Search Results (134)

Partial organic substitution (POS) is a promising strategy to enhance soil fertility and agricultural sustainability. However, the mechanisms by which varying organic substitution ratios affect soil quality and latex yields in rubber plantations remain unclear. We conducted a two-year field experiment in a rubber plantation with six treatments: no fertilizer (CK), 100% synthetic fertilizer (NPK), and synthetic nitrogen fertilizer substituted with 25% (25 M), 50% (50 M), 75% (75 M), and 100% (100 M) manure. The results indicated that POS treatments significantly increased pH, soil organic carbon (SOC), total phosphorus (TP), total nitrogen (TN), NH₄⁺-N, enzyme activity, and leaf nutrient (C, N, and P) content compared to NPK. Compared with NPK, the soil quality (evaluated through the soil quality index, SQI) increased by 15.30–43.42% under POS across both years, with maximal values observed at 50 M (2020) and 75 M (2021); similarly, the latex yield increased by 2.10–18.60%. SOC, NO₃⁻-N,C:P ratio, TN, and pH are the key factors that influence soil quality and latex yield. Structural equation modeling indicated that fertilization and soil factors collectively explained 82% of the variation in latex yield. These results demonstrated that POS effectively alleviated soil acidity, enhanced soil quality, and improved latex productivity, with 50% manure substitution treatment (50M) identified as the optimal short-term substitution strategy in rubber plantations. Full article

Red soil regions commonly experience land degradation and low nutrient availability. Excessive fertilizer use in recent years has intensified these challenges, necessitating scientifically informed fertilization strategies to ensure agricultural sustainability. To identify optimal fertilization strategies for maize cultivation in Yunnan’s red soil regions, this study conducted field experiments involving partial substitution of nitrogen fertilizer with organic manure to determine whether this approach improves soil health and boosts maize yield. Four treatments were compared in a randomized complete block design over one growing season: no fertilization (NF), soil testing and formula fertilization (STF), 15% organic fertilizer (swine manure) replacing nitrogen fertilizer (OF15), and 30% organic fertilizer replacing nitrogen fertilizer (OF30). The results indicated that substituting organic fertilizer for nitrogen fertilizer reduced soil acidification while increasing total phosphorus (TP) and available phosphorus (AP), thereby enhancing soil physicochemical properties. Maize grown under OF30 exhibited improved agronomic traits including plant height, stem diameter, ear height, and ear length. Additionally, the partial replacement of synthetic fertilizer with organic fertilizer notably increased maize yield and the weight of 100 grains, but there was no significant difference (p < 0.05) between OF15 and OF30. Moreover, the OF30 treatment generated the highest economic return of 25,981.73 CNY·ha⁻¹. Correlation and principal component analyses revealed that substituting organic fertilizer for nitrogen fertilizer notably influenced total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), and yield, with maize yield positively correlated with TP and AP content. This study presents evidence that replacing 30% of nitrogen fertilizer with organic fertilizer is a viable strategy to enhance soil health, maize productivity, and profitability in Yunnan’s red soil regions, providing a crucial scientific foundation to support sustainable agricultural development in the region. Full article

Excessive chemical fertilizers degrade soil and increase greenhouse gas (GHG) emissions. Organic substitution of nitrogen fertilizers is recognized as a sustainable agricultural-management practice, yet its dual role in carbon sequestration and emissions renders the net GHG balance (NGHGB) uncertain. To assess the GHG mitigation potential of organic substitution strategies, this study analyzed GHG fluxes, soil organic carbon (SOC) dynamics, indirect GHG emissions, and Net Primary Productivity (NPP) based on a long-term field positioning experiment initiated in 2016. Six fertilizer regimes were systematically compared: no fertilizer control (CK); only phosphorus and potassium fertilizer (PK); total chemical fertilizer (NPK); 1/3 chemical N substituted with sheep manure (OF1); dual substitution protocol with 1/6 chemical N substituted by sheep manure and 1/6 substituted by straw-derived N (OF2); complete chemical N substitution with sheep manure (OF3). The results showed that OF1 and OF2 maintained crop yields similar to those under NPK, whereas OF3 reduced yield by over 10%; relative to NPK, OF1, OF2, and OF3 significantly increased SOC sequestration rates by 50.70–149.20%, reduced CH₄ uptake by 7.9–70.63%, increased CO₂ emissions by 1.4–23.9%, decreased N₂O fluxes by 3.6–56.2%, and mitigated indirect GHG emissions from farm inputs by 24.02–63.95%. The NGHGB was highest under OF1, 9.44–23.99% greater than under NPK. These findings demonstrate that partial organic substitution increased carbon sequestration, maintained crop yields, whereas high substitution rates increase the risk of carbon emissions. The study results indicate that substituting 1/3 of chemical nitrogen with sheep manure in maize cropping systems represents an effective fertilizer management approach to simultaneously balance productivity and ecological sustainability. Full article

The Mediterranean region is increasingly confronted with intersecting environmental, agricultural, and socio-economic challenges, including biowaste accumulation, soil degradation, and high dependency on imported fossil fuels. Biomethane, a renewable substitute for natural gas, offers a strategic solution that aligns with the region’s need for sustainable energy transition and circular resource management. This review examines the current state of biomethane production in the Mediterranean area, with a focus on anaerobic digestion (AD) technologies, feedstock availability, policy drivers, and integration into the circular bioeconomy (CBE) framework. Emphasis is placed on the valorisation of regionally abundant feedstocks such as olive pomace, citrus peel, grape marc, cactus pear (Opuntia ficus-indica) residues, livestock manure, and the Organic Fraction of Municipal Solid Waste (OFMSW). The multifunctionality of AD—producing renewable energy and nutrient-rich digestate—is highlighted for its dual role in reducing greenhouse gas (GHG) emissions and restoring soil health, especially in areas threatened by desertification such as Sicily (Italy), Spain, Malta, and Greece. The review also explores emerging innovations in biogas upgrading, nutrient recovery, and digital monitoring, along with the role of Renewable Energy Directive III (RED III) and national biomethane strategies in scaling up deployment. Case studies and decentralised implementation models underscore the socio-technical feasibility of biomethane systems across rural and insular territories. Despite significant potential, barriers such as feedstock variability, infrastructural gaps, and policy fragmentation remain. The paper concludes with a roadmap for research and policy to advance biomethane as a pillar of Mediterranean climate resilience, energy autonomy and sustainable agriculture within a circular bioeconomy paradigm. Full article

Partial substitution of mineral N fertilizer with manure (organic substitution) is considered as an effective way to reduce N input in intensive agroecosystems. Here, based on a 3-year field experiment, we assessed the influence of different organic substitution ratios (15%, 30%, 45%, and 60%, composted chicken manure applied) on vegetable productivity and soil physicochemical and biochemical properties as well as microbiome (metagenomic sequencing) in an intensive greenhouse production system (cucumber-tomato rotation). Organic substitution ratio in 30% got a balance between stable vegetable productivity and maximum N reduction. However, higher substitution ratios decreased annual vegetable yield by 23.29–32.81%. Organic substitution (15–45%) improved soil fertility (12.18–19.94% increase in soil total organic carbon content) and such improvement was not obtained by higher substitution ratio. Soil mean enzyme activity was stable to organic substitution despite the activities of some selected enzymes changed (catalase, urease, sucrase, and alkaline phosphatase). Organic substitution changed the species and functional structures rather than diversity of soil microbiome, and enriched the genes related to soil denitrification (including nirK, nirS, and nosZ). Besides, the 30% of organic substitution obviously enhanced soil microbial network complexity and this enhancement was mainly associated with altered soil pH. At the level tested herein, organic substitution ratio in 30% was suitable for greenhouse vegetable production locally. Long-term influence of different organic substitution ratios on vegetable productivity and soil properties in intensive greenhouse system needs to be monitored. Full article

Integrated application of chemical fertilizers with organic manure might improve crop yields and N-use efficiency (NUE, grain yield per unit N uptake), but the underlying physiological mechanisms are unclear. In this study, we aimed to examine the effects of combined inorganic and organic fertilizers on wheat biomass allocation, root growth, water-soluble carbohydrates (WSCs) translocation, leaf senescence, N uptake, and their relationship with yield and NUE. We established a 2-year factorial field experiment with five nutrient treatments with ratios of inorganic: organic fertilizers from 0 to 1, and three varieties—two new: Weilong169 and Zhongmai578; and one reference: Xiaoyan22. The yield ranged from 3469 to 8095 kg ha⁻¹, and it generally declined in response to a higher proportion of organic fertilizer. The NUE increased when there was a higher proportion of organic fertilizer. Weilong169 exhibited higher NUE than Zhongmai578, and both new cultivars outperformed the reference variety in the N harvest index. The yield correlated with leaf senescence traits and harvest index, and NUE was associated with WSC translocation and N uptake. The combination of fertilizers with a low portion of organic maintained yield and improved NUE; Weilong169 had the highest yield, NUE, and N harvest index. A low portion of organic manure substitution for chemical fertilizer suited all varieties. A new variety with a higher yield, N harvest index, and NUE highlights the importance of N traits in breeding programs. Full article

Afforestation with Pinus sylvestris var. mongolica in northern China is hindered by soil degradation. This study evaluated a ternary amendment combining sewage sludge (SS), cattle manure (CM), and maize straw (MS) to rehabilitate degraded sandy soils in the Horqin Sandy Land. Five treatments were tested: control (CK), SS (T1), SS + CM (T2), SS+MS (T3), and SS + CM + MS (T4). The ternary amendment (T4) achieved optimal outcomes: soil pH decreased from 8.02 to 7.79, organic carbon increased 2.5–fold, and total nitrogen (127%) and phosphorus (87.5%) were enhanced compared to CK. Pinus sylvestris exhibited a 65.6% greater basal diameter and 29.5% height increase under T4, while heavy metal concentrations (Cd: −54.6%, Cu: −35.1%, Pb: −12.2% and Zn: −27.6%) were reduced. These findings highlight a synergistic waste valorization strategy for dryland afforestation, balancing soil fertility improvement with ecological safety. Future studies should prioritize long-term microbial community dynamics and field-scale validation. Full article

Replacing partial chemical fertilizers with organic fertilizer can increase organic carbon input, change soil nutrient stoichiometry and microbial metabolism, and then affect soil organic carbon (SOC) storage. A 6-year field experiment was used to explore the mechanism of SOC storage under different ratios of manure substitution in northeast China, with treatments including chemical fertilizer application alone (nitrogen, phosphorus, and potassium, NPK) and replacing 1/4 (1/4M), 2/4 (2/4M), 3/4 (3/4M), and 4/4 (4/4M) of chemical fertilizer N with manure N. Soil nutrients, enzymatic activity, and SOC fractions were analyzed to evaluate the effect of different manure substitution ratios on SOC storage. A high ratio of manure substitution (>1/4) significantly increased soil total N, total P, total K, and available nutrients (NO₃⁻-N, available P, and available K), and the 4/4M greatly decreased the C/N ratio compared to the NPK. Manure incorporation increased microbial biomass carbon (MBC) by 18.3–53.0%. Treatments with 50%, 75%, and 100% manure substitution (2/4M, 3/4M, and 4/4M) enhanced bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and total microbial necromass carbon (MNC) by 31.9–63.5%, 25.5–107.1%, and 27.4–94.2%, respectively, compared to the NPK treatment. Notably, the increase in FNC was greater than that of BNC as the manure substitution ratio increased. The increasing manure substitution significantly enhanced particulate organic C (POC) and total SOC but did not affect mineral-associated organic C (MAOC). High soil N and P supplies decreased leucine aminopeptidases (LAPs) and alkaline phosphatase activities but increased the activity ratio of β-glucosidase (BG)/(N-acetyl-glucosaminidase (NAG) + LAP). Treatments with 25% manure substitution (1/4M) maintained maize and soybean yield, but with increasing manure rate, the maize yield decreased gradually. Overall, the high ratio of manure substitution enhanced SOC storage via increasing POC and MNC, and decreasing the decomposition potential of manure C and soil C resulting from low N- and P-requiring enzyme activities under high nutrient supplies. This study provides empirical evidence that the rational substitution of chemical fertilizers with manure is an effective measure to improve the availability of nutrients, and its effect on increasing crop yields still needs to be continuously observed, which is still a beneficial choice for enhancing black soil fertility. Full article

Circular economy in the context of municipal organic waste management has boosted the emergence of novel composting scenarios, such as community composting and decentralized urban composting in small installations, which favors localized management and valorization of organic waste streams. However, there is little information about the agronomic use of the composts obtained from these new organic waste management systems as an alternative for inorganic fertilization in crop production. In this work, municipal solid waste-derived composts from two decentralized composting scenarios (CM1 and CM2 from community composting, and CM3 and CM4 from decentralized urban small-scale composting plants) were applied and mixed in the top layer of a calcareous clayey-loam soil to assess their effects as alternative substitutes for conventional soil inorganic fertilization (IN) during two successive cultivation cycles of lettuce (Lactuca sativa L.) grown in pots with the amended soils. These treatments were also compared with an organic waste (goat–rabbit manure, E) and a control treatment without fertilization (B). The effects of the fertilizing treatments on the crop yield and quality, as well as on the properties of the soil considered were studied. In general, the application of the different composts did not produce negative effects on lettuce yield and quality. The compost-derived fertilization showed similar lettuce yields compared to the inorganic and manure-derived fertilizations (IN and E, respectively), and higher yields than the soil without amendment (B), with increases in the initial yield values of B, for the first cycle from 34.2% for CM1 to 53.8% for CM3, and from 20.3% for CM3 to 92.4% for CM1 in the second cycle. Furthermore, the organically amended soils showed a better crop development, obtaining higher values than the control treatment in the parameters studied. In addition, the incorporation of the organic treatments improved the soil characteristics, leading to 1.3 and 1.2 times higher organic matter contents in the soils with CM2 and in the soils with CM1, CM3, and E, respectively, compared to the control soil without fertilizing treatment (B), and 2.0 and 1.8 times greater organic matter contents, respectively, compared to soil with inorganic fertilization (IN). Therefore, the use of municipal solid waste-derived composts from these new organic waste management systems, such as the decentralized composting scenarios studied (community composting and urban decentralized small-scale composting plants), is presented, not only as a sustainable valorization method, but also as an alternative for the use of inorganic fertilizers in lettuce cultivation, while enhancing soil properties, contributing to increasing the circularity of agriculture. Full article

Green manure effectively improves soil nutrients and crop yields, yet its partial substitution for chemical nitrogen fertilizer (CF) in maize systems remains underexplored in ecologically fragile Karst landscapes. To assess the effect of alfalfa green manure on maize yield, soil nutrients, enzymes, and microorganisms, we conducted a two-year field experiment comprising eight treatments: four CF levels (100%, 80%, 60%, and 0% of recommended CF) applied alone or combined with alfalfa green manure (CF100, AL_CF100, CF80, AL_CF80, CF60, AL_CF60, CF0, AL_CF0). The results showed that maize grain yield decreased with the sole reduction of chemical N fertilizer. Compared to the CF100 treatment, the AL_CF100 and AL_CF80 treatments significantly increased grain yield by an average of 21.8% and 16.9%, respectively. Additionally, the AL_CF60 treatment maintained maize grain yield in 2020 and significantly increased it in 2021. The AL_CF100 treatment significantly enhanced soil available N (AN) content, while soil Olsen-P (SOP) content and soil quality index (SQI) were significantly improved in the AL_CF100, AL_CF80, and AL_CF60 treatments. Alfalfa green manure application had no significant effect on soil bacterial and fungal communities. However, the CF rates positively influenced the relative abundances of bacterial phyla (Bacteroidota, Myxococcota, and Patescibacteria) and genera (Intrasporangium, Streptomyces, and Quadrisphaera), as well as fungal genera (Exophiala and Setophoma). α-Diversity analysis revealed that partial substitution of CF with alfalfa green manure did not significantly affect soil bacterial diversity (Ace, Shannon, and Sobs indices) or richness (Chao value). In contrast, chemical N fertilizer rates significantly altered the β-diversity of both bacteria and fungi. The soil AN, AK, sucrase activity, and the relative abundances of Bacteroidota, Streptomyces, and Instrasporangium showed significant positive relationship with maize grain yield. This study demonstrates that substituting 20% CF with alfalfa green manure optimizes maize productivity while enhancing soil health in Karst agroecosystems. Full article

Balancing food security with fertilizer-driven climate impacts remains critical in intensive agriculture. While organic–inorganic substitution enhances soil fertility, its effects on nitrous oxide (N₂O) and nitric oxide (NO) emissions remain uncertain. This study evaluated N₂O/NO emissions, crop yields, and agronomic parameters in a subtropical wheat–maize rotation under four fertilization regimes: inorganic-only (NPK), manure-only (OM), and partial substitution with crop residues (CRNPK, 15%) or manure (OMNPK, 30%), all applied at 280 kg N ha⁻¹ yr⁻¹. Emissions aligned with the dual Arrhenius–Michaelis–Menten kinetics and revised “hole-in-the-pipe” model. Annual direct emission factors (EF_d) for N₂O and NO were 1.01% and 0.11%, respectively, with combined emissions (1.12%) exponentially correlated to soil nitrogen surplus (p < 0.01). CRNPK and OMNPK reduced annual N₂O+NO emissions by 15–154% and enhanced NUE by 10–45% compared with OM, though OMNPK emitted 1.7–2.0 times more N₂O/NO than CRNPK. Sole OM underperformed in yield, while partial substitution—particularly with crop residues—optimized productivity while minimizing environmental risks. By integrating emission modeling and agronomic performance, this study establishes CRNPK as a novel strategy for subtropical cereal systems, reconciling high yields with low greenhouse gas emissions. Full article

Potassium chloride (KCl) is the main source of potassium (K) in Brazilian agriculture, but its high import dependency and the need for split applications increase costs and expose the system to supply and efficiency risks. Understanding the availability and release kinetics of potassium (K) from biochar-based fertilizers (K-BBFs) is crucial for optimizing their use as full or partial substitutes for KCl in Brazilian agriculture. This study evaluated biochars derived from banana peel (BP), coffee husk (CH), and chicken manure (CM), both in their pure form and co-pyrolyzed with KCl (composites) at 300 °C and 650 °C, as K sources for corn grown in two contrasting Oxisols. For pure biochars, feedstock type and pyrolysis temperature significantly influenced K content and release kinetics. Higher pyrolysis temperatures increased K content in BP and CH biochars but not in CM, while also slowing K release in CH and CM. Co-pyrolysis with KCl increased biochar yield, ash content, and K availability. Composites released more K than pure biochar but less than KCl, and at a slower rate. Notably, banana peel biochar co-pyrolyzed with KCl at 650 °C (CBP650) exhibited 36% slower K release and reduced KCl use by 82% while maintaining similar K use efficiency and corn growth. All K-BBFs matched KCl in promoting robust corn growth in clay soil, increasing biomass by 5.3 times and K uptake by 9 times compared to unfertilized (no K addition) plants. In sandy Oxisol, K-BBFs boosted biomass by up to 3.5 times compared to unfertilized plants, though some pure biochars were less effective than KCl in supporting full corn growth. Soil texture strongly influenced K availability, with sandier soils exhibiting higher K levels in solution. These findings suggest that kinetic release studies in abiotic systems, such as lysimeters with sand, are not suitable for evaluating K-BBFs as slow-release fertilizers. Due to lower K retention in sandy soil and solution K levels exceeding 1100 mg L⁻¹, split applications of some K-BBFs are recommended to prevent corn cation uptake imbalances and soil K leaching. Additionally, granulating biochar–KCl composites may enhance K retention and regulate its release in sandy Oxisols. Full article

Sustainable agricultural intensification requires innovative approaches to simultaneously enhance productivity and mitigate environmental impacts—a challenge critical to global food security and climate change mitigation. The traditional fertilization system, with a single application of nitrogen fertilizer, while effective for crop yields, often leads to soil organic carbon (SOC) depletion, whereas green manure systems offer a dual benefit of nitrogen supply and SOC sequestration potential. However, the mechanisms by which green manure substitution enhances soil carbon sequestration (SCS) remain systematically underexplored in comparison to chemical fertilization. This review systematically examines (1) the mechanisms underlying SOC sequestration, (2) SOC losses associated with traditional fertilization practices, and (3) the theoretical foundation and practical applications of green manure as a nitrogen fertilizer substitute. We provide an in-depth analysis of the mechanisms through which green manure substitution drives SCS. Furthermore, we identify three critical areas for future investigation: (i) optimization of green manure management strategies to enhance SCS efficiency; (ii) comprehensive assessment of green manure’s ecological benefits through long-term, multi-scale studies; and (iii) evaluation of green manure’s climate change adaptation capacity and carbon sequestration potential across diverse climatic scenarios. These findings fundamentally advance our understanding of green manure’s role in sustainable agriculture by establishing its dual function as both a nitrogen source and carbon sequestration driver. In addition, these insights have immediate relevance for agricultural policy and practice, particularly in regions where soil health and carbon storage are prioritized alongside crop yield. Full article

Chemical phosphorus (P) fertilizers generally exhibit low utilization efficiency. The combined application of chemical fertilizers and organic manure is considered an effective strategy to improve soil P availability and crop yields. However, the long-term effects of partially substituting chemical P fertilizer with organic manure on P fertilizer efficiency and crop yield remain poorly understood. To address this, a 5-year field experiment was conducted in a double-rice cropping system to evaluate the impact of substituting chemical P fertilizer with organic manure on rice yield, apparent P recovery (APR), and soil P availability. Our results showed that compared to conventional chemical fertilization (NPK), substituting 20% of P with organic manure, while maintaining the same total N, P, and K inputs (CM(P)), increased grain yield by 4.59% and soil Olsen-P content by 25.48%. In contrast, 20% swine manure substitution with reduced P input (CM(-P)) sustained rice yield and soil Olsen-P levels comparable to NPK. Additionally, treatments CM(P) and CM(-P) increased APR by 59.91% and 82.50%, respectively, and the P activation coefficient by 139.13% and 171.74%. Rice yield and APR were significantly positively correlated with soil Olsen-P, suggesting that manure-induced improvements in soil P availability promoted both rice yield and APR. Overall, our study demonstrates that partial substitution of chemical P fertilizer with organic manure, particularly with reduced P input, is a sustainable fertilization strategy for enhancing P fertilizer efficiency and maintaining crop yields. Full article

Anaerobically digested liquid pig manure (LPM) is enriched with nutrients and thus can be used as an alternative nutrient source and substitute for chemical fertilizer (CF) in rice (Oryza sativa L.) farming. However, there are concerns regarding the contamination of the surrounding water due to the discharge of ponding water containing dissolved organic carbon (DOC), nitrogen (N), and phosphorus (P) from rice paddies fertilized using LPM. This study investigated the effects of the co-application of fly ash (FA) and zeolite (Z) amendments (FAZ amendments) on the concentration of DOC, N, and P in the ponding water of rice paddies fertilized with LPM at two different rates (standard (LPM_S) and double (LPM_D) at 11 and 22 g N m⁻², respectively). Rice was cultivated using four nutrient treatments, including no input, CF (11 g N m⁻²), LPM_S, and LPM_D, with or without FAZ amendments. When FAZ was not amended, LPM_S and LPM_D application increased the DOC concentration by 32% and 41%, respectively, compared to CF treatments (11 g N m⁻²), reflecting a high DOC concentration in LPM. The total N and P concentrations in the ponding water were lower in LPM_S treatment (by 5 and 8%, respectively) but higher (by 94% and 47%, respectively) in LPM_D treatment compared to CF treatments in the absence of FAZ, indicating a high potential for water pollution with a double LPM application rate. With a given nutrient treatment, FAZ amendments decreased DOC by 15–39%, supporting the immobilization of DOC by Z. FAZ consistently decreased the NH₄⁺ concentration by 6–51% across the nutrient treatments, likely via the sorption of NH₄⁺ onto the negatively charged sites of Z, but its effect on total N concentration was not consistent. Unexpectedly, total P concentration increased (by 77–167%) following the FAZ amendment. FAZ amendments tended to increase rice biomass and grain yield for LPM treatments, but these rice growth parameters were poor compared to CF regardless of FAZ amendment. Our results show that the application of LPM as a complete replacement for CF may hamper rice yield while increasing the likelihood of water pollution with DOC and P, although the co-application of FAZ may help to reduce rice yield loss and decrease DOC and NH₄⁺ concentrations. Full article