Plant diversity enhances soil carbon retention

As agricultural expansion and intensive farming practices continues to degrade soils and release carbon into the atmosphere, finding ways to enhance soil carbon storage is critical. Given that over 40% 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 maximize soil carbon storage. A team of researchers led by Luiz Domeignoz-Horta from the University of Zurich 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 CO?, the researchers measured microbial carbon use efficiency. By analyzing 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 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 labor-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.”