Search Results (257)

Secondary salinization in mulched drip-irrigated cotton fields of arid oasis–desert transition zones in Xinjiang imposes coupled root-zone constraints, including salt-induced aggregate structural degradation and ionic stress. However, field evidence remains limited on whether integrating a structure-oriented soil conditioner with humic acid can generate stable improvements across growing seasons. A two-year field experiment with a randomized block design (three replicates) was conducted to evaluate four treatments: control (CK), polyacrylamide (PAM, 30 kg ha⁻¹), humic acid (HA, 450 kg ha⁻¹), and PAM + HA. Soil physical and chemical properties and aggregate-size distribution were determined after harvest, while enzyme activities and root traits were assessed at the flowering–boll stage. Structural equation modeling (SEM) and random forest (RF) analysis were used to explore soil–root–yield linkages and identify key soil predictors associated with yield variation. Treatment effects were most evident in the 0–20 cm layer, with PAM + HA showing the greatest overall improvement. In the topsoil, PAM + HA lowered soil pH from 8.35 to 7.88 in 2024 (p < 0.05), increased soil organic carbon (SOC) to 4.29 g kg⁻¹ in 2025 (p < 0.01), and increased NO₃⁻–N to 25.51 and 30.27 mg kg⁻¹ in 2024 and 2025, respectively (both p < 0.05). PAM + HA also enhanced cellulase activity from 6.17 to 16.85 mg glucose g⁻¹ 72 h⁻¹ in 2024 and increased seed cotton yield to 6683.69 and 5996.89 kg ha⁻¹ in 2024 and 2025, with a 51.0% yield increase over CK in 2024. SEM showed that root development had the strongest direct positive effect on yield (β = 0.79, R² = 0.63; goodness of fit (GOF) = 0.74), while random forest identified alkaline phosphatase, cellulase, and NO₃⁻–N as the main yield predictors (out-of-bag R² (OOB R²) = 0.672, p = 0.01). This study elucidated the effects of the combined application of a structure-oriented soil conditioner and humic acid on the root-zone environment of mulched drip-irrigated cotton fields in arid regions, providing a theoretical basis for the coordinated regulation of soil structural improvement and nutrient activation in saline–sodic cotton fields. Full article

Black Soldier Fly larvae (BSFL) bioconvert a wide variety of organic waste into value compounds including the residual frass, a by-product exploitable as compost for plant growth. The use of a non-standardized waste diet that varies in terms of properties does not ensure the maintenance of a highly fertile and healthy BSF colony able to produce viable inoculum (5–7-day-old larvae) for waste bioconversion. The Gainesville diet (GD) is a balanced formulation to ensure full larval development in fertile adults, resulting in a stable rearing colony. On a large scale, the bioconversion supply chain can produce different types of frass. Frass derived from the Gainesville diet (GDf), from fruit and vegetable waste (FVWf), and from milled fruit and vegetable waste (MWf) was composted and then compared to evaluate its fertilizing effect on lettuce growth in two pot-growing experiments. Each compost was added at concentrations of 2.5, 5, and 10%. The growth of lettuce improved significantly with the addition of composted frass in a dose-dependent manner when compared to unfertilized soil. GDf 10% gave the significantly best performance in terms of plant height (20.8 cm versus 17.9 cm) and fresh weight (113.5 g versus 87.7 g) compared to FVWf. In the experiment, the combined use of composted frass at 10% of both GDf and FVWf with a double mineral fertilizer application showed no significant differences compared to triple application. However, GDf provided significantly greater chlorophyll content than FVWf. These results highlight how, under the conditions tested in the present work, the frass of the entire productive chain of BSF is a high value by-product. Full article

Hydrogels have emerged as promising functional materials for improving water management and nutrient delivery in agriculture, particularly under conditions of increasing water scarcity and declining soil fertility. However, most commercially available superabsorbent hydrogels are based on petroleum-derived polymers, raising concerns regarding their persistence in soils, potential microplastic formation and long-term environmental impact. In response, significant research efforts are being directed toward the development of biodegradable hydrogels derived from renewable biopolymers. This review provides a critical overview of recent advances in hydrogel systems designed for agricultural applications, with a particular focus on biopolymer-based materials. First, the current landscape of hydrogel technologies used as soil conditioners and controlled-release systems for agrochemicals is contextualized, highlighting the limitations of conventional synthetic hydrogels. Subsequently, the main classes of natural polymers explored for hydrogel fabrication, including polysaccharides (e.g., chitosan, alginate, cellulose and starch) and proteins (e.g., gelatin, keratin and soy protein), are analyzed in terms of raw material sources, gelation mechanisms and structure–property relationships. Their performance in key agricultural functions, such as water retention, controlled nutrient release, soil conditioning and enhancement of plant growth, is also discussed. Finally, the review identifies major challenges that currently hinder large-scale implementation, including mechanical stability, degradation behavior in complex soil environments, nutrient release control and economic scalability. By integrating recent progress and outlining emerging research directions, this work aims to support the rational design of next-generation biodegradable hydrogels capable of contributing to sustainable agriculture and circular bioeconomy strategies. Full article

The growing demand for sustainable soil management strategies has intensified interest in hydrochar (HC), a waste-derived amendment produced via hydrothermal carbonization (HTC). This review synthesizes recent advances in HC production, characterization, and agri-environmental applications within a waste-to-resource framework. It covers studies conducted mainly over the last decade, encompassing a wide range of feedstocks, including agricultural residues, sewage sludge, animal manures, and food waste. HTC is typically performed at 130–280 °C under autogenous pressure (2–15 MPa), generating HCs with low intrinsic surface area (<50 m²g⁻¹) and oxygen-containing functional groups that govern nutrient dynamics and soil interactions. Reported application rates vary broadly between 10 and 60 t ha⁻¹, with most experiments conducted under greenhouse conditions. Positive effects on soil pH, cation exchange capacity, water retention, and phosphorus availability are frequently observed. However, plant responses vary according to the type of stimulation promoted by HC, as well as its processing conditions, application rates, and the soil characteristics in which it is applied. Advanced molecular-level analyses (e.g., FT-ICR-MS, GC-MS, and ¹³C-NMR) have provided mechanistic insights into carbon stability, nutrient release, and interaction with soil organic matter. Reusing HTC process water offers an additional pathway for nutrient recovery, although concerns about phytotoxic compounds remain. Despite promising short-term results, long-term field evaluations and standardized assessment protocols are still limited. This review integrates structural, functional and agri-environmental perspectives to identify critical knowledge gaps and guide the optimized and context specific use of hydrochar in sustainable agricultural systems. At the same time, it emphasizes its role in advancing carbon sequestration and in operationalizing resource-circular strategies, thereby underscoring its broader practical and strategic relevance. Full article

Biochar, produced by pyrolyzing biomass under limited oxygen, can improve soil quality while supporting long-term carbon sequestration. This study compared two wheat-straw biochars (BC) made at 450 °C (BC1) and 600 °C (BC2), with a commercial hardwood biochar produced at 1280 °C (BC3) using lettuce in a sandy, nutrient-poor soil under a carbon capture, utilization, and storage (CCUS) perspective. Higher pyrolysis temperature increased fixed carbon, ash, and alkalinity and reduced volatile matter, indicating greater carbon stability (BC2 > BC1). Germination tests showed good compatibility, with BC1 performing best, likely because moderate temperatures retain more labile organic fractions. In growth-chamber trials (0.75% w/w), biochar boosted lettuce biomass and root development mainly when combined with mineral fertilization, with BC2 (25% and 59%, respectively) and BC3 (18% and 52%, respectively) yielding the strongest gains; unfertilized plants responded little, confirming that biochar is mainly a soil conditioner rather than a nutrient source. Biochar also stimulated soil enzymes linked to C, N, and P cycling and improved leaf chlorophyll, nitrogen status, and antioxidant capacity under fertilization. The nutrient profiles differed by biochar: BC1 increased K and nitrate, while BC2/BC3 lowered nitrate and BC3 enhanced Ca, Mg, and P uptake. Overall, agronomic outcomes depend on feedstock and pyrolysis temperature: mid-temperature biochars enhance productivity and soil biological activity, whereas high-temperature biochars maximize carbon permanence. Full article

The progressive decline in fertility in nutrient-poor sandy soils has increased interest in soil conditioners that improve nutrient availability. Rising costs and the need to restore biological fertility have shifted attention towards fertilizers that not only enhance productivity but also improve soil biological activity. This study aims to evaluate the effects of biochar (3% w/w; BC) and wood distillate (one irrigation intervention per week at 2% v/v; WD), applied individually or in combination (BC + WD), on a nutrient-poor soil, evaluating soil fertility and basil plant physiology and growth but also antioxidant responses in a pot experiment. Soil NPK content and enzymatic activity were assessed, while plant growth, macronutrient uptake, gas exchange, and antioxidant system responses were monitored after 28 and 56 days of treatment. BC treatment, followed by BC + WD treatment, increased soil P availability by 36% and 37%, respectively, after 56 days compared to untreated soil (CNT). A similar pattern was evidenced for the exchangeable K and pH of the soil. Although BC led to a reduction in soil enzymatic activity, the BC + WD treatment enhanced urease and acid phosphatase activity after 56 days by 26% and 7%, respectively, compared to CNT. Similarly, P uptake by plants was improved by BC + WD after 56 days, while potassium, K, uptake increased in both the BC and BC + WD treatments by 38% and 75% at the final sampling. BC or BC + WD resulted in improved photosynthesis and gas exchange, while WD influenced responses related to redox balance and antioxidant activity over time. Moreover, BC + WD slightly stimulated an increase in dehydroascorbate reductase (+52%), ascorbate peroxidase (+78%), and glutathione reductase (+41%) activity compared to CNT, enforcing the plant antioxidant system. Therefore, the positive antioxidant responses were primarily attributed to the use of BC rather than WD. Both BC and BC + WD proved to be effective and sustainable soil conditioners with beneficial effects on soil P and K availability, as well as certain enzymatic activities. For plants, the effects were more pronounced with BC treatment, showing antioxidant responses within the first 56 days. In general, BC improved soil fertility, and WD acted as a modulator of nutrient dynamics and plant physiological responses, especially when combined with BC. Full article

The objective of this study was to evaluate the effects of hydrogel polymer application on the antioxidant activity and physiological performance of colored-fiber cotton cultivars grown under different levels of water restriction. Two experiments were conducted under greenhouse conditions. In the first experiment, the effects of the hydrogel polymer, cultivars, and irrigation replacement levels were evaluated; in the second, the residual effect of the hydrogel polymer applied in the first experiment was assessed using the same cultivars and irrigation depths. Water restriction negatively affected relative water content, gas exchange, chlorophyll a fluorescence, and antioxidant activity, and increased electrolyte leakage in cotton cultivars. Water deficit reduced relative water content, gas exchange, chlorophyll a fluorescence, and antioxidant activity, while increasing electrolyte leakage in the cultivars. However, hydrogel polymer application up to 6.5 g dm⁻³ of soil and its residual effect in subsequent cycles were beneficial. The polymer increased relative water content and antioxidant activity, in addition to improving gas exchange and chlorophyll fluorescence, suggesting maintenance of plant physiological health. Residual polymer doses also enhanced relative water content, antioxidant activity, gas exchange, and chlorophyll fluorescence in plants during Experiment II. Full article

Soil salinization threatens crop production; however, in multi-crop field systems, evidence for the effectiveness of waste biomass-functional microorganism composite amendments remains limited. Here, we developed a composite microbial soil conditioner (F2) using pine needles and crushed corn cobs as carriers combined with salt-tolerant strains Bacillus subtilis (K1), Azotobacter chroococcum (Y1), and Bacillus gelatinus (J3) to remediate moderately saline-alkali soil from central Gansu (pH 8.36 ± 0.18; EC 1658 ± 55.24 μS·cm⁻¹). Saturation screening identified an optimal carrier ratio of pine needles:corn cobs = 1:2 and an inoculum ratio of K1:Y1:J3 = 1:2:1. In pot experiments, F2 increased soil organic matter and water-holding capacity, enhanced alkaline phosphatase, urease, and sucrase activities, and significantly reduced soil pH and EC. Maize seedling height and chlorophyll content increased by 53.87% and 38.88%, respectively. Amplicon-based microbiome profiling indicated enrichment of beneficial microbial taxa and strengthened primary metabolic functions under F2. Field validation across five crops (flax, potato, edible sunflower, sorghum, and maize) showed consistent growth and yield-related improvements. Overall, these results demonstrate that the biomass–microbe composite amendment effectively alleviates saline-alkali constraints by jointly improving soil properties, microbial functions, and crop performance. Full article

This study evaluates the potential of fine-grained waste gneiss as a soil improver, with particular emphasis on its chemical and grain composition and its effects on plant growth. The experimental material consisted of mixtures of fine-grained waste gneiss with varying proportions (from 0.38% to 7.5% in the pot) supplemented with varying proportions of dolomite (from 0.14% to 0.22% in the pot). Pot experiments were conducted for 57 days under controlled conditions using selected crops. Plant response was assessed based on growth rate, green mass production, and dry mass. For most tested variants, the results demonstrated a dose-dependent enhancement in plant productivity associated with gneiss supplementation. Compared to the control, experiments containing higher proportions of fine-grained gneiss resulted in an increase in green and dry mass from 8.14% to 78.73% and by 12.5% to 96.88%, respectively. Additionally, strong positive correlations between gneiss content and yield parameters (Pearson’s r > 0.8) were observed. In contrast, the dolomite fraction mainly conceptually affected soil chemical properties, including calcium and magnesium availability and pH stabilization. Overall, the findings suggest that fine-grained waste gneiss acts as a growth-promoting soil conditioner, as evidenced by the marked improvement in plant biomass. The findings confirm the high potential of waste gneiss as a functional soil improver, supporting sustainable resource management and aligning with the principles of the circular economy. Full article

Wildfires are increasingly frequent and intense due to climate change, resulting in degraded soils with diminished microbial activity, reduced water retention, and low nutrient availability. In many regions, previously restored areas face repeated burning events, which further exhaust soil fertility and limit the potential for natural regeneration. Traditional reforestation approaches such as seed scattering or planting seedlings often fail in these conditions due to extreme aridity, erosion, and lack of biological support. To address this multifaceted problem, this study proposes a living, biodegradable hydrogel that integrates an engineered soil-beneficial microorganism consortium, designed to deliver beneficial compounds and nutrients combined with endemic plant seeds into a single biopolymeric matrix. Acting simultaneously as a biofertilizer, soil conditioner, and reforestation aid, this 3-in-1 system provides a microenvironment that retains moisture, supports microbial diversity restoration, and facilitates plant germination even in nutrient-poor, arid soils. The concept is rooted in circular economy principles, utilizing polysaccharides from food industry by-products for biopolymer formation, thereby ensuring environmental compatibility and minimizing waste. The encapsulated microorganisms, a Bacillus subtilis strain and a Nostoc oryzae strain, are intended to enrich the soil with useful compounds. They are engineered based on synthetic biology principles to incorporate specific genetic modules. The B. subtilis strain is engineered to break down large polyphenolic compounds through laccase overexpression, thus increasing soil bioavailable organic matter. The cyanobacterium strain is modified to enhance its nitrogen-fixing capacity, supplying fixed nitrogen directly to the soil. After fulfilling its function, the matrix naturally decomposes, returning organic matter, while the incorporation of a quorum sensing-based kill-switch system is designed to prevent the environmental escape of the engineered microorganisms. This sustainable approach aims to transform post-wildfire landscapes into self-recovering ecosystems, offering a scalable and eco-friendly alternative to conventional restoration methods while advancing the integration of synthetic biology and environmental engineering for climate resilience. Full article

Converting marine biowaste into nano-bioproducts for their application as bio-sourced, circular biostimulants to enhance crop productivity is a promising approach. This study evaluated chitosan–TPP nanoparticles (nanochitosan, ~38 nm) derived from blue crab (Callinectes sapidus) shells as a soil-applied biostimulant and conditioner for tomato (Solanum lycopersicum) grown in loam soil without mineral fertilizer. Our results showed that nanochitosan application as a soil supplement by drench improved the soil moisture content (39% vs. 22%), water-holding capacity (84% vs. 70%), total nitrogen (3.8 vs. 1.4 gm N kg⁻¹), and organic carbon content (48.4 vs. 34.1 gm C kg⁻¹) in nanochitosan-amended soil compared with the non-amended soil. This was accompanied by higher biomass, better root/shoot development and synthesis of phytohormones leading to increased shoot length, early flowering, and increased total soluble solids of fruits in nanochitosan-amended soil compared with control, suggesting that nanochitosan can act both as a beneficial soil conditioner and as a plant biostimulant. The results further show that nanochitosan-based formulations may be used not only as fertilizer-saving bio-inputs but also as bio-based nanochitosan plant biostimulants, which can partly substitute mineral fertilizer application for sustainable production of tomato. Moreover, generic fabrication of such nanochitosan from marine biowaste would support the circular-bioeconomy model to further improve sustainability of agroecosystems. Full article

Soil salinization remains a critical constraint on global land sustainability, severely limiting agricultural output and ecosystem resilience. To address this issue, a field trial was implemented to investigate the interactive benefits of vermicompost (VC) and a novel soil conditioner derived from coal gasification slag-based soil conditioner (CGSS) in mitigating saline–alkali stress. The perennial forage grass Leymus chinensis, valued for its ecological robustness and economic potential under adverse soil conditions, served as the test species. Five treatments were established: CK (unamended), T1 (CGSS alone), T2 (VC alone), T3 (CGSS:VC = 1:1), T4 (CGSS:VC = 1:2), and T5 (CGSS:VC = 2:1). Study results indicate that the combined application of CGSS and VC outperformed individual amendments, with the T4 treatment demonstrating the most effective results. Compared to CK, T4 reduced soil electrical conductivity (EC) by 12.00% and pH by 5.17% (p < 0.05), while markedly enhancing key fertility indicators—including soil organic matter and the availability of nitrogen, phosphorus, and potassium. Thus, these improvements translated into superior growth of L. chinensis, reflected in significantly greater dry biomass, expanded leaf area, and increased plant height. Additionally, the T4 treatment increased soil microbial richness (Chao1 index) by 21.5% and elevated the relative abundance of the Acidobacteria functional group by 16.9% (p < 0.05). Hence, T4 treatment (CGSS: 15,000 kg·ha⁻¹; VC: 30,000 kg·ha⁻¹) was identified as the optimal remediation strategy through a fuzzy comprehensive evaluation that integrated multiple soil and plant indicators. From an economic perspective, the T4 treatment (corresponding to a VC-CGSS application ratio of 2: 1) exhibits a lower cost compared to other similar soil conditioners and organic fertilizer combinations for saline–alkali soil remediation. This study not only offers a practical and economically viable approach for reclaiming degraded saline–alkali soils but also advances the circular utilization of coal-based solid waste. Furthermore, it deepens our understanding of how integrated soil amendments modulate the soil–microbe–plant nexus under abiotic stress. Full article

Biochar is known to enhance soil potassium (K) availability and promote plant K uptake; however, its influence on the transformation pathways of fertilizer potassium and the mechanisms regulating crop potassium accumulation remains insufficiently understood. This study conducted a pot experiment using three soil types—Albic, Brown, and Sandy soils—with different biochar application rates (0, 10, and 20 g·kg⁻¹) in combination with potassium fertilizer, to systematically evaluate the regulation of soil K forms, K fertilizer transformation rates, K use efficiency, and K uptake and accumulation in soybeans. The results demonstrated that the combined application of biochar and K fertilizer significantly increased the contents of available, water-soluble, exchangeable, and non-exchangeable K across all three soils. At the highest biochar application rate (20 g·kg⁻¹), available K increased by 15.37%, 16.78%, and 11.77% in the Albic, Sandy, and Brown soils, respectively, compared to the control. Furthermore, biochar altered the transformation pathways of fertilizer K; it consistently reduced the conversion rate of fertilizer K into exchangeable K across all soils, redirecting it toward the water-soluble and non-exchangeable K pools, thus functioning as a potassium “scheduling center”. Adsorption–desorption experiments revealed that biochar exhibits a strong multilayer adsorption capacity for K ions, with most of the adsorbed K not easily desorbed, providing mechanistic support for the observed shift in transformation pathways. In terms of K use efficiency, biochar reduced the K of agronomic efficiency (KAE) due to a “dilution effect” from its inherent K content. Under the high application rate (20 g·kg⁻¹), the KAE decreased by 11.79% in Albic soil, 88.48% in Sandy soil, and 71.73% in Brown soil, while significantly increasing the partial factor productivity of K (PFPK) and apparent recovery efficiency of K (AREK). Ultimately, the co-application of biochar and K fertilizer significantly enhanced total K accumulation and seed yield in soybeans by increasing K concentrations in various plant parts and promoting dry matter accumulation. At the biochar application rate of 20 g·kg⁻¹, the potassium accumulation and soybean yield under biochar treatment reached maximum increases of 70.77% (in Brown soil) and 42.63% (in Albic soil), respectively. This study demonstrates that biochar can synergistically reduce potassium (K) leaching and improve fertilizer use efficiency by regulating K transformation pathways. This provides a practical guideline for utilizing biochar as a dual-function amendment, which acts as both a supplemental K source and a soil conditioner, thereby supporting the development of more sustainable potassium management practices in diverse cropping systems. Full article

Soil amendments play a critical role in improving soil health and supporting sustainable crop production, especially under declining soil fertility and climate-related stress. However, their impact varies because each amendment influences the soil through different biogeochemical processes rather than a single universal mechanism. This review synthesizes current knowledge on a wide range of soil amendments, including compost, biosolids, green and animal manure, biochar, hydrochar, bagasse, humic substances, algae extracts, chitosan, and newer engineered options such as metal–organic framework (MOF) composites, highlighting their underlying principles, modes of action, and contributions to soil function, crop productivity, and soil carbon dynamics. Across the literature, three main themes emerge: improvement of soil physicochemical properties, enhancement of nutrient cycling and nutrient-use efficiency, and reinforcement of plant resilience to biotic and abiotic stresses. Organic nutrient-based amendments mainly enrich the soil and build organic matter, influencing soil carbon inputs and short- to medium-term increases in soil organic carbon stocks. Biochar, hydrochar, and related materials act mainly as soil conditioners that improve structure, water retention, and soil function. Biostimulant-type amendments, such as algae extracts and chitosan, influence plant physiological responses and stress tolerance. Humic substances exhibit multifunctional effects at the soil–root interface, contributing to improved nutrient efficiency and, in some systems, enhanced carbon retention. The review highlights that no single amendment is universally superior, with outcomes governed by soil–crop context. Its novelty lies in its mechanism-based, cross-amendment synthesis that frames both yield and carbon outcomes as context-dependent rather than universally transferable. Within this framework, humic substances and carbon-rich materials show potential for climate-smart soil management, but long-term carbon sequestration effects remain uncertain and context-dependent. Full article

Food security is threatened in the semiarid region of Brazil, which is susceptible to climate change and has low-fertility soils degraded by inadequate agricultural practices. This study aimed to evaluate safflower’s adaptation to the region and the benefits to the soil and crop of applying biochar and wood vinegar (WV). Biochar, pure or WV-added (Wv-biochar), was applied to the soil at doses of 3.0, 6.0, and 9.0 t ha⁻¹. Determinations performed in three harvests of safflower were plant height, number of capitula per plant, number of seeds per capitulum, mass of 1000 seeds, seed yield, and oil content. The maximum safflower yields (1818.52 kg ha⁻¹) and oil content (45.50%), and the average values of mass of 1000 seeds (35.55 g) were consistent with results reported in literature. Evidence of better performance of the variables under the effect of Wv-biochar than of pure biochar was observed, and, in general, the curves obtained showed quadratic behavior, with maximum values at intermediate doses. The seed yield and oil content achieved indicate that safflower is a promising crop for the region, particularly when more adapted genotypes and improved management practices are employed. The most pronounced effects on safflower production and oil content were observed at doses of 5 to 6 t ha⁻¹ of Biochar and Wv-biochar, which are economical and sustainable alternatives due to their use of organic waste and the benefits they provide for soil and food security. Full article