Figure 5. Mineralization quotient (qM)</figcaption></figure>

3. Biochar co-application did not influence significantly Q₁₀ among all treatments, although biochar combined with MC reduced the Q₁₀ by ~5% (Figure 6).

<figure><img src="image_17.png" /><figcaption>Figure 6. Temperature sensitivity (Q₁₀)</figcaption></figure>

## CONCLUSION

### The co-application of biochar yields synergistic benefits, enhancing the soil C sequestration by attenuating the rate of C degradation from the organic fertilizers

**References:** (1) Chen, J., Sun, X., Zheng, J., Zhang, X., Liu, X., Bian, R., Li, L., Cheng, K., Zheng, J., Pan, G., 2018. Biochar amendment changes temperature sensitivity of soil respiration and composition of microbial communities 3 years after incorporation in an organic carbon-poor dry cropland soil. Biol. Fertil. Soils 54 (2), 175-188. (2) Zhang, S., Fang, Y., Luo, Y., Li, Y., Ge, T., Wang, Y., Wang, H., Yu, B., Song, X., Chen, J., Zhou, J., Li, Y., Chang, S.X., 2021. Linking soil carbon availability, microbial community composition and enzyme activities to organic carbon mineralization of a bamboo forest soil amended with pyrogenic and fresh organic matter. Sci. Total Environ. 801, 149717.

**Acknowledgements:** This research was supported by the Ministry of Science and Innovation ("BIOGEOCHAR" Project grant France in Spain ref. TED2021-132342B-100). M.J.C thanks to the Embassy of France for supporting her postdoctoral stay in the Biogéosciences Unit and MINECO for her "Juan de la Cierva-Formación" postdoctoral contract.

<footnote n="1">¹ Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas, Serrano 115 bis, 28006 Madrid, Spain (mjose.carpio@ica.csic.es)</footnote>

<footnote n="2">² Biogéosciences, UMR 6282 CNRS, Université Bourgogne Franche-Comté, Dijon, France</footnote>