Organo-monomers coated slow-release fertilizers: Current understanding and future prospects

The increasing urge to make an impactful contribution towards attaining nutritional security amidst the ever-rising demand for food, changing climate and maintaining environmental health and safety has become the main focal point for today's researchers globally. Slow-release fertilizers (SRFs) are a broad, dynamic, and advance category of fertilizers but despite its environmental benefits and scientifically proven results it often faces some critical challenges, primarily due to its high cost, often stemming from synthetic coatings, deteriorating soil health and with unrevealed potential environmental impacts. Organo-monomers have gained immense popularity due to their organic origin, biodegradable nature, biocompatibility, bio-sustainability and as a targeted delivery of nutrients in the plant system leading to increase in nutrient use efficiency (NUE). They can form strong bond with other monomers, fertilizers elements and improve the soil quality, carbon sequestration and holistically the environment. This review emphasizes on organo-monomers based SRFs, its synthesis, application and deliberate mechanism of nutrient release; boosting crop productivity and global economy. In conclusion, provided the significant challenges posed by the classical or synthetically coated fertilizers; the application of organo-monomers based SRFs demonstrates immense potential for achieving sustainable yield, to help build a global nutritionally secure population.

Humic Acid-Functionalized Lignin-Based Coatings Regulate Nutrient Release and Promote Wheat Productivity and Grain Quality

The rational application of fertilizers is crucial for achieving high crop yields and ensuring global food security. The use of biopolymers for slow-release fertilizers (SRFs) development has emerged as a game-changer and environmentally sustainable pathway to enhance crop yields by optimizing plant growth phases. Herein, with a renewed focus on circular bioeconomy, a novel functionalized lignin-based coating material (FLGe) was developed for the sustained release of nutrients. This innovative approach involved the extraction and sustainable functionalization of lignin through a solvent-free esterification reaction with humic acid─an organic compound widely recognized for its biostimulant properties in agriculture. The primary objective was to fortify the hydration barrier of lignin by reducing the number of its free hydroxyl groups, thereby enhancing release control, while simultaneously harnessing the agronomic benefits offered by humic acid. After confirming the synthesis of functionalized lignin (FLGe) through 13C NMR analysis, it was integrated at varying proportions into either a cellulosic or starch matrix. This resulted in the creation of five distinct formulations, which were then utilized as coatings for diammonium phosphate (DAP) fertilizer. Experimental findings revealed an improved morphology and hardness (almost 3-fold) of DAP fertilizer granules after coating along with a positive impact on the soil's water retention capacity (7%). Nutrient leaching in soil was monitored for 100 days and a substantial reduction of nutrients leaching up to 80% was successfully achieved using coated DAP fertilizer. Furthermore, to get a fuller picture of their efficiency, a pot trial was performed using two different soil textures and demonstrated that the application of FLGe-based SRFs significantly enhanced the physiological and agronomic parameters of wheat, including leaf evolution and root architecture, resulting in an almost 50% increase in grain yield and improved quality. The results proved the potential of lignin functionalization to advance agricultural sustainability and foster a robust bioeconomy aligning with the premise "from the soil to the soil".

Wood-derived bio-coating materials incorporating hydrophobic lignin and hierarchically porous biochar for high-efficiency coating slow-release fertilizers

Coating slow-release fertilizers (CSRFs) have gained significant attention for their potential to improve nutrient utilization efficiency and prevent environmental pollution through mitigating soil and water contamination. This study developed a novel wood waste-derived composition as a bio-coating material for urea slow-release by integrating modified lignin (PCL) and activated biochar (ABC). PCL was prepared by grafting palmitoyl chloride (PC) with hydrophobic groups to the lignin via an esterification reaction. ABC with a high surface area and hierarchically porous structure created rich channels for ion transportation. These results increased the water-retention ability with a reduced absorbing/expelling rate and confer an excellent Cr(VI) adsorption capacity to the PCL and ABC hybrid coating material (PCL/ABC). The as-prepared PCL/ABC-based CSRF (PCL/ABC-CSRF) showed improving fertilizer slow-release properties for real application (nitrogen release persistence for 40 days at soil). The rice (Oryza sativa L.) hydroponics study suggested that such novel PCL/ABC was conducive to the rice growth in micro metallic contaminated hydroponics by eliminating the accumulation of chromium metal in rice roots. Overall, this study provides an attractive platform for developing biodegradable, heavy-metal adsorbable, and high-efficient CSRFs and a feasible and effective way for functionalized utilization of wood waste.

Evaluation of Physicochemical Properties of Sustained-Release Membranes Based on Analytic Hierarchy

In this paper, the optimal analytic hierarchy process was used to establish a comprehensive evaluation model for the physicochemical properties of composite sustained-release membrane materials based on water absorption (XS), water permeability (TS), tensile strength (KL), elongation at break (DSL), fertilizer permeability (TF), and viscosity (ND), and the optimal ratio parameters of membrane material were determined. Analytic hierarchy process (AHP) combined with correlation analysis was used to construct the judgment matrix of physicochemical properties, which passed the consistency test, and to determine the weight and ranking of each index: TF (0.6144) > XS (0.1773) > KL (0.1561) > ND (0.1311) > TS (0.0775) > DSL (0.0520). The comprehensive scores of sustained-release membrane materials under different treatments were calculated based on normalized data samples and weights. It was determined that the percentage of each component in the best comprehensive performance of the slow-release membrane material was as follows: polyvinyl alcohol, polyvinylpyrrolidone, zeolite, and epoxy resin were 7.3%, 0.7%, 0.5%, and 2%, respectively.

Synthesis and performance evaluation of slow-release fertilizers produced from inverse vulcanized copolymers obtained from industrial waste

To improve crop nutrient uptake efficacy (NUE) and better manage fertilization, slow-release fertilizers (SRFs) are developed by either coating the urea granules or making a composite. Several materials have already been developed, nevertheless, scalability of those materials is still a challenge due to their inherit drawbacks (such as hydrophilicity, crystallinity, non-biodegradability, etc.). Herein, we utilized a biodegradable, green and sustainable copolymer produced from industrial waste (sulfur-petroleum industry waste and myrcene-citrus industry waste) to coat the urea using a facile coating method to develop novel SRFs and achieve better agronomic and environmental advantages. The copolymer was first synthesized using a facile, solvent-free one-pot method called inverse vulcanization followed by Fourier transform infrared spectroscopy (FTIR) analysis to confirm the successful reaction between myrcene and sulfur subsequently coating the copolymer on urea granule. The morphology and coating thickness of coated fertilizers were analysed using scanning electron microscopy (SEM), followed by a nitrogen release test in distilled water and a soil burial test to confirm the biodegradability. The nitrogen release test revealed that the SRF with the maximum coating thickness of 1733 μm releases only 16% of its total nitrogen after 4 days of incubation compared to the pristine urea which releases all its nutrient within 1 day. The soil burial test confirms the biodegradability of the copolymer, as after 50 days of incubation in soil the copolymer loses almost 18.25% of its total weight indicating that the copolymer is degrading.

Systematic review on lignin valorization in the agro-food system: From sources to applications

Lignocellulosic biomass is the most abundant renewable resource on earth and currently most of this biomass is considered a low-value waste. Specifically, lignin is an underrated bioresource that is mostly burned for energy production and few value-added products have been created. Since the agro-food industry produces large amounts of wastes that can be potential sources of high-quality lignin, scientific efforts should be directed to this industry. Thus, this review provides a systematic overview of the trends and evolution of research on agro-food system-derived lignin (from 2010 to 2020), including the extraction of lignin from various agro-food sources and emergent applications of lignin in the agro-food chain. Crops with the highest average production/year (n = 26) were selected as potential lignin sources. The extraction process efficiency (yield) and lignin purity were used as indicators of the raw material potential. Overall, it is notable that research interest on agro-food lignin has increased exponentially over the years, both as source (567%) and application (128%). Wheat, sugarcane, and maize are the most studied sources and are the ones that render the highest lignin yields. As for the extraction methods used, alkaline and organosolv methods are the most employed (∼50%). The main reported applications are related to lignin incorporation in polymers (∼55%) and as antioxidant (∼24%). Studies on agro-food system-derived lignin is of most importance since there are numerous possible sources that are yet to be fully valorized and many promising applications that need to be further developed.

Circular Hazelnut Protection by Lignocellulosic Waste Valorization for Nanopesticides Development

Hazelnut represents a relevant agro-food supply chain in many countries worldwide. Several biological adversities threaten hazelnut cultivation, but among them bacterial blight is one of the most feared and pernicious since its control can be achieved only by prevention through the observation of good agricultural practices and the use of cupric salts. The aim of this work was to evaluate the lignocellulosic biomasses obtained from hazelnut pruning and shelling residues as a renewable source of cellulose nanocrystals and lignin nanoparticles and to investigate their antimicrobial properties against hazelnut bacterial blight. Cellulose nanocrystals were obtained through an acid hydrolysis after a chemical bleaching, while lignin nanoparticles were synthesized by a solvent–antisolvent method after an enzymatic digestion. Both collected nanomaterials were chemically and morphologically characterized before being tested for their in vitro and in vivo antibacterial activity and biocompatibility on hazelnut plants. Results indicated the selected biomasses as a promising starting material for lignocellulosic nanocarriers synthesis, confirming at the same time the potential of cellulose nanocrystals and lignin nanoparticles as innovative tools to control hazelnut bacterial blight infections without showing any detrimental effects on the biological development of treated hazelnut plants.

Mechanical Activation of Smectite-Based Nanocomposites for Creation of Smart Fertilizers

This research presents the mechanical creation of smart fertilizers from a mixture of smectite and urea in a 3:2 ratio by using the planetary milling technique. The smectite–urea composites show intercalation between urea and mineral, which increases steadily with increasing activation time. A shift of X-Ray Diffraction basal reflections, intensities of Fourier transform infrared spectroscopy (FTIR) peaks, and weight losses in thermogravimetric analysis (TG) document the systematic crystallo-chemical changes of the composites related to nitrogen interaction with activation. Observations of the nanocomposites by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) corroborate the inference. Nitrogen intercalates with smectite in the interlayer space and remains absorbed either within micro-aggregates or on the surface of activated smectites. Soil leaching tests reveal a slower rate of nitrogen than that of traditional urea fertilizers. Different forms of nitrogen within the composites cause their differential release rates to the soil. The formulated nanocomposite fertilizer enhances the quality and quantity of oat yield.

Micronutrients encapsulation by starch as an enhanced efficiency fertilizer

Developing different paths to achieve sustainable agriculture is no longer an option; it is a necessity. EEF materials are alternatives to improve the efficacy of the agrochemicals in the soil and plant, reducing wasting and environmental contamination. The present work aims to develop EEF materials based on starch and micronutrients, considering few works address EEFs materials with micronutrients. Monoelementary dispersions of gelatinized starch with micronutrients (Fe, Cu, Mn) were spray-dried and thermally, structurally, and morphologically characterized. We evaluated water-medium nutrient release, release kinetics, and the swelling degree. Different micronutrients affect morphology, size distribution, swelling degree, release, kinetics, and interaction between polymer-nutrient. Bigger particle sizes achieved a higher swelling degree, which led to decreased micronutrient release in the water. The Peppas-Sahlin model mainly ruled the release kinetics (fitted to all the materials). This result confirmed our hypothesis that a swelling starch delays the release.

A new method for the treatment of kitchen waste: Converting it into agronomic sprayable mulch film

This report describes a new method for converting kitchen waste (KW) with high water content into mulch films that can be applied in agricultural production. Specifically, the KW was emulsion polymerized with acrylic monomers (in various proportions) to obtain a series of sprayable bio-based KW-acrylate mulch films. The films' properties and performances were evaluated, and the experimental results showed that the KW-acrylate mulch films exhibited excellent sprayability, membrane formation, and mechanical properties, which allowed them to effectively reduce soil water evaporation (by 13-50%) and increase soil temperature (by 1.9-6.7%). Compared with bare soil, the soil treated with the optimized KW-acrylate mulch film increased the germination rate of rapeseeds by 20% and the yield of Chenopodium album by 0.7 times; the mulch film biodegradation then reached 70% after 100 days.