13 December 2023

Calcium is the soil’s secret weapon against CO2 leakage


Addition of calcium to soil promotes sequestration and increase in organic matter. A Canadian study provides new insights for maintaining and improving soil quality while mitigating climate change

by Matteo Cavallito


Adding calcium to soil contributes to increased organic matter and carbon sequestration. This is claimed by scientists from Cornell and Purdue University in a study conducted at the Canadian Light Source, a research laboratory at the University of Saskatchewan, Canada. Researchers, in particular, have discovered a previously unknown mechanism.

“We showed that by adding calcium to soil, we changed the community of microbes in the soil and the way they process organic matter,” explained Itamar Shabtai, assistant professor of science at the Connecticut Agricultural Experiment Station and lead author of the investigation in a statement released by the laboratory. Microorganisms, in particular, reportedly acted more efficiently: “they processed it in a more efficient manner – more carbon was retained in the soil and less was lost to the atmosphere as CO2.”

The experiment

Researchers used laboratory equipment to measure the amount of decomposed plant matter following the addition of calcium by examining samples of topsoil collected from an experimental field in Ithaca, New York State. The collected soil, the study says, “was air-dried, sieved to 2 mm, and visible plant detritus removed.” The samples were treated with a calcium chloride solution and examined after about four months.

The authors, in particular, observed how calcium affects the microbial transformation of the litter and the formation of mineral-associated organic matter.

“Calcium additions,” they explain, “promote hyphae-forming bacteria, which often specialize in colonizing surfaces, and increase incorporation of litter into microbial biomass and carbon use efficiency by approximately 45% each.” They also “reduce cumulative CO2 production by 4%, while promoting associations between minerals and microbial byproducts of plant litter.”

A support for farmers

Adding calcium to soil is certainly not a new practice in agriculture. Farmers have always used this element for many reasons related to increasing crop yields, including pH regulation and improving soil structure. The findings that emerged in the study “expand the role of Ca in soil organic carbon persistence from solely a driver of physico-chemical reactions to a mediator of coupled abiotic-biotic cycling of soil organic carbon.”

The results of the investigation, in other words, provide additional knowledge for maintaining and improving organic matter in soils. “Now that we have a better understanding of how calcium can impact how microbes improve soil carbon,” Shabtai explains. “We can perhaps use soil amendments that contain calcium and are already being used by farmers – such as lime and gypsum – in a way that can benefit soil organic matter.”

New knowledge for carbon farming

The study also emerges as an additional contribution to knowledge about carbon farming. Or the set of agricultural practices that help increase carbon sequestration in the soil. Promoting its health and mitigating the effects of climate change. “Soils that contain more carbon are generally healthier,” explains Shabtai. “They are better able to hold on to water in drought conditions. Soils with higher amounts of organic carbon are also are able to deliver nutrients more efficiently to plants and promote plant growth, and they’re more resistant to erosion.”

Globally, the researcher explains, the amount of carbon stored in the soil exceeds the amount in plants and the atmosphere combined. “If we can increase carbon in soil, we can perhaps make a dent in the increase in atmospheric CO2 that we’re seeing.”