Alginate-based composites as novel soil conditioners for sustainable applications in agriculture: A critical review

The potential of seaweed-derived polysaccharides as sustainable biostimulants in agriculture

Seaweed polysaccharides such as alginate, carrageenan, agar, and ulvan are emerging as key bioresources in sustainable agriculture due to their unique structural characteristics and functional properties. This review highlights their potential as eco-friendly biostimulants capable of enhancing soil health, plant growth, and stress resilience. Specific mechanisms, including the gel-forming capacity of alginate, ion exchange abilities, and the hydrophilic nature of these polysaccharides, enable improved water retention, nutrient uptake, and plant productivity under adverse conditions, including drought, salinity, and extreme temperatures. Moreover, their role as hydrogels and bio-elicitors introduces novel approaches to addressing global challenges in agriculture, such as climate change and food security. Real-world applications, such as the use of Ascophyllum nodosum extract for drought tolerance and Gracilaria tenuistipitata var. liui to boost grain yields, underscore the practicality and success of these biostimulants. Despite their promising applications, challenges like variability in seaweed quality, high extraction costs, and limited product standardization hinder their scalability. This review provides an integrated analysis of their biochemical properties, agricultural applications, and commercial products while proposing solutions to optimize their use for advancing sustainable farming practices.

Effects of bentonite/sodium alginate/nanocellulose composites on soil properties and their biodegradability over time

This study investigates the effects of bentonite/sodium alginate/nanocellulose (BAN) composites on soil properties. The composites, formulated with different bentonite/sodium alginate/nanocellulose ratios (50:30:20, 70:20:10 and 80:15:5) at three concentrations (1%, 2% and 3%), were applied to soil samples. Field emission scanning electron microscopy (FESEM) images showed that the composites improved soil structure, with the B50/A30/N20 ratio exhibiting improved dispersion and stability. The results showed that the application of BAN composites significantly increased the water holding capacity (WHC), with the 3% concentration showing a ∽25% increase compared to the control treatment. Soil respiration rates were highest at the 3% concentration, with a 50-100% increase in CO2 emission compared to the control treatment. Biodegradability tests showed that the B50/A30/N20 composite had the highest degradation rate (52%), while the B80/A15/N5 composite showed the lowest rate (17.13%). The total organic carbon (TOC) content was increased by up to 40-100% in the soils treated with 2% and 3% BAN, with the B50/A30/N20 treatment showing the greatest increase. The pH values were slightly acidified, with a decrease in pH and an increase in EC. In addition, treatment with the composite resulted in a significant improvement in soil aggregation, with the mean weight diameter (MWD) and geometric mean diameter (GMD) significantly increased by treatment with B50/A30/N20 (3%). The microbial populations (bacteria and fungi) were significantly higher in the treated soils compared to the untreated soils. These results indicate that BAN composites can significantly improve the physical and biological properties of the soil and thus offer potential for sustainable agricultural practices.

Positive effects of composite material immobilized enzymes in 2,4,6-trichlorophenol degradation on soil properties and plant growth

2,4,6-Trichlorophenol (2,4,6-TCP) is recognized as a bio-toxic compound which is widely present in water and soil, and immobilized enzymes technology is widely used to degrade 2,4,6-TCP efficiently. However, previous studies have primarily focused on the degradation capability of immobilized enzymes towards 2,4,6-TCP, while the impacts on soil after degradation remain largely unexplored. In this study, sodium alginate/hydroxyapatite/chitosan microspheres immobilized with enzymes were used for 2,4,6-TCP degradation, and the impacts of degradation on soil properties and plant growth were explored. The results indicated that sodium alginate/hydroxyapatite/chitosan microsphere-immobilized enzymes achieved a removal rate of 94.72% for 160 mg L-1 2,4,6-TCP over 24 h and 73.17% for 160 mg kg-1 2,4,6-TCP contaminated soil over 72 h. Soil dehydrogenase and catalase activities were enhanced during degradation. The inhibitory effects of 2,4,6-TCP on wheat root and leaf elongation were mitigated by immobilized enzymes that degrade 2,4,6-TCP. Nutrients, such as fast-acting phosphorus and fast-acting potassium, were increased by immobilized enzymes that release nutrient elements. The changes of wheat growth observed in the soil after 2,4,6-TCP degradation by immobilized enzymes were driven by nutrients and degradation. These insights may facilitate the advancement of future applications of immobilized enzyme degradation technologies, contributing to sustainable soil management and ecological restoration.

Inducing Drought Resilience in Maize Through Encapsulated Bacteria: Physiological and Biochemical Adaptations

Droughts are projected to become prevalent throughout the 21st century, endangering agricultural productivity and global food security. To address these challenges, novel strategies to enhance water management and augment plant resilience are imperative. Bacterial encapsulation has emerged as a promising approach, offering benefits such as enhanced bacterial survival, soil compatibility, and sustainable plant growth. This study evaluated the osmotolerance of bacteria from arid environments and determined their plant growth-promoting ability in drought conditions. The encapsulation of these bacteria in bio-compatible capsules led to a substantial enhancement in the performance of maize plants under drought stress. Maize plants treated with encapsulated bacteria demonstrated a 35% increase in root biomass and a 28% enhancement in shoot growth compared to untreated controls. Furthermore, significant physiological and biochemical adaptations were observed, including a 45% increase in photosynthetic pigment concentration and higher osmolyte levels, which contributed to improved drought stress tolerance. The findings of this study demonstrate the potential of encapsulated bacteria to enhance maize resilience to drought, thereby supporting robust growth under water-limited conditions. This approach presents a sustainable strategy to improve drought tolerance, and it may reduce irrigation dependency and maintain crop yields in the face of increasing climate uncertainty.

A novel scaffold for biofilm formation by soil microbes using iron-cross-linked alginate gels

This study aimed to evaluate the suitability of alginate gels, specifically ferric-ion-cross-linked alginate (Fe-alginate) and calcium-ion-cross-linked alginate (Ca-alginate), as scaffolds for soil microbial attachment and biofilm formation in soil. Staining with crystal violet and observations with scanning electron microscopy showed that microorganisms formed biofilms on Fe-alginate surfaces in the soil. When the soil was incubated with Fe-alginate, microbial biomass, estimated by adenosine triphosphate content, increased not only in the Fe-alginate but also in the surrounding soil. The weight of Ca-alginate in the soil decreased with time owing to chemical dissolution. However, the weight of Fe-alginate in the soil did not decrease, likely because it was protected by the microbial biofilm that formed on its surface. These results demonstrate that the use of Fe-alginate, in contrast to Ca-alginate, as a scaffold may allow for more efficient use of soil microbial functions in agriculture and bioremediation.

Development of multifunctional immobilized bacterial agents for multi-pesticides degradation and environment remediation

The proliferation of weeds, pests, and plant diseases in crop cultivation has driven the increased application of herbicide lactofen, insecticide acetamiprid, and fungicide carbendazim, contributing to environmental pollution. Microorganisms are requently employed to remove pesticide residues from the environment. However, Liquid bacterial agents encounter difficulties in transportation and preservation during application and the current immobilized bacterial agents have a single degradation function. This study developed immobilized bacterial agents containing the lactofen-degrading strain Bacillus sp. Za, the acetamiprid-degrading strain Pigmentiphaga sp. D-2, and the carbendazim-degrading strain Rhodococcus sp. djl-6. Preparation conditions, including activated carbon concentration, sodium alginate (SA), CaCl2, and immobilization time, were optimized using the response surface method (RSM). The degradation performance of the immobilized bacteria was evaluated, with degradation rates exceeding 70% for all three pesticides under conditions of 30 °C, pH 7.0, and 6% inoculation over 48 h. The immobilized bacterial agents were stored at pH 7.0 and 4 °C for 180 days, maintaining a preservation rate of 51.26% with a viable cell count of 1.04 × 108 CFU/g. These agents effectively remediated soil and water contaminated with multi-pesticides, achieving degradation rates of 92.50% and 98.50% for lactofen, 91.05% and 99.89% for acetamiprid, 88.43% and 98.99% for carbendazim within 21 in soil and 7 days in water, respectively. This study provides essential technical support for developing microbial agents capable of degrading multi-pesticides residues, with significant potential applications in agriculture and environmental protection.

Pleiotropic regulation of bacterial toxin production and Allee effect govern microbial predator-prey interactions

Bacteria are social organisms, which are constantly exposed to predation by nematodes or amoebae. To counteract these predation pressures, bacteria have evolved a variety of potent antipredator strategies. Bacteria of the genus Pseudomonas, for instance, evade amoebal predation by the secretion of amoebicidal natural products. The soil bacterium Pseudomonas fluorescens HKI0770 produces pyreudione alkaloids that can kill amoebae. Even though the mode of action of the pyreudiones has been elucidated, the spatiotemporal dynamics underlying this predator-prey interaction remain unknown. Using a combination of microscopy and analytical techniques, we elucidated the intricate relationship of this predator-prey association. We used the chromatic bacteria toolbox for intraspecific differentiation of the amoebicide-producing wildtype and the non-producing mutant within microcosms. These allow for variations in nutrient availability and the emergence of predation-evasion strategies of interacting microorganisms. Imaging of the co-cultures revealed that the amoebae initially ingest both the non-producer as well as the toxin-producer cells. The outcomes of predator-prey interactions are governed by the population size and fitness of the interacting partners. We identified that changes in the cell density coupled with alterations in nutrient availability led to a strong Allee effect resulting in the diminished production of pyreudione A. The loss of defense capabilities renders P. fluorescens HKI0770 palatable to amoebae. Such a multifaceted regulation provides the basis for a model by which predator-prey populations are being regulated in specific niches. Our results demonstrate how the spatiotemporal regulation of bacterial toxin production alters the feeding behavior of amoeba.

Investigating the barriers to drone implementation in sustainable agriculture: A hybrid fuzzy-DEMATEL-MMDE-ISM-based approach

Drone integration in sustainable agriculture has emerged as a transformative technological advancement, enabling farmers to achieve accurate crop health monitoring, soil analysis, weed mapping, precise spraying, and livestock monitoring. It facilitates many sustainable measures, such as conserving freshwater resources, reducing soil erosion and pesticide overuse, minimizing agriculture waste, and enhancing productivity and resilience. Despite its benefits, drone adoption faces several barriers, highlighting the requirement of well-structured mitigation strategies to overcome these challenges and ensure successful implementation. We propose a hybrid fuzzy-DEMATEL-MMDE-ISM-based approach for analysing the barriers to drone implementation in sustainable agriculture. We obtain a list of 15 potential barriers by exploring the relevant literature and finalizing the 13 critical barriers based on the experts' opinions. We adopt the fuzzy-Decision Making Trial and Evaluation Laboratory (fuzzy-DEMATEL) technique to segregate casual and effect barriers. Then, we apply the Maximum Mean De-Entropy (MMDE) method to determine the threshold value for the Interpretive Structural Modelling (ISM) method for constructing the three-level hierarchical structure of the barriers. The insights signify that the most crucial barriers are stability and reliability, drone sensor quality, and drone payload capacity. Flight duration, high initial cost, and maintenance infrastructure serve as linkage barriers between crucial barriers and public perception and psychological barrier. We also find some barriers with minimal or no interdependence on other barriers that should be handled separately. We suggest mitigation strategies to address the underlying challenges of drone implementation in sustainable agriculture. We can extend this study by incorporating additional barriers and applying different methods in other countries to examine the variations in the model.

Enhancing catalyst stability: Immobilization of Cu-Fe catalyst in sodium alginate matrix for methyl orange removal via Fenton-like reaction

This study aims to enhance the stability and effectiveness of heterogeneous catalysts in Fenton-like reactions, explicitly addressing the acidity limitations inherent in traditional Fenton processes. Copper-iron was synthesized through co-precipitation, and a catalyst bead was produced from hydrogel formation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirm phases in the bimetallic Copper-iron, aligning with the intended composition. Modification with alginate led to reduced metal leaching compared to the bare bimetallic counterpart, as confirmed by atomic absorption spectroscopy (AAS). Additionally, Fourier-transform infrared spectroscopy (FTIR) revealed the deactivation of alginate through the disappearance of carboxyl groups, indicating the depolymerization of the catalyst bead. Under the suggested conditions (Methyl Orange concentration of 25 mg/L, initial solution pH of 7, 2 g/L catalyst loading, concentration of hydrogen peroxide 100 mM in a 120-min reaction time), the catalyst demonstrated remarkable decolorization efficiency of Methyl Orange, achieving 97.67 %. Further highlighting its practicality, the catalyst exhibited outstanding reusability over four cycles under identical conditions, showcasing robust immobilization capabilities and sustained performance. Notably, the catalyst's magnetic properties facilitated easy separation using an external magnet. In conclusion, the developed catalyst beads offer a solution with high reusability, magnetic separability, and reduced iron leaching. The advantageous characteristics underscore its potential as a heterogeneous catalyst for wastewater treatment applications, warranting further exploration under practical conditions.

Experimental assessment of biostimulants on mung bean growth on a soilless culture system using superabsorbent pectin based hydrogel

Sustainable agriculture initiatives are needed to ensure the food security of the people all over the world. Soilless cultivation methods using hydrogels may give a revolutionary response as well as a more ecological and productive alternative to conventional farming. This study attempted extraction of pectin from the rind of albedo yellow passion fruit (Passiflora edulis var. flavicarpa Degener)and hydrogels from pectin and activated carbon was compared with pure pectin hydrogel; Pectin- Activated Carbon hydrogels (PAC) showed a microporous structure with excellent hydrophilicity and showed superior water holding capacity. Then the prepared hydrogels were examined with various instrumental techniques like FTIR, SEM, XRD, Raman, BET and rheological properties. In the BET analysis, PAC3 shows the highest surface area of 28.771 m2/g when compared to PAC0 at 15.063 m2/g. The germination experiments were performed using mung beans. This study provides an opportunity for the application of pectin hydrogels in agriculture field specifically for home garden or rooftop cultivation.

Agriculture 4.0: Polymer Hydrogels as Delivery Agents of Active Ingredients

The evolution from conventional to modern agricultural practices, characterized by Agriculture 4.0 principles such as the application of innovative materials, smart water, and nutrition management, addresses the present-day challenges of food supply. In this context, polymer hydrogels have become a promising material for enhancing agricultural productivity due to their ability to retain and then release water, which can help alleviate the need for frequent irrigation in dryland environments. Furthermore, the controlled release of fertilizers by the hydrogels decreases chemical overdosing risks and the environmental impact associated with the use of agrochemicals. The potential of polymer hydrogels in sustainable agriculture and farming and their impact on soil quality is revealed by their ability to deliver nutritional and protective active ingredients. Thus, the impact of hydrogels on plant growth, development, and yield was discussed. The question of which hydrogels are more suitable for agriculture-natural or synthetic-is debatable, as both have their merits and drawbacks. An analysis of polymer hydrogel life cycles in terms of their initial material has shown the advantage of bio-based hydrogels, such as cellulose, lignin, starch, alginate, chitosan, and their derivatives and hybrids, aligning with sustainable practices and reducing dependence on non-renewable resources.

Microbial- and seaweed-based biopolymers: Sources, extractions and implications for soil quality improvement and environmental sustainability - A review

Improving soil quality without creating any environmental problems is an unescapable goal of sustainable agroecosystem management, according to the United Nations 2030 Agenda for Sustainable Development. Therefore, sustainable solutions are in high demand. One of these is the use of biopolymers derived from microbes and seaweed. This paper aims to provide an overview of the sources of extraction and use of microbial (bacteria and cyanobacteria) and seaweed-based biopolymers as soil conditioners, the characteristics of biopolymer-treated soils, and their environmental concerns. A preliminary search was also carried out on the entire Scopus database on biopolymers to find out how much attention has been paid to biopolymers as biofertilizers compared to other applications of these molecules until now. Several soil quality indicators were evaluated, including soil moisture, color, structure, porosity, bulk density, temperature, aggregate stability, nutrient availability, organic matter, and microbial activity. The mechanisms involved in improving soil quality were also discussed.

Water resistant, biodegradable and flexible corn starch/carboxymethyl cellulose composite film for slow-release fertilizer coating materials

The inherent limitations of Cornstarch (CS) and Carboxymethyl Cellulose (CMC) membranes, such as brittleness, fragility, and water solubility, limit their use in controlled-release fertilizers. This study reports on the synthesis of crosslinked CMC/CS-20-E composite membranes using the casting technique, with epichlorohydrin (ECH) as the crosslinking agent in an acidic environment to crosslink CS and CMC. The synthesized composite film demonstrates remarkable water resistance, as evidenced by the insignificant alteration in its morphology and structure post 72 h of water immersion. Its flexibility is reflected in its capacity to endure knotting and bending, with an elongation at break reaching 78.1 %. Moreover, the degradation rate surpasses 90 % within a span of seven days. The CMC/CS-20-E-x-urea controlled-release fertilizer was subsequently produced using a layer-by-layer self-assembly technique, where urea particles were incorporated into the crosslinked composite solution. This CMC/CS-20-E-x-urea controlled-release fertilizer displayed superior controlled-release performance over a duration of seven days when juxtaposed with pure urea. In particular, the CMC/CS-20-E-3 %-urea controlled-release fertilizer showed a cumulative release rate of 84 % by the seventh day. The controlled-release fertilizers developed in this study offer a promising strategy for creating eco-friendly options that are crucial for fertilizing crops with short growth cycles.

Hydrogel capsules as new delivery system for Trichoderma koningiopsis Th003 to control Rhizoctonia solani in rice (Oryza sativa)

The incorporation of biological control agents (BCAs) such as Trichoderma spp. in agricultural systems favors the transition towards sustainable practices of plant nutrition and diseases control. Novel bioproducts for crop management are called to guarantee sustainable antagonism activity of BCAs and increase the acceptance of the farmers. The encapsulation in polymeric matrices play a prominent role for providing an effective carrier/protector and long-lasting bioproduct. This research aimed to study the influence of biopolymer in hydrogel capsules on survival and shelf-life of T. koningiopsis. Thus, two hydrogel capsules prototypes based on alginate (P1) and amidated pectin (P2), containing conidia of T. koningiopsis Th003 were formulated. Capsules were prepared by the ionic gelation method and calcium gluconate as crosslinker. Conidia releasing under different pH values of the medium, survival of conidia in drying capsules, storage stability, and biocontrol activity against rice sheath blight (Rhizoctonia solani) were studied. P2 prototype provided up to 98% survival to Th003 in fluid bed drying, faster conidia releasing at pH 5.8, storage stability greater than 6 months at 18 °C, and up to 67% of disease reduction. However, both biopolymers facilitate the antagonistic activity against R. solani, and therefore can be incorporated in novel hydrogel capsules-based biopreparations. This work incites to develop novel biopesticides-based formulations with potential to improve the delivery process in the target site and the protection of the active ingredient from the environmental factors.

Nano-Pesticides and Fertilizers: Solutions for Global Food Security

Nanotechnology emerges as an important way to safeguard global food security amid the escalating challenges posed by the expansion of the global population and the impacts of climate change. The perfect fusion of this breakthrough technology with traditional agriculture promises to revolutionize the way agriculture is traditionally practiced and provide effective solutions to the myriad of challenges in agriculture. Particularly noteworthy are the applications of nano-fertilizers and pesticides in agriculture, which have become milestones in sustainable agriculture and offer lasting alternatives to traditional methods. This review meticulously explores the key role of nano-fertilizers and pesticides in advancing sustainable agriculture. By focusing on the dynamic development of nanotechnology in the field of sustainable agriculture and its ability to address the overarching issue of global food security, this review aims to shed light on the transformative potential of nanotechnology to pave the way for a more resilient and sustainable future for agriculture.

Mechanochemical Degradation of Biopolymers

Mechanochemical treatment of various organic molecules is an emerging technology of green processes in biofuel, fine chemicals, or food production. Many biopolymers are involved in isolating, derivating, or modifying molecules of natural origin. Mechanochemistry provides a powerful tool to achieve these goals, but the unintentional modification of biopolymers by mechanochemical manipulation is not always obvious or even detectable. Although modeling molecular changes caused by mechanical stresses in cavitation and grinding processes is feasible in small model compounds, simulation of extrusion processes primarily relies on phenomenological approaches that allow only tool- and material-specific conclusions. The development of analytical and computational techniques allows for the inline and real-time control of parameters in various mechanochemical processes. Using artificial intelligence to analyze process parameters and product characteristics can significantly improve production optimization. We aim to review the processes and consequences of possible chemical, physicochemical, and structural changes.