The study, published in the journal SOIL, examined greenhouse soils in two intensive vegetable-growing regions of Liaoning Province, where protected agriculture has flourished since the 1970s and 1980s. The team, led by Boyuan Tan of Shenyang Agricultural University, compared loam soils in one region with sandy loam soils in another. Both soil types had received roughly 41 tonnes of cow and pig manure compost per hectare every year, supplying about 11.6 tonnes of carbon per hectare annually, alongside standard chemical fertilizers and drip irrigation. By sampling plots of different ages, the researchers effectively compressed five decades of soil history into a single snapshot.

The headline finding is striking. In the loam, soil organic carbon content stabilized after about twenty years of manure application, settling between 33.1 and 37.0 grams of carbon per kilogram of soil, with a total stock of roughly 77.5 tonnes of carbon per hectare. In the sandy loam, equilibrium arrived almost immediately: within just two years, carbon content plateaued at 13.3 grams per kilogram, a stock of about 33 tonnes per hectare. Under identical manure inputs, the loam ended up storing two to three times more carbon than its sandier counterpart, and the gap widened rather than narrowed as the years accumulated.

Even more sobering was the fate of the carbon itself. The researchers calculated a sequestration rate, expressing how much of the cumulative manure carbon actually remained in the soil. In the sandy loam, nearly 55 percent of the added carbon was retained after two years, but that figure collapsed to just 4 percent after three decades. The loam fared better, holding a sequestration rate of 16.1 percent at the twenty-year mark, yet even there the rate steadily declined, falling to 7.2 percent after nearly fifty years. In other words, the warmer, more humid greenhouse environment, with temperatures often between 18 and 35 degrees Celsius and humidity around 65 to 80 percent, kept microbes digesting organic matter so vigorously that most of the applied carbon simply returned to the atmosphere as carbon dioxide.

To understand why the two soils behaved so differently, the team dissected soil organic carbon into its component pools. Labile fractions, such as easily oxidizable carbon, dissolved organic carbon, and microbial biomass carbon, turn over quickly and respond to management within seasons. Particulate organic carbon, split into coarse and fine fractions, represents partially decomposed plant and manure residues. Mineral-associated organic carbon, by contrast, is the gold standard of soil carbon storage: organic molecules bound to clay and silt particles, protected from decomposition for years or even centuries. The loam held significantly higher amounts of easily oxidizable carbon, particulate carbon, and mineral-associated carbon than the sandy loam, and its mineral-associated pool kept growing for decades, peaking at 21.83 grams per kilogram after nearly fifty years of manure application.

The sandy loam told a very different story. Its mineral-associated carbon plateaued after only four years, hovering between 6.21 and 7.54 grams per kilogram, and its fine particulate carbon actually declined over time, dropping from a peak of 3.08 grams per kilogram at two years to 1.81 grams per kilogram by year thirty. Correlation analysis revealed why: in the loam, total soil organic carbon was strongly and positively linked to every major fraction, suggesting a cooperative pipeline in which labile and particulate carbon were progressively converted into stable mineral-bound forms. In the sandy loam, carbon was positively correlated only with easily oxidizable and mineral-associated carbon, and negatively with fine particulate carbon, hinting that fresh particulate inputs may even have stimulated the loss of existing stable carbon through priming effects.

The molecular details came from solid-state carbon-13 nuclear magnetic resonance spectroscopy, a technique that reveals the chemical architecture of soil organic matter. In the loam, long-term manure application enriched aromatic and carbonyl carbon, functional groups that resist microbial attack, and raised the aromaticity index by nearly 250 percent compared with unfertilized control fields, an overall gain of about 55 percent in carbon stability. The sandy loam moved in the opposite chemical direction: alkyl carbon increased while aromatic carbon declined, shifting the soil toward hydrophobic, waxy compounds rather than genuinely recalcitrant ones. Structural equation modeling then showed that in the loam, particulate carbon fed the mineral-associated pool, whereas in the sandy loam that pathway was essentially broken, leaving easily oxidizable carbon as the only meaningful precursor of stable carbon.

These results illuminate two distinct stabilization mechanisms operating in the same climate and under the same management. Fine-textured loams, rich in clay and silt, offer abundant mineral surfaces that adsorb organic molecules and shield them from microbes, allowing even metabolically active carbon fractions to contribute to long-term storage. Coarse sandy loams, with limited binding sites, can only protect carbon through hydrophobicity, a weaker defense that depends on the continuous replenishment of fresh labile inputs. The authors conclude that the long-term sequestration rate is not determined by the quantity of external inputs alone but by the efficiency with which labile fractions are transformed into mineral-associated organic carbon, an efficiency that is fundamentally governed by soil composition and mineral properties.

For greenhouse growers, the practical message is that manure is not a one-size-fits-all solution. On sandy soils, piling on more manure year after year yields diminishing returns, because the soil simply cannot hold what it is given. Matching application rates to soil texture, and investing in practices that build mineral protection capacity, may achieve more than sheer volume. The study also carries a caution for carbon accounting: greenhouse agriculture, with its accelerated decomposition, may store far less carbon than open-field experiments suggest, meaning that climate benefits attributed to manure application in protected cultivation could be systematically overestimated. The authors note that future work combining long-term experiments with microbial sequencing and mineralogical analysis will be needed to fully untangle how soil texture, mineral chemistry, and microbial communities jointly decide whether applied carbon becomes a lasting asset or a fleeting guest.

Subject of Research: Long-term soil organic carbon accumulation and stabilization under manure application in greenhouse loam and sandy loam soils

Article Title: Differences in organic carbon fractions and stability explain limited accumulation in loam and sandy loam under greenhouse conditions

Article References: Tan, B., Yang, L., Xiao, X., Li, C., Tan, J., An, N., Meng, L., Yi, Y., Qian, F., Li, N., Liu, X., Li, S., & Han, W. (2026). Differences in organic carbon fractions and stability explain limited accumulation in loam and sandy loam under greenhouse conditions. SOIL, 12(2), 855-869. https://doi.org/10.5194/soil-12-855-2026

Image Credits: AI Generated

DOI: 10.5194/soil-12-855-2026

Keywords: soil organic carbon, greenhouse agriculture, manure application, mineral-associated organic carbon, particulate organic carbon, soil texture, carbon sequestration, 13C NMR spectroscopy, loam, sandy loam, soil fertility, carbon stabilization

The study, published this week in Applied and Environmental Microbiology, an open-access journal of the American Society for Microbiology, was led by microbiologist Eric Déziel of the Institut national de la recherche scientifique (INRS) in Quebec, Canada. Déziel describes C. michiganensis as a genuinely problematic pathogen, particularly in greenhouse settings where dense planting, shared equipment, and constant human handling create ideal conditions for transmission. Once the bacterium gains a foothold in a facility, it typically establishes itself in one section before workers inadvertently carry it from plant to plant as they prune, tie, and harvest. The result is a creeping wave of infection that is notoriously difficult to contain with conventional tools.

What makes the new research distinctive is its dual focus. Most studies of biological control agents, Déziel notes, tend to concentrate on a single objective: either suppressing a pathogen or stimulating plant growth. The Canadian team set out to find microbes capable of doing both at once. Their screening strategy was deliberately broad and systematic, drawing on a resource the laboratory had been building for roughly two decades. For about twenty years, researchers in Déziel’s group have pursued biological solutions to agricultural problems, accumulating a large collection of bacterial strains isolated from a wide variety of food plants and environments.

The opportunity to apply that collection to tomato canker arose a few years ago, during the COVID-19 pandemic, when tomato growers brought the problem of bacterial canker in greenhouses to the lab’s attention. Déziel admits he had never heard of the disease at the time, but the growers’ concerns were enough to launch an intensive search for answers. The team began at home, so to speak, testing some 500 strains from their own collection for the ability to antagonize C. michiganensis in laboratory assays. These strains had been isolated from strawberries, lettuce, apples, and other foods, and had been recovered from leaves, roots, and other plant parts. Crucially, none of them had previously been isolated from bacteria-infected plants or fruits, meaning the researchers were working with microbes drawn from healthy contexts rather than from diseased tissue.

The initial screen was designed to cast a wide net. In antagonism assays, candidate bacteria are grown alongside the pathogen, allowing researchers to observe whether the candidate produces compounds, competes for resources, or otherwise interferes with the pathogen’s growth. From the 500 strains tested, a few dozen showed promising activity against C. michiganensis. That shortlist then faced a second, more demanding filter: the strains had to do more than fight the pathogen. They also needed to promote plant growth, a property that matters enormously for any biocontrol agent intended for real-world agriculture, since growers are far more likely to adopt a treatment that delivers a visible agronomic benefit in addition to disease protection.

The evaluation proceeded in stages, moving from simple bacterial cultures to living plants. This progression is essential in biocontrol research because activity observed on a laboratory plate does not always translate to the complex environment of a plant’s surfaces and internal tissues. When the team tested their shortlisted strains on tomato plants infected with bacterial canker, the experiments ultimately yielded three bacterial strains that demonstrated a clear dual benefit. One of these, Pantoea agglomerans SO16PY, originally isolated from the leaf of a healthy tomato plant, proved especially interesting: it delayed the onset of canker symptoms in infected plants by up to a week and reduced the overall severity of the disease. The other two strains, both members of the species Pseudomonas marginalis, similarly restricted both the development and the severity of the disease in infected plants.

The significance of a week’s delay should not be underestimated in commercial greenhouse production. Bacterial canker moves quickly through a crop, and every day of slowed progression gives growers additional time to detect the outbreak, remove affected plants, and adjust handling practices to limit the spread that occurs through workers’ hands and tools. Reduced disease severity, meanwhile, translates directly into preserved yield and plant vigor. Combined with the growth-promoting effects observed in the same strains, these microbes appear to function as what researchers sometimes describe as plant probiotics: living allies that shift the balance of the plant’s microbial environment away from pathogens and toward health.

The practical context for this work is particularly important for organic growers. Déziel points out that bacterial canker can be a significant problem for organic farmers, who have fewer chemical options available to them. Although organic producers can purchase seeds that are certified or guaranteed to be free of the pathogen, the bacterium may still find its way into a greenhouse through contaminated equipment, infected transplants, or residual inoculum in the facility. Once inside, the disease follows its familiar pattern of localized establishment followed by mechanical spread through routine work. Today’s treatment solutions are limited, Déziel adds, and the few commercial options that do exist show poor efficacy, leaving growers with largely preventive measures and little recourse once infection takes hold.

That gap between need and available tools is precisely where the three beneficial strains could eventually make a difference. The researchers emphasize, however, that considerable development work remains before these microbes could be harnessed for commercial use. The central challenge is formulation and delivery: the bacteria must be stabilized in a product form that maintains their viability and effectiveness over time. As Déziel explains, the team needs to find a way to stabilize the bacteria so that their shelf life is long enough for the product to be actually usable in a greenhouse. A biocontrol agent that loses potency within days of manufacture is of little value to a grower who needs to apply it on a schedule determined by the crop and the disease, not by the laboratory.

If that stabilization challenge can be solved, the payoff could be substantial. The three strains identified in this study represent a sustainable, environmentally friendly approach to improving plant health in agriculture, one that works with the natural antagonisms among microbes rather than against them. For an industry grappling with a seedborne pathogen that spreads easily and resists conventional treatment, bacteria that can both hold the disease at bay and help the crop grow stronger offer a genuinely new kind of tool. The work also underscores the value of long-term microbial collections and of listening to growers: a problem brought to the lab’s attention during a pandemic has now produced candidate biocontrol agents isolated from healthy tomato leaves and other food plants, strains that had been sitting in a freezer for years waiting for the right question to be asked of them.

Subject of Research: Identification of beneficial bacterial strains that suppress tomato bacterial canker and promote tomato plant growth

Article Title: Beneficial bacteria support tomato growth & suppress disease

Article References: Beneficial bacteria support tomato growth & suppress disease. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: tomato, bacterial canker, Clavibacter michiganensis, biological control, Pantoea agglomerans, Pseudomonas marginalis, plant growth promotion, greenhouse agriculture, seedborne disease, microbiome, organic farming, Applied and Environmental Microbiology

The study, published in the journal Microplastics and Nanoplastics, was led by Enrique Rodríguez Noya and colleagues at the University of Almería’s Research Centre for Mediterranean Intensive Agrosystems and Agri-Food Biotechnology, working alongside Maria Dolores Hernando of the Spanish National Research Council’s Experimental Station of Arid Zones. Their target was a set of four polymers that dominate the plastic footprint of greenhouse farming: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT), a biodegradable polyester increasingly used in mulching films. Each of these materials behaves differently in soil, and each demands careful handling if analysts hope to recover it intact and identify it correctly.

The core problem the researchers confronted is one that plagues microplastic science everywhere: soil is a chemically hostile matrix, packed with organic matter and mineral particles that can mask, bind to or outright mimic plastic fragments. Before any microscope or spectrometer can count microplastics, the sample must be stripped of everything that is not plastic. This means digesting organic material, dispersing soil aggregates and separating low-density polymer particles from dense mineral matter — all without dissolving, degrading or fragmenting the very particles the analyst is trying to count. Every reagent added to achieve this cleanliness is a potential threat to the target particles, so the choice of chemistry is everything.

To find the best combination, the team systematically evaluated multiple extraction agents across three chemical families. Two inorganic salt solutions, sodium chloride (NaCl) and calcium chloride (CaCl₂), were tested for their ability to float plastic particles out of suspension. Four surfactants — sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), Tween 20 and Triton X-114 — were assessed for their capacity to disperse soil particles and detach plastics from organic coatings. Finally, two oxidative reagents, sodium persulfate (Na₂S₂O₈) and Fenton’s reagent, were compared for their efficiency in digesting soil organic matter without destroying the polymer particles themselves. The researchers determined which combination maximised microplastic recovery across the different polymer types and particle morphologies.

The optimised method was then validated using reference microparticles as small as 50 micrometres — roughly the width of a human hair. This size threshold matters enormously. Most conventional protocols are comfortable quantifying particles above a few hundred micrometres, but the smallest fraction of the microplastic population is both the most numerous and the most likely to interact with soil organisms and crop roots. Achieving reliable recovery at 50 micrometres pushes the analytical window into territory where contamination risks and losses escalate sharply. The validation demonstrated recovery rates above 75 percent for most particle-type and polymer combinations, a performance level that gives the protocol genuine credibility for routine monitoring work.

With the method proven on reference materials, the team turned it loose on real greenhouse soils from Almería, home to Europe’s largest concentration of plastic-covered cultivation. The results were striking. Microplastic concentrations ranged from 1,133 to 8,500 particles per kilogram of soil — a wide spread that likely reflects differences in land-use history, plastic management practices and soil conditions across the sampled greenhouses. Even the lower bound of that range represents thousands of plastic particles in every kilogram of soil in which food crops are grown, a figure that underscores how thoroughly plastic has permeated the growing medium of intensive horticulture.

The morphological profile of the recovered particles told its own story. Fragments dominated the assemblage, accounting for 62 percent of all particles identified, and the majority of these sat in the 100 to 250 micrometre size range. This size class sits squarely within the range that most previous studies of agricultural soils have struggled to capture, which suggests that earlier surveys may have systematically underestimated the true particle burden. Fragment dominance is consistent with the mechanical breakdown of agricultural plastic films — mulches, greenhouse covers and irrigation components that are abraded, torn and shattered by weathering, machinery and repeated handling over growing seasons.

Chemical identification, performed using micro-Fourier transform infrared spectroscopy (µ-FTIR), added a second layer of insight. Polypropylene emerged as the most abundant polymer, making up 70 percent of the identified particles, followed by PET at 16 percent and polyethylene at 6 percent. The dominance of PP is notable because polypropylene is ubiquitous in agricultural settings — in twine, ropes, irrigation fittings, plant trays and woven fabrics — yet it has often been underreported in soil studies where analytical protocols favour other polymers. The presence of PET points to contributions from polyester fibres and rigid packaging, while the PE fraction reflects the polyethylene films that literally define the Almerían landscape. The inclusion of PBAT in the target list also matters: as biodegradable mulch films see wider adoption, tracking their fragmentation products in soil becomes essential for assessing whether these materials genuinely disappear or simply break into smaller and smaller pieces.

Beyond its regional findings, the study’s lasting contribution may be the protocol itself. By documenting recovery rates, reagent performance and validation thresholds for particles down to 50 micrometres, the researchers have provided a robust, reproducible analytical tool that other laboratories can adopt for monitoring microplastic contamination in intensive agricultural environments. Standardised, validated methods are the prerequisite for comparing contamination levels across regions, tracking trends over time and evaluating the effectiveness of mitigation measures such as improved plastic waste management or the substitution of conventional films with biodegradable alternatives. Without such comparability, the growing body of microplastic literature remains a patchwork of numbers that cannot be meaningfully compared.

The work also carries a broader significance for global food production. Protected agriculture — cultivation under plastic-covered structures — has expanded dramatically worldwide, from the Mediterranean basin to China and Latin America, and Almería serves as a bellwether for what this intensification means for soil health. The finding that greenhouse soils there carry thousands of microplastic particles per kilogram, dominated by small fragments of the very polymers used in farming infrastructure, transforms an abstract environmental concern into a quantified, chemically characterised reality. Whether these particles affect soil physics, microbial communities, nutrient cycling or crop uptake remains an open question for future research, but answering it will depend on the kind of rigorous, validated measurement that this new protocol now makes possible.

Subject of Research: Optimised extraction and identification of small microplastics in greenhouse agricultural soils

Article Title: Optimized analytical protocol for quantifying small microplastics in greenhouse agricultural soils

Article References: Rodríguez Noya, E., Flores Morales, J. J., Cortes-Corrales, L., Sahai, H., Hernando, M. D., R. Fernández-Alba, A., & Martinez Bueno, M. J. (2026). Optimized analytical protocol for quantifying small microplastics in greenhouse agricultural soils. Microplastics and Nanoplastics. https://doi.org/10.1186/s43591-026-00233-1

Image Credits: AI Generated

DOI: 10.1186/s43591-026-00233-1

Keywords: microplastics, greenhouse agriculture, soil contamination, polypropylene, polyethylene, PET, PBAT, FTIR spectroscopy, Almería, mulching films, analytical protocol, soil organic matter