Rapid synthesis of a corncob-based semi-interpenetrating polymer network slow-release nitrogen fertilizer by microwave irradiation to control water and nutrient losses

A review on recent progress in polysaccharide/protein hydrogels in winter sports: Classification, synthesis routes, and application

In today's world, emerging materials play prominent roles in competitive sport applications. Among them, hydrogels gained increasing attention in winter sports applications owing to their unique advantages, such as flexibility, conductivity, and adhesion. However, traditional hydrogels prepared by synthetic routes from petroleum materials lose performance at freezing temperatures below zero degrees, limiting their direct use in winter sports. The emergence of natural polymer materials has brought new opportunities for winter sports. Polysaccharide or protein (polysaccharides/proteins) hydrogels obtained from biomass resources are renewable and abundant, especially when taking into consideration the depletion of resources and environmental pollution in contemporary society. The development and utilization of polysaccharide/protein hydrogels may contribute to solving the resource shortage problem. In this paper, the latest research dealing with natural polymer hydrogels for winter sports applications is reviewed. In the first section, recent research trends of hydrogel classification and crosslinking methods are summarized. The performance advantages and specific applications of polysaccharide/protein hydrogels in winter sports are then discussed, with the application scope covering index monitoring, event violation detection, protective equipment, rehabilitation, and venues. Finally, the practical challenges faced by polysaccharide/protein hydrogels in winter sports are prospected along with the innovation and optimization design routes, such as the introduction of natural crosslinking agents and bionic structures. These insights aim to provide a reference for the development of advanced materials for winter sports applications.

Next-generation water-saving strategies for greenhouses using a nexus approach with modern technologies

The escalating food and water crisis, propelled by population growth, urbanization, and climate change, demands a reimagining of agricultural practices. Traditional water-saving irrigation methods have reached their limits, necessitating the exploration of innovative approaches. This perspective explores the potential of utilizing excess light and water in greenhouse cultivation through advanced materials and engineering technologies. We investigate the potential of four key technologies-sorption-based atmosphere water harvesting (SAWH), superabsorbent polymer water holding materials (SPWH), radiative cooling (RC), and seawater desalination. The perspective proposes suitable application methods and future development directions for greenhouse water conservation, aiming to introduce novel water-saving strategies and smarter resource management.

Amide modified cellulose-g-poly acrylic acid as a supple superabsorbent for water retention and soil conditioner

Acrylamide has high hydrophilic properties due to the presence of hydrophilic amide functional groups and is frequently used to synthesize superabsorbents. However, the toxic and carcinogenic properties of acrylamide have caused environmental concerns. The main goal of this paper is the synthesis of superabsorbent with high water absorption from biodegradable and biocompatible cellulose polymer containing amide groups in the backbone of it instead of grafting harmful acrylamide monomers to cellulose. The supple superabsorbent of amide-2,4 modified cellulose-g-poly acrylic acid (Am-2,4 modified cellulose-g-poly (AA)) to reduce water consumption in agriculture and facilitate rooting and root penetration in clay was used. To investigate the effectiveness of superabsorbent in agriculture, its water retention in treated soil (0.2 %) with different temperatures, pHs, and soil textures (sandy loam (SL), sandy clay loam (SCL), clay loam (CL), and loam (L)) was studied. Also, water retention in SCL soil in 2 cycles showed good results. Furthermore, the study includes the optimization of the parameters affecting the water absorption capacity of the superabsorbent, which leads to the absorption of 1253.20 ± 49.67 g/g in distilled water, 86.88 ± 13.36 g/g in 1.0 wt% NaCl solution, and 395 ± 14.86 g/g in tap water under optimal conditions.

A Review on Sustainable Slow-Release N, P, K Fertilizer Hydrogels for Smart Agriculture

The agricultural sector of any country plays a pivotal role in its economy. Irrigation and the provision of appropriate nutrient levels in soil are essential for optimizing plant growth and enhancing crop productivity. To support the increasing need for food due to the growing population worldwide, synthetic fertilizers have been widely used in the agricultural sector. These fertilizers could readily dissolve in the irrigation water or soil moisture, causing excessive release of the nutrients that plants cannot uptake from the root zone. The excess nutrients in the soil further harm the environment via surface run-off, leaching, and volatilization. Thus, materials with high water absorption and retention capacity, and precise control over the prolonged fertilizer release offer a potential solution to address these issues. To meet these requirements, the development of slow-release fertilizer hydrogels (SRFHs) represents a promising approach. SRFHs serve as natural agrochemicals to enhance crop growth and yield through controlled and self-sustained delivery of water and nutrients. This review provides a comprehensive study on the recent advancements in SRFHs, including their preparation methods, properties, slow-release behavior, and applications in smart agriculture. The response of soil microbial diversity to slow-release fertilizers is briefly discussed, and the future potential of SRFHs is highlighted herein.

Rosemary-Mediated Green Synthesis of ZnO Nanoparticles and their Integration into Hydrogel Matrices: Evaluating Effects on Wheat Growth and Antibacterial Properties

In this study, the impact of zinc oxide nanoparticles (ZnO-NPs) generated using rosemary extract, synthesized using environmentally friendly processes and integrated into a cross-linked polymer matrix, on growth performance of wheat is evaluated. Rosemary extract used as coating, stabilizing, and reducing agents in this green synthesis method. Fourier transform infrared spectroscopy analyses demonstrated the presence of phytochemical constituents of the plant extract that served as capping agents during the synthesis process. The nanoparticles are sprayed to the plant leaves. The effects of nanoparticles within the hydrogel on plant development are compared with the effects of nanoparticles in suspension. The percentage of seed germination is unaffected by either rosemary- or raw-ZnO-NPs; however, the root and shoot elongation are considerably impacted by the nanoparticle treatments. The threshold concentrations are determined as 3000 mg L-1 for rosemary-ZnO-NPs and 2000 mg L-1 for raw-ZnO-NPs. Additionally, antibacterial test results showed that the activity level on Escherichia coli is higher for rosemary-ZnO-NPs compared to raw-ZnO-NPs. The results of this research may provide guidance on how green synthesis methods and the use of nanoparticle-hydrogel composites in plant breeding can be used in future agricultural applications. This can be considered an important step in terms of agricultural innovations and sustainability.

Recent Advances in Superabsorbent Hydrogels Derived from Agro Waste Materials for Sustainable Agriculture: A Review

Superabsorbent hydrogels made from agro waste materials have the potential to promote sustainable agriculture and environmental sustainability. These hydrogels not only help reduce water consumption and increase crop yields but also contribute to minimizing waste and lowering greenhouse gas emissions. Recent research on superabsorbent hydrogels derived from agro wastes has focused on the preparation of hydrogels based on natural polymers isolated from agro wastes, such as cellulose, hemicellulose, and lignin. This review provides an in-depth examination of hydrogels developed from raw agro waste materials and natural polymers extracted from agro wastes, highlighting that these studies start with raw wastes as the main materials. The utilization strategies for specific types of agro wastes are comprehensively described. This review outlines different methods utilized in the production of these hydrogels, including physical cross-linking techniques such as dissolution-regeneration and freeze-thawing, as well as chemical cross-linking methods involving various cross-linking agents and graft polymerization techniques such as free radical polymerization, microwave-assisted polymerization, and γ radiation graft polymerization. Specifically, this review explores the applications of agro waste-based superabsorbent hydrogels in enhancing soil properties such as water retention and slow-release of fertilizers for sustainable agriculture.

Rational Design of a Multifunctional Hydrogel Trap for Water and Fertilizer Capture: A Review

Water scarcity and land infertility pose significant challenges to agricultural development, particularly in arid and semiarid regions. Improving soil-water-retention capacity and fertilizer utilization efficiency through the application of soil additives has become a pivotal approach in agricultural practices. Hydrogels exhibit exceptional water absorption and fertilizer retention capabilities, making them extensively utilized in the fields of agriculture, forestry, and desert control. Currently, most reviews primarily focus on the raw materials, classification, synthesis methods, and application prospects of hydrogels, with limited attention given to strategies for enhancing water-retention performance, mechanisms underlying fertilizer absorption, and environmental risks. This review covers the commonly used cross-linking methods in hydrogel synthesis and the structure-activity relationship between hydrogels and water as well as fertilizer. Additionally, a thorough analysis of the ecological benefits and risks associated with hydrogels is presented. Finally, future prospects and challenges are delineated from the perspectives of material design and engineering applications.

Design and manufacture of new hybrid hydrogel and superabsorbent polymer for controlled release of fulvic acid based on grafted xanthan gum/gelatin using electron irradiation and its use in fodder corn cultivation

A humic acid-gelatin (HA-Gel) hydrogel, a gallic acid-xanthan gum (GA-XG) hydrogel, a HA-Gel/GA-XG hydrogel, and superabsorbent polymer (SAP) of HA-Gel/GA-XG/polyacrylamide (PAM) hydrogel were synthesized using electron beam irradiation method. The capability of synthesized hydrogels in loading and controlled release of fulvic acid (FA) was studied. The chemical and physical structure of sorbents was confirmed by various analyses. The effect of irradiation dose on mechanical properties, gel percentage, swelling, and absorbency under load (AUL) of the sorbents was investigated. By changing the hydrogel structures into the SAP form, its swelling capacity was increased from 37 to 320 g/g. Both hybrid hydrogel and SAP were reusable for up to 7 cycles. The maximum fertilizer loading capacities for SAP and hybrid hydrogel were 402.1 and, 175.5 mg g-1, respectively. In comparison to hydrogels, the SAP showed a slower FA-release performance. Thus, in soil media, 86 % of FA was released in 15-20 days from the hybrid hydrogel while with the SAP, 81 % of FA was released in 30-35 days. The significant improvement in the growth of fodder corn treated with FA-loaded SAP in the greenhouse media in comparison to the control groups showed the effective performance of the designed SAP, favoring its practical applications.

Sustainable SMART fertilizers in agriculture systems: A review on fundamentals to in-field applications

Agriculture will face the issue of ensuring food security for a growing global population without compromising environmental security as demand for the world's food systems increases in the next decades. To provide enough food and reduce the harmful effects of chemical fertilization and improper disposal or reusing of agricultural wastes on the environment, will be required to apply current technologies in agroecosystems. Combining biotechnology and nanotechnology has the potential to transform agricultural practices and offer answers to both immediate and long-term issues. This review study seeks to identify, categorize, and characterize the so-called smart fertilizers as the future frontier of sustainable agriculture. The conventional fertilizer and smart fertilizers in general are covered in the first section of this review. Another key barrier preventing the widespread use of smart fertilizers in agriculture is the high cost of materials. Nevertheless, smart fertilizers are widely represented on the world market and are actively used in farms that have already switched to sustainable technologies. The advantages and disadvantages of various raw materials used to create smart fertilizers, with a focus on inorganic and organic materials, synthetic and natural polymers, along with their physical and chemical preparation processes, are contrasted in the following sections. The rate and the mechanism of release are covered. The purpose of this study is to provide a deep understanding of the advancements in smart fertilizers during the last ten years. Trends are also recognized and studied to provide insight for upcoming agricultural research projects.

Maleic acid as an important monomer in synthesis of stimuli-responsive poly(acrylic acid-co-acrylamide-co-maleic acid) superabsorbent polymer

Poly(acrylic acid-co-acrylamide-co-maleic acid) (p(AA-co-AM-co-MA)) superabsorbent polymer was synthesized from acrylic acid (AA), acrylamide (AM), and maleic acid (MA) via free radical copolymerization. Results showed the presence of maleic acid in structure of superabsorbent has the key and superior role in creating a smart superabsorbent. The structure, morphology, and strength of the superabsorbent were characterized using FT-IR, TGA, SEM, and rheology analysis. The effect of different factors was investigated to determine the ability of water absorbency of the superabsorbent. According to optimized conditions, the water absorbency capacity of the superabsorbent in distilled water (DW) was 1348 g/g and in a solution containing 1.0 wt.% NaCl (SCS) was 106 g/g. The water retention ability of the superabsorbent was also investigated. The kinetic swelling of superabsorbent was identified by Fickian diffusion and Schott's pseudo-second-order model. Furthermore, the reusability of superabsorbent was studied in distilled water and saline solution. The ability of superabsorbent was investigated in simulated urea and glucose solutions, and very good results were obtained. The response ability of the superabsorbent was confirmed by swelling and shrinking behavior against changes of temperature, pH, and ionic strength.

Environmentally friendly hydrogel: A review of classification, preparation and application in agriculture

Superabsorbent hydrogel (SH) is three-dimensional (3D) cross-linked hydrophilic polymer that can absorb and retain large quantities of water or other aqueous solutions. SH is made of water-affinity monomers and is widely used in biomedicine, wastewater treatment, hygiene and slow-release fertilizers (SRFs). This article focused on the preparation methods of SH, superabsorbent hydrogel composite and the application of SH in agriculture. By selecting various synthetic technologies and cross-linking agents, a series of chemical cross-linking or physical networks can be designed and tailored to meet specific applications. In view of the excellent characteristics of water absorption, biodegradability, water retention and slow-release capacity, SH occupies a dominant position in the SRFs market. In this work, the agricultural application of SH in double coated SRFs and nutrients carriers is also discussed. Some mechanisms related to the nutrient release were analyzed by mathematical models. In addition, some agronomic benefits of using superabsorbent hydrogels in improving water absorption, water holding capacity and increasing crop yields were also discussed. Although SH has certain shortcomings, from the perspective of long-term development, it will further show great potential in sustainable agriculture.

Development of Biodegradable PLA/PBAT-Based Filaments for Fertilizer Release for Agricultural Applications

The aim of this work was to produce filaments of PLA/PBAT and NPK fertilizer adsorbed on organophilized bentonite intended for application in the prototyping of biodegradable agricultural artifacts in 3D printing, using the Fused Deposition Modeling (FDM) technique. This is the first time that we have reported this composite for a 3D printing approach. Systems containing PLA/PBAT, organobentonite and NPK were initially processed in an internal mixer and later extruded as filaments in a single-screw extruder. The prototypes were printed by FDM. Structural, morphological and thermal properties, as well as NPK releasing, were investigated. The results suggest that exfoliated and/or intercalated nanocomposites were obtained by the organoclay addition to the PLA/PBAT blend. The morphological analysis revealed a good surface quality of the impressions. Systems containing organobentonite released approximately 22% less fertilizer in 24 h compared to the systems without organobentonite. This difference is due to the higher concentration of nanoparticles that generate more barriers to the diffusion of NPK. The release data for these systems had a better fit to the kinetic model of Korsmeyer-Peppas. Thus, studied filaments have the potential to retard the release of fertilizer and are suitable for further development of structures for agricultural applications by FDM.

The preparation of slow-release fertilizers with biomass ash and water/waste acid solutions from desulfurization and denitrification of flue gas

In this study, a method of preparing fertilizers with the fly ash from biomass power plants and the waste acid solution from flue gas desulfurization and denitrification was disclosed. In addition, the study also explored the effects of added fine particles, unburned biochar, and other commercial fertilizers on soil water retention and slow-release effect of fertilizers. The analysis was done by comparing the aggregation degrees of crystalline salt and the variations of the chemical bonds. The experimental results showed that the added fine particles could effectively increase the water absorption of fertilizers, which helped to improve soil water retention. Meanwhile, the fine particles could strengthen the special adsorption of basic compounds containing N, P, and other nutrients by biochar and enhance the slow-release effect of fertilizers. Although adding part commercial fertilizers weakened the water absorption of fertilizers slightly, it had only a relatively small effect on the aggregation of water-soluble crystalline salt on the surfaces of fine particles and biochar. Furthermore, the microwave was applied to promote the absorption of N by unburned biochar, during which only small amounts of volatile were released and lost. The experiments had confirmed that microwave irradiation could promote the agglomeration of biochar on crystalline salt effectively, thus enhancing the slow-release effect of crystalline salt in fertilizers. Finally, pot experiments demonstrated that the self-prepared fertilizer improved plant growth by its better water absorption and slow-release properties during the whole growth period, which had promising application potential as the slow-release fertilizer in the plant growth field.

Synergistic Effect of Hydrogen Bonds and Chemical Bonds to Construct a Starch-Based Water-Absorbing/Retaining Hydrogel Composite Reinforced with Cellulose and Poly(ethylene glycol)

The hydrogel prepared by graft copolymerization of starch (ST) and acrylamide (AM) is a commonly used absorbent material; however, due to their irregular network structure and a limited number of hydrophilic groups, starch-based hydrogels have poor water absorption and water retention. To overcome this, here, we provide a new preparation method for starch-based hydrogels. Using cerium ammonium nitrate (CAN) as an initiator, the starch-acrylamide-cellulose (CMC)/poly(ethylene glycol) (S-A-M/PEG) superabsorbent hydrogel was prepared by graft copolymerization. The starch-acrylamide-cellulose/poly(ethylene glycol) hydrogel network is constructed through the synergistic effect of hydrogen bonds and chemical bonds. The experimental results showed that the starch-acrylamide-cellulose/poly(ethylene glycol) superabsorbent hydrogel has a complete network structure that does not easily collapse due to its superior mechanical properties. The water swelling rate reached 80.24 times, and it reached 50.61% water retention after 16 days. This hydrogel has excellent water-absorbing and water-retaining properties, biocompatibility, and degradability, making it useful for further studies in medical, agricultural, and other fields.

Construction of Porous Starch-Based Hydrogel via Regulating the Ratio of Amylopectin/Amylose for Enhanced Water-Retention

The performance of hydrogels prepared with traditional natural starch as raw materials is considerable; the fixed ratio of amylose/amylopectin significantly limits the improvement of hydrogel structure and performance. In this paper, starch hydrogels were prepared by physical blending and chemical grafting, with the aid of ultrasonic heating. The effects of different amylose/amylopectin ratios on the microstructure and water retention properties of starch hydrogels were studied. The results show that an increase in amylopectin content is beneficial to improve the grafting ratio of acrylamide (AM). The interaction between the AM grafted on amylopectin and amylose molecules through hydrogen bonding increases the pores of the gel network and thins the pore walls. When the amylopectin content was 70%, the water absorption (swelling 45.25 times) and water retention performance (16 days water retention rate 44.17%) were optimal. This study provides new insights into the preparation of starch-based hydrogels with excellent physical and chemical properties.

Synthesis of a novel superabsorbent with slow-release urea fertilizer using modified cellulose as a grafting agent and flexible copolymer

In this work, a number of glucose unites in polymeric structure of cellulose was converted to 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy)butanal (cellulose containing di aldehyde units (CCDAUs)) by oxidation with sodium periodate, followed by condensation with acetone to produce 5,7-dihydroxy-6-((1-hydroxy-4-oxopent-2-en-1-yl)oxy)hept-3-en-2-one unites (cellulose containing di ene units (CCDEUs)). This modified cellulose was characterized by different methods and applied as a copolymer and grafting agent to synthesize an eco-friendly (CCDEUs-g-poly(AA)/urea) superabsorbent with slow-release urea fertilizer. The created double bonds in C₂ and C₃ positions of β-d-glucose units increased the linkage between cellulose and acrylic acid, leading to the formation of a strong network for slow-release urea fertilizer. Also, this modification created an expanded network for storage a high amount of water by increasing the cellulose flexibility. The reaction conditions for modification and synthesis of the superabsorbent, the oxidation degree value of glucose units, kinetics models, the effect of different saline solutions, various pH and reswelling time on the water absorbency, water retention capacity, reusability, biodegradability, and slow-release property were investigated. Also, the effect of synthesized CCDEUs-g-poly(AA)/urea on plant growth was tested and excellent results were obtained.

A comparison of microwave and ultrasound routes to prepare nano-hydroxyapatite fertilizer improving morphological and physiological properties of maize (Zea mays L.)

Hydroxyapatite nanoparticles have a remarkable potential to be used as nano-fertilizers with great effects on improving the yield of plants. These nano-compounds were synthesized using microwave and ultrasound methods, which decrease the particle size distribution of the products. To investigate the effects of two types of simple and triple superphosphate fertilizers on some properties of maize plant (Zea mays L.), a factorial experiment was conducted based on a completely randomized block design. The fertilizer treatments included in this study were simple superphosphate, triple superphosphate, microwave nano-hydroxyapatite, and ultrasound nano-hydroxyapatite and examined at five concentration levels. The results showed that the application of nano-hydroxyapatite phosphate fertilizers improved the growth and physiological properties of maize plant. This would raise better results in comparison to the simple and triple superphosphate fertilizers. Considering the positive effects of nano-hydroxyapatite fertilizers and high production levels, the results of this experiment revealed that the synthetic nano-hydroxyapatite methods prevent phosphorus loss; therefore, it is recommended to use nano-phosphate fertilizers in food resource management to achieve a favorable quantitative yield. Moreover, they can be regarded as a favorable solution to deal with the environmental problems.

Controlled Release Fertilizers: A Review on Coating Materials and Mechanism of Release

Rising world population is expected to increase the demand for nitrogen fertilizers to improve crop yield and ensure food security. With existing challenges on low nutrient use efficiency (NUE) of urea and its environmental concerns, controlled release fertilizers (CRFs) have become a potential solution by formulating them to synchronize nutrient release according to the requirement of plants. However, the most significant challenge that persists is the "tailing" effect, which reduces the economic benefits in terms of maximum fertilizer utilization. High materials cost is also a significant obstacle restraining the widespread application of CRF in agriculture. The first part of this review covers issues related to the application of conventional fertilizer and CRFs in general. In the subsequent sections, different raw materials utilized to form CRFs, focusing on inorganic and organic materials and synthetic and natural polymers alongside their physical and chemical preparation methods, are compared. Important factors affecting rate of release, mechanism of release and mathematical modelling approaches to predict nutrient release are also discussed. This review aims to provide a better overview of the developments regarding CRFs in the past ten years, and trends are identified and analyzed to provide an insight for future works in the field of agriculture.

Development of polymer composites and encapsulation technology for slow-release fertilizers

The fertilizer manufacturing faces an ongoing challenge to develop its products to raise the effectiveness of their application, mainly of nitrogenous fertilizers, as well as to reduce any probable adverse ecological effect. In general, chemical fertilizers are very necessary for agricultural lands to provide the essential nutrients for plant growth, which are lost and leached into the surrounding environment during irrigation, which then leads to unwanted side effects, such as crop failure or increased losses to the environment. To solve this problem of nutrients being wasted, the most effective way is to use slow or controlled-release fertilizers (S/CRFs). The current review provides an insight vision into the methods used to save agricultural fertilizers from being wasted due to irrigation. The functional materials or physical techniques are used to maintain a steady release of nutrients. Fertilizers are encapsulated with various compounds based on synthetic or natural polymers to be used as SRFs. In this review paper, a comprehensive survey is presented on SRFs as an effective method in dealing with the problem of fertilizer wastage during irrigation. This review discusses the technology and applications of the latest research findings in this field.

Biochar reduced Chinese chive (Allium tuberosum) uptake and dissipation of thiamethoxam in an agricultural soil

Information about the effect of biochar on the environmental fate of pesticide thiamethoxam (THI) in soil-vegetable ecosystems is limited. Therefore, the influence of a wood-derived biochar produced at 450 °C (BC450) on the uptake of THI by Chinese chive (Allium tuberosum) and its dissipation in soil was investigated using a 42-day pot experiment. BC450 addition decreased THI uptake and its metabolite clothianidin (CLO) by 22.8 % and 37.6 %, respectively. However, the half-life of THI in soil rose from 89.4-120 days, indicating that BC450 increased soil THI's persistence. The decreased bioavailability and increased persistence of THI resulted mainly from the higher sorption capacity of BC450 to THI and CLO, which, in turn, enhanced the soil sorption capacity. Consequently, the application of BC450 increased the soil microbial diversity and altered the structure of the microbial community. Although the abundance of Actinobacteria associated with the biodegradation of THI, increased the persistence of THI in the BC450-amended soil, mainly due to the decrease in bioavailable THI. Our findings provide valuable information about the effect of biochar on the fate of THI and its metabolites in agricultural soil and will help to guide the practical application of biochar to remediate soils contaminated with neonicotinoid pesticides.

Dimethylolurea as a Novel Slow-Release Nitrogen Source for Nitrogen Leaching Mitigation and Crop Production

Rapid hydrolysis of urea results in further fertilization frequency and excessive nitrogen (N) input. A modified urea, dimethylolurea (DMU), was synthesized in this study. The structure of the sample was characterized by Fourier transform infrared and nuclear magnetic resonance analysis, manifesting the formation of DMU. N release investigation confirmed that DMU enabling provided a gradual N supply. The N leaching experiment indicated that increasing the applied DMU significantly reduced the NH₄⁺-N, NO₃^--N, and total N leaching, compared with urea application alone. The application effect on maize and wheat was evaluated. The results revealed that singly applied DMU with 100% or 80% N input, irrespective of the amount, promoted crop yield and agronomic characteristic and N use efficiency (NUE) of maize and wheat, beyond urea with two split applications at the recommended rate. Thus, the potential availability of DMU was proven; this could be widely used in agricultural fields as a slow-release fertilizer.

Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 1. Microscopic Structure, Water Absorbency, and Degradation Performance

Few studies have been conducted on the use of general nanotechnology-based principles for providing nutrients to crops. Water and fertilizer are the most important inputs in determining crop yield and profit. In this paper, super-absorbent polymers SAP_WS (grafting wheat straw (WS) to poly(acrylic-co-acrylamide), which is WS-g-P(AA-co-AM)) and SAP_HEC (HEC (hydroxyethyl cellulose)-g-P(AA-co-AM)) and their semi-interpenetrating polymer network (semi-IPN) nanocomposites SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC (formed by chemical bonding of SAP_WS or SAP_HEC with PSRF (NPK-containing polymeric slow-release fertilizer)) were prepared. Due to the differences between activity and number of functional groups in WS and HEC, the water absorption properties and degradation performances of SAP_WS and SAP_HEC and their chemically bonded function nanocomposites SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC are different. The maximum water absorption ratios of SAP_WS, SAP_HEC, SI-PSRF/SAP_WS, and SI-PSRF/SAP_HEC can reach 200.00 g/g, 240.00 g/g, 119.91g/g, and 127.43 g/g, respectively. Effects of the structures of these four materials on their degradation performances were studied via a tomato pot experiment. The changes in microstructures of these materials during the degradation processes were characterized by TEM, SEM, FTIR, XRD, XPS, and other techniques. Results show that the degradation rate of the chemically bonded functional nanocomposites with a semi-IPN structure SI-PSRF/SAP system is higher than that of SAP+PSRF (the simple physically mixed system of PSRF and SAP). Due to the differences among the activities and quantities of functional groups in WS and HEC, the water absorption properties of SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC are different, and there are different degradation rates for these two functional nanocomposites.

A biodegradable biomass-based polymeric composite for slow release and water retention

Slow-release fertilizer has been proven to be more effective than traditional fertilizer for providing a long-term stable nutrient supply. Although such fertilizers have been widely investigated, their water-retention properties and biodegradability have not been fully analysed. Composites of fertilizers and polymers provide opportunities to prepare new types of fertilizer with enhanced properties for real applications. Chicken feather protein-graft-poly(potassium acrylate)-polyvinyl alcohol semi-interpenetrating networks forming a super absorbent resin combined with nitrogen (N) and phosphorus (P) (CFP-g-PKA/PVA/NP semi-IPNs SAR) was prepared. The chemically bonded or physically embedded fertilizer compound could be released form the resin matrix to the surrounding soil under irrigation. The synthesis mechanism, morphology, and chemical and mechanical structure of the synthesized composites were investigated. The reactant doses were optimized through response surface methodology (RSM). A 30-day field trial of the prepared SAR was applied to detect the influence of sample particle size, soil salinity, pH, and moisture content on the slow-release behaviour of N and P. The maximum release values of N and P from the composites were 69.46% N and 65.23% P. A 120-day soil burying experiment and 30-day Aspergillus niger (A. niger) inoculation were performed, and the biodegradability and change in microstructure were monitored. The addition of SAR to soil could also improve the water-retention ability of the soil.

Slow release fertilizer hydrogels: a review

Slow release fertilizer hydrogels combine fertilizer and hydrogel into one system.

Plant growth promotion and alleviation of salinity stress in Capsicum annuum L. by Bacillus isolated from saline soil in Xinjiang

To maintain the growth and development of pepper in saline condition, candidates of plant growth promoting rhizobacteria (PGPR) were isolated, and detected to plant growth promoting (PGP) potential under salt stress was investigated. Thirteen bacterial strains with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, WU-1-13, were isolated from saline soil in Xinjiang, China. The isolates were shown to belong to the genera Bacillus by partial sequencing analysis of their respective 16 S rRNA genes. Seven isolates had the ability to solubilize phosphate. Moreover, the amount of solubilized phosphate was significantly high (P < 0.05), which ranged from 157.33 μg/mL to 922.41 μg/mL. All tested bacterial strains were shown to produce a large amount of ACC deaminase and NH₃. Furthermore, nine strains were detected for siderophore production. On the aspect of extracellular enzyme, all bacterial isolates produced lipase, amylase and cellulose, whereas only a minority produced chitinase (15.4%) and 10 isolates produced β-glucanase or protease. In growth room experiments, the results showed that the strain WU-5 exhibited better growth promotion of pepper seedlings in terms of fresh weight (75.60%), dry weight (86.68%), shoot length (12.12%) and root length (146.52%) over the control under saline stress followed by WU-13. Furthermore, seedlings accumulated high amounts of proline induced by the different PGPR inoculation treatments to alleviate the negative effects of salt stress. Further growth-promoting assays under different salt stress were set up to confirm that the fresh and dry weight, shoot and root length of pepper plants inoculated by three strains all were significantly higher than non-inoculated control under different saline stress. In summary, the results demonstrated that WU-9, which induced high levels of proline production and antioxidant enzyme activities, and three strains (WU-5, WU-9 and WU-13) can be of great value in maintaining the growth and development of seedlings on saline lands.

Slow-release NPK fertilizer encapsulated by carboxymethyl cellulose-based nanocomposite with the function of water retention in soil

In this study, new slow release fertilizer encapsulated by superabsorbent nanocomposite was prepared by in-situ graft polymerization of sulfonated-carboxymethyl cellulose (SCMC) with acrylic acid (AA) in the presence of polyvinylpyrrolidone (PVP), silica nanoparticles and nitrogen (N), phosphorous (P), and potassium (K) (NPK) fertilizer compound. The prepared materials were characterized by FT-IR, XRD and scanning electron microscopy (SEM) techniques. The incorporation of NPK fertilizer into hydrogel nanocomposite network was verified by results of these analyses. Also, the swelling behavior in various pH and saline solutions as well as water retention capability of the prepared hydrogel nanocomposite was evaluated. The fertilizer release behavior of the NPK loaded hydrogel nanocomposite was in good agreement with the standard of Committee of European Normalization (CEN), indicating its excellent slow release property. These good characteristics revealed that the hydrogel nanocomposite fertilizer formulation can be practically used in agricultural and horticultural applications.