An example of mixed cropping to reduce CO2 emissions – Sesbania rostrata plants are intercropped with a sugarcane crop. The leaves of this Indian plant are used as green manure.
Photo: © Shutterstock/Alchemist of India

Plant diversity enhances soil carbon retention

A new international study shows that increasing plant diversity in agriculture can be used to improve the carbon sequestration potential of agricultural soils. As the agricultural sector strives to reduce its carbon footprint, promoting biodiversity in agricultural practices could be the key to more sustainable and climate-friendly food production systems.

With agricultural expansion and intensive farming practices continuing to degrade soils and release carbon into the atmosphere, finding ways to enhance soil carbon storage is critical. Given that over 40 per cent of the planet’s land is used for farming, agroecosystems need to play a major role in climate mitigation strategies.

However, the limited understanding of plant-microbe interactions has so far hindered efforts to maximise soil carbon storage. An international team of researchers led by Luiz Domeignoz-Horta from the University of Zurich in Switzerland has uncovered new insights into how increasing plant diversity in agriculture can significantly improve soil carbon retention.

Barley interplanted with up to eight other plant species
 

The researchers conducted their study using the TwinWin experiment, located in Finland, which explores how different levels of plant diversity, combined with barley, affect microbial processes in the soil. Barley was grown either alone or undersown with up to eight different plant species, including nitrogen-fixing and deep-rooting varieties selected for their potential to improve soil health.

As a measure of how effectively microbes convert carbon inputs into new biomass rather than releasing it as CO2, the researchers measured microbial carbon use efficiency. By analysing microbial growth, soil respiration and community dynamics through molecular sequencing and stable isotope tracking, they traced the movement of carbon through the soil microbial communities.

“We found that higher plant diversity fostered stronger positive interactions between microbes in the rhizosphere – the area around plant roots – which ultimately improved the community’s carbon use efficiency,” explains first author Luiz Domeignoz-Horta.

Plant biomass improves with biodiversity
 

Notably, plant diversity also increased overall plant biomass production without reducing barley yields, making the practice viable for maintaining crop output while simultaneously improving soil carbon retention. The findings highlight the critical role that plant diversity plays in influencing microbial physiology in the soil. Increasing diversity not only promotes healthier, more resilient ecosystems but also offers a sustainable approach to agricultural carbon sequestration.

“The implementation of plant diversity in farming systems is labour-intensive, particularly for small-scale farmers who are the key to sustainability,” concedes Domeignoz-Horta. “Nevertheless, our results suggest that with the right policy support, encouraging diverse crop mixtures could become a key component of ‘carbon farming’, helping to sequester more carbon in soils while maintaining agricultural productivity. This could pave the way for new climate-resilient farming practices that benefit both the environment and farmers.”

(UZH/wi)

 

Reference

Domeignoz-Horta, L.A., Cappelli, S.L., Shrestha, R. et al. Plant diversity drives positive microbial associations in the rhizosphere enhancing carbon use efficiency in agricultural soils. Nature Communications. 14 September 2024. DOI: 10.1038/s41467-024-52449-5

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