About 40% of the planet's land area is covered with agriculture, upon which the majority of human sustenance comes.
Since the agricultural sector is a major emitter of greenhouse gases, it must be taken into account in mitigation measures by improving agricultural practices' management to enhance carbon sequestration.
Soil comprises various communities, including microorganisms, insects, plants, and more. However, we tend to focus only on plants because they are visible on the surface. Researchers investigate these communities to enhance their understanding of soils and their carbon retention capabilities.
Hence, an international team of scientists led by “Luiz Domeignoz Horta”, Assistant Professor at INRAE UMR ECOSYS - Campus Agro Paris-Saclay, revealed how plant diversity in the soil enhances carbon retention. The study, published in Nature Communications in September 2024, highlights the beneficial impact of plant diversity on the positive interactions between microbes in the soil, improving carbon use efficiency in agricultural soils.
We reached out to Dr. Luiz Dominose Horta, the first author of the study, for an exclusive interview. Here is the text of the interview:
1- There are intricate interactions between microbes, plants, and soil, can you explain this?
Yes, plants and microorganisms in the soil are in constant communication, sometimes competing for resources or benefiting each other by providing the nutrients plants need to grow. If we better understand how plants and microorganisms interact under different conditions this might help us understand how we could influence changes in agroecosystems to foster sustainability goals.
2- What inspired you to investigate the impact of plant diversity on these interactions?
Previous studies have shown that higher plant diversity results in higher productivity (plants producing more biomass). This is an important factor if we want to increase carbon in soils, as we do need higher carbon inputs. The idea behind evaluating the interactions under higher plant diversity was to better understand how plant diversity may impact microbial processes in the soil that influence carbon retention.
3- Could you briefly explain your field experience mentioned in the study?
The TwinWin experiment is a very interesting experiment because it all started with farmers contacting researchers and asking how they could modify their practices to improve the potential for carbon sequestration in their soils. This is how everything started. And since then farmers and researchers have worked in close collaboration to run this experiment. The choice of undersown crops done here was done with discussions with farmers and based on their previous experiences for example.
4- How does plant diversity contribute to improving soil carbon sequestration capacity?
In this experiment, we observe that plant diversity acts in different ways to improve soil carbon retention. The first aspect is that plant diversity increases plant biomass and with this the input of C into the soil. The second aspect important is that plant diversity modified the associations within the microorganisms in the soil enhancing positive associations which increased their growth efficiency and therefore generated more microbial biomass which should result in more necromass formation in these soils. These two aspects helped to understand how plant diversity can help improve carbon retention potential. One aspect that needs more studies is to evaluate in which case diversification doesn't reduce crop yields. In our study diversification did not decrease yields, but this might not be the case for all crop combinations. this is an aspect that requires us to be careful as farmers must keep their productivity.
5- How can agricultural practices be utilized, as a solution, to mitigate the impacts of climate change, in your view?
I agree with some colleagues when they say: "We need carbon for soils, not soils for carbon". We can use agricultural practices to improve sustainability and retain more carbon in soils, however, we should not forget that agricultural soils are crucial to feed the world and changes we make to increase carbon sequestration should always take into account how they impact the capacity of those soils to produce food. Some practices that are known to improve carbon in soils while at the same time improving soil health are: cover crops and no-tillage and now we also know that increasing plant diversity can help too.
