The researchers evaluated two commercially cultivated cucumber varieties, CU 999 and Monalisa, at three plant spacings—75 × 25, 75 × 50 and 75 × 75 cm—and four NPK rates of 0, 100, 200 and 300 kg ha−1. The treatments were arranged in a split-split-plot randomized complete block design with three replications per trial. Each sub-subplot covered 6 m², with 0.5 m alleys between plots and 1 m between blocks. Fruit was harvested at commercial maturity, defined as 10–12 days after anthesis, with uniform dark-green skin and a length of 14–18 cm. Five randomly selected fruits from the middle two rows of each sub-subplot, excluding border plants, were taken for laboratory analysis.

CU 999 generally produced firmer fruit, while Monalisa consistently had greener skin. In the second 2019 trial, firmness averaged 1.35 kg for CU 999 compared with 1.15 kg for Monalisa; in the second 2020 trial, the corresponding values were 1.20 and 1.05 kg. Wider spacing also supported firmness, with fruits at 75 × 75 cm reaching 1.35 kg in the second 2019 trial compared with 1.07 kg at 75 × 25 cm. Fertilizer rate also affected firmness, but the response was not consistently linear: the highest mean occurred at 100 kg ha−1 in the first 2019 trial, at the unfertilized control in the second 2019 trial, and at 300 and 200 kg ha−1 in the two 2020 trials. In the first 2020 trial, the firmest treatment combination was CU 999 at 75 × 75 cm with 300 kg ha−1, at 1.46 kg.

Monalisa’s advantage in green coloration was more consistent than any fertilizer effect. Its CIELAB a* values were more negative than those of CU 999 in all four trials, indicating greener skin. In the second 2019 trial, the values were −12.13 for Monalisa and −10.54 for CU 999; in the first 2020 trial, they were −7.94 and −3.52, respectively. Spacing altered skin color significantly in every trial, although wider spacing produced greener fruit in only two trials. A rate of 200 kg ha−1 generally corresponded to greener skin than lower or higher rates, but this pattern was not uniform. Significant three-way interactions among variety, spacing and fertilizer were recorded for both firmness and color in all four trials, showing that the best combination depended on season and the trait under examination.

The clearest nutritional response was associated with the highest fertilizer rate. NPK at 300 kg ha−1 significantly increased vitamin A in every trial, reaching 35.93 µg/100 g in the second 2019 trial compared with 30.39 µg/100 g in the unfertilized control. It also produced the highest vitamin K values in all four trials, including 19.05 µg/100 g versus 15.84 µg/100 g under the control in the first 2019 trial. Vitamin C responded significantly to fertilizer rate in each trial, but not in a uniformly dose-dependent fashion: the highest mean occurred at 100 kg ha−1 in the first 2019 trial, 300 kg ha−1 in the second, and 200 and 300 kg ha−1 in the two 2020 trials. Monalisa generally had slightly more vitamin A than CU 999, while the varieties did not differ significantly in vitamin K in most trials.

Plant spacing was especially influential for vitamin K and vitamin C. The 75 × 75 cm treatment produced the highest vitamin K concentration in every trial, including 17.55 µg/100 g compared with 16.50 µg/100 g at 75 × 25 cm in the second 2019 trial. It also yielded the highest mean vitamin C concentration in the second 2019 trial and both 2020 trials, while the first 2019 trial instead favored 75 × 50 cm. These observations are consistent with the broader pattern in which reduced competition at wider spacing was associated with more concentrated fruit constituents. The relationship was not simply a matter of maximizing every vitamin at once: riboflavin, identified in the study as vitamin B2, remained uniformly low at 0.03–0.04 mg/100 g, and the 300 kg ha−1 fertilizer rate increased it significantly only in the two 2020 trials.

Fruit composition showed the same tension between output and concentration. The closest spacing maximized per-hectare yield, but its fruit contained less vitamin C in the study’s interpretation, consistent with nutrient dilution at high plant density. Wider spacing generally increased dry matter. NPK at 300 kg ha−1 gave the highest dry matter in three of four trials, including 5.27 g/100 g in the first 2020 trial, compared with 3.46 g/100 g in the control. The 75 × 75 cm treatment generally produced higher dry matter, while the 75 × 50 cm treatment sometimes gave the highest carbohydrate level. Fiber ranged from 0.25 to 0.50 g/100 g, with wider spacing and higher NPK rates generally associated with higher values. Fat remained low throughout, at 0.10–0.15 g/100 g, and did not differ significantly between varieties.

The multivariate analysis summarized the combined pattern. CU 999 at 75 × 75 cm with 300 kg ha−1 achieved the highest TOPSIS closeness coefficient, 0.768, indicating the strongest overall position across the measured postharvest and nutritional criteria. By contrast, CU 999 at 75 × 25 cm with the same fertilizer rate was the yield-maximizing recommendation. Principal component analysis placed vitamin content, dry matter and firmness together along the first component, while moisture and proximate fractions dominated the second. Treatments receiving 300 kg ha−1 consistently shifted toward higher scores on the first component. The moisture content was strongly inversely correlated with dry matter, with r = −0.93, and negatively associated with most vitamins. Firmness correlated positively with dry matter at r = 0.72 and with vitamin K at r = 0.68.

These results show why a single “best” treatment cannot summarize the experiment. The study analyzed each season independently because planting date, rainfall and soil conditions differed, and the four trials did not support a combined multi-environment analysis without explicit site-year covariates. ANOVA and Fisher’s least significant difference were used for treatment comparisons, while correlation, principal component analysis and TOPSIS were used to examine the combined profile. The 75 × 75 cm and 300 kg ha−1 combination should therefore be interpreted as a quality-oriented option rather than a definitive commercial recommendation. It uses fewer plants per unit area and requires a high fertilizer input, so profitability, fertilizer efficiency and environmental risk remain unresolved.

The findings nevertheless offer a clear experimental distinction for southwestern Nigerian cucumber production: close spacing favored volume, whereas wider spacing repeatedly favored dry matter and selected vitamins; CU 999 favored firmness, and Monalisa favored green skin color. The authors also identify limitations that constrain interpretation. Trials were conducted at one site over two years, economic feasibility was not tested, and vitamins A and K were quantified spectrophotometrically rather than by the more selective HPLC method. The study therefore demonstrates a management-linked trade-off in cucumber quality under tropical open-field conditions, while further location-based, economic and environmental studies are needed before the highest NPK rate can be presented as a broadly optimal production choice.

Subject of Research: Field study of cucumber variety, spacing and NPK effects on yield, postharvest quality and nutritional composition

Article Title: Variety, plant spacing, and NPK fertilizer rate influence postharvest quality and nutritional composition of cucumber fruits in Southwest Nigeria

Article References: Falaiye, O. O., Kasali, A. O., Adeyemi, N. O., Oni, O. E., Somoye, R. A., Falaiye, O. M., & Adekunle, E. A. (2026). Variety, plant spacing, and NPK fertilizer rate influence postharvest quality and nutritional composition of cucumber fruits in Southwest Nigeria. Discover Plants, 3(1), Article 473. https://doi.org/10.1007/s44372-026-00957-7

Image Credits: AI Generated

DOI: 10.1007/s44372-026-00957-7

Keywords: cucumber, crop management, plant spacing, NPK fertilizer, food nutrition, postharvest quality, Nigeria, yield trade-offs, CU 999, Monalisa, Variety, plant

The experiment was set up on a soil that was slightly alkaline, with a pH of 7.5, and notably poor in organic carbon, nitrogen, and available phosphorus. That starting point mattered. Nutrient-limited soils are precisely the kind of environment where a fertilizer input is most likely to reveal differences between plant genotypes, because each ecotype’s internal physiology must decide how to spend the newly available resources. The researchers hypothesized that organic manure and NPK fertilizer would not act identically across ecotypes, and instead would differentially regulate vegetative and reproductive traits depending on the plant’s origin.

To test this, the team obtained three ecotypes of summer savory, from Mashhad, Shiraz, and Karaj, and subjected them to five fertilization treatments: an unfertilized control, organic manure at 25 and 50 tonnes per hectare, and NPK fertilizer at 50 and 100 kilograms per hectare. The trial was laid out as a factorial randomized complete block design with three replicates, a standard but rigorous arrangement that allows the effects of ecotype, fertilizer, and their interaction to be separated statistically. The researchers then measured a broad panel of morphological, physiological, and phytochemical traits, from plant height and leaf biomass to chlorophyll and anthocyanin content, flower number, and the percentage of essential oil in the harvested material.

The analysis, which combined analysis of variance (ANOVA), principal component analysis (PCA), and structural equation modeling (SEM), delivered a clear verdict: both ecotype and fertilizer mattered, and crucially, so did their interaction. For reproductive traits and pigment-related traits in particular, the ecotype-by-fertilizer interaction was statistically significant, meaning that the best fertilizer for one ecotype was not necessarily the best for another. This kind of genotype-by-environment interplay is exactly what breeders and agronomists watch for when deciding whether a crop recommendation can be generalized or must be tailored to a specific seed lot or region.

Some of the standout combinations were striking. The Shiraz ecotype fertilized with the higher rate of organic manure, 50 tonnes per hectare, produced the greatest vegetative growth, the highest leaf biomass, and the highest chlorophyll a content of any treatment in the trial. In other words, when the goal is green, leafy, photosynthetically active biomass, the Shiraz population responded most enthusiastically to a heavy dose of organic matter. By contrast, the Karaj ecotype under the highest rate of NPK fertilizer, 100 kilograms per hectare, produced more flowers and accumulated more anthocyanins, the red-purple pigments that often signal a shift in a plant’s metabolic priorities. And across the board, the high-rate NPK treatment was associated with a higher percentage of essential oil in the plant tissue.

That split is the conceptual heart of the paper. The authors interpret these patterns as evidence of distinct resource allocation strategies between biomass-related traits and essential-oil-related traits, rather than a uniform response to fertilization. In plain terms, a plant cannot spend its nitrogen budget twice: resources channeled into building stems, leaves, and chlorophyll are not simultaneously available for synthesizing the terpenoid compounds that make up the essential oil, and vice versa. The fact that organic manure mainly favored biomass and pigment accumulation while high-rate NPK favored oil percentage and reproductive output suggests that the two fertilizer types are not interchangeable levers but rather push the plant along different metabolic trajectories.

The multivariate statistics sharpened this picture considerably. Principal component analysis grouped the measured traits into two coordinated modules, one linking growth and biomass characteristics and the other gathering metabolite-related traits, which is consistent with the idea that these two suites of characteristics are regulated at least partly independently. Structural equation modeling then went a step further, testing hypothesized causal pathways among the trait groups. The SEM results indicated positive associations between physiological traits, phytochemical traits, and essential-oil-related traits, suggesting that a plant that is photosynthesizing efficiently and accumulating pigments also tends to be one that produces more oil. But there was a twist: phenology, the timing of developmental stages such as flowering, was negatively associated with essential oil percentage, hinting that plants that rush into reproduction may do so at the expense of oil accumulation in the harvested tissue.

For growers of medicinal and aromatic plants, the practical implications are potentially significant. Summer savory is cultivated commercially for its essential oil, which is used in food flavoring, cosmetics, and traditional medicine, and the oil content of the harvest is often the single most economically important quality metric. If the choice between organic manure and mineral NPK fertilizer, and the rate at which either is applied, can shift the balance between raw biomass and oil concentration, then fertilizer recommendations for this crop may need to be written per ecotype rather than per species. A farmer growing the Shiraz ecotype for leafy green biomass would be advised to reach for well-rotted manure, while one targeting oil yield from the Karaj ecotype might do better with a higher rate of mineral NPK, at least under the soil and climate conditions of this trial.

The authors are careful to frame their conclusions within the limits of the study. The experiment was conducted at a single location over a single growing season, which means that the observed ecotype-by-fertilizer interactions, while statistically robust within the trial, have not yet been tested across the range of soils, climates, and years in which summer savory is actually grown. Essential oil composition in particular is notoriously sensitive to environmental conditions, harvest timing, and post-harvest handling, so the authors call for multi-location and multi-season studies to clarify the mechanisms underlying fertilizer-induced changes in oil chemistry. Until such studies are done, the findings should be read as a strong signal rather than a final prescription.

Even so, the study adds to a growing body of evidence that in medicinal and aromatic crops, the old agronomic habit of treating fertilization as a purely yield-oriented decision is due for an update. When the product of the crop is not just bulk but a specific chemical fingerprint, the fertilizer decision becomes a chemistry decision as well. For summer savory, at least, the new data suggest that the ecotype a grower plants and the nutrient regime applied to it together determine whether the harvest will be a pile of lush green leaves or a distillation flask full of aromatic oil, and that getting the pairing right may be worth as much as any single input itself.

Subject of Research: Effects of organic manure and NPK fertilizer on growth, biomass, pigments, and essential oil of Satureja hortensis ecotypes

Article Title: Multi-dimensional analysis of fertilizer-treated Satureja hortensis L. ecotypes: growth dynamics, biomass production, and phytochemical fingerprints

Article References: Ghanbari Moheb Seraj, R., Esmaeili, H., Tariverdizadeh, N., Hasanzadeh, A., & Mohebodini, M. (2026). Multi-dimensional analysis of fertilizer-treated Satureja hortensis L. ecotypes: growth dynamics, biomass production, and phytochemical fingerprints. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10217-1

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10217-1

Keywords: summer savory, Satureja hortensis, organic manure, NPK fertilizer, essential oil, chlorophyll, anthocyanins, phenology, ecotypes, medicinal plants, plant physiology, agronomy

The team selected Kanchanpur purposively because of its considerable potential for wheat cultivation, and carried out the research during March and April of 2022. Using a simple random sampling technique, they systematically chose one hundred wheat-farming households across the district. Primary data were collected through pre-tested semi-structured questionnaires administered in face-to-face interviews, while secondary data were drawn from relevant journals and official records. This dual approach allowed the researchers to capture both quantitative production figures and the lived experience of farmers struggling with unreliable inputs and market access.

To determine which variables actually drive wheat production, the researchers applied a multiple regression model to their survey data. The analysis revealed that four factors exerted a significant positive influence on output: the quantity of applied NPK fertilizer, meaning the combined nutrients nitrogen, phosphorus, and potassium; the educational level of the household head; the extent of wheat-cultivated land equipped with irrigation facilities; and the farmers’ years of experience in the field. Each of these variables, when increased, was associated with measurably higher wheat production in the study area.

The fertilizer finding is particularly consequential. Nitrogen, phosphorus, and potassium are the backbone of modern cereal nutrition, and inadequate or poorly timed application directly limits grain filling and tillering in wheat. In Kanchanpur, however, farmers frequently cannot obtain chemical fertilizer at all during the critical growth periods when the crop needs it most. The study identifies this unavailability of fertilizer during key developmental stages as the single most severe constraint on wheat production in the district, a problem that undermines even the most experienced farmers’ efforts.

Education emerged as another powerful lever. Households headed by individuals with more formal schooling tended to produce more wheat, a pattern consistent with the idea that educated farmers are better positioned to interpret agronomic recommendations, calculate appropriate input doses, adopt improved technologies, and navigate extension services. Similarly, the area of wheat land with reliable irrigation proved decisive. Wheat in the Terai plains is often grown after rice on residual soil moisture, and access to controlled water supply allows farmers to time irrigation at critical stages such as crown root initiation and grain filling, protecting yields against the erratic rainfall that increasingly characterizes the region.

Experience also mattered. Farmers with more years in the field achieved higher production, reflecting accumulated knowledge of local soil behavior, sowing windows, variety selection, and pest management. This finding suggests that extension programs could gain leverage by pairing experienced lead farmers with newer producers, transferring practical know-how that formal training alone often fails to convey. It also hints at a generational risk: as older, seasoned farmers retire from cultivation, their tacit agronomic knowledge may not be replaced quickly enough to sustain district-level output.

Beyond the regression results, the researchers used an indexing method to rank the major constraints farmers face. After fertilizer unavailability, the second most damaging problem was crop destruction by wild animals and stray cattle. In Kanchanpur, proximity to forest areas and wildlife corridors means that nilgai, wild boar, monkeys, and roaming domestic livestock frequently invade fields overnight, flattening standing crops and eating grain. Farmers respond with watch huts, night patrols, and noise deterrents, but these measures demand labor and rarely provide complete protection, effectively taxing every harvest.

The indexed ranking also highlighted the lack of access to improved seeds and irrigation as a major constraint. Improved, disease-resistant wheat varieties can raise yields substantially, but many farmers in the district continue to sow saved or uncertified seed because quality seed is not available locally or is priced beyond reach. Combined with limited irrigation infrastructure, this leaves crops vulnerable to moisture stress and to the diseases and pests that the study lists among the significant production challenges. Inadequate market access rounds out the constraint list, with farmers facing poor roads, weak price information, and limited buyer networks that reduce the incentive to invest in higher inputs.

The comparative context sharpens the urgency of these findings. Districts such as Kailali, Banke, Kapilbastu, and Rupandehi, operating under similar weather patterns, achieve higher wheat productivity than Kanchanpur, which indicates that the yield gap is not dictated by climate but by controllable factors: input supply chains, irrigation coverage, seed systems, and market institutions. The study’s authors argue that addressing these bottlenecks could unlock the district’s considerable prospective for wheat cultivation, contributing to national food security at a time when cereal imports and price volatility weigh heavily on Nepal’s economy.

For policymakers, the message is that raising wheat output in Kanchanpur requires coordinated intervention rather than isolated fixes. Ensuring timely fertilizer availability during critical growth periods, expanding irrigation infrastructure, improving the distribution of improved seed, managing human-wildlife conflict around farmland, and strengthening market linkages together form the pathway the evidence points toward. The regression results show that farmers respond strongly when given the means, more nutrients, more water, more knowledge, and more experience, while the constraint indexing shows exactly where the system currently fails them. Closing that gap between potential and performance could transform wheat farming in Kanchanpur from a marginal enterprise into a reliable contributor to Nepal’s grain supply.

Subject of Research: Factors affecting wheat productivity and production constraints in Kanchanpur district, Nepal

Article Title: An assessment of factors affecting productivity and production limitations of wheat farming in Kanchanpur district of Nepal

Article References: Kafle, K., & Joshi, P. P. (2024). An assessment of factors affecting productivity and production limitations of wheat farming in Kanchanpur district of Nepal. Innovations in Agriculture, 7, 1–8. https://doi.org/10.3897/ia.2024.124216

Image Credits: AI Generated

DOI: 10.3897/ia.2024.124216

Keywords: wheat farming, Nepal, Kanchanpur, crop productivity, NPK fertilizer, irrigation, improved seeds, multiple regression, wild animal damage, market access, agricultural constraints, food security

The experiment took place at Palampur in Kangra district, at an elevation of roughly 1,290 metres, on a silty clay loam Alfisol classified as Typic Hapludalf. The starting soil was acidic, with a pH of 5.63, moderate organic carbon of 7.89 grams per kilogram, and available nitrogen, phosphorus and potassium of 255.2, 17.5 and 188.6 kilograms per hectare respectively. Rainfall during the June-to-October 2022 maize season totalled an abundant 1,847.4 millimetres, and the crop was grown entirely rainfed with no supplemental irrigation. The researchers sowed the maize variety Kanchan at 20 kilograms of seed per hectare and applied the recommended fertilizer dose of 120:60:40 kilograms of nitrogen, phosphorus pentoxide and potassium oxide per hectare through urea, single superphosphate and muriate of potash, splitting the nitrogen between a basal application and two top-dressings at knee-high and pre-tasselling stages.

What made the trial distinctive was its nine-treatment structure, arranged in a randomized block design with three replications, which pitted full, moderate and reduced mineral fertilizer levels against combinations of farmyard manure, vermicompost and a mixed inoculant of Azotobacter and Bacillus species. The organic amendments differed meaningfully in composition: vermicompost carried 1.27 percent nitrogen on a dry-matter basis against 0.89 percent in farmyard manure, along with somewhat higher phosphorus. The bioinoculants, obtained from the university’s Department of Organic Agriculture and Natural Farming, were mixed into the organic amendment before field application, a practical delivery method that farmers could replicate. The central question was how much mineral fertilizer could be trimmed while still sustaining yield, nutrient uptake, soil fertility and economic returns in a system where cation exchange capacity, microbial biomass and enzyme activity jointly govern fertilizer efficiency.

The answer, at least under these conditions, was 25 percent. The treatment combining 75 percent of the recommended NPK with 5 tonnes of vermicompost per hectare and the Azotobacter-Bacillus consortium produced the highest observed grain yield of 40.8 quintals per hectare and stover yield of 62.5 quintals per hectare. Compared with the conventional full-fertilizer control, that represents a 34.4 percent increase in grain yield, a figure that will catch the attention of any agronomist who has watched yield stagnate under fertilizer-only regimes. Total nutrient uptake told the same story: the leading treatment accumulated 121.0 kilograms of nitrogen, 31.3 kilograms of phosphorus and 92.2 kilograms of potassium per hectare, increases of 36.6, 78.9 and 53.4 percent respectively over sole mineral fertilization. Grain protein and ash content also peaked under the integrated packages, reflecting the tighter coupling between nutrient supply and grain filling.

Importantly, the researchers were careful about their statistics. The vermicompost-based treatment did not differ significantly from its farmyard manure counterpart at 75 percent NPK for most measured responses; the two formed a single leading statistical group across yield components, nutrient uptake and most soil indicators. Available soil potassium was the only variable that separated them significantly, favouring the vermicompost package. This nuance matters because it means farmers with ready access to either amendment have viable options, with the choice potentially driven by local availability and price rather than by a fixed agronomic hierarchy. The study also showed that the integration cannot be reduced to a single ingredient: the responses reflect the combined effect of fertilizer level, amendment type and inoculation within each package, and the trial design did not isolate the bioinoculant effect factorially.

The soil story may prove even more consequential than the yield numbers. Post-harvest measurements revealed that the integrated treatments lowered bulk density, improved water-holding capacity, and raised soil organic carbon to 8.48 grams per kilogram under the leading treatment. Microbial biomass carbon reached 112 milligrams per kilogram and dehydrogenase activity 4.4 micrograms of triphenyl formazan per gram per hour, gains of 32.9 and 51.7 percent respectively over the full-fertilizer control. Dehydrogenase activity is a particularly telling metric because it quantifies the oxidative metabolism of living microbial communities rather than a static chemical pool, so its sharp rise signals a genuine reactivation of the soil’s biological machinery. DTPA-extractable iron, manganese, zinc and copper also peaked under the integrated treatments, linking micronutrient availability to the broader fertility response.

To understand whether these individual improvements were connected, the team turned to principal component analysis of the post-harvest soil indicators. Two components explained 93.40 percent of the total variance, with the first alone accounting for 85.45 percent. That dominant axis aligned water-holding capacity, organic carbon, available nitrogen and phosphorus, micronutrients and microbial biomass carbon, while bulk density loaded in the opposite direction. The correlation matrix confirmed strong positive associations among organic carbon, available nutrients, micronutrients and the biological indicators, and consistent negative associations between bulk density and nearly every fertility measure. Soil pH, by contrast, barely moved, remaining in a narrow and statistically non-significant range of 5.6 to 5.7 across treatments. The authors interpret this covariance structure as evidence that the response to integrated nutrient management was functionally integrated across physical, chemical and biological domains, driven by enhanced nutrient buffering and biologically mediated nutrient cycling rather than by nutrient addition alone.

Economics added a final, pragmatic dimension. The vermicompost-based package generated gross returns of 99,340 rupees per hectare, equivalent to about 1,264 US dollars, net returns of 59,722 rupees per hectare, and an economic efficiency of 567.66 rupees per hectare per day, the highest of any treatment. Yet the conventional full-fertilizer control retained the best benefit-cost ratio and return per rupee invested simply because its input costs were lower. This distinction is crucial for policy: the integrated package delivered the strongest productivity and soil outcomes, but only when yield gains were large enough to offset the additional expense of amendments and inoculants. At 50 percent NPK, that equation failed. The heavily reduced treatments improved several soil and biological indicators relative to the control but could not sustain comparable nutrient acquisition or profitability, demonstrating that organic and microbial inputs require an adequate mineral backbone to function.

The study’s conclusions are deliberately bounded. The findings come from a single season at a single site in an acidic Himalayan Alfisol, and the authors state plainly that wider recommendation requires multi-season and multi-location validation of nutrient-recovery efficiency, residual fertility, inoculant persistence, carbon stabilization and direct greenhouse-gas emissions, which were not measured here. Even so, the message is a significant one for a world grappling with fertilizer price volatility and widespread soil degradation. Fertilizer reduction, the authors argue, should not be approached as a simple decrease in mineral input but as a redesign of nutrient supply through mineral, organic and biological integration. Where vermicompost is available, pairing 75 percent of the standard NPK dose with the Azotobacter-Bacillus consortium offers a practical, economically defensible template for growing more maize while rebuilding the soil that makes future harvests possible.

Subject of Research: Integrated nutrient management combining vermicompost, Azotobacter-Bacillus inoculation and reduced mineral NPK for sustainable maize production

Article Title: Vermicompost-assisted Azotobacter and Bacillus inoculation enables partial substitution of mineral NPK and improves maize yield, nutrient uptake, soil fertility, and biological activity

Article References: Bahman, M., Singh, D., Venkateswarlu, M., Sankhyan, N. K., Thakur, P., & Kumari, S. (2026). Vermicompost-assisted Azotobacter and Bacillus inoculation enables partial substitution of mineral NPK and improves maize yield, nutrient uptake, soil fertility, and biological activity. Discover Soil, 3(1), Article 176. https://doi.org/10.1007/s44378-026-00336-4

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00336-4

Keywords: maize, integrated nutrient management, vermicompost, Azotobacter, Bacillus, NPK fertilizer, soil fertility, microbial biomass carbon, dehydrogenase activity, nutrient uptake, Alfisol, sustainable agriculture

The research team, led by Clara U. Nwankwo and corresponding author Michael E. Ikehi, set out to answer a practical question that has grown more urgent in recent years. Global disruptions to fertilizer supply chains have sent prices soaring and left many farmers in developing regions unable to afford synthetic nutrients at the recommended rates. At the same time, demand for carrot foliage as livestock feed has been rising, turning what was once agricultural waste into a marketable secondary product. The authors frame this as a dual-market challenge: optimize nutrients for the taproot, optimize them for the leaves, or find a middle path. Their experiment was designed to test all three possibilities under identical conditions so the outcomes could be compared directly.

The methodology was deliberately straightforward. The researchers used a completely randomized design with three replicates, growing the Kuroda carrot variety over a 12-week period in four treatment groups. One group served as an unamended control, receiving no nutrient additions at all. A second received poultry manure, representing the organic option. A third received NPK 15:15:15, a balanced synthetic fertilizer supplying nitrogen, phosphorus, and potassium in equal proportions, representing the inorganic option. The fourth received a combination of poultry manure and NPK, representing integrated nutrient management. Data were analyzed using means, and analysis of variance was applied to test the null hypotheses at the 0.05 significance level, the conventional threshold in agricultural science for judging whether differences between treatments are likely to be real rather than the product of random variation.

When it came to what happens above the ground, the integrated treatment dominated. Carrots grown with the combined poultry manure and NPK treatment reached an average height of 34.39 millimeters, taller than those grown with inorganic fertilizer alone at 28.54 millimeters, organic manure alone at 32.35 millimeters, and the untreated control at 26.39 millimeters. Leaf biomass followed the same pattern, with the integrated treatment producing a value of 12.23, compared with 11.37 for organic manure, 9.10 for inorganic fertilizer, and 8.44 for the control. The pattern makes agronomic sense: organic manures release nutrients slowly as they mineralize, while synthetic fertilizers deliver an immediate pulse, and combining the two gives plants both a steady background supply and readily available nitrogen during peak vegetative growth.

Below the ground, however, the ranking flipped. Carrots grown with inorganic NPK fertilizer alone developed the longest taproots, averaging 17.86 millimeters, and the heaviest taproots, averaging 59.52 grams. The integrated treatment came in second at 14.84 millimeters and 54.15 grams, followed by organic manure at 13.35 millimeters and 42.48 grams, and the control at 11.55 millimeters and 31.25 grams. In other words, the synthetic fertilizer delivered roughly 90 percent more root weight than doing nothing at all, while the organic treatment delivered about 36 percent more. For a farmer whose income depends on selling graded taproots at market, those numbers carry real economic weight, and they explain why synthetic fertilizers have remained attractive even as their cost and availability have become less predictable.

The statistical analysis added an important layer of nuance to these numbers. While the integrated treatment produced numerically higher values for leaf biomass, the differences among treatments for that parameter did not reach statistical significance at the 0.05 level. Root tuber performance, by contrast, showed a statistically significant difference among treatments, meaning the advantage of inorganic fertilizer for taproot length and weight is unlikely to be a fluke of this particular experiment. The authors are careful to acknowledge this distinction, and it matters for how the findings should be used. A farmer choosing a fertilizer strategy to boost foliage would be making a decision on weaker statistical ground than one choosing a strategy to boost roots, and future replication studies could help firm up the biomass conclusions.

One of the more intriguing results concerns the organic treatment. Although integrated nutrient management produced the tallest plants and the highest leaf biomass score, the authors note that organic manure application alone was associated with a higher optimum harvestable root yield in their interpretation of the results, positioning it as a viable option for growers who want to avoid synthetic inputs altogether. Poultry manure is widely available and inexpensive in many parts of the global South, often generated as a byproduct of the region’s rapidly expanding poultry industry. Recycling it onto vegetable fields closes a nutrient loop, reduces waste disposal problems, and improves soil organic matter over time, benefits that extend beyond a single season’s yield even if they are harder to capture in a 12-week trial.

The broader context of the study is what gives it its urgency. The authors write that amid global fertilizer supply chain disruptions and the emerging dual-market demand for carrot taproots and leafy biomass, optimizing nutrient management is now essential for sustainability. Imported synthetic fertilizer exposes farmers in the global South to currency fluctuations, shipping delays, and geopolitical shocks that they have little power to influence. Integrated nutrient management offers a partial hedge, because a farmer who can meet part of the crop’s nutrient demand from local manure needs to purchase less synthetic product, reducing both cost and risk. The study’s results suggest that this hedge does not necessarily cost much in yield terms, since the integrated treatment was statistically comparable or superior in most measured parameters.

The dual-market angle is equally significant for the economics of smallholder carrot production. If the goal is cultivating carrots primarily for leafy biomass destined for livestock feed, the integrated treatment emerges as the optimal strategy in this experiment, maximizing the above-ground vegetative parameters that define that harvest. If the goal is the traditional taproot market, inorganic fertilizer remains the top performer, though organic manure offers a respectable and more affordable alternative. This goal-oriented framing is a departure from the usual framing of the organic-versus-conventional debate, which tends to ask which approach is universally better. The Nigerian team’s data suggest the more useful question is which approach is better for a specific product, market, and risk profile.

The study, conducted by researchers in the Department of Agricultural Education at the University of Nigeria, Nsukka, the Department of Environmental Management and Toxicology at the University of Delta, Agbor, and the Department of Home Economics and Hospitality Management at the University of Nigeria, received no specific financial support and was published as open access research. The authors conclude that adopting targeted organic and integrated nutrient management practices could provide sustainable, goal-oriented pathways to optimize agricultural production while buffering domestic farming in the global South against global challenges in food production. For a crop as familiar and widely grown as the carrot, that is a quietly radical proposition: the future of sustainable vegetable farming may depend less on choosing sides in the fertilizer debate than on matching the nutrient strategy to the harvest a farmer actually intends to bring to market.

Subject of Research: Comparative effects of organic, inorganic, and integrated nutrient management on carrot growth and yield

Article Title: A comparative analysis of organic, inorganic manures, and integrated nutrient management in carrot growth and yield in the global south

Article References: Nwankwo, C. U., Ikehi, M. E., Ashikodi, M. O., Ugwu, E. I., Nosakhare, D. O., & Ifeanyieze, F. O. (2026). A comparative analysis of organic, inorganic manures, and integrated nutrient management in carrot growth and yield in the global south. Discover Sustainability. https://doi.org/10.1007/s43621-026-04876-1

Image Credits: AI Generated

DOI: 10.1007/s43621-026-04876-1

Keywords: carrot, Daucus carota, integrated nutrient management, poultry manure, NPK fertilizer, leafy biomass, root yield, sustainable agriculture, global South, soil fertility, livestock feed, fertilizer supply chain

The research draws on one of the longest running field experiments in the region, established during the Kharif season of 1985 at the research farm of CCS Haryana Agricultural University. The site sits in a hot semi-arid climate classified as BSh under the Köppen system, receiving just 443 millimeters of annual rainfall, most of it between July and September. Summer temperatures can climb to 47 degrees Celsius while winter minima fall to 1 degree. The soil is a sandy loam classified as Typic Ustochrept, and the experimental plots follow an annual pearl millet and wheat rotation. From twelve treatments in a randomized complete block design, the team selected five for metagenomic analysis: an unfertilized control, NPK fertilizer alone, and three integrated treatments combining NPK with farmyard manure, wheat straw or green manure grown from dhaincha, a Sesbania species.

To read the bacterial census of these soils, the researchers extracted DNA and sequenced the V3-V4 region of the 16S rRNA gene, the standard molecular barcode for identifying bacteria. After quality filtering with the QIIME2 pipeline and chimera removal, more than 409,000 high-quality sequences were classified against the SILVA reference database. The team then computed alpha diversity metrics including observed species, Shannon index and Faith’s phylogenetic diversity, and assessed beta diversity using Bray-Curtis and UniFrac distances, visualized through principal coordinate analysis and hierarchical clustering.

The results were striking. Across all five samples, three phyla dominated: Proteobacteria, Firmicutes and Actinobacteria, with smaller contributions from Chloroflexi, Acidobacteria and Bacteroidetes. But the balance shifted dramatically depending on the treatment. In the control, NPK-only and NPK plus green manure soils, Proteobacteria and Firmicutes together accounted for more than 60 percent of all phyla. In the NPK plus farmyard manure and NPK plus wheat straw soils, Proteobacteria and Actinobacteria rose above Firmicutes, signaling a genuine compositional reorganization rather than a minor fluctuation.

Diversity metrics told an even clearer story. The number of observed species ranged from just 260 in the untreated control to 1,250 in the NPK plus farmyard manure soil, nearly a fivefold difference. The control consistently recorded the lowest values for richness, evenness and phylogenetic diversity, while the farmyard manure and wheat straw treatments ranked highest on all three measures. The NPK-only and green manure treatments fell in between. At the genus level, the control and NPK soils were dominated by Pseudomonas and Bacillus, whereas the farmyard manure soil was characterized by Sphingomonas, and the wheat straw soil carried notable abundances of Bacteroides and Nocardioides. The green manure soil hosted elevated levels of Stenotrophomonas, Delftia, Achromobacter and Coxiella.

Statistical tests confirmed that these differences were not noise. Principal coordinate analysis separated the organically amended soils from the control and NPK-only soils along the first two axes, which together explained nearly 74 percent of the variation. A permutational multivariate analysis of variance found that 63 percent of the differences in microbial signatures were directly linked to whether a soil belonged to the unamended or organically amended group, a remarkably high value indicating a coordinated ecological shift rather than random sampling variation. A similarity percentage analysis identified Bacillus, Sphingomonas and Delftia as the largest contributors to the dissimilarity, with just four genera accounting for over 55 percent of the community variance between groups.

Perhaps the most intriguing finding came from differential network analysis, which maps how bacterial genera interact with one another. The unamended and NPK-only soils formed densely connected networks with highly linked hub taxa such as Bacillus, Pseudomonas and Streptomyces. The organically amended soils, by contrast, showed sparser networks with more negative associations. Counterintuitively, the researchers argue this structural loosening is a sign of a healthier ecosystem. Dense, highly interdependent networks are vulnerable, because a disturbance hitting a single hub taxon can cascade through the whole community. Sparser, more compartmentalized networks imply niche partitioning and functional redundancy, where multiple taxa can perform overlapping roles such as nutrient cycling without the system depending on any single vulnerable species.

The specific bacteria enriched under each amendment also make ecological sense. Farmyard manure introduces complex, recalcitrant carbon compounds, favoring metabolically versatile Sphingomonas species equipped with enzymes that degrade aromatic compounds and tough biopolymers. Green manure from Sesbania delivers a rapid pulse of fresh, nitrogen-rich plant tissue, selecting for fast-growing copiotrophs like Stenotrophomonas that excel at breaking down easily decomposable material. Many of the genera detected across the treatments are known plant growth promoters: Bacillus, Pseudomonas and Streptomyces solubilize phosphorus and suppress pathogens, while Bradyrhizobium and related rhizobia fix atmospheric nitrogen. Nitrogen fixers such as Methylobacterium and Acetobacter appeared under NPK treatment, and decomposers like Megasphaera and Succinivibrio were unique to the wheat straw soil.

The study does carry a methodological caveat. Soil from the four field replicates of each treatment was pooled before DNA extraction, which prevents statistical assessment of variation within treatments. The authors acknowledge this limitation but note that the macro-level divergence between the two groups remained statistically robust, supported by the high PERMANOVA value and consistent clustering across multiple analyses. The raw sequence data have been deposited in the NCBI Sequence Read Archive, allowing other researchers to scrutinize and extend the findings.

For a world that must raise agricultural output by an estimated 70 to 100 percent by 2050 to feed a population exceeding nine billion, the message from this semi-arid Indian field is timely. Nearly four decades of combining inorganic fertilizers with farmyard manure, straw or green manure did not merely maintain soil fertility; it cultivated a richer, more resilient bacterial ecosystem beneath the surface. As the authors conclude, aligning agricultural practices with the functional complexity of soil microbial communities may be one of the most powerful and underappreciated levers for building farming systems that can endure the pressures of the coming decades.

Subject of Research: Effects of long-term integrated nutrient management on soil bacterial diversity and community structure

Article Title: Long term integrated nutrient management promotes soil bacterial diversity and beneficial community structure

Article References: Ahlawat, V., Ahalawat, N., Boora, N., Dadarwal, R. S., Dhanda, D., Sangwan, P., Kumar, V., Kumar, R., Kumar, V., & Yadav, P. K. (2026). Long term integrated nutrient management promotes soil bacterial diversity and beneficial community structure. Discover Soil, 3(1), Article 133. https://doi.org/10.1007/s44378-026-00286-x

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00286-x

Keywords: soil microbiome, integrated nutrient management, 16S rRNA sequencing, farmyard manure, green manure, wheat straw, NPK fertilizer, bacterial diversity, Proteobacteria, Actinobacteria, sustainable agriculture, microbial networks

The study was designed to address a persistent gap in soil ecology. Although many investigations have examined how fertilization affects individual groups of soil organisms, comparatively few have traced the consequences across the entire food web, spanning microbes at the base to earthworms near the top, and fewer still have done so over a time frame long enough to capture the slow, cumulative changes that define soil health. To fill that gap, a team of researchers led by first and corresponding author Professor Yunfeng Chen of the Hubei Academy of Agricultural Sciences compared four long-term treatments: chemical fertilizer supplying nitrogen, phosphorus and potassium, known as NPK; organic manure alone; a combined treatment of manure plus NPK; and an unfertilized control plot that served as the experimental baseline.

The measurement strategy was deliberately broad. Rather than tracking a single indicator organism, the team quantified biomass or abundance across key taxonomic and functional groups, including microorganisms, protozoa, nematodes, mites, collembolans, enchytraeids and earthworms. They also calculated nematode ecological indices, a set of established metrics that soil ecologists use to infer the structure and maturity of soil food webs. Together, these measurements allowed the researchers to evaluate the relative strength of two competing regulatory forces: bottom-up control, in which the availability of resources such as organic carbon and nutrients determines how many organisms higher trophic levels can support, and top-down control, in which predators and higher consumers suppress or structure the populations below them.

The headline finding was unambiguous. Long-term fertilization increased the inputs of resources entering the soil, and that surge in resources enhanced most of the functional groups the team measured. Fertilized plots supported larger and more complex communities than the unfertilized control, confirming that sustained nutrient management is a powerful lever for shaping the living architecture of agricultural soils. But the differences among fertilization strategies proved just as consequential, and here the organic treatments stood out clearly.

Manure alone and the combined manure-plus-NPK treatment outperformed pure chemical fertilizer across most groups. When the researchers expressed these gains as relative increases compared with the NPK treatment, the manure plots showed improvements ranging from 20.69 to 972.52 percent, with an average of 241.62 percent, while the combined plots ranged from 26.55 to 792.30 percent, averaging 189.02 percent. Those are not marginal differences; they represent order-of-magnitude shifts in the abundance of some soil organisms. The practical implication is that organic amendments, whether applied alone or alongside mineral fertilizers, deliver substantially more nourishment to the soil food web than chemical fertilizer alone.

Interestingly, the manure-only and combined treatments did not differ significantly from each other. The researchers attribute this convergence to high soil fertility: once fertility reaches a sufficiently high level, the distinction between the two organic approaches diminishes, and both support similarly rich communities. In other words, the food web appears to saturate, and beyond a certain threshold of resource abundance, adding mineral fertilizer on top of manure yields little additional biological benefit even though it may still matter for crop nutrition.

The evidence for bottom-up regulation was strong and came from multiple independent lines. Functional groups showed positive correlations with one another, a pattern consistent with resources flowing upward through the web and lifting every level together rather than predators imposing their own structure from above. The enrichment index, a nematode-based metric that signals an abundance of opportunistic, resource-responsive organisms, rose by 51.27 percent under manure and 28.49 percent under the combined treatment relative to chemical fertilizer alone. The enrichment footprint, a complementary measure that captures the cumulative enrichment signal across the food web, increased even more dramatically, by 11.80 percent under manure and 47.17 percent under the combined treatment relative to NPK.

To synthesize these patterns into a causal framework, the team employed partial least squares path modeling, a statistical technique well suited to disentangling direct and indirect pathways among correlated variables. The modeling confirmed what the correlations and indices had suggested: bottom-up forces predominantly determined both the structure and the total biomass of the soil food web. Resource availability, shaped by decades of fertilization, was the dominant driver, while top-down influences played a comparatively minor role in this system. For a rice–wheat rotation, where flooded and aerobic phases alternate and organic matter dynamics are complex, this finding provides a clear conceptual anchor for future soil management research.

The implications extend well beyond the experimental plots. Soil food webs underpin essential ecosystem services, including decomposition, nutrient mineralization, suppression of plant pathogens and the maintenance of soil structure. A food web enriched through bottom-up channels is, in effect, a soil with greater biological capacity to sustain crop productivity over time. The study suggests that sustained organic inputs, particularly when integrated with mineral fertilizers, effectively enhance both the complexity and the size of the soil food web primarily through this bottom-up regulatory mechanism. For farmers and policymakers weighing the trade-offs between organic and conventional inputs, the results add a biological argument in favor of manure-based strategies, whether used alone or in combination with chemical fertilizer.

The research also carries a cautionary note for the long term. Because the experiment spanned thirty years, it captured changes that short-term studies inevitably miss, including the slow accumulation of soil organic matter and the gradual response of larger, slower-reproducing organisms such as earthworms and enchytraeids. The authors’ conclusion is that fertilization is not merely a plant nutrition tool but a food-web engineering instrument, and that its effects compound over decades. As agriculture worldwide faces pressure to maintain yields while restoring degraded soils, this long-term evidence from a major cereal rotation offers a template: feed the base of the soil food web, and the rest of the web, along with the services it provides, is likely to follow.

Subject of Research: Long-term effects of chemical and organic fertilization on the soil food web in a rice–wheat cropping system

Article Title: Long-term fertilization enriches soil food web mainly through bottom-up regulation in a rice–wheat cropping system

Article References: Long-term fertilization enriches soil food web mainly through bottom-up regulation in a rice–wheat cropping system. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: soil food web, long-term fertilization, rice–wheat rotation, bottom-up regulation, manure, NPK fertilizer, nematodes, earthworms, soil fertility, enrichment index, agroecology, soil biodiversity