The experiment began in autumn 1973 at the Nagyhörcsök Research Station of the HUN-REN Centre for Agricultural Research, on a calcareous chernozem soil with a water pH of 8.24, a cation exchange capacity of 28.3 meq per 100 grams, and an initial organic carbon content of 3.04 percent in the top 20 centimetres. Plots received one of four annual nitrogen doses: zero, 100, 200 or 300 kilograms of nitrogen per hectare, applied as calcium ammonium nitrate and split between autumn and spring. For the first decades, the plots grew a rotating sequence of field crops under conventional ploughing, with stalks and residues ploughed back into the soil after harvest. Then, in autumn 2000, the entire experimental area was sown with a mixture of eight grass species, and the sward was mown once or twice a year with all above-ground biomass removed.

The researchers sampled the topsoil at three pivotal moments: in 1990 after 17 years of cultivation, in 2000 after 27 years of cropping, and in 2020 after two decades of grassland management. SOC was determined with the modified Walkley–Black method, while POXC was measured by shaking one gram of soil with 20 millimolar potassium permanganate solution and reading the absorbance at 550 nanometres, a protocol chosen because it has proven effective for distinguishing land-use effects in chernozem soils. Bulk density was measured with sampling cylinders, and SOC stocks were calculated for the 0–20 centimetre layer. The team then deployed repeated measures linear mixed models and structural equation modelling to disentangle the direct and indirect pathways linking fertiliser, plant biomass, biodiversity and soil carbon.

The cropland results tell a sobering story about the cost of ploughing. In the unfertilised control plots, SOC content fell significantly from 1.91 percent in 1990 to 1.74 percent in 2000, equivalent to a staggering loss of 471 kilograms of carbon per hectare every year. Even after 27 years of cropping, the soil had still not reached a new equilibrium; depletion was ongoing. But nitrogen fertiliser changed the picture dramatically. Across the fertilised treatments, the average annual SOC stock change dropped to just 41 kilograms per hectare per year, a roughly 90 percent reduction in the rate of loss. Notably, even the highest dose of 300 kilograms of nitrogen per hectare could not flip the trend into net carbon gain under continuous cropping, but a modest 100 kilograms per hectare was enough to essentially halt the decline.

The mechanism, the structural equation models suggest, runs almost entirely through plant biomass. Nitrogen fertiliser boosts crop growth, and the extra residues returned to the soil replenish some of the carbon that tillage strips away. Interestingly, in the early years of the experiment nitrogen had little effect on crop biomass on this naturally nitrogen-rich chernozem, which explains why SOC differences between treatments only emerged clearly by the 2000 sampling. The crops, with their relatively short growing seasons, simply could not use more than about 100 kilograms of nitrogen per hectare effectively, so higher doses brought no additional biomass and no additional carbon benefit.

Then came the grassland conversion, and with it a reversal of fortune. Twenty years of mown grassland lifted SOC content to an average of 2.24 percent, the highest of the three land-use phases, and in the unfertilised plots carbon accumulated at a rate of 425 kilograms per hectare per year, a figure consistent with other studies of cropland-to-grassland conversions in temperate zones, which typically report 400 to 580 kilograms per hectare annually. Yet here nitrogen fertiliser worked against the soil. At the 200-kilogram dose, the sequestration rate fell to just 164 kilograms per hectare per year. The authors point to several likely explanations: mowing removes most of the above-ground carbon, so soil inputs depend heavily on roots, and high nutrient supply can suppress root growth; meanwhile, abundant mineral nitrogen can stimulate microbial decomposition of existing organic matter. Even after two decades of grass, the SOC content of 2.30 percent in the best plots remained far below the original 3.04 percent measured in 1973, underscoring how slow carbon recovery really is.

The grassland also revealed a tension between two ecological goods. Nitrogen fertilisation cut plant species diversity by about 20 percent, eliminated legumes from all but the control plots, and shifted the sward toward nutrient-loving perennials. Ecological theory and prior studies suggest that higher biodiversity should accelerate carbon sequestration, and the researchers had hypothesised that diversity might mediate part of the fertiliser effect. The structural equation models told a different story: when biomass and biodiversity were tested as parallel mediators, the biodiversity pathway was negligible compared with the biomass pathway. In other words, on this intensively managed, fertilised grassland, the sheer quantity of plant production mattered far more for soil carbon than the variety of species producing it, and nitrogen’s suppression of diversity did not override its biomass-driven effects.

The labile carbon fraction, POXC, behaved less predictably. Averaged across the three sampling dates, POXC rose from 352 milligrams per kilogram in the unfertilised controls to 399 at the highest nitrogen dose, but the response flipped between time points: the 100-kilogram dose produced the highest POXC in 1990 yet the lowest in 2000 and 2020. Land use proved more decisive than fertilisation, with POXC dropping to a low of 308 milligrams per kilogram at the end of the cropping period and rebounding to 413 under grassland. Crucially, the correlation between POXC and total SOC weakened progressively as nitrogen doses increased, suggesting that elevated nitrogen accelerates the microbial mineralisation of labile, nitrogen-rich residues and decouples the fast carbon pool from the slow one.

That decoupling has practical consequences for the growing number of farmers and researchers who use POXC as a quick soil-health test. The study concludes that POXC works reasonably well as a proxy for SOC dynamics only at fertilisation rates of 100 kilograms of nitrogen per hectare or less; above that, its reliability breaks down. The POXC-to-SOC ratio, which fell during cropping and began climbing again under grassland, may still serve as an early-warning indicator of management-driven shifts, but even it responded inconsistently to fertilisation across land uses. The authors also caution that their interpretations are constrained by the 0–20 centimetre sampling depth, which captures the plough layer but misses deeper carbon dynamics, and by the fact that bulk density had to be measured decades after the original samplings.

The broader message is one of nuance in an era when soils are increasingly counted among climate solutions. Nitrogen fertiliser is neither hero nor villain: on tilled cropland it prevented nearly all of the carbon that would otherwise have been lost, while on restored grassland it quietly throttled the very sequestration the conversion was meant to deliver. For the world’s chernozem black soils, which are both major carbon stores and the backbone of global food production, the study suggests that the most effective carbon strategy is land use itself, with fertiliser playing a supporting role that must be tuned to the system. Leave residues on the field and fertilise moderately, and arable soil can hold its carbon. Convert to grassland and keep fertiliser low, and the soil will begin, slowly, to give it back.

Subject of Research: Effects of nitrogen fertilisation and land use on soil organic carbon and labile carbon in a calcareous chernozem

Article Title: Effect of nitrogen fertilisation under different land use on the total and labile organic carbon content in a calcareous chernozem under temperate climate

Article References: Effect of nitrogen fertilisation under different land use on the total and labile organic carbon content in a calcareous chernozem under temperate climate. (n.d.). https://doi.org/10.1007/s11104-026-09114-1

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09114-1

Keywords: soil organic carbon, nitrogen fertilisation, chernozem, grassland, cropland, POXC, labile carbon, carbon sequestration, biodiversity, plant biomass, long-term field experiment, soil health

The research team, led by Mohamed T. Selim and Nashaat N. Mahmoud of the Botany and Microbiology Department, took a deliberately comparative approach. Rather than examining a single plant part or a single solvent, they prepared extracts of dried stems, leaves, and flowers using five solvents spanning a wide range of polarity: petroleum ether, ethyl acetate, acetone, methanol, and water. This polarity gradient matters because different classes of plant metabolites dissolve preferentially in solvents of different chemical character. Non-polar solvents such as petroleum ether tend to pull out lipids, waxes, and steroids, while highly polar water and methanol extract sugars, glycosides, tannins, and other hydrophilic compounds. By running the full spectrum, the researchers could determine exactly where the plant’s chemical treasure is concentrated.

Before any extraction began, the team characterized the proximate composition of each plant part, and the results revealed striking differences. The flowers carried the highest moisture content at 9.40 percent, while the stems were unusually mineral-rich, showing an ash content of 18.58 percent that exceeded both leaves and flowers. The flowers also proved to be the most nutritionally dense tissue, with a lipid content of 4.33 percent, a carbohydrate content of 66.16 percent, and a crude protein content of 15.29 percent. These baseline measurements are more than academic bookkeeping; they help determine which plant part is worth processing for which purpose, since a tissue dominated by carbohydrates will behave very differently in extraction and formulation than one rich in lipids or minerals.

When it came to extraction efficiency, solvent choice dominated the outcome. Water extracts delivered the highest percentage yield across the plant parts, followed by methanol, acetone, ethyl acetate, and finally petroleum ether. Among the plant tissues, leaves produced the maximum extract yield, with flowers and stems trailing behind. This pattern is chemically intuitive: oleander tissues are loaded with polar glycosides and phenolic compounds that dissolve readily in water and methanol but remain locked away from non-polar solvents. For anyone hoping to industrialize the process, the message is clear: the cheapest and greenest solvent, plain water, is also the most productive one, an encouraging alignment of economic and environmental incentives.

The phytochemical screening painted a detailed portrait of the plant’s defensive arsenal. Across the different parts, the researchers detected alkaloids, flavonoids, tannins, glycosides, steroids, coumarins, quinones, phenols, cardiac glycosides, and terpenoids, the full roster of secondary metabolites that plants typically deploy against microbes and herbivores. Two classes were conspicuously absent: saponins and anthraquinones were not found in any part of the plant. Anthocyanins, the pigments responsible for red and purple coloration, appeared exclusively in the flowers and were completely absent from stems and leaves. This tissue-specific distribution underscores a key principle of natural product chemistry: a plant is not a uniform bag of chemicals but a mosaic of specialized tissues, each with its own metabolic profile.

Quantitative assays sharpened that picture considerably. The acetone extract of the flowers emerged as the phytochemical powerhouse, registering the greatest levels of total phenols at 157.12 milligrams of gallic acid equivalents per gram, total flavonoids at 187.43 milligrams of quercetin equivalents per gram, and tannins at 89.93 milligrams of tannic acid equivalents per gram. At the opposite extreme, the petroleum ether extract of stems contained the lowest amounts of all three, at just 5.45, 6.43, and 3.45 milligrams per gram respectively. The roughly thirtyfold spread between these extremes illustrates how dramatically solvent polarity and plant tissue interact to determine the composition of an extract, and why screening studies of this kind are essential before any product development can begin.

The antimicrobial testing then put these chemical inventories to work. Using the agar well diffusion method, a standard technique in which extract-loaded wells are cut into plates seeded with microorganisms and zones of inhibited growth are measured, the team challenged six strains. The panel included Gram-positive bacteria Staphylococcus aureus ATCC 6538 and Bacillus subtilis ATCC 6633, Gram-negative bacteria Pseudomonas aeruginosa ATCC 9027, Salmonella Typhimurium ATCC 14028, and Escherichia coli ATCC 11229, and the unicellular fungal pathogen Candida albicans ATCC 10231. The extracts showed the ability to inhibit representatives of all these groups, a breadth of activity that spans both major bacterial membrane architectures as well as a eukaryotic pathogen responsible for serious infections in immunocompromised patients.

That broad-spectrum activity is significant in the context of the global antimicrobial resistance crisis. Gram-negative bacteria such as Pseudomonas aeruginosa and E. coli are wrapped in an outer membrane that excludes many conventional antibiotics and makes new drug development notoriously difficult, which is why the World Health Organization has flagged carbapenem-resistant Pseudomonas among its priority pathogens. Plant phenolics, tannins, and flavonoids are known to attack microbial cells through multiple mechanisms simultaneously, including membrane disruption, enzyme inhibition, and interference with quorum sensing, and this multi-target action makes resistance harder to evolve. The oleander extracts’ activity against both Gram-positive and Gram-negative organisms, along with Candida, suggests a complex mixture whose components complement one another rather than a single narrow-spectrum compound.

The study also carries a sustainability angle that fits squarely within the green chemistry movement. Oleander is fast-growing, drought-tolerant, and widely cultivated as an ornamental, which means substantial biomass is already generated through routine pruning in parks and along roadsides. Converting that low-value biomass into standardized bioactive extracts would require no dedicated agricultural land, and the finding that water, the greenest solvent of the five tested, gives the highest yields strengthens the environmental case further. The researchers note that the collection of plant material complied with WHO guidelines for the assessment of herbal medicines, and the work was conducted at the Faculty of Science of Al-Azhar University in Cairo with open access funding provided through Egypt’s Science, Technology and Innovation Funding Authority and the Egyptian Knowledge Bank.

Important caveats remain before oleander extracts could ever reach a pharmacy shelf or a food-preservation line. The plant’s cardiac glycosides, including the compounds known as oleandrin and nerine referenced in the study, are potently toxic to humans and animals, so any practical application would demand rigorous fractionation, toxicity testing, and dosage control to separate antimicrobial benefit from systemic danger. The current work was conducted in vitro, meaning the results demonstrate inhibition on agar plates rather than efficacy in living organisms, and standardization of extract composition would be essential given the natural variability of plant chemistry. Still, as a foundational map of where oleander’s bioactive chemistry lives, which solvents unlock it, and which microbes it can suppress, the study provides a credible starting point. It transforms a familiar poisonous shrub from a hazard into a candidate feedstock for the search for new natural antimicrobials at a moment when such candidates are urgently needed.

Subject of Research: Phytochemical composition and antimicrobial activity of Nerium oleander extracts obtained with different solvents

Article Title: Green extraction routes for conversion of Nerium oleander L. biomass into bioactive agents: phytochemical insights and antimicrobial promise

Article References: Selim, M. T., & Mahmoud, N. N. (2026). Green extraction routes for conversion of Nerium oleander L. biomass into bioactive agents: phytochemical insights and antimicrobial promise. BMC Complementary Medicine and Therapies, 26(1), Article 288. https://doi.org/10.1186/s12906-026-05594-x

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05594-x

Keywords: Nerium oleander, phytochemistry, green extraction, antimicrobial activity, natural products, phenolics, flavonoids, cardiac glycosides, antimicrobial resistance, plant biomass, solvent extraction, Candida albicans

The research team, led by Maulik Chauhan of Balkrishna Industries Limited together with Bhakti Patel and Rupande Desai of L. D. College of Engineering in Ahmedabad, India, started from a simple chemical insight. Natural rubber latex gloves are made from polyisoprene, a polymer extracted from the Hevea brasiliensis tree, along with one to two percent non-rubber substances such as proteins, lipids, and carbohydrates. Because polyisoprene is a natural organic compound already circulating through what scientists call the isoprene cycle, the authors reasoned that finely ground glove material might enrich soil organic matter rather than poison it.

The experimental protocol was deliberately thorough. Waste gloves collected from non-contaminated industrial and laboratory sources were washed in distilled water, boiled for an hour to strip away surface impurities, sterilized in a diluted antimicrobial solution containing chlorhexidine and ethanol, dried, and mechanically crushed into fine particles. These particles were then mixed into nursery soil at a loading of ten percent by weight—a ratio chosen after preliminary trials balancing soil workability, moisture retention, and mixing uniformity. Every laboratory experiment was run in triplicate to strengthen statistical reliability.

The team then put the amended soil to work across four phases of testing. In the first, onion bulbs were planted in paired vessels of 500 grams of soil each, one with glove particles and one without, under identical light, irrigation, and temperature conditions. Photographic records taken on days 1, 17, 25, and 32 showed that germination began earlier in the glove-amended soil, and by harvest the treated plants had accumulated noticeably more biomass. Fresh weights were measured immediately, while dry biomass was determined after oven-drying at 60 degrees Celsius for 24 hours until constant weight.

The second phase repeated the design with bean plants and produced the same pattern: improved root development, healthier stems, and consistent gains in plant height and biomass across triplicate runs. Crucially, the researchers observed no toxicity symptoms—no leaf discoloration, no delayed germination, no stunted growth. The third phase moved outdoors, with two two-by-two-meter plots of Napier grass planted under natural conditions of 28 to 35 degrees Celsius. One plot received commercial fertilizer, the other only processed glove particles. After 30 days, the glove-fertilized plot held its own on propagation rate, stem thickness, and plant density.

The fourth phase delivered perhaps the most visually striking result. Flowering plants grown in glove-amended garden soil produced denser, faster blooms than those fed conventional market fertilizer. The authors link this to a surge in available manganese, a micronutrient central to photosynthesis whose deficiency is common in soils with pH above 6. Cereal crops, beans, and potatoes are among the plants that favor higher manganese levels, hinting at where this approach might pay off most.

The laboratory soil analysis told a consistent story. Elemental testing using standard agricultural methods—the Kjeldahl method for nitrogen, the Olsen method for phosphorus, and flame photometry for potassium—revealed increases of 7.94 percent in phosphorus, 36.07 percent in copper, 51.90 percent in manganese, and 5.75 percent in sulfur compared with control soil. Soil pH remained stable, meaning the gloves preserved the soil’s original chemical character. Nitrogen rose slightly, attributed to the protein content of natural latex, while salt levels improved by roughly ten percent. Potassium, notably, did not budge—unsurprising, the authors note, since neither the polymer nor the glove additives contain it.

Statistical analysis confirmed that the growth differences were significant, with treated plants showing approximately 20 to 35 percent higher biomass than controls at p below 0.05. The mechanism, the researchers argue, is a combination of factors rather than rapid rubber degradation. Vulcanized polyisoprene breaks down slowly because sulfur crosslinking locks the polymer network together. Instead, the gains likely come from hydrophilic proteins holding moisture, improved soil aeration, and the gradual release of biodegradable non-rubber constituents and micronutrient-bearing additives such as zinc oxide activators, sulfur curatives, and carbamate and thiazole accelerators—compounds that, at low concentrations, can even act as mild fungicides and insecticides.

The authors are careful not to oversell the result. They explicitly state that waste latex gloves should not replace conventional fertilizers but rather supplement them within integrated nutrient management. And they flag serious open questions: vulcanized rubber fragments slowly and may generate microplastic particles over time; additives such as zinc compounds could accumulate to ecotoxicological levels with repeated application; and the long-term effects on soil microbial communities, nutrient transport, and root interactions remain unquantified. Establishing safe application limits will require dedicated studies on biodegradation behavior, additive migration, and soil ecotoxicology.

Still, the waste-to-wealth logic is compelling, and the future applications extend beyond ordinary farmland. Because the glove particles improve moisture retention and soil stabilization, the authors suggest the approach could benefit arid and erosion-prone regions where water is scarce and soils are weak—potentially reducing both fertilizer and irrigation demand. A ten-year projection of plant biomass included in the study sketches the scale of what controlled, long-term use might achieve. If follow-up research confirms environmental safety, the humble disposable glove may yet trade its place in the landfill for a productive role in the ground.

Subject of Research: Using processed waste natural rubber latex gloves as a soil amendment to enhance soil fertility and plant growth

Article Title: Enhancement of soil fertility using waste natural rubber latex gloves

Article References: Chauhan, M., Patel, B., & Desai, R. (2026). Enhancement of soil fertility using waste natural rubber latex gloves. Discover Soil, 3(1), Article 110. https://doi.org/10.1007/s44378-026-00272-3

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00272-3

Keywords: natural rubber latex, soil fertility, soil amendment, waste management, circular economy, polyisoprene, soil organic matter, micronutrients, manganese, sustainable agriculture, plant biomass, germination