The challenges confronting today’s farmers form an interconnected web that resists simple solutions. Rising production and distribution costs, chronic labor shortages, shifting trade agreements and policy regulations, evolving pest pressures, a changing climate, and increasingly uncertain water availability each place their own strain on agricultural operations. Together, these factors compound a quieter but equally consequential problem: the steady depletion of microscopic nutrients in the soil itself. As these pressures intensify, the farmers who must navigate them are becoming fewer and more isolated. According to USDA figures, the number of farms in the United States has fallen by roughly 72 percent from its peak of 6.8 million in 1935 to 1.88 million in 2024. Over the same span, direct employment on farms has collapsed from 25 percent of the national population to just one to two percent, leaving a shrinking workforce to shoulder an expanding set of trials.

Jilling’s expertise lies in how nutrients move through soil systems, a specialization that positions her at the center of one of agriculture’s most consequential scientific debates. Her USDA-funded projects are designed to understand how soils can be managed to support healthy, climate-resilient and productive ecosystems. The stakes are considerable: soil is not merely the physical substrate in which crops grow but a living reservoir of carbon, nitrogen and countless other elements whose availability determines whether a season ends in abundance or shortfall. Managing that reservoir intelligently, she argues, requires knowing far more about its internal architecture than science has historically possessed.

One of her two lead projects examines how climate change, expressed through erratic rainfall, intense storms and increasing drought, affects the storage of soil carbon and the availability of nitrogen for future crops. For generations, farmers and soil scientists have counted on soil organic matter as a key reservoir of plant nutrients, a bank of fertility that pays out steadily even in heavily fertilized systems. The central challenge, as Jilling frames it, is to measure and manage soil organic matter so that nutrients are released in the right ways and at the right times to benefit growing plants. That task has grown more urgent as weather patterns grow less predictable, because the mechanisms that lock nutrients away or set them free are far more sensitive to moisture than researchers once believed.

A closer look at soil’s composition reveals why. Soil organic matter comes in two fundamentally different forms. The first consists of partially broken-down plant matter that cycles quickly, responds sensitively to farming methods, and serves as an active, fast-moving supplier of nutrients. The second type, which constitutes the majority of soil organic matter, is tightly bound to minerals such as clay. Once these mineral-bound particles form, they can persist for decades or even centuries, and they have therefore long been regarded as stable, slow to change, and largely indifferent to farm management practices such as tillage or to external environmental forces. That assumption of permanence has shaped decades of soil science, agronomic advice and federal measurement standards.

Jilling’s work has upended that assumption. Her research has discovered that certain moisture conditions can unlock these mineral-bound reservoirs prematurely, releasing stored nutrients into the environment before plants have any opportunity to use them. To understand the scope of this vulnerability, she and her team are gathering samples of different soil types from Oklahoma, Virginia, South Carolina and Arkansas and running controlled laboratory experiments that expose the samples to moisture regimes mimicking the unprecedented wet-dry fluctuations that climate change is expected to bring. The experiments are designed to reveal precisely when and how mineral-bound organic matter destabilizes, and which soil types face the greatest risk of losing their long-term fertility stores.

Projected shifts in climate change suggest increases in droughts and a general intensification of wet-dry cycling, Jilling notes. Our goal is to help identify which agricultural soils are most vulnerable as the climate shifts. That identification task is far from academic. If scientists can pinpoint which soils are prone to premature nutrient release under alternating drought and deluge, farmers and policymakers can prioritize those lands for amended management practices, adjusted crop rotations or targeted conservation investments before irreversible losses occur. The research also carries implications for carbon accounting, since mineral-bound organic matter represents one of the largest long-term stores of carbon in agricultural landscapes, and its destabilization would mean that carbon, like nitrogen, could escape into the atmosphere or waterways.

The second project translates these fundamental insights into a practical policy test. The Jilling Lab is collecting data that could help the USDA’s Natural Resources Conservation Service decide whether to begin tracking mineral-bound organic matter as an official measure of soil health. Currently, the agency’s dynamic soil properties include partially broken-down plant matter but exclude its mineral-bound counterpart, reflecting the older view that the mineral-bound fraction changes too slowly to matter for management decisions. Jilling’s findings challenge that logic directly. If mineral-bound organic matter can become unstable and lose both carbon and nitrogen under certain conditions, then it may be just as dynamic, and just as informative, as the rapidly cycling fraction that regulators already monitor.

To build the evidence base for that decision, her team is collecting soil samples from annual and perennial cropland across the deliberately contrasting regions of South Carolina, from the clay-rich Piedmont to the sandy Coastal Plain. By comparing mineral-bound organic matter behavior across these divergent soil types and cropping systems, the researchers aim to assess whether the mineral-bound fraction deserves a place on the USDA’s official list of soil health indicators. A positive finding could ultimately reshape how soil health is measured and reported on farms nationwide, giving producers a more complete diagnostic picture of the fertility they are managing and giving federal agencies a sharper tool for targeting conservation programs.

Underlying both projects is a broader scientific evolution that Jilling describes with evident enthusiasm. Our understanding of soil has evolved to include a growing appreciation of factors such as the reactivity of mineral surfaces and microbe-mineral interactions, making mineral-bound organic matter much more susceptible to disruption than previously thought, she says. Previous research has shown that mineral-bound organic matter can be impacted by some types of land use and external elements, and we hope to add to that knowledge base by studying both the role of moisture in forming mineral-bound reservoirs and, across both projects, how plant-microbe-mineral interactions can destabilize them. In that three-way interplay of roots, microbes and minerals, Jilling and her collaborators are mapping the fault lines along which America’s agricultural foundation may shift, and providing the knowledge needed to reinforce it before the next drought, storm or shifting season arrives.

Subject of Research: USDA-funded research on how climate-driven moisture fluctuations destabilize mineral-bound soil organic matter and affect soil health measurement

Article Title: Andi Jilling leads USDA-funded projects to protect America’s soil health

Article References: Andi Jilling leads USDA-funded projects to protect America’s soil health. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: soil health, soil organic matter, mineral-bound organic matter, USDA, climate change, nitrogen availability, soil carbon, Natural Resources Conservation Service, agriculture, drought, wet-dry cycling, soil fertility

At the heart of the analysis lies a deceptively simple metric known as the Q10 coefficient. The Q10 value describes how much a biological process, in this case the microbial breakdown of soil organic matter, speeds up when temperature rises by 10 degrees Celsius. A Q10 of 2 means the rate doubles; a Q10 of 3 means it triples. Because soils hold vast stores of organic carbon, often centuries’ worth of accumulated plant and microbial residues, even modest differences in Q10 translate into enormous differences in how much carbon dioxide and nitrous oxide escape to the atmosphere under warming. The authors, Kamrun Nahar Sheuly, Khalid Syfullah and Zakaria M. Solaiman, argue that Q10 is a pivotal regulator of soil-atmosphere greenhouse gas exchanges in temperate ecosystems, and that its variability has been chronically underappreciated.

The synthesis identifies soil texture and mineralogy as first-order controls on thermal sensitivity. Clay-rich soils abundant in short-range ordered minerals, such as the allophane and ferrihydrite characteristic of volcanic Andisols, consistently show low Q10 values, typically between 1.3 and 2.0. The reason is mechanistic rather than coincidental. These reactive mineral surfaces bind organic matter into mineral-associated organic matter, physically and chemically shielding it from microbial enzymes. When microbes and their extracellular enzymes cannot easily access their substrate, warming produces only a muted acceleration of decomposition. In effect, certain soils come with built-in thermal insulation for their carbon stocks, a property that current broad-scale models frequently fail to capture.

The contrast with coarse-textured and disturbed soils is stark. Sandy soils, and agricultural soils degraded by intensive tillage, exhibit Q10 values exceeding 3.0, meaning their decomposition rates more than triple with each 10-degree warming increment. In these systems, organic matter is comparatively exposed, sitting in loose aggregates or free particulate fractions where enzymes operate with little impediment. Tillage compounds the problem by breaking apart soil aggregates that would otherwise occlude organic matter, effectively handing microbes fresh access to previously protected carbon. The implication is unsettling for agricultural regions: disturbed temperate farmland may become a disproportionately large carbon source as heatwaves and warm seasons intensify, releasing legacy carbon at accelerating rates.

Substrate quality adds a second layer of complexity through what the authors describe via the carbon quality-temperature hypothesis. This framework holds that chemically complex, recalcitrant substrates, such as lignin-rich plant litter, demand more enzymatic effort to decompose and therefore display higher temperature sensitivity than simple, labile compounds like sugars and dissolved organic carbon. As easily decomposed pools are exhausted under warming, microbial communities shift toward tougher substrates, causing the apparent Q10 of a soil to rise over time. This dynamic means that a soil measured today at moderate sensitivity may become markedly more explosive in its carbon release as climate change progressively strips away its labile fractions, a feedback loop with uncomfortable consequences for long-term projections.

Microbial physiology emerges as a third governing force. The review highlights carbon use efficiency, the ratio of microbial biomass production to carbon uptake, as a key modulator of mineralization responses. When microbes operate at high efficiency, more of the carbon they consume is locked into their own biomass and eventually stabilized in soil, rather than respired as carbon dioxide. Enzyme kinetics, described through the Michaelis-Menten parameters of maximum reaction velocity and substrate affinity, further shape how decomposition responds to heat, since enzyme performance, substrate binding and diffusion all carry their own temperature dependencies. The composition of microbial functional groups matters as well; in the nitrogen cycle, ammonia-oxidizing bacteria and archaea govern the transformation of ammonium into nitrate, and their distinct thermal optima influence how much nitrogen, and consequently how much nitrous oxide, temperate soils emit as they warm.

Seasonal extremes introduce yet another dimension of unpredictability. Freeze-thaw cycles in winter and sudden rewetting events after summer drought can physically rupture aggregates, lyse microbial cells and flush pulses of dissolved organic carbon into the soil solution. These disturbances momentarily overwhelm the protective mechanisms that normally constrain decomposition, producing episodic bursts of carbon and nitrogen mineralization that can rival or exceed the fluxes of entire warm seasons. The review emphasizes that microbial communities also acclimate, adjusting their enzyme production and community composition over weeks to months in response to sustained warming, so that short-term laboratory measurements of Q10 may systematically misrepresent sensitivity under field conditions.

Land-use history proves equally decisive. The synthesis documents that transitions such as tillage, afforestation and the application of organic amendments significantly alter Q10 by reshaping soil aggregation, the accessibility of organic matter and the structure of microbial communities. Converting cropland to forest generally rebuilds aggregates and restores mineral protection, lowering thermal sensitivity, whereas repeated tillage does the opposite. Organic amendments such as compost and manure can either stabilize carbon on mineral surfaces or supply fresh labile substrate, depending on soil mineralogy, meaning that identical management practices can yield opposite climate outcomes in different soils. These findings carry direct weight for soil-based climate mitigation strategies, which often assume uniform responses across landscapes.

Perhaps the review’s most consequential critique targets Earth system models, the large-scale simulations underpinning international climate assessments. The authors find that such models commonly assign a single, fixed Q10 value to vast regions, overlooking the spatiotemporal heterogeneity that six decades of field and laboratory studies have documented. This simplification limits prediction accuracy precisely where it matters most, in forecasting how the temperate carbon sink will behave as warming accelerates. The authors call for models that integrate depth-resolved mineralogical traits, microbial acclimation and management history into climate-soil feedback frameworks, arguing that such mechanistic grounding is essential for improving biogeochemical projections and for designing credible mitigation policies.

The broader significance of the work extends beyond modeling. By mapping which soils are thermally vulnerable and which are mineralogically armored, the synthesis offers land managers a scientific basis for prioritizing interventions, from reduced tillage in sandy agricultural soils to afforestation on degraded land. It also reframes temperate soils not as passive victims of warming but as active, heterogeneous systems whose response to heat is written in their mineralogy, their microbial residents and their human history. As global temperatures continue to climb, understanding that a clay-rich Andisol and a tilled sandy loam respond to the same warming with radically different carbon losses may prove one of the most important distinctions in the effort to keep soil carbon in the ground and greenhouse gases out of the atmosphere.

Subject of Research: Temperature sensitivity of soil carbon and nitrogen mineralization across temperate soil types

Article Title: Temperature sensitivity (Q10) and soil type influence carbon and nitrogen mineralization in temperate ecosystems

Article References: Temperature sensitivity (Q10) and soil type influence carbon and nitrogen mineralization in temperate ecosystems. (n.d.). https://doi.org/10.1007/s10533-026-01368-2

Image Credits: AI Generated

DOI: 10.1007/s10533-026-01368-2

Keywords: soil carbon, nitrogen mineralization, Q10 temperature sensitivity, soil mineralogy, soil organic matter, carbon use efficiency, land-use change, temperate ecosystems, climate change, biogeochemistry, Earth system models, greenhouse gases