These were descriptive differences in a participatory demonstration program, not statistically established treatment effects. The program was implemented during the 2025–2026 cropping season through 25 Krishi Vigyan Kendras, or KVKs, across Uttar Pradesh under the Central Sector Scheme for awareness and demonstrations of FOM and liquid FOM. Although 224 frontline demonstrations were conducted, the published analysis included only records with sufficiently complete and consistent field-level data.

It used 40 rice and 110 wheat demonstrations in farmers’ fields, together with 6 rice and 11 wheat demonstrations at KVK instructional farms. Each farmers’ field treatment occupied 1,200 square metres, while instructional-farm plots covered 400 square metres per treatment. Progressive farmers were selected by the KVKs, and scientists supervised the demonstrations, but formal plot-level randomization was not used.

The remaining demonstrations were excluded because required field-level information was incomplete or unavailable. The treatments were arranged to compare fertilizer quantity with manure supplementation. At instructional farms, seven combinations were evaluated: 100% recommended inorganic fertilizer alone; that fertilizer rate with 75%, 100%, or 125% FOM; 75% recommended inorganic fertilizer alone; and 75% fertilizer with 100% or 125% FOM.

Farmers’ field demonstrations compared full-rate inorganic fertilizer with the same fertilizer rate plus 100% or 125% FOM. Both rice and wheat received a recommended nutrient rate of 120 kg nitrogen, 60 kg phosphorus pentoxide and 40 kg potassium oxide per hectare. The base FOM rates were 1.25 tonnes per hectare for rice and 8 tonnes per hectare for wheat.

Locally adapted high-yielding varieties were used, and irrigation, weed management and plant-protection practices followed the recommendations of the respective KVKs. Grain yield, straw yield, harvest index, crop-growth attributes, post-harvest soil measurements and economic returns were recorded. FOM was prepared from locally available farmyard manure, cattle dung and urine, crop residues, green biomass and jaggery.

The ingredients were fermented for approximately 30–45 days with periodic turning and suitable moisture and aeration conditions. The resulting material had a moisture content of 30–40%, a pH of 6.5–7.5 and an electrical conductivity no higher than 4 decisiemens per metre. Its combined total nitrogen, phosphorus pentoxide and potassium oxide content was at least 1.2%, while total organic carbon was at least 14% and the carbon-to-nitrogen ratio was below 20:1.

Batch-wise characterization was not consistently available across all participating locations, a limitation that may have contributed to variation in the manure’s nutrient contribution and performance. At the KVK instructional farms, mean rice grain yield under T₃ was 5,330 kg per hectare, 7.3% above the 4,968 kg per hectare recorded with full-rate inorganic fertilizer alone. Mean wheat yield reached 4,461 kg per hectare, 12.7% above the reference treatment’s 3,958 kg per hectare.

T₃ also recorded the highest numerical straw yields and harvest indices at these sites: 6,839 kg per hectare and 43.8% for rice, and 5,322 kg per hectare and 45.6% for wheat. In farmers’ fields, the corresponding T₃ means were 5,320 kg per hectare for rice and 4,641 kg per hectare for wheat, representing increases of 6.4% and 10.8% over inorganic fertilizer alone. T₂, combining full-rate fertilizer with 100% FOM, also exceeded the fertilizer-only reference numerically in both settings: rice yield was 5,188 kg per hectare at instructional farms and 5,232 kg per hectare in farmers’ fields, while wheat yield was 4,353 and 4,445 kg per hectare, respectively.

The 75%-fertilizer treatment without FOM generally produced the weakest growth and yield means at instructional farms. Crop-growth measurements followed the same descriptive pattern as yield. Under T₃ at instructional farms, rice had a mean plant population of 47 hills per square metre, 467 effective tillers per square metre, 183 grains per panicle, a panicle length of 26.5 cm and a 1,000-grain weight of 27.5 g.

The full-fertilizer treatment without FOM recorded 46 hills, 422 tillers, 164 grains per panicle, 23.2 cm and 26.6 g, respectively. Under T₃ in farmers’ fields, wheat had 241 plants and 545 effective tillers per square metre, 41 grains per spike, a 10.8 cm spike length and a 35.4 g 1,000-grain weight. The corresponding fertilizer-only means were lower for each of these numerical measures.

Researchers did not directly measure nutrient release, nutrient uptake or nutrient-use efficiency, so the parallel changes in growth, yield and soil properties should be interpreted as observed associations rather than demonstrated mechanisms. Soil measurements showed their clearest numerical separation after the complete rice–wheat cycle. At instructional farms, mean soil organic carbon (SOC) under T₃ increased from 0.271% before the cycle to 0.304% after wheat harvest, an absolute gain of 0.033 percentage points and a relative increase of 12.18%.

Available nitrogen rose from 125.3 to 164.3 kg per hectare, available phosphorus from 15.6 to 20.3 kg per hectare and available potassium from 165.1 to 185.5 kg per hectare. By contrast, under inorganic fertilizer alone, SOC declined from 0.271% to 0.269%, while the three available-nutrient measures fell to 118.5, 14.9 and 160.8 kg per hectare. The full-fertilizer treatment receiving 100% FOM also recorded post-cycle means of 0.298% SOC and 158.3, 18.9 and 182.0 kg per hectare of available nitrogen, phosphorus and potassium.

At instructional farms, T₇—75% fertilizer plus 125% FOM—also reached 0.304% SOC, although its post-cycle available-nutrient values were lower than those under T₃. Farmers’ field soils began with a higher mean SOC concentration of 0.447%. Following the cycle, T₃ increased it to 0.515%, a gain of 0.068 percentage points or 15.21% relative to the initial value.

Available nitrogen, phosphorus and potassium rose from initial means of 221.2, 16.9 and 176.1 kg per hectare to 261.8, 22.3 and 199.7 kg per hectare. Under fertilizer alone, SOC fell to 0.429%, available nitrogen to 214.3 kg per hectare and available phosphorus to 16.4 kg per hectare, while potassium was nearly unchanged at 176.0 kg per hectare. T₂, with full-rate fertilizer plus 100% FOM, ended with 0.495% SOC and available nitrogen, phosphorus and potassium values of 259.1, 20.8 and 196.0 kg per hectare.

These measurements cover one evaluated cropping cycle and should not be interpreted as evidence of durable long-term soil improvement or carbon sequestration. Higher productivity did not translate into the strongest net economics because FOM added costs for production, transportation, labor and field application. At KVK instructional farms, T₃ generated the highest mean gross return for rice, ₹139,946 per hectare, but its cultivation cost was ₹58,708 per hectare, leaving a net return of ₹81,238 and a benefit–cost ratio of 1.38.

Fertilizer alone had a higher benefit–cost ratio of 1.58. For wheat, T₃ produced the highest gross return, ₹127,491 per hectare, but a net return of ₹57,702 and a benefit–cost ratio of 0.83, compared with ₹68,968 and 1.52 under fertilizer alone. Farmers’ fields showed the same pattern: the full-rate fertilizer treatment without FOM had the highest mean net returns and benefit–cost ratios for both crops, even though T₃ had the highest gross returns.

In farmers’ rice fields, fertilizer alone recorded a net return of ₹79,969 per hectare and a benefit–cost ratio of 1.52, compared with ₹75,259 and 1.16 under T₃. For farmers’ wheat, the corresponding values were ₹78,262 and 1.82 for fertilizer alone, versus ₹61,802 and 0.87 under T₃. The findings therefore separate agronomic performance from profitability.

FOM-integrated treatments were associated with higher numerical yields, straw production, harvest indices and selected soil-fertility measurements, while its cost reduced or failed to improve net returns in several settings. The analysis is limited by its use of descriptive means without inferential testing, incomplete exclusion of demonstrations, variation among soils, varieties, management practices and input prices, and inconsistent FOM characterization. Multi-season, replicated trials with formal randomization, standardized manure analysis and appropriate statistical evaluation are needed to determine whether these responses are reproducible and whether locally produced FOM can remain economically viable after its full production and delivery costs are included.

Subject of Research: Fermented organic manure effects on rice–wheat productivity, soil fertility and economics in Uttar Pradesh

Article Title: Integrated effects of fermented organic manure on soil fertility, productivity, and economic performance of the rice–wheat cropping system in Uttar Pradesh

Article References: Singh, R., Singh, A. K., Yadav, P., Yadav, S., Singh, A., Pandey, S. R., Singh, V. K., Raghubanshi, N., Singh, Y. P., Kumar, M., Singh, S., & Kumari, R. (2026). Integrated effects of fermented organic manure on soil fertility, productivity, and economic performance of the rice–wheat cropping system in Uttar Pradesh. Frontiers in Sustainable Food Systems, 10, Article 1968370. https://doi.org/10.3389/fsufs.2026.1968370

Image Credits: AI Generated

DOI: 10.3389/fsufs.2026.1968370

Keywords: fermented organic manure, rice–wheat cropping system, grain yield, soil organic carbon, available nutrients, integrated nutrient management, economic returns, field demonstrations, Uttar Pradesh, Integrated, effects, fermented

The study, conducted by researchers at Banaras Hindu University in Varanasi and published in the journal Discover Soil, grew out of a growing anxiety about potassium mining in one of the world’s most intensively farmed regions. The rice-wheat cropping system that dominates the Indo-Gangetic plains supplies more than half of the food consumed in India, occupying roughly 27 percent of the country’s agricultural land. Yet fertilizer use in India has become badly skewed: between 1971-72 and 2021-22, nitrogen consumption surged 11.3-fold and phosphorus 14.2-fold, while potassium rose only 5.71-fold. The current national ratio of nitrogen to phosphorus to potassium stands at 6.7:2.4:1, far from the 4:2:1 ratio long recommended by the Fertiliser Association of India. An estimated 72 percent of India’s agricultural land is now considered potassium deficient.

Why does this imbalance matter? Potassium is not a minor player in crop physiology. It governs enzyme activation, water regulation, photosynthesis, and the transport of sugars, all of which feed directly into yield, grain quality, and the plant’s resilience to stress. When farmers skimp on potassium while piling on nitrogen, they quietly draw down the soil’s native reserves, a process scientists call potassium mining. Crop residues complicate the picture further: rice and wheat straw is extraordinarily rich in potassium, containing 80 to 85 percent of the nutrient taken up by the plant, and returning it to the field can substitute for 20 to 50 percent of potassium fertilizer. In conservation agriculture systems, where residues are retained on the soil surface and tillage is minimized, this recycling loop changes the chemistry of potassium availability in ways that conventional soil tests were never designed to capture.

To find out which chemical extractants best reflect reality under these conditions, the team turned to a long-term experiment established in 2012 at the university’s agricultural research farm. The site sits on sandy loam soils of the Typic Ustochrept family in a humid subtropical climate with about 1,110 millimeters of annual rainfall. The experiment followed a split-plot design with four crop establishment methods, ranging from full conventional tillage to full conservation agriculture with residue retention in both seasons, crossed with three nutrient management levels. After eleven complete crop cycles, the researchers sampled soil from all 36 plots at a depth of 0 to 15 centimeters and subjected it to a battery of twelve different potassium extractants.

The extractants spanned four mechanistic families. Distilled water and dilute salt solutions such as calcium chloride, barium chloride, ammonium acetate, sodium acetate, and sodium tetraphenyl boron target the potassium held in soil solution and on exchange sites. Multi-nutrient extractants, including ammonium bicarbonate-DTPA and the Mehlich solutions, pull several nutrients simultaneously. Acidic extractants, including strontium chloride mixtures and boiling nitric acid, attack the mineral lattice itself, releasing the non-exchangeable potassium locked between the layers of clay minerals. The logic is that plants do not simply sip from the soil solution; as roots deplete it, potassium desorbs from exchange sites and, over longer timescales, is released from mineral interlayers. A good soil test should mimic that whole cascade.

The results were striking. Boiling nitric acid extracted the most potassium, between 1,042 and 1,189 milligrams per kilogram of soil, followed by sodium tetraphenyl boron at 407.8 to 495.5 milligrams per kilogram, because both tap the non-exchangeable reservoir. At the other extreme, distilled water pulled out a mere 13.98 to 20.63 milligrams per kilogram. The workhorse ammonium acetate test extracted between 46.33 and 62.86 milligrams per kilogram, a middling figure that belies its global status. Among exchangeable-potassium extractants, barium chloride was the most aggressive, yielding 251.15 to 277.41 milligrams per kilogram, likely because barium is not preferentially adsorbed and does not collapse the expanded clay structures that hold potassium.

Correlation analysis revealed the real story. Sodium acetate emerged as the standout performer, correlating strongly with sodium tetraphenyl boron (r = 0.979), with relative grain yield (r = 0.927 to 0.984), with plant potassium uptake (r = 0.930 to 0.974), and with key soil indices such as cation exchange capacity, specific surface area, and organic carbon. The conventional ammonium acetate test performed respectably but less impressively, with correlations of 0.80 to 0.94 against plant indices. The acidic extractants fared worst: strontium chloride at 0.002 molar showed correlations as weak as 0.231 and no significant relationship with yield, while even boiling nitric acid, despite extracting the largest quantity of potassium, correlated poorly with what plants actually achieved. The researchers attribute sodium acetate’s advantage to its ability to pull water-soluble and exchangeable potassium along with a fraction of the non-exchangeable pool, capturing a broader spectrum of the potassium a crop can access during a growing season.

The team also established critical concentration thresholds using the Cate-Nelson statistical procedure, which partitions soil test values into ranges below which crops respond to fertilizer and above which they do not. Most extractants predicted critical levels with high coefficients of determination between 0.63 and 0.76. The critical value for ammonium acetate ranged from 51 to 54 milligrams per kilogram, while sodium acetate fell between 108 and 116 milligrams per kilogram. Boiling nitric acid produced the highest critical concentration, 1,224 milligrams per kilogram, but with the weakest predictive power, a coefficient of determination of only 0.35 to 0.46. Notably, critical values differed between rice and wheat for the same extractant, a reminder that soil test interpretation cannot be divorced from crop identity.

The agronomic findings were equally telling. Plots under full conservation agriculture, with residue retention in both seasons and minimal soil disturbance, outyielded conventionally tilled plots by 8.47 percent in rice and 10.72 percent in wheat, and recorded the highest potassium uptake, reaching 135.7 kilograms per hectare in rice and 112.4 kilograms per hectare in wheat. Residues appear to work through two mechanisms: their decomposition releases organic acids that dissolve potassium-bearing minerals, and the straw itself delivers a substantial potassium input back to the soil. Full conservation agriculture also raised cation exchange capacity by 19.4 percent relative to conventional tillage and boosted easily oxidizable organic carbon by 64.32 percent, changes that increase the number of adsorption sites available to hold and release potassium. Interestingly, additional potassium fertilizer did not significantly raise grain yields in this experiment, underscoring how much the residue-recycling system was already supplying.

The implications ripple outward from a single research farm in eastern Uttar Pradesh. Soil test calibration is inherently local, dependent on soil mineralogy, climate, and cropping system, and no single extractant works universally. But the message from Varanasi is clear: the global default test for potassium, ammonium acetate, captures only part of the story in soils where non-exchangeable potassium feeds crops, and it may systematically misjudge the potassium supplying power of conservation agriculture systems. Sodium acetate and the multi-nutrient extractants AB-DTPA, Mehlich I, and Mehlich III, which tap all or part of the non-exchangeable pool, tracked crop performance more faithfully. For a country where potassium fertilizer is expensive and farmers already under-apply it, a soil test that better reflects what the soil can actually deliver could save money, slow the mining of native reserves, and help sustain the rice-wheat system that feeds hundreds of millions. The researchers caution that their calibration must be validated across wider cropping systems, but the direction is unmistakable: the chemistry of measuring potassium needs to catch up with the agriculture it is meant to serve.

Subject of Research: Evaluation of chemical soil extractants for measuring plant-available potassium in long-term conservation agriculture rice-wheat systems

Article Title: Evaluating suitability of chemical extractants for measuring available soil potassium under long term conservation agriculture

Article References: Deepak, Jha, S., Singh, U. P., & Rakshit, A. (2026). Evaluating suitability of chemical extractants for measuring available soil potassium under long term conservation agriculture. Discover Soil, 3(1), Article 170. https://doi.org/10.1007/s44378-026-00330-w

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00330-w

Keywords: soil potassium, chemical extractants, conservation agriculture, rice-wheat system, ammonium acetate, sodium acetate, soil testing, Indo-Gangetic plains, non-exchangeable potassium, critical concentration, Cate-Nelson, crop residue retention

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