Inorganic Fertilizer Research Articles

Long-term organic fertilization reduces cadmium bioavailability via enhanced binding to organic fractions and Fe-bearing minerals.

Interfacial engineering-tailored Mn-clay-based nanozyme for glyphosate laccase-amplified sensing and inhibitor screening.

Organic–inorganic compound fertilizer application technology is a key technology for chemical fertilizer efficiency improvement, and stable grain yield increase. However, current agricultural machinery is unable to achieve uniform application of both organic and inorganic fertilisers. This study has compared two modeling methods and optimally selected the EDEM-Fluent coupled method. It aims to investigate the mechanism by which four factors—namely inorganic fertilizer drop location (Polar angle: −80° to 80°, polar radius: 60 mm to 180 mm), organic fertilizer flow rate (875–3500 g·s−1), inorganic fertilizer proportion (10–50%), and fertilizer spreading disc rotational speed (300–700 r·min−1)—influence inorganic fertilizer uniformity. A Box–Behnken test was designed with the pole angle and pole diameter of the drop location, organic fertiliser flow rate, spreading disc rotational speed, and coefficient of variation in the uniformity of the inorganic fertilisers as indexes. The Box–Behnken test divided the fertiliser drop location into left and right parts and established a mathematical model of fertiliser drop location, rotational speed, and organic fertiliser flow rate. Finally, the predictive performance of the model was verified in the field by testing four scenarios: low speed–low flow rate, low speed–high flow rate, high speed–low flow rate, and high speed–high flow rate. The root mean square error (RMSE) between the EDEM-Fluent coupled test and the bench test is 1.53, which is better than the RMSE (2.55) between the EDEM test and the bench test. Before optimization, the coefficients of variationof inorganic fertilizer (ICV) under four operating conditions were 28.93%, 32.43%, 38.17%, and 29.32% respectively. After optimization, the corresponding values were 19.34%, 23.78%, 21.45%, and 23.10% respectively. Compared with the pre-optimization results, the organic fertilizer coefficient of variation (OCV) remained stable, while the inorganic fertilizer coefficient of variation (ICV) decreased by an average of 10.29%. This study greatly improved the uniformity of inorganic fertiliser in the organic–inorganic spreader and provides a basis for subsequent intelligent spreaders.

Reduction in crop growth potential is major hurdle in reaching the desired crop productivity under rice-maize (RM) cropping system. To address the issue, the experiment was conducted at Indian Council of Agricultural Research-Central Rice Research Institute (ICAR-CRRI), Cuttack during 2022-23 and 2023-24 with four production systems: Conventional + Sole Crop (CSC), Conventional + Inter Crop (CIC), Conservation Agriculture + Sole Crop (CASC) and Conservation Agriculture + Inter Crop (CAIC) under three nutrient management strategy: Recommended dose of fertilizer (RDF) (NR), 25 % N (N25) and 50 % N (N50) based substitution of RDF with FYM (farm yard manure) using split plot design. The results reflect that the overall crop growth was significantly affected by both production systems and nutrient management practices. The plant height, leaf area index (LAI) and dry matter accumulation (DMA) were found higher under conventional system. The N25 and N50 performed better than NR though not to a significant extent. The experiment concludes that substituting inorganic fertilizers with organic sources and conservation agriculture practices can enhance the crop growth under RM cropping system.

Continuous and excessive use of inorganic fertilizers underlies current global crop production; therefore, reducing fertilizer use while increasing crop productivity is critical for ensuring agricultural sustainability and food security. Here we show that the natural variant of RCN2, a rice TERMINAL FLOWER 1/CENTRORADIALIS homolog, enhances photosynthesis, nitrogen assimilation and grain yield by restricting chromatin loop extrusion. RCN2 competitively inhibits the interaction between growth-repressing DELLA proteins and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE transcription factors, breaking the green revolution trade-off between plant growth and metabolism of carbon and nitrogen. We demonstrate that targeting CCCTC-containing insulator elements at the RCN2 locus confers not only decoupling tillering and panicle branching without affecting beneficial semi-dwarfism, but also improves source-to-sink carbon allocation and nitrogen-use efficiency, consequently increasing harvest index and rice yield at low nitrogen fertilization levels. Precise modulation of loop extrusion thus enables new breeding strategies to reduce nitrogen fertilizer use in high-yield cereal crops.

Purpose The purpose of this paper is to examine the complex relationship between agricultural input subsidies and environmental sustainability in India. It specifically looks at how fertilizer, power and irrigation subsidies affect the environment and compares how much they contribute to greenhouse gas (GHG) emissions from farming activities. Design/methodology/approach The study utilizes an autoregressive distributed lag model within a time-series framework, examining data from 1981 to 2020. The model delineates both the short-term and long-term interactions between input subsidies and GHG emissions, thereby quantifying the degree to which subsidized inputs exacerbate environmental externalities. Findings The results show that subsidies for fertilizer and power greatly raise emissions, with the power subsidy having the most intense emissions. The irrigation subsidy, on the other hand, has no effect on emissions. These results show that different parts of the subsidy have different effects on the environment. They also show the tradeoffs between making farming more productive and keeping the environment healthy. Research limitations/implications This study extends the subsidy–productivity framework by empirically linking input subsidies to greenhouse gas emissions, thereby illustrating a rebound effect akin to the Jevons Paradox in Indian agriculture. It highlights the need to incorporate environmental dimensions into existing theories that have traditionally focused only on yield enhancement and farmer welfare. Practical implications The findings underscore the need to redesign subsidy programs by gradually shifting away from inorganic fertilizer subsidies toward cash transfers that incentivize organic and low-carbon alternatives. Policymakers should integrate agri-environmental schemes, promote renewable energy use in farming and provide farmer training on climate-smart practices to align agricultural productivity goals with long-term sustainability. Originality/value This research provides original insights by measuring the varying emission intensities of agricultural input subsidies in India. The study provides a comprehensive framework by combining empirical evidence with policy implications, facilitating the formulation of environmentally sustainable agricultural policies that mitigate emissions while maintaining productivity.

This study evaluated the impact of various organic amendments on yield, nutrient uptake and protein content in mung bean (Vigna radiata L.) during the Kharif 2022 in a randomized block design (RBD) with four replications and eleven treatments. The results indicated that the application of TRDF + R + J (Recommended dose of fertilizers + Rhizobium + Jeevamrutam) significantly increased the grain yield compared to TRDF (Recommended dose of fertilizers) and was statistically at par with TRDF + R (Recommended dose of fertilizers + Rhizobium). However, the treatment TRDF + V + R + J (Recommended dose of fertilizers + Vermicompost + Rhizobium + Jeevamrutam) resulted in a significantly higher grain yield compared to TRDF + V + R (Recommended dose of fertilizers + Vermicompost + Rhizobium). The combined application of organic manures specifically a mixture of vermicompost, Rhizobium and Jeevamrutam (TV+R+J) significantly enhanced nitrogen (N) and phosphorus (P) uptake in both grain and straw compared to individual applications. Notably, the application of recommended doses of fertilizers (TRDF) yielded higher N uptake in grain relative to Jeevamrutam and vermicompost alone, but did not surpass the combined organic amendment application. Enhanced N and P uptake was also observed with (TRDF) in conjunction with organic amendments, particularly when combined with Rhizobium and vermicompost. Furthermore, protein content in mung bean grains significantly increased with the application of (TV+R+J), outperforming single applications of Rhizobium, Jeevamrutam and vermicompost. While (TRDF) alone raised protein levels compared to Jeevamrutam, it was not significantly different from (TV+R+J). The study concludes that integrated organic amendments provide superior benefits in nutrient uptake and protein enhancement in mung bean, suggesting a sustainable approach to improve crop yield and nutritional quality. These findings underscore the importance of combining organic and inorganic fertilizers for optimal mung bean cultivation.

Animal manure application is widely recognized for its agronomic benefits in enhancing soil fertility and crop productivity through organic matter enrichment and nutrient supply, but the critical application time governing its greenhouse gas emission trade-offs remains unresolved. The objective of this study was to investigate the effects of pig manure compost application timing on nitrous oxide (N2O) emissions and maize yields in Northeast China through a four-year field experiment. The treatments included: (1) inorganic fertilizers (NPK); (2) NPK plus pig manure compost applied in spring (NPK-MS); and (3) NPK plus pig manure compost applied in autumn (NPK-MA). The N2O fluxes, NH4+-N contents, NO3−-N contents, and maize yields were analyzed. The results showed that compared with NPK, NPK-MA increased N2O emissions by 44.4%. Applying pig manure compost in autumn promotes N2O emissions during the freeze–thaw period. However, there was no significant effect of NPK-MS on N2O emissions compared with NPK (p > 0.05). Spring-applied manure compost (NPK-MS) resulted in an 11.9% increase in maize yield compared to NPK. In contrast, autumn-applied manure compost (NPK-MA) did not significantly affect maize yield (p > 0.05). Furthermore, yield-scaled N2O emissions were significantly increased in NPK-MA (p < 0.05). Overall, spring application of pig manure compost is recommended for increasing maize yield without significantly increasing N2O emissions while in Northeast China.

The objective of this work was to evaluate the effect of organic and inorganic fertilization on the physiological and productive variables of tomato-mate crops grown in a greenhouse. A completely randomized design was used with four treatments T1 (100% worm leachate), T2 (65% worm leachate + 35% nutrient solution), T3 (50% worm leachate + 50% nutrient solution) and a control (100% nutrient solution). The response variables evaluated were plant growth, yield and fruit size. The results indicated that T3 produced a higher yield of 171.6 t ha⁻¹, being significantly superior to the other treatments in fruit size and weight, while T1 showed nutritional limitations in growth and development. The combination of worm leachate and nutrient solution (T3) reduced the use of chemical fertilizers by 50%, promoting more sustainable agriculture and maintaining high levels of productivity

<p>The response of soil structure to nutrient management may vary across environments. Poultry manure (PM) and/or inorganic fertilizers (IF) effects on soil pH, organic carbon (SOC), and hydraulic properties were assessed in derived savannah sandy-clay-loam Ultisols and rainforest sandy-loam Alfisols of Nigeria during 2013-2015. The Ultisols were inherently lower in soil pH and SOC than the Alfisols. Three PM rates (0, 5, and 10 t ha<sup>–1</sup>), each with four NPK/Urea-based IF levels (0, 50, 100, and 150%), were applied in 2013 and 2014 but not in 2015. At crop (maize) maturity, treatment affected the Ultisols more distinctly than the Alfisols. Regardless of IF level, PM<sub>10</sub> and PM<sub>5 </sub>resulted in optimal soil pH (Ultisols) and hydraulic properties (Alfisols), respectively. Treatment PM<sub>10</sub>+IF<sub>50</sub> produced overall optimal effects in 2014 and 2015, being among the highest for SOC in the Ultisols (13.30 and 10.23 g kg<sup>–1</sup>, respectively) and Alfisols (16.10 and 11.60 g kg<sup>–1</sup>, respectively). Its substitutes for soil pH and hydraulic properties were PM<sub>10</sub>+IF<sub>0</sub> (Ultisols) and PM<sub>5</sub>+IF<sub>0</sub> (Alfisols). Unlike most PM-based treatments, sole IFs, especially PM<sub>0</sub>+IF<sub>150</sub>, had pronounced soil-acidifying effects in the Ultisols. The SOC and permeability depended almost entirely on PM across IF levels. Soil pH and SOC were positively correlated with total porosity (Ultisols) and permeability (both soils), with <em>r</em> = 0.60-0.93 (Ultisols) and 0.42-0.66 (Alfisols). Effective PM+IF may not always outperform PM regarding soil pH/SOC, whose influence on soil hydraulic properties can be location-specific. This calls for pre-adoption validation of promising PM+IF options in new tropical agro-environments.</p>

The use of compost in extensive cropping systems is not economically viable due to the high application rates required to meet nutrient requirements. However, compost pelleting increases nutrient concentration while reducing storage, distribution, and application costs. This study evaluated the effects of compost pellets fertilization compared to conventional management on agronomic efficiency and environmental impact in wheat production. Eleven treatments were applied in triplicate to 24m² plots during the 2022-2023 wheat cycle, combining high phosphorus pellets at sowing (50kg P ha-¹) and high-nitrogen pellets at tillering (150kg N ha-¹). Fertilizers included (i) organic pellets (OF) enriched with agri-food by-products, (ii) organic-mineral pellets (OMF), and (iii) synthetic fertilizers (IN). Soil nutrient availability (Pext, N-NH₄⁺, N-NO₃-) and physico-chemical properties were assessed at day 0 and after harvest (210 days). Yield, grain quality, and greenhouse gas emissions (GHG) were monitored to evaluate the environmental impact of these fertilizers. The results showed that compost pellets combined with inorganic fertilizers achieved wheat yields comparable to conventional fertilization, maintaining grain quality while reducing GHG emissions in the OMF treatments. Therefore, organo-mineral pellet fertilizers represent a promising strategy for nutrient cycling in agroecosystems, reducing reliance on inorganic fertilizers and maintaining wheat productivity under Mediterranean conditions without increasing GHG emissions.

Soil acidity is a global problem that limits crop production worldwide. It is the major crop yield-limiting factor in Ethiopia. The experiment was conducted in the Guagusa Shikudad district in western Amhara during the 2021 and 2022 cropping seasons to improve the productivity of faba bean through integrated vermicompost and lime applications. The spacing between rows and plants was 40 and 10 cm, respectively and the gross plot size was 8.4 m². The treatments were zero, half and full lime factorially combined with 0, 5, 10, and 15 t ha ⁻ ¹ vermicompost. Vermicompost and lime were applied separately in rows at planting. The experiment was laid out in a randomized complete block design with three replications. Before planting, a composite surface soil sample at 0–20 cm depth and after harvest from each plot was collected for the determination of soil chemical properties. The soil analysis result indicated that vermicompost and lime significantly increased soil pH and decreased exchangeable acidity. The result also revealed vermicompost and lime significantly (p < 0.001) increased faba bean grain and biomass yield. The maximum faba bean grain yield (2.41 t ha ⁻ ¹) was recorded from the applied 10 t ha ⁻ ¹ vermicompost and full dose of lime (5.6 t ha ⁻ ¹), while the maximum faba bean biomass (5.90 t ha ⁻ ¹) was recorded from the treatment of 15 t ha ⁻ ¹ vermicompost and full dose of lime applied. The minimum grain and biomass yield of faba bean was recorded from the control (vermicompost and lime not applied). Application of 5 t ha ⁻ ¹ vermicompost and a full dose of lime gave an optimum and economical faba bean grain yield. Application of integrated organic and inorganic fertilizers with lime is suggested for the improvement of faba bean grain yield by restoring non-responsive, strongly acidic agricultural soils in the study area and similar agroecology.

Capsicum (Capsicum annuum L.) is a commercially grown vegetable crop that requires an adequate and balanced nutrient supply for optimal yield and quality. The imbalanced use of inorganic fertilizers has detrimental effects on the soil as well as on the environment. The adoption of Integrated Nutrient Management (INM) thus offers a holistic solution that ensures both immediate and sustained nutrient availability by limiting the use of chemical fertilizers. Keeping this in view, the present investigation was conducted to evaluate the effect of the integrated application of nutrients from different sources on the major nutrient composition and uptake by capsicum plants. The experiment was laid out in a randomized block design (RBD) at the Vegetable farm, Department of Horticulture, Banaras Hindu University, Varanasi, during two rabi seasons 2022-23 and 2024. The experiment consisted of eleven treatments and three replications, with various combinations of organic manures namely, vermicompost, farmyard manure, poultry manure, recommended doses of fertilizers (RDF: 150:60:60 NPK kg/ha), and biofertilizers (Azospirillum and phosphate-solubilizing bacteria). Results revealed that INM treatments significantly enhanced the nitrogen, phosphorus, and potassium content and their uptake as compared to sole organic or inorganic sources. The treatment T8 (RDF 75% + Vermicompost 25% + Azospirillum and PSB 2.5 kg/ha each) consistently recorded the highest nutrient contents: nitrogen (3.61%), phosphorus (0.64%), and potassium (3.96%). Treatment T8 also displayed the maximum uptake of nitrogen (103.61 kg/ha), phosphorus (25.88 kg/ha), and potassium (59.07 kg/ha) across both years. The study suggests that application of organic manures and biofertilizers in combination with inorganic fertilizers improves nutrient uptake and offers a sustainable approach for better productivity of capsicum.

Dependence on chemical fertilizers has caused a decline in soil quality, groundwater contamination, and rising agricultural production costs due to unstable fertilizer prices. In recent years, frequent fertilizer crises have revealed the fragility of reliance on inorganic fertilizers within the national agricultural system. Hence, a transformation toward environmentally friendly and sustainable agriculture is urgently required. This study employed a scoring technique to analyze field observation data, which were narrated based on the written methodology. Respondents’ answers were categorized and classified according to their assumptions or opinions, with scores determined using a Likert scale. The Likert scale measures attitudes, opinions, and perceptions of individuals or groups regarding specific social phenomena. The results showed that key driving factors—such as affordable fertilizer prices, support from agricultural extension workers, and social encouragement from the community—achieved scores above 82%. This finding indicates that external conditions are quite favorable for promoting the use of organic fertilizers. However, major challenges remain, including the limited availability of organic fertilizers in the field and farmers’ long-standing dependency on chemical fertilizers. To address these challenges, it is essential to enhance the market availability of liquid organic fertilizers (POC) through collaboration between producers and farmer groups. Continuous technical assistance should be provided, including demonstration plots that display tangible improvements in rice yields using POC. Furthermore, government support in the form of targeted subsidies or special incentives for farmers transitioning to organic fertilizers is vital, while strengthening the role of farmer groups and agricultural extension workers as catalysts for the adoption of environmentally friendly innovations.

BackgroundSoil microbes play a central role in nutrient recycling in soils: however, the genetic mechanisms governing their responses to long-term fertilization remain poorly understood. While the agronomic benefits of long-term fertilization are well-documented, the genetic mechanisms and ecological processes underlying microbial community responses to different fertilization regimes remain poorly understood, particularly in unique soil systems such as black soils (Mollisols), which are critical for global food security. A deeper insight into how organic and inorganic fertilizers influence microbial assembly, functional potential, and community stability is essential for developing sustainable soil management practices.ResultsThis study deciphers microbial assembly mechanisms, functional gene dynamics, and community restructuring in black soils subjected to 44 years of chemical fertilizer (CF), manure amendment (M), and integrated chemical fertilizer with manure (CFM) treatments. Results revealed that CF significantly enhances functional gene abundance related to carbon (C) degradation (e.g., starch, cellulose, chitin and lignin) and nitrification, accelerating the conversion of recalcitrant C to labile C pools and ammonium to nitrate. Conversely, M and CFM treatments promote microbial diversity and stability while decelerating nutrient transformation processes. In addition, microbial assembly mechanisms shift from stochastic to deterministic processes with long-term fertilizer application in CF. The structural equation modeling (SEM) indicated that soil chemical properties shape both the diversity and composition of taxonomic and functional gene communities which subsequently regulate microbial -mediated nutrient cycling processes and crop yield.ConclusionsOur findings highlight the trade-offs between microbial functional potential and community stability under contrasting fertilization strategies, emphasizing the need to integrate microbial metrics into sustainable land management frameworks.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40793-025-00791-6.

India's food security plan relies heavily on wheat, which is grown second only to rice. But because of its heavy production with chemical fertilizers, soil health has declined, input costs have gone up, and ecological issues have arisen. A sustainable method for preserving soil fertility and raising agricultural profitability is Integrated Nutrient Management (INM), which blends inorganic fertilizers, organic additions, and biofertilizers. This study assessed the effects of INM on soil health metrics and the economics of growing wheat under nine treatments using a randomized block design. It was carried out at the Agronomy Research Farm of Himgiri Zee University, Dehradun, during the Rabi season of 2023–2024. In addition to lowering pH and electrical conductivity, the results demonstrated that the combined application of 80% RDF + vermicompost (2.9 t/ha) + biofertilizers (Azotobacter + PSB) greatly increased soil organic carbon (0.58%), available nitrogen (155.25 kg/ha), and phosphorus (14.51 kg/ha), indicating improved soil health. In terms of economics, the 100% RDF treatment produced the highest net return (₹36,945/ha) and benefit-cost (B:C) ratio (1.32), even though this integrated treatment had the highest gross return (₹72,250/ha). The results emphasize that although INM promotes sustainable production and enhances soil quality, increased input costs may short-term restrict economic returns. Therefore, improving sustainability and profitability in wheat-based cropping systems requires optimizing the mix of nutrient sources.

The loss of nitrogen and phosphorus and their environmental impacts have global relevance. The loss of nitrogen and phosphorus threatens aquatic organisms but also poses a potential threat to the human living environment and health. This issue mainly stems from the extensive use of these elements in agricultural activities. Agriculture is the main consumer of nitrogen and phosphorus globally, and excessive use of nitrogen and phosphorus fertilizers has led to serious pollution problems. This study examined the source control of nitrogen and phosphorus loss mechanisms through reducing fertilizer levels and combining organic and inorganic fertilizers in wheat‒rice double-cropping fields. Field plot experiments were carried out for ten consecutive years (2014–2023), and three treatments were set up: conventional fertilization (CK), fertilizer reduction (10% reduction in seasonal nitrogen and phosphorus in wheat, 15% reduction in seasonal nitrogen and phosphorus in rice) (KF), and combined application of organic and inorganic fertilizer (BMP). This article only analyzes data related to 2023. Compared with CK treatment, BMP treatment reduced the average mass concentration of total nitrogen (TN) and total phosphorus (TP) in the runoff water by 10.92% and 7.96%, respectively. Compared with CK treatment, BMP treatment in leached water reduced the average mass concentration of total nitrogen (TN) by 14.65% and 11.00%, and total phosphorus (TP) by 22.63% and 4.99% in wheat and rice seasons, respectively. Compared with those of CK, the TN contents of wheat and rice treated with BMP significantly decreased by 22.39% and 14.86%, and the TP losses decreased by 20.00% and 12.98%, respectively. The implications of these findings are promising: the combined application of organic and inorganic fertilizers in the wheat‒rice rotation mode can ensure crop yield, increase soil nutrient retention, reduce nitrogen and phosphorus loss, and maintain the soil nutrient balance.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-19459-9.

IntroductionOrganic amendments like manures, sludges, and composts have significant potential to enhance soil’s physical, chemical, and microbiological conditions, aiding in the restoration of soils disturbed by intensive agricultural practices and compensating for losses due to plant pathogens. This study investigates the effects of background fertilization with organic amendments and inorganic fertilizers on the root-knot nematode (RKN) disease in cucumber and the functioning of the soil ecosystem.MethodsField trials were conducted in a greenhouse infested with Meloidogyne incognita, applying six background fertilization treatments: fresh cow manure, composted cow manure, fresh chicken manure, pelletized chicken manure, slow-release inorganic fertilizer, and fast-release inorganic fertilizer. Each amendment was adjusted to provide equivalent units of N-fertilization. After 120-day crop cycles, total fruit production and RKN-disease severity were evaluated, along with nematode-based indices.ResultsThe fresh chicken manure treatment yielded the highest cucumber production, despite no significant differences in RKN-disease severity between treatments. Different organic amendments influenced RKN mortality at transplanting, with fresh chicken manure being the most effective in reducing RKN abundances in soil, followed by pelletized chicken manure, fresh cow manure, and composted cow manure. The inorganic fertilizers were the least effective in reducing RKN soil abundances. Organic amendments increased the complexity of the soil food web, whereas fast-release inorganic fertilizers led to its degradation and simplification. Cucumber cultivation and fertigation throughout the crop cycle enriched the soil with nutrients, intensified the bacteria-dominated organic matter degradation channel, and further simplified the soil food web.DiscussionThis study demonstrates the potential of organic amendments to enhance soil health and partially suppress root-knot nematode disease in cucumber.

The present study observation on the synergistic effects of inorganic fertilizers combined with Jeevamrutha and Beejamrutha on soil microbial and enzymatic properties in pearl millet cultivation during 2023 and 2024. The experiment assessed key soil parameters, including dehydrogenase, urease, and phosphatase activities, as well as microbial biomass nitrogen (MBN), microbial biomass carbon (MBC), and populations of nitrogen fixers, phosphorus solubilizers, and actinomycetes at 0-20 cm soil depth. Results demonstrated that the integrated application of Jeevamrutha and Beejamrutha with inorganic fertilizers significantly enhanced soil microbial activity across all parameters studied. The highest dehydrogenase and urease activities were observed in treatments with 100% RDF + Jeevamrutha + Beejamrutha (T11), reaching 62 µg TPF g-1 soil-1 day-1 and 61 µg NH₄⁺-N g-1 soil hr-1 in 2023, respectively. Similarly, microbial biomass carbon and nitrogen also increased significantly in T11, with values of 381 µg C g-1 soil and 46 µg N g-1 soil in 2023. The integration of organic amendments improved nutrient cycling, microbial biomass, and overall soil fertility. These findings indicate that combining organic bioenhancers with conventional inorganic fertilizers offers a promising approach to enhancing soil health and sustainability in agricultural practices.

Abstract Macroalgal extracts offer an alternative option to increase crop yields and plant performance whilst reducing reliance on inorganic chemical fertilisers. Macroalgae have high concentrations of bioactive compounds capable of enhancing crop growth, stress tolerance and pest resistance. This study investigated whether seasonal variation in the chemical composition of three brown seaweeds Ascophyllum nodosum, Fucus serratus and Fucus vesiculosus affected plant growth in Arabidopsis thaliana, Beta vulgaris and Lactuca sativa through different extract concentrations. Crops were treated with 1:20, 1:50 and 1:100 dilutions from macroalgal extracts and compared to controls tap water, deionised water and one commercial macroalgae-based fertiliser made from A. nodosum. Dry weight assessment results revealed that moderately diluted dosages had better effects on plant growth than concentrated dosages, showing that the most suitable concentrations of all macroalgae extracts are 1:50 for Arabidopsis; no trend was detected in B. vulgaris or L. sativa growth. Overall, there were peaks of increased plant growth when treated with extracts harvested in June and August, which correlates with fertility peaks in commercial brown macroalgae in the wild. These results suggest that the optimal harvest for A. nodosum, F. serratus and F. vesiculosus for plant stimulant products should occur between May and August at sustainable harvest levels. Soil respirometry trials using the extracts showed no differences in CO2 fluxes between the macroalgal species, different harvesting seasons, or correlation with plant biomass. It is therefore likely that macroalgal extracts impact the plant directly and produce minor impact on soil microbiota. Thus, these results support the use of macroalgal fertilizers as a low-cost and environmentally friendly alternative to chemical fertilisers.