Controlled release micronutrient fertilizers for precision agriculture - A review

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.

Nano hybrid fertilizers: A review on the state of the art in sustainable agriculture

The advent of Nanohybrid (NH) fertilizers represents a groundbreaking advancement in the pursuit of precision and sustainable agriculture. This review abstract encapsulates the transformative potential of these innovative formulations in addressing key challenges faced by modern farming practices. By incorporating nanotechnology into traditional fertilizer matrices, nanohybrid formulations enable precise control over nutrient release, facilitating optimal nutrient uptake by crops. This enhanced precision not only fosters improved crop yields but also mitigates issues of over-fertilization, aligning with the principles of sustainable agriculture. Furthermore, nanohybrid fertilizers exhibit the promise of minimizing environmental impact. Their controlled release mechanisms significantly reduce nutrient runoff, thereby curbing water pollution and safeguarding ecosystems. This dual benefit of precision nutrient delivery and environmental sustainability positions nanohybrid fertilizers as a crucial tool in the arsenal of precision agriculture practices. The intricate processes of uptake, translocation, and biodistribution of nutrients within plants are examined in the context of nanohybrid fertilizers. The nanoscale features of these formulations play a pivotal role in governing the efficiency of nutrient absorption, internal transport, and distribution within plant tissues. Factors affecting the performance of nanohybrid fertilizers are scrutinized, encompassing aspects such as soil type, crop variety, and environmental conditions. Understanding these variables is crucial for tailoring nanohybrid formulations to specific agricultural contexts, and optimizing their impact on crop productivity and resource efficiency. Environmental considerations are integral to the review, assessing the broader implications of nanohybrid fertilizer application. This review offers a holistic overview of nanohybrid fertilizers in precision and sustainable agriculture. Exploring delivery mechanisms, synthesis methods, uptake dynamics, biodistribution patterns, influencing factors, and environmental implications, it provides a comprehensive understanding of the multifaceted role and implications of nanohybrid fertilizers in advancing modern agricultural practices.

Selenium nanoparticles induce coumarin metabolism and essential oil production in Trachyspermum ammi under future climate CO2 conditions

Research on nanoparticles (NPs) and future elevated CO2 (eCO2) is extensive, but the effects of SeNPs on plant growth and secondary metabolism under eCO2 remain uncertain. In this study, we explored the impact of SeNPs and/or eCO2 on the growth, physiology, chemical composition (primary metabolites, coumarins, and essential oils), and antioxidant capacity of Trachyspermum (T.) ammi. The treatment with SeNPs notably improved the biomass and photosynthesis of T. ammi plants, particularly under eCO2 conditions. Plant fresh and dry weights were improved by about 19, 33 and 36% in groups treated by SeNPs, eCO2, and SeNPs + eCO2, respectively. SeNPs + eCO2 induced photosynthesis, consequently enhancing sugar and amino acid levels. Similar to the increase in total sugars, amino acids showed variable enhancements ranging from 6 to 42% upon treatment with SeNPs + eCO2. At the level of the secondary metabolites, SeNPs + eCO2 substantially augmented coumarin biosynthesis and essential oil accumulation. Consistently, there were increases in coumarins and essential oil precursors (shikimic and cinnamic acids) and their biosynthetic enzymes. The enhanced accumulation of coumarins and essential oils resulted in increased overall antioxidant activity, as evidenced by improvements in FRAP, ORAC, TBARS, conjugated dienes, and inhibition % of hemolysis. Conclusively, the application of SeNPs demonstrates significant enhancements in plant growth and metabolism under future CO2 conditions, notably concerning coumarin metabolism and essential oil production of T. ammi.

Advancing horizons in vegetable cultivation: a journey from ageold practices to high-tech greenhouse cultivation-a review

Vegetable cultivation stands as a pivotal element in the agricultural transformation illustrating a complex interplay between technological advancements, evolving environmental perspectives, and the growing global demand for food. This comprehensive review delves into the broad spectrum of developments in modern vegetable cultivation practices. Rooted in historical traditions, our exploration commences with conventional cultivation methods and traces the progression toward contemporary practices emphasizing the critical shifts that have refined techniques and outcomes. A significant focus is placed on the evolution of seed selection and quality assessment methods underlining the growing importance of seed treatments in enhancing both germination and plant growth. Transitioning from seeds to the soil, we investigate the transformative journey from traditional soil-based cultivation to the adoption of soilless cultures and the utilization of sustainable substrates like biochar and coir. The review also examines modern environmental controls highlighting the use of advanced greenhouse technologies and artificial intelligence in optimizing plant growth conditions. We underscore the increasing sophistication in water management strategies from advanced irrigation systems to intelligent moisture sensing. Additionally, this paper discusses the intricate aspects of precision fertilization, integrated pest management, and the expanding influence of plant growth regulators in vegetable cultivation. A special segment is dedicated to technological innovations, such as the integration of drones, robots, and state-of-the-art digital monitoring systems, in the cultivation process. While acknowledging these advancements, the review also realistically addresses the challenges and economic considerations involved in adopting cutting-edge technologies. In summary, this review not only provides a comprehensive guide to the current state of vegetable cultivation but also serves as a forward-looking reference emphasizing the critical role of continuous research and the anticipation of future developments in this field.

Selenium Nanomaterials Enhance the Nutrients and Functional Components of Fuding Dabai Tea

Theanine, polyphenols, and caffeine not only affect the flavor of tea, but also play an important role in human health benefits. However, the specific regulatory mechanism of Se NMs on fat-reducing components is still unclear. In this study, the synthesis of fat-reducing components in Fuding Dabai (FDDB) tea was investigated. The results indicated that the 100-bud weight, theanine, EGCG, total catechin, and caffeine contents of tea buds were optimally promoted by 10 mg·L-1 Se NMs in the range of 24.3%, 36.2%, 53.9%, 67.1%, and 30.9%, respectively. Mechanically, Se NMs promoted photosynthesis in tea plants, increased the soluble sugar content in tea leaves (30.3%), and provided energy for the metabolic processes, including the TCA cycle, pyruvate metabolism, amino acid metabolism, and the glutamine/glutamic acid cycle, ultimately increasing the content of amino acids and antioxidant substances (catechins) in tea buds; the relative expressions of key genes for catechin synthesis, CsPAL, CsC4H, CsCHI, CsDFR, CsANS, CsANR, CsLAR, and UGGT, were significantly upregulated by 45.1-619.1%. The expressions of theanine synthesis genes CsTs, CsGs, and CsGOGAT were upregulated by 138.8-693.7%. Moreover, Se NMs promoted more sucrose transfer to the roots, with the upregulations of CsSUT1, CsSUT2, CsSUT3, and CsSWEET1a by 125.8-560.5%. Correspondingly, Se NMs enriched the beneficial rhizosphere microbiota (Roseiarcus, Acidothermus, Acidibacter, Conexicter, and Pedosphaeraceae), enhancing the absorption and utilization of ammonium nitrogen by tea plants, contributing to the accumulation of theanine. This study provides compelling evidence supporting the application of Se NMs in promoting the lipid-reducing components of tea by enhancing its nitrogen metabolism.

Integrated Ca, Mg, Cu, and Zn supply upregulates leaf anatomy and metabolic adjustments in Eucalyptus seedlings

Adaptive responses to abiotic stresses such as soil acidity in Eucalyptus-the most widely planted broad-leaf forest genus globally-are poorly understood. This is particularly evident in physiological and anatomical disorders that inhibit plant development and wood quality. We aimed to explore how the supply of Ca and Mg through liming (lime), combined with Cu and Zn fertilization (CZF), influences physiological and anatomical responses during Eucalyptus grandis seedlings growth in tropical acid soil. Therefore, related parameters of leaf area and leaf anatomy, stomatal size, leaf gas exchange, antioxidant system, nutrient partitioning, and biomass allocation responses were monitored. Liming alone in Eucalyptus increased specific leaf area, stomatal density on the abaxial leaf surface, and Ca and Mg content. Also, Eucalyptus exposed only to CZF increased Cu and Zn content. Lime and CZF increased leaf blade and adaxial epidermal thickness, and improved the structural organization of the spongy mesophyll, promoting increased net CO2 assimilation, and stomatal conductance. Fertilization with Ca, Mg, Cu, and Zn positively affects plant nutrition, light utilization, photosynthetic rate, and antioxidant performance, improving growth. Our results indicate that lime and CZF induce adaptive responses in the physiological and anatomical adjustments of Eucalyptus plantation, thereby promoting biomass accumulation.

Split application of polymer-coated urea combined with common urea improved nitrogen efficiency without sacrificing wheat yield and benefits while saving 20% nitrogen input

Controlled-release nitrogen fertilizer (CRNF) has been expected to save labor input, reduce environmental pollution, and increase yield in crop production. However, the economic feasibility is still controversial due to its high cost. To clarify the suitable application strategy of CRNF in promoting the yield, nitrogen use efficiency and income on wheat grown in paddy soil, four equal N patterns were designed in 2017-2021 with polymer-coated urea (PCU) and common urea as material, including PCU applied once pre-sowing (M1), PCU applied 60% at pre-sowing and 40% at re-greening (M2), 30% PCU and 30% urea applied at pre-sowing, 20% PCU and 20% urea applied at re-greening (M3), and urea applied at four stage (CK, Basal:tillering:jointing:booting=50%:10%:20%:20%). In addition, M4-M6, which reduced N by 10%, 20% and 30% respectively based on M3, were designed in 2019-2021 to explore their potential for N-saving and efficiency-improving. The results showed that, compared with CK, M1 did not significantly reduce yield, but decreased the average N recovery efficiency (NRE) and benefits by 1.63% and 357.71 CNY ha-1 in the four years, respectively. M2 and M3 promoted tiller-earing, delayed the decrease of leaf area index (LAI) at milk-ripening stage, and increased dry matter accumulation post-anthesis, thereby jointly increasing spike number and grain weight of wheat, which significantly increased yield and NRE compared with CK in 2017-2021. Due to the savings in N fertilizer costs, M3 achieved the highest economic benefits. With the 20% N reduction, M5 increased NRE by 16.95% on average while decreasing yield and net benefit by only 6.39% and 7.40% respectively, compared with M3. Although NRE could continue to increase, but the yield and benefits rapidly decreased after N reduction exceeds 20%. These results demonstrate that twice-split application of PCU combined with urea is conducive to achieving a joint increase in yield, NRE, and benefits. More importantly, it can also significantly improve the NRE without losing yield and benefits while saving 20% N input.

Enhanced use of chemical fertilizers and mitigation of heavy metal toxicity using biochar and the soil fungus Bipolaris maydis AF7 in rice: Genomic and metabolomic perspectives

Chemical fertilizers are the primary source of crop nutrition; however, their increasing rate of application has created environmental hazards, such as heavy metal toxicity and eutrophication. The synchronized use of chemical fertilizers and eco-friendly biological tools, such as microorganisms and biochar, may provide an efficient foundation to promote sustainable agriculture. Therefore, the current study aimed to optimize the nutrient uptake using an inorganic fertilizer, sulfate of potash (SOP) from the plant growth-promoting fungus Bipolaris maydis AF7, and biochar under heavy metal toxicity conditions in rice. Bioassay analysis showed that AF7 has high resistance to heavy metals and a tendency to produce gibberellin, colonize the fertilizer, and increase the intake of free amino acids. In the plant experiment, the co-application of AF7 +Biochar+MNF+SOP significantly lowered the heavy metal toxicity, enhanced the nutrient uptake in the rice shoots, and improved the morphological attributes (total biomass). Moreover, the co-application augmented the glucose and sucrose levels, whereas it significantly lowered the endogenous phytohormone levels (salicylic acid and jasmonic acid) in the rice shoots. The increase in nutrient content aligns with the higher expression of the OsLSi6, PHT1, and OsHKT1 genes. The plant growth traits and heavy metal tolerance of AF7 were validated by whole-genome sequencing that showed the presence of the heavy metal tolerance and detoxification protein, siderophore iron transporter, Gibberellin cluster GA4 desaturase, and DES_1 genes, as well as others that regulate glucose, antioxidants, and amino acids. Because the AF7 +biochar+inorganic fertilizer works synergistically, nutrient availability to the crops could be improved, and heavy metal toxicity and environmental hazards could be minimized.

Exhausted fire-extinguishing powders: A potential source of mineral nutrients for reuse and valorisation in compost enrichment for soilless cultivation

Fire-extinguishing powders (FEPs) are constituted by an inner mineral core of (NH4)H2PO4 and (NH4)2SO4 salts (>95 %, by weight) externally coated with Si-based additives, which make problematic reuse after their service life has expired (36 months). This study aimed to assess the feasibility of using the composting process as an environmentally friendly strategy to lyse the external coating and recycle this nutrient-rich solid waste for replacement of inorganic fertilization in soilless cultivation of horticultural crops. A microcosm-scale experiment with lettuce plants grown into a soil/quartz sand mixture under controlled conditions for 28 days was used to investigate plant responses (fresh and dry biomass, chlorophyll fluorescence parameters, root morphology, ash and nutrients content) to amendment with increasing dosages (equivalent at 0, 10, 20 and 30 t ha-1) of an exhausted FEPs-enriched compost. Chemical properties (pH, EC, TOC, TN) and content of soluble nutrients (Na+, K+, Mg2+, Ca2+, NH4+, H2PO4-, SO42-, NO3-, Cl-) released into the growing substrate were also monitored. Non-amended microcosms and non-enriched compost treatments were taken as controls. Results showed, beside the expected rise of phosphate, sulphate and ammonium ions, exhausted FEPs contributed Ca2+, Mg2+ and Na+ content. Whereas compost determined a dose-dependent release of K+, which was particularly useful in maintaining the K/Na ratio in a range not harmful to plant physiology. It was also found that the compost enriched with 5 % (w/w) exhausted FEPs was no phytotoxic to lettuce. On the contrary, it stimulated the plant growth, increased the photosynthetic efficiency and the shoot biomass accumulation, thus incrementing the shoot/root ratio. Moreover, it oriented the root morphology development and promoted the plant uptake of both water and solutes. To sum up, composting represents a suitable alternative to chemical treatment to recover readily available nutrients contained in exhausted FEPs and produce an enriched compost for use in soilless cultivation.

Chitosan microspheres-based controlled-release nitrogen fertilizers improve the biological characteristics of Brassica rapa ssp. pekinensis and the soil

Present study investigates the impact of chitosan microspheres-based controlled-release nitrogen fertilizer (Cm-CRNFs) on biological characteristics of Brassica rapa ssp. pekinensis (Chinese cabbage) and soil. The study was carried out under various four treatments, urea (0.8033 g), blank chitosan microspheres (without urea), Cm-CRNFs (0.8033 g), and a control group (CK). The results indicated that Cm-CRNFs significantly prolonged the nitrogen release and enhanced the plant shoot length, shoot diameter, number of branches, pods, total amino acids, and vitamin C of Brassica rapa ssp. pekinensis as well as increased the soil nutrient availability. Chao index of bacterial diversity analysis showed a significant reduction of 15.89 % in Cm-CRNFs, but the Shannon index value in Cm-CRNFs was increased by 23.55 % compared to CK. Furthermore, Cm-CRNFs treatment significantly influenced genus richness level of Arthrobacter, Archangium, Bacillus, and Flavihumibacter. Moreover, relative abundance of bacteria significantly enhanced Cm-CRNFs, including Acidobacteriota, Acitinobacteriota, Cloroflexi, Cyanobacteria, and Patescibacteria. Soil enzyme activity such as: urease, acid phosphatase, and catalase enzymes in Cm-CRNFs and urea treatment significantly increased. Besides, other enzymes such as: cellulase and β-glucosidase activity decreased in the Cm-CRNFs treatment. It was concluded that Cm-CRNFs potentially prolonged discharge of micro/macronutrients and improved soil bacterial diversity, which ultimately enhanced the soil fertility and improved the soil enzyme activity.

Plasma membrane-localized H+-ATPase OsAHA3 functions in saline-alkaline stress tolerance in rice

KEY MESSAGE

A novel function of plasma membrane-localized H+-ATPase, OsAHA3, was identified in rice, which is involved in saline-alkaline tolerance and specifically responds to high pH during saline-alkaline stress. Saline-alkaline stress causes serious damage to crop production on irrigated land. Plants suffer more severe damage under saline-alkaline stress than under salinity stress alone. Plasma membrane-localized proton (H+) pump (H+-ATPase) is an important enzyme that controls plant growth and development by catalyzing H+ efflux and enabling effective charge balance. Many studies about the role of plasma membrane H+-ATPases in saline-alkaline stress tolerance have been reported in Arabidopsis, especially on the AtAHA2 (Arabidopsis thaliana H+-ATPase 2) gene; however, whether and how plasma membrane H+-ATPases play a role in saline-alkaline stress tolerance in rice remain unknown. Here, using the activation-tagged rice mutant pool, we found that the plasma membrane-localized H+-ATPase OsAHA3 (Oryza sativa autoinhibited H+-ATPase 3) is involved in saline-alkaline stress tolerance. Activation-tagged line 29 (AC29) was identified as a loss-of-function mutant of OsAHA3 and showed more severe growth retardation under saline-alkaline stress with high pH than under salinity stress. Moreover, osaha3 loss-of-function mutants generated by CRISPR/Cas9 system exhibited saline-alkaline stress sensitive phenotypes; staining of leaves with nitrotetrazolium blue chloride (NBT) and diaminobenzidine (DAB) revealed more reactive oxygen species (ROS) accumulation in osaha3 mutants. OsAHA3-overexpressing plants showed increased saline-alkaline stress tolerance than wild-type plants. Tissue-specific expression analysis revealed high expression level of OsAHA3 in leaf, sheath, glume, and panicle. Overall, our results revealed a novel function of plasma membrane-localized H+-ATPase, OsAHA3, which is involved in saline-alkaline stress tolerance and specifically responds to high pH.

A comprehensive review on starch: Structure, modification, and applications in slow/controlled-release fertilizers in agriculture

This comprehensive review thoroughly examines starch's structure, modifications, and applications in slow/controlled-release fertilizers (SRFs) for agricultural purposes. The review begins by exploring starch's unique structure and properties, providing insights into its molecular arrangement and physicochemical characteristics. Various methods of modifying starch, including physical, chemical, and enzymatic techniques, are discussed, highlighting their ability to impart desirable properties such as controlled release and improved stability. The review then focuses on the applications of starch in the development of SRFs. It emphasizes the role of starch-based hydrogels as effective nutrient carriers, enabling their sustained release to plants over extended periods. Additionally, incorporating starch-based hydrogel nano-composites are explored, highlighting their potential in optimizing nutrient release profiles and promoting plant growth. Furthermore, the review highlights the benefits of starch-based fertilizers in enhancing plant growth and crop yield while minimizing nutrient losses. It presents case studies and field trials demonstrating starch-based formulations' efficacy in promoting sustainable agricultural practices. Overall, this review consolidates current knowledge on starch, its modifications, and its applications in SRFs, providing valuable insights into the potential of starch-based formulations to improve nutrient management, boost crop productivity, and support sustainable agriculture.

Nanoscale ZnO Improves the Amino Acids and Lipids in Tomato Fruits and the Subsequent Assimilation in a Simulated Human Gastrointestinal Tract Model

With the widespread use of nanoenabled agrochemicals, it is essential to evaluate the food safety of nanomaterials (NMs)-treated vegetable crops in full life cycle studies as well as their potential impacts on human health. Tomato seedlings were foliarly sprayed with 50 mg/L ZnO NMs, including ZnO quantum dots (QDs) and ZnO nanoparticles once per week over 11 weeks. The foliar sprayed ZnO QDs increased fruit dry weight and yield per plant by 39.1% and 24.9, respectively. It also significantly increased the lycopene, amino acids, Zn, B, and Fe in tomato fruits by 40.5%, 15.1%, 44.5%, 76.2%, and 12.8%, respectively. The tomato fruit metabolome of tomatoes showed that ZnO NMs upregulated the biosynthesis of unsaturated fatty acids and sphingolipid metabolism and elevated the levels of linoleic and arachidonic acids. The ZnO NMs-treated tomato fruits were then digested in a human gastrointestinal tract model. The results of essential mineral release suggested that the ZnO QDs treatment increased the bioaccessibility of K, Zn, and Cu by 14.8-35.1% relative to the control. Additionally, both types of ZnO NMs had no negative impact on the α-amylase, pepsin, and trypsin activities. The digested fruit metabolome in the intestinal fluid demonstrated that ZnO NMs did not interfere with the normal process of human digestion. Importantly, ZnO NMs treatments increased the glycerophospholipids, carbohydrates, amino acids, and peptides in the intestinal fluids of tomato fruits. This study suggests that nanoscale Zn can be potentially used to increase the nutritional value of vegetable crops and can be an important tool to sustainably increase food quality and security.

Investigation of the incidence of heavy metals contamination in commonly used fertilizers applied to vegetables, fish ponds, and human health risk assessments

Overuse of fertilizers on agricultural lands and fish ponds may result in serious pollution problems, such as heavy metals that can enter the food chain and pose serious health problems. Due to this, the present study investigates the incidence of heavy metals in commonly used fertilizers and its association with heavy metals in vegetables, soil, fish species, and pond water. Samples were collected from different sites (fields and ponds) in district Kohat, where the application of fertilizers was common and control groups (no fertilizers used). Heavy metal analysis was carried out through a spectrophotometer. Results showed higher Cd and Cr concentrations in triple superphosphate (TSP), Cu and Pb in nitrogen, phosphorus, and potassium (NPK), while lower concentrations were found in gypsum. In vegetables (onion, tomato, brinjal, and potato) and associated soil, most of the heavy metals concentrations were significantly higher (P < 0.05) in fertilizer-applied sites than in the control. Also, the Cd concentration in potatoes and Pb level in all vegetables obtained from sites were greater than the WHO/FAO standard limit. In the case of fish species (Hypophthalmichthys molitrix and Cyprinus carpio) muscles and their habitat (water), all the understudy heavy metals were notably higher (P < 0.05) in fertilizer-applied sites (ponds) than the control group. Collectively, in all vegetables and muscles of fish species, the bioaccumulation factor was higher in sites compared to the control. The estimated daily intake (EDI) and target hazard quotient (THQ) values were also higher in fertilizer-applied sites (fields and ponds) than control. The health index (HI) value was > 1 in vegetables (onion, tomato, and potato) and fish muscles collected from different sites compared to the control. Thus, there is the possibility of severe health risks. The use of fertilizers must be carefully monitored in order to ensure that humans and animals are safe from exposure to heavy metals.

Insights into the Potential of Biopolymeric Aerogels as an Advanced Soil-Fertilizer Delivery Systems

Soil fertilizers have the potential to significantly increase crop yields and improve plant health by providing essential nutrients to the soil. The use of fertilizers can also help to improve soil structure and fertility, leading to more resilient and sustainable agricultural systems. However, overuse or improper use of fertilizers can lead to soil degradation, which can reduce soil fertility, decrease crop yields, and damage ecosystems. Thus, several attempts have been made to overcome the issues related to the drawbacks of fertilizers, including the development of an advanced fertilizer delivery system. Biopolymer aerogels show promise as an innovative solution to improve the efficiency and effectiveness of soil-fertilizer delivery systems. Further research and development in this area could lead to the widespread adoption of biopolymer aerogels in agriculture, promoting sustainable farming practices and helping to address global food-security challenges. This review discusses for the first time the potential of biopolymer-based aerogels in soil-fertilizer delivery, going through the types of soil fertilizer and the advert health and environmental effects of overuse or misuse of soil fertilizers. Different types of biopolymer-based aerogels were discussed in terms of their potential in fertilizer delivery and, finally, the review addresses the challenges and future directions of biopolymer aerogels in soil-fertilizer delivery.

Valorisation of food waste for valuable by-products generation with economic assessment

This study assessed the techno-economic feasibility of a biorefinery for valuable by-products (mainly hydrogen, ethanol and fertilizer) generation from food waste. The plant was designed to be built in Zhejiang province (China) with a processing capacity of 100 t food waste per day. It was found that the total capital investment (TCI) and annual operation cost (AOC) of the plant were US$ 7625549 and US$ 2432290.7 year^-1, respectively. After the tax, US$ 3141867.6 year^-1 of net profit could be reached. The payback period (PBP) was 3.5 years at a 7% discount rate. The internal rate of return (IRR) and return on investment (ROI) were 45.54% and 43.88%, respectively. Shutdown condition could happen with the feed of food waste less than 7.84 t day^-1 (2587.2 t year^-1) for the plant. This work was beneficial for attracting interests and even investment for valuable by-products generation from food waste in large scale.

Improvement of tomato yield and quality using slow release NPK fertilizers prepared by carnauba wax emulsion, starch-based latex and hydrogel nanocomposite combination

The modern agriculture is working on introducing new generation of fertilizers that apt to slow down the nutrients release to be more in synchrony with plant's need throughout growth season, enhance fertilizer performance, and decrease nutrient losses into the environment. The aim of this research was to develop an advanced NPK slow-release fertilizer (SRF) and investigate its effect on yield, nutritional and morphological responses of tomato plant (Lycopersicon esculentum Mill.) as a model crop. To this goal, three water-based bio-polymeric formulations including starch-g-poly (acrylic acid-co-acrylamide) nanocomposite hydrogel, starch-g-poly(styrene-co-butylacrylate) latex, and carnauba wax emulsion were synthesized and used for production of NPK-SRF samples. Different samples of coated fertilizers (urea, potassium sulfate, and superphosphate granules) were prepared using different ratios of latex and wax emulsion, and for phosphorus and potash (R-treatment). Moreover, some of coated fertilizers (15 and 30 wt.%) was replaced with nanocomposite hydrogel containing fertilizers, named D and H treatments, respectively. The effect of SRF samples were compared with commercial fertilizers (NPK treatment) and a commercial SRF (T treatment), on the growth of tomato in the greenhouse, at two different levels (100 and 60). The efficiency of all the synthesized formulations were higher than NPK and T treatments, and among them, H100 significantly improved the morphological and physiological characteristics of tomato. For instance, amount of residual elements (nitrogen, phosphorus and potassium) as well as micro elements of calcium, iron and zinc in tomato cultivation bed and accordingly the uptake of these elements in the roots, aerial parts and fruits were increased in the R, H, and D treatments. The highest yield (1671.54 g), highest agricultural agronomy efficiency of fertilizer, and the highest dry matter percentage (9.52%) were obtained in H100. The highest amount of lycopene, antioxidant capacity and vitamin C was also observed in H100. Nitrate accumulation in tomato fruit in the synthesized SRF samples were decreased significantly compared to NPK100, and the lowest amount was observed in H100, which was 55.24% less than NPK100. Accordingly, it is suggested that combination of natural-based nanocomposite hydrogels along with coating latexes and wax emulsions can be a successful method to synthesize efficient NPK-SRF formulations for improvement of crop growth and quality.

Eco-Efficient Systems Based on Nanocarriers for the Controlled Release of Fertilizers and Pesticides: Toward Smart Agriculture

The excessive application of pesticides and fertilizers has generated losses in biological diversity, environmental pollution, and harmful effects on human health. Under this context, nanotechnology constitutes an innovative tool to alleviate these problems. Notably, applying nanocarriers as controlled release systems (CRSs) for agrochemicals can overcome the limitations of conventional products. A CRS for agrochemicals is an eco-friendly strategy for the ecosystem and human health. Nanopesticides based on synthetic and natural polymers, nanoemulsions, lipid nanoparticles, and nanofibers reduce phytopathogens and plant diseases. Nanoproducts designed with an environmentally responsive, controlled release offer great potential to create formulations that respond to specific environmental stimuli. The formulation of nanofertilizers is focused on enhancing the action of nutrients and growth stimulators, which show an improved nutrient release with site-specific action using nanohydroxyapatite, nanoclays, chitosan nanoparticles, mesoporous silica nanoparticles, and amorphous calcium phosphate. However, despite the noticeable results for nanopesticides and nanofertilizers, research still needs to be improved. Here, we review the relevant antecedents in this topic and discuss limitations and future challenges.

Nanofertilizers: Types, Delivery and Advantages in Agricultural Sustainability

In an alarming tale of agricultural excess, the relentless overuse of chemical fertilizers in modern farming methods have wreaked havoc on the once-fertile soil, mercilessly depleting its vital nutrients while inflicting irreparable harm on the delicate balance of the surrounding ecosystem. The excessive use of such fertilizers leaves residue on agricultural products, pollutes the environment, upsets agrarian ecosystems, and lowers soil quality. Furthermore, a significant proportion of the nutrient content, including nitrogen, phosphorus, and potassium, is lost from the soil (50–70%) before being utilized. Nanofertilizers, on the other hand, use nanoparticles to control the release of nutrients, making them more efficient and cost-effective than traditional fertilizers. Nanofertilizers comprise one or more plant nutrients within nanoparticles where at least 50% of the particles are smaller than 100 nanometers. Carbon nanotubes, graphene, and quantum dots are some examples of the types of nanomaterials used in the production of nanofertilizers. Nanofertilizers are a new generation of fertilizers that utilize advanced nanotechnology to provide an efficient and sustainable method of fertilizing crops. They are designed to deliver plant nutrients in a controlled manner, ensuring that the nutrients are gradually released over an extended period, thus providing a steady supply of essential elements to the plants. The controlled-release system is more efficient than traditional fertilizers, as it reduces the need for frequent application and the amount of fertilizer. These nanomaterials have a high surface area-to-volume ratio, making them ideal for holding and releasing nutrients. Naturally occurring nanoparticles are found in various sources, including volcanic ash, ocean, and biological matter such as viruses and dust. However, regarding large-scale production, relying solely on naturally occurring nanoparticles may not be sufficient or practical. In agriculture, nanotechnology has been primarily used to increase crop production while minimizing losses and activating plant defense mechanisms against pests, insects, and other environmental challenges. Furthermore, nanofertilizers can reduce runoff and nutrient leaching into the environment, improving environmental sustainability. They can also improve fertilizer use efficiency, leading to higher crop yields and reducing the overall cost of fertilizer application. Nanofertilizers are especially beneficial in areas where traditional fertilizers are inefficient or ineffective. Nanofertilizers can provide a more efficient and cost-effective way to fertilize crops while reducing the environmental impact of fertilizer application. They are the product of promising new technology that can help to meet the increasing demand for food and improve agricultural sustainability. Currently, nanofertilizers face limitations, including higher costs of production and potential environmental and safety concerns due to the use of nanomaterials, while further research is needed to fully understand their long-term effects on soil health, crop growth, and the environment.

Valorisation of phyto-biochars as slow release micronutrients and sulphur carrier for agriculture

Slow release micronutrients and sulphur sources are required for higher use efficiency of fertilizers in agriculture. The present investigation was undertaken to examine the salt soluble, desorbed and specifically sorbed fractions of micronutrients and sulphur in nutrient enriched phyto-biochars incubated at 15, 25 and 35°C for 48 h after pyrolysis of Lantana sp., Pinus sp. needles and wheat straw at 300 and 450 °C. The highest salt soluble fractions of Zn, Cu, Fe, Mn and B were recorded with pine needle biochar pyrolyzed at 300 °C, whereas that of S with lantana biochar pyrolyzed at 300 °C. The highest desorbed contents of Zn, Cu and Mn were with pine needle biochar (300 °C) and that of B and S with wheat straw biochar (450 °C) and lantana biochar (300 °C), respectively. An increase in incubation temperature from 15 to 25 °C increased the salt soluble contents of Zn and specifically sorbed contents of Fe and B but decreased salt soluble contents of Fe and B and desorbed amount of S significantly. Further, increase in incubation temperature from 25 to 35 °C significantly decreased the salt soluble contents of all nutrients except Mn and desorbed amount of S but increased specifically sorbed amount of Fe, B and S. Considering the salt soluble and desorbed contents of nutrients in enriched phyto-biochars, especially pine needle biochar pyrolyzed at 300 °C and treated with marginal or deficient nutrients for 2 d at 15-25 °C appeared to be suitable as a slow release fertilizer.

Engineered nanoparticles in plant growth: Phytotoxicity concerns and the strategies for their attenuation

In the agricultural sector, the use of engineered nanoparticles (ENPs) has been acclaimed as the next big thing for sustaining and increasing crop productivity. A vast amount of literature is available regarding the growth-promoting attributes of different ENPs. In this context, it has been emphasized that the ENPs can bolster vegetative growth, leaf development, and seed setting and also help in mitigating the effects of abiotic and biotic stresses. At the same time, there have been a lot of speculations and concerns regarding the phytotoxicity of ENPs off-late. In this connection, many research articles have presented the negative effects of ENPs on plant systems. These studies have highlighted that almost all the ENPs impart a certain degree of phytotoxicity in terms of reduction in growth, biomass, impairment of photosynthesis, oxidative status of plant cells, etc. Mostly, the ENPs based on metal or metal oxides (Cd, Cr, Pb, Ag, Ce, etc.) and nonmetals (C) that are introduced into the environment are known to incite inhibitory effects. However, the phytotoxicity of ENPs are known to be determined mostly by the chemical nature of the element, size, surface charge, coating molecules, and abiotic factors like pH and light. This review article, therefore, elucidates the phytotoxic properties of different ENPs and the plant responses induced at the molecular level subjected to nanoparticle exposure. Moreover, the article highlights the probable strategies that may be adopted for the suppression of the phytotoxicity of ENPs to ensure the safe and sustainable application of ENPs in crop fields.

Effect of methods application of copper nanoparticles in the growth of avocado plants

The aim of this greenhouse study was to evaluate root irrigation, foliar spray, and stem injection in order to find the best method for the nanofertilization of avocado plants with green synthesized CuNPs. One-year-old avocado plants were supplied four times (every 15 days) with 0.25 and 0.50 mg/ml of CuNPs through the three fertilization methods. Stem growth and new leaf formation were evaluated over time and after 60 days of CuNPs exposure, several plant traits (root growth, fresh and dry biomass, plant water content, cytotoxicity, photosynthetic pigments, and total Cu accumulation in plant tissues) were evaluated for CuNPs improvement. Regarding the control treatment, stem growth and new leaf appearance were increased by 25 % and 85 %, respectively, by the CuNPs supply methods of foliar spray>stem injection>root irrigation, with little significant differences among NPs concentrations. Avocado plants supplied with 0.25 and 0.50 mg/ml CuNPs maintained a hydric balance and cell viability ranged from 91 to 96 % through the three NPs application methods. TEM did not reveal any ultrastructural organelle changes induced by CuNPs in leaf tissues. The concentrations of CuNPs tested were not high enough to exert deleterious effects on the photosynthetic machinery of avocado plants, but photosynthetic efficiency was also found to be improved. The foliar spray method showed improved uptake and translocation of CuNPs, with almost no loss of Cu. In general, the improvement in plant traits indicated that the foliar spray method was the best for nanofertilization of avocado plants with CuNPs.

Decoupled motion planning of a mobile manipulator for precision agriculture

Thanks to recent developments in service robotics technologies, precision agriculture (PA) is becoming an increasingly prominent research field, and several studies were made to present and outline how the use of mobile robotic systems can help and improve farm production. In this paper, the integration of a custom-designed mobile base with a commercial robotic arm is presented, showing the functionality and features of the overall system for crop monitoring and sampling. To this aim, the motion planning problem is addressed, developing a tailored algorithm based on the so-called manipulability index, that treats the base and robotic arm mobility as two independent degrees of motion; also developing an open source closed-form inverse kinematics algorithm for the kinematically redundant manipulator. The presented methods and sub-system, even though strictly related to a specific mobile manipulator system, can be adapted not only to PA applications where a mobile manipulator is involved but also to the wider field of assistive robotics.

Composting of limed fleshings generated in a tannery: sustainable waste management

In tanneries, limed fleshing is an unavoidable waste generated in beamhouse operation. Proper management of limed fleshing with protein, fat, lime, and sulfide will help to protect the natural environment and at least reduce the pollution that ends up in it. In this study, excluding any pretreatment, limed fleshing is used for compost production. Chopped and mixed limed fleshing with chicken manure, cow dung, and sawdust was heaped onto a horizontal bamboo frame. Three composting heaps were fabricated weighing 720, 700, and 760 kg. The turning of composting materials in the heaps causes temperature changes in the thermophilic range. The thermophilic temperatures in these heaps were 69.07 °C (heap 1), 69.9 °C (heap 2), and 69.19 °C (heap 3) which ensured the death of the pathogenic organism. The quality of compost was assessed based on the nutrients-nitrogen (N), phosphorous (P), potassium (K), and sulfur (S) content. NPKS in the compost fulfils the requirements of the investigated materials as compost. The largest amounts of metals- zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), and nickel (Ni) of the compost detected in the heaps were, respectively, 200.3, 37.4, 20.3, 12.0, and 3.9 mg/kg. Cadmium (Cd) in the compost was below the detection limit. Scanning electron microscope (SEM) photographs show the decomposing of composting materials. This study indicates that limed fleshing can be converted into nutrient-enriched compost without any pretreatment. Using an easy, simple, and adaptable technique could reduce the volume of solid waste generated in the tannery to reduce environmental pollution.

Analytical solution of Nye-Tinker-Barber model by Laplace transform

The Nye-Tinker-Barber model is a classical convection-diffusion model for nutrient uptake by plant roots in cylindrical coordinates and has one nonlinear left Robin boundary condition with Michaelis-Menten function of concentration. First the Michaelis-Menten function is fitted into a function of time by numerical concentration at root surface from difference scheme, and then the Laplace and numerical inverse Laplace transforms - Zakian inversion method are taken to obtain the approximate analytical solution. Compared with other solutions made by difference scheme, Stehfest inversion method and previous analytical methods, it is found that the analytical solution obtained by Laplace and Zakian inversion transforms has higher accuracy and computation efficiency. This analytical method can be extended to other nutrient uptake models with Michaelis-Menten function.

Farmland nutrient pollution and its evolutionary relationship with plantation economic development in China

Contradiction between growing plantation economic demand and agro-ecological degradation has always restricted sustainable development of agricultural countries. This study applied the unit inventory analysis to evaluate the productions and discharges of farmland non-point source (FNPS) nitrogen (TN) and phosphorus (TP) among China's nine national-level agricultural districts over 1999-2019. On this basis, we quantified the evolutionary relationship between plantation economic output and FNPS pollution based on optimal regression fitting. The results showed that over 1999-2019, farmland cumulative TN and TP discharges for the whole China were approximately 15807 × 10⁴ t and 1312 × 10⁴ t, with prominent district heterogeneity. According to FNPS discharge magnitudes, China's agricultural districts can be classified into three categories: high, moderate and slight discharge zones. Huang-Huai-Hai Plain and Middle-lower Yangtze Plain were identified as the main severely-polluted districts. Mineral fertilizer is the primary contributor to FNPS pollution. Annual FNPS load showed a trend of increasing followed by decreasing, and the peak interval was recorded in 2014-2016. Spatiotemporal dynamics in FNPS discharge intensities were disparate from that in discharge magnitudes. SC has the highest TN discharge intensity, with an annual average intensity of 0.068 t/ha, followed by MLYP (0.044 t/ha) and HHHP (0.041 t/ha). HHHP has the highest TP discharge intensity, with an annual average intensity of 0.0051 t/ha, followed by SC (0.0038 t/ha) and MLYP (0.0031 t/ha). District-based agro-ecological restoration strategies were accordingly proposed considering FNPS discharge magnitude and intensity concurrently. In most agricultural districts, with the growing economic output in plantation, the FNPS load showed an increase followed by a decrease or to leveling off. Furthermore, with the increasing TN/TP economic partial productivity, the FNPS TN/TP discharge intensities reached the climax, then declined or tended to be flattening out.

Fe and Zn Metal Nanocitrates as Plant Nutrients through Soil Application

Nanocitrates of iron (Fe) and zinc (Zn) in the form of plant nanonutrients were examined for their behavior in soil and the uptake of these by 20-day old groundnut (Arachis hypogaea) seedlings under greenhouse conditions. The Fe (0.04 to 0.008 mmol/kg of soil) and Zn (0.02 to 0.004 mmol/kg of soil) nanocitrates were applied to soil and compared with commercial counterparts (FeSO₄, ZnSO₄, nano-Fe, nano-Zn, Fe-EDTA, Zn-EDTA). The combined nanocitrate compositions were also formulated by physical means and characterized. The plant uptake of Fe and Zn was determined through atomic absorption spectrometry (AAS). All the treated plants showed good germination and higher vigor indexes compared to the control treatments. The highest available Fe and Zn soil contents after leaching were 150.5 and 18.9 mg/kg, respectively, in combined nanocitrate compositions, whereas in the control (untreated) soil, the Fe and Zn contents were 6.0 and 0.7 mg/kg, respectively. The plant's Fe content was 0.48 mg/pot for the combined nanocitrate composition, and that of the untreated plant sample was 0.02 mg/pot. The plant's Zn content was 82.3 μg/pot for pure zinc citrate, and the respective untreated-plant Zn content was 2.1 μg/pot. These values are better than those observed for commercial fertilizers. Additionally, no trend in promotional and antagonistic correlations between Fe and Zn in combined nanocitrates was observed in the studied period (20 days in duration). Among the 34 synthesized citrates, six nanocitrates show promising trends for evaluation under field conditions with higher stability.

Design and Prototyping of an Interchangeable and Underactuated Tool for Automatic Harvesting

In the field of precision agriculture, the automation of sampling and harvesting operations plays a central role to expand the possible application scenarios. Within this context, this work presents the design and prototyping of a novel underactuated tool for the harvesting of autonomous grapevines. The device is conceived to be one of several tools that could be automatically grasped by a robotic manipulator. As a use case, the presented tool is customized for the gripper of the robotic arm mounted on the rover Agri.Q, a service robot conceived for agriculture automation, but it can be easily adapted to other robotic arm grippers. In this work, first, the requirements for such a device are defined, then the functional design is presented, and a dimensionless analysis is performed to guide the dimensioning of the device. Later, the executive design is carried out, while the results of a preliminary experimental validation test are illustrated at the end of the paper.

Innovative bio-waste-based multilayer hydrogel fertilizers as a new solution for precision agriculture

The aim of the research work was to present a multilayer hydrogel capsule with controlled nutrient release properties as an innovative fertilizer designed for sustainable agriculture. Preparation of the capsules included the following steps: sorption of micronutrients (Cu, Mn, Zn) on eggshells (1) and their immobilization in sodium alginate, with the crosslinking agent being the NPK solution (2). The capsules were coated with an additional layer of a mixture of biopolymers (0.79% alginate, 0.24% carboxymethylcellulose and 8.07% starch)by means of dipping and spraying techniques. The biocomposites were characterized by limited (<10% within 100 h for the structures encapsulated by the dipping method) release of fertilizer ions (except for small K⁺ ions). The hydrogel fertilizer formulations were analyzed for physicochemical properties such as macro- and micronutrient content, surface morphology analysis, coating structure evaluation, mechanical properties, swelling and drying kinetics. High nutrient bioavailability was confirmed in vitro (extraction in water and neutral ammonium citrate). Germination and pot tests have revealed that the application of multicomponent hydrogel fertilizers increases the length of cucumber roots by 20%, compared to the commercial product.

The potential for biochar application in "Shatangju" (Citrus reticulate cv.) orchard on acid red soil: Biochar prepared from its organic waste in an orchard

Carbonization of agricultural and forestry wastes is the main use of biochar application in agriculture. In this study, the effects of biochar on the physical and chemical properties of soil and diversity in rhizosphere microorganisms, leaf nutrients and fruit quality of acid red soil in "Shatangju" (Citrus reticulate cv.) orchard were studied using organic wastes and small-scale carbonization furnaces from orchards were used to produce biochar. The results showed that the finished rate of biochar produced from the organic wastes in the orchard was approximately 37%, and the carbon content of the finished product was as high as 80%. The results suggested that the biochar produced in the orchard could meet the annual consumption of the orchard. Applying biochar can improve the physical and chemical properties of acid soil in the "Shatangju" orchard by enhancing the availability of various mineral nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium and boron. The species and quantity of root and rhizosphere microbial communities (fungi, bacteria and archaea) increased, and the dominant bacterial group changed, manifested in the increase in microbial diversity. Biochar directly affected the soil pH value and increased the soil organic carbon content, which may be the main reason for the change in microbial diversity in the soil and rhizosphere of "Shatangju" in the orchard and pot tests. The fruit quality of each treatment group with biochar was also better than that of the control group and improved fruit coloring. In the pure soil test, whether or not chemical fertilizer was applied, 3% biochar amendments can provide a suitable pH value for "Shatangju" growth and are relatively stable. Regardless of whether or not fertilizer was applied, 1.5%-3% biochar improved the soil in the pot test. In the field, the biochar at a rate of 2.4 kg/plant to 3.6 kg/plant, respectively, was the best in improving soil physical and chemical properties, foliar nutrition and fruit quality. Therefore, the amount of biochar added in the open environment (if the garden) can be slightly adjusted according to the results of the closed environment test (pure soil test and pot test). In this experiment, we explored the self-recycling of organic carbon, mainly through the preparation of a simple small-scale biochar furnace suitable for the use by orchards, and selected the appropriate amount of biochar to improve the physical and chemical conditions of "Shatangju" orchard soil and increase fruit quality.

Multicomponent biodegradable hydrogels based on natural biopolymers as environmentally coating membrane for slow-release fertilizers: Effect of crosslinker type

This work aims to explore the suitable crosslinker type for synthesizing multicomponent biodegradable hydrogels of cassava starch (CSt) grafted with acrylic acid (AA) semi-interpenetrated by natural rubber (NR)/polyvinyl alcohol (PVA) blend (CSt-g-PAA/NR/PVA, CSB semi-IPN hydrogel) as coating membranes for slow-release urea fertilizers. Three crosslinker types (ethylene glycol dimethacrylate (EGDMA), glutaraldehyde (GA) and N,N'- methylene-bis-acrylamide (MBA)) were employed to investigate their influences on the properties of CSB semi-IPN hydrogels. The results revealed that the different crosslinkers clearly exhibited different water-retention capacity, biodegradation, slow release and plant growth performance of the CSB semi-IPN hydrogels. The CSB-G2 hydrogel (crosslinked with GA at 2 wt%) remained higher water-retention at 30 days (20.2 %), greater rate of degradation (1.37 %/day) and better biosafety (OD600 = 2.26) compared to CSB-M2 and CSB-E2 hydrogels. After urea pellets were coated by CSB hydrogels and wax layers (UCSBw formulation), the urea release rates from the UCSBw-M2, UCSBw-E2 and UCSBw-G2 formulations in 30 days were 67.7 %, 68.7 % and 78.3 %, respectively, corresponding well with swelling ratio and pore size. Besides, the UCSBw-G2 formulation yielded the greater plant growth performance (height, leaf length and product weight) than other two formulations and commercial fertilizer. In conclusion, GA is the suitable crosslinker for synthesizing the CSB-g-PAA/NR/PVA hydrogels with high water-retention, excellent biodegradation, less negative impact on environments, acceptable slow-release rate, good biosafety and reasonable price for slow-release fertilizers.

Optimization of microwave-assisted synthesis process for water-soluble ammonium polyphosphate from urea phosphate and urea

Ammonium polyphosphate (APP) is rich in nitrogen (N) and phosphorus (P), which is a raw material for the high-efficiency water-soluble fertilizer production. In this work, the water-soluble APP was directly synthesized using commercial grade-urea phosphate and urea in a microwave reactor. The effects of the molar ratio of urea to phosphate urea (UP), microwave power and reaction time on the quality of APP were also studied. Single-factor experiments indicate that with the optimal conditions: the molar ratio of 0.4, the microwave power of 720 W, and the reaction time of 9 min, the average polymerization degree of APP was 18.91, and the solubility was 6.31 g/100 g H2O. Orthogonal experiment indicates that the order of significant factors for APP production is molar ratio > reaction time > microwave power. Based on the results of the range analysis and analysis of variance, the optimized conditions were found at the molar ratio of 0.6, the microwave power of 720 W, and the reaction time of 9 min, the average polymerization degree of the APP was 21.7 and the solubility was 6.03 g/100 g H2O at 25 °C. The TGA analysis showed that the synthesized APP had a good thermal stability. Its XRD spectrum was the same as the crystalline form I.

Seed germination studies on Chickpeas, Barley, Mung beans and Wheat with natural biomass and plastic waste derived C-dots

Agronomical providence of nanoparticles in enhancing food productivity has brought new revolution in agricultural sector. However, the comprehensive ingenuity of their synergetic impact on environment and living flora and fauna is still poorly explored. The current study endeavours to tackle this apprehension by systematically exploring the agronomical paradigm of six different types of C-dots derived from natural biomass and plastic waste on the four different types of seeds viz. black chick peas (Cicer arietinum), barley (Hordeum vulgare), mung beans (Vigna radiata) and wheat (Triticum aestivum) at room temperature. C-dots have displayed a dose responsive effect (250 to 5000 mg/L) on the growth of chosen seeds, including the elongation of root length and coleoptile length. The development of seedlings under atmospheric conditions exhibited excellent physiological stability in presence of synthesized C-dots for all types of seeds with concentrations as high as 3000 mg/L for dry seed. The direct exposure of C-dots resulted in enhanced growth as compared to the water exposure and considered as the most important novel aspect of present work. The developed C-dots provide more nutrient content and easy penetration to the seeds due to their enhanced surface area and very small size. The germination and Vigor index have also been augmented in presence of C-dots after 7 days of exposure. C-dots have affected the chlorophyll content in mung beans as a function of time and concentration. The developed C-dots possess excellent biocompatible behaviour and help in the complete growth of the different types of seeds which suggest their enhanced utilization in the agronomical field. This is one of the detailed studies, which explore the impact of C-dots on widely used food crops with the non-toxic and biocompatible C-dots. The information achieved herein will allow the usage of C-dots as a capable nanopriming agent for the natural germination of seeds.

Dual effects of nZVI on maize growth and water use are positively mediated by arbuscular mycorrhizal fungi via rhizosphere interactions

Nanoscale zero-valent iron (nZVI) might generate positive and negative effects on plant growth, since it acts as either hazardous or growth-promotion role. It is still unclear whether such dual roles can be mediated by arbuscular mycorrhizal fungi (AMF) in plant-AMF symbiosis. We first identified that in 1.5 g kg^-1 nZVI (≤1.5 g kg^-1 positively), maize biomass was increased by 15.83%; yet in 2.0 g kg^-1 nZVI, it turned to be declined by 6.83%, relative to non-nZVI condition (CK, p < 0.05), showing a negative effect. Interestingly, the inoculation of AMF massively improved biomass by 45.18% in 1.5 g kg^-1 nZVI, and relieved the growth inhibition by 2.0 g kg^-1 nZVI. The event of water use efficiency followed similar trend as that of biomass. We found that proper concentration of nZVI can positively interact with rhizosphere AMF carrier, enabling more plant photosynthetic carbon to be remobilized to mycorrhiza. The scanning of transmission electron microscopy showed that excessive nZVI can infiltrate into root cortical cells and disrupt cellular homeostasis mechanism, significantly increasing iron content in roots by 76.01% (p < 0.05). Simultaneously, the images of scanning electron microscopy showed that nZVI were attached on root surface to form an insoluble iron ion (Fe³⁺) layer, hindering water absorption. However, they were efficiently immobilized and in situ intercepted by extraradical hyphae in mycorrhizal-nZVI symbiosis, lowering iron translocation efficiency by 6.07% (p < 0.05). Herein, the optimized structure remarkably diminished aperture blockage at root surface and improved root activities by 30.06% (p < 0.05). Particularly, next-generation sequencing demonstrated that appropriate amount of nZVI promoted the colonization and development of Funneliformis mosseae as dominant species in rhizosphere, confirming the positive interaction between AMF and nZVI, and its regulatory mechanism. Therefore, dual effects of nZVI can be actively mediated by AMF via rhizosphere interactions. The findings provided new insights into the safe and efficient application of nanomaterials in agriculture.

Fuzzy Neural Network PID Strategy Based on PSO Optimization for pH Control of Water and Fertilizer Integration

In the process of crop cultivation, the application of a fertilizer solution with appropriate pH value is more conducive to the absorption of nutrients by crops. If the pH of the irrigation water and fertilizer solution is too high, it will not only be detrimental to the absorption of nutrients by the crop, but will also damage the structure of the soil. Therefore, the precise regulation of pH in water and fertilizer solutions is very important for agricultural production and saving water and fertilizer. Firstly, the article investigates the hybrid control of fertilizer and water conditioning systems, then builds a fuzzy preprocessing controller and a neural network proportional–integral–differential controller, and optimizes the neural network parameters by means of an improved particle swarm algorithm. The effectiveness of the controller was verified by comparison with the common proportional–integral–differential control and fuzzy algorithm control for fertilizer control and fuzzy preprocessing neural network control. Simulation experiments for this study were designed through the MATLAB/Simulink simulation platform, and the simulation results show that the algorithm has good tracking and regulation capabilities in the system. Finally, the four control algorithms are experimentally validated under different pH regulations using designed field experiments. The results show that, compared with other control algorithms, the control algorithm in this paper has a smaller overshoot and good stability with a shorter rise time, which can achieve the purpose of better regulating the fertilizer application system.

A landscape review of controlled release urea products: Patent objective, formulation and technology

Fertiliser has been a vital part of agriculture due to it boosting crop productivity and preventing starvation throughout the world. Despite this huge contribution, the application of nitrogen (N) fertilisers results in N leaching and the formation of greenhouse gases, which threaten the environment and human health. To minimise the impacts, slow/controlled release fertilisers (S/CRFs) have been being developed since the beginning of the 20th century. Despite the efforts made over a century, the basic terminological and classification information of these fertilisers remains vague. The scientific knowledge published in S/CRF patents has also been overlooked since the beginning. This review focused on the information gaps, clarified the definitions, differentiation and classification methods that have been randomly used in previous literature. The objectives, formulations and technologies of 109 controlled release urea patents involving sulphur coated urea, polymer coated urea and urea matrix fertilisers published in the years since these products emerged were also reviewed to 1) highlight the overlooked scientific knowledge in the patents; 2) understand the evolutionary processes and current research states of the products; 3) clarify research preferences and challenges to date; 4) identify remaining gaps for the future direction. It is expected that the organised basic information and the patent knowledge highlighted in this paper can be new resources and foster the development of S/CRFs in the future.

Recycling of nutrients from landfill leachate: A case study

The continuous increase in the consumption of natural resources requires different solutions directed to the recovery and recycling of different materials and products, including the nutrients used as fertilizers for food production. In this context, this research assessed the feasibility of using landfill leachate as a source of nutrients for the growth of maize. Leachate was treated to precipitate struvite, a rich magnesium, phosphate, and ammonium mineral that can be applied directly as fertilizer. It was used for the growth of maize, which was sowed in three different parcels. A commercial DAP + urea mixture was used to compare, and non-fertilized parcels were used as controls. Struvite was successfully obtained and applied in the fields. A marginal higher maize yield was achieved in two sites when using struvite (6.36% and 2.16%) compared to the commercial fertilizer, even if it was applied in a lower dose to weather conditions. An increase in N and Mg in soil could be observed, which allowed for the assimilation of nutrients in the plants. Concerning safety, the use of struvite did not produce the transfer of heavy metals or pathogens to the soil or plants. This research shows a promising way of dealing with leachate, which could be attractive in countries where organic waste is buried in landfills.

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Landfill leachate can be used as a source of nutrients for the grow of maize by precipitation of struvite.

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A field trial in real scale was performed.

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A marginal higher maize yield was achieved in two of the sites (6.36% and 2.16%) when compared to the commercial fertilizer.

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Struvite did not cause presence of pathogens or heavy metals in the crops.

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It offers an alternative to conventional leachate treatment options, aligned with the principles of the circular economy.

Biochar-based slow-release of fertilizers for sustainable agriculture: A mini review

Increasing global population and decreasing arable land pose tremendous pressures to agricultural production. The application of conventional chemical fertilizers improves agricultural production, but causes serious environmental problems and significant economic burdens. Biochar gains increasing interest as a soil amendment. Recently, more and more attentions have been paid to biochar-based slow-release of fertilizers (SRFs) due to the unique properties of biochar. This review summarizes recent advances in the development, synthesis, application, and tentative mechanism of biochar-based SRFs. The development mainly undergoes three stages: (i) soil amendment using biochar, (ii) interactions between nutrients and biochar, and (iii) biochar-based SRFs. Various methods are proposed to improve the fertilizer efficiency of biochar, majorly including in-situ pyrolysis, co-pyrolysis, impregnation, encapsulation, and granulation. Considering the distinct features of different methods, the integrated methods are promising for fabricating effective biochar-based SRFs. The in-depth understanding of the mechanism of nutrient loading and slow release is discussed based on current knowledge. Additionally, the perspectives and challenges of the potential application of biochar-based SRFs are described. Knowledge surveyed from this review indicates that applying biochar-based SRFs is a viable way of promoting sustainable agriculture.

Characteristics and preparation of oil-coated fertilizers: A review

As the slow-release fertilizer, oil-coated fertilizer can not only slow down the nutrients loss, but also have outstanding advantages in controlling the nutrients release. Based on a large number of literature, this paper systematically investigated the composition, classification, properties and preparation of oil-coated fertilizers, summarizes the challenges faced by the oil-coated fertilizers and offers a few suggestions for the future research. Through literature research, some important conclusions were found: (1) Oil-coated fertilizers are generally composed of core fertilizers and coated oil layers, and some have active interlayers. (2) Vegetable oils has the characteristics of easy degradation, water resistance and impact resistance, and the nutrient release curves of vegetable oil coated fertilizer in soil and still water are "S" type. (3) The modified polyurethane exhibits good compatibility with urea, and can control the release of N in a long period of time, which is 30 days longer than the N release life of ordinary polyurethane-coated fertilizers. (4) Oil-coated fertilizers can reduce the loss of N by slowing down the hydrolysis rate of urea and the nitrification from NH₄⁺ to NO₃^-, which reduces the N₂O release by 70-80% compared to the uncoated fertilizers. Moreover, the paper also proposes a new preparation method of oil-coated material.

On Demand Sequential Release of (Sub)Micron Particles Controlled by Size and Temperature

Polymeric devices capable of releasing submicron particles (subMP) on demand are highly desirable for controlled release systems, sensors, and smart surfaces. Here, a temperature-memory polymer sheet with a programmable smooth surface served as matrix to embed and release polystyrene subMP controlled by particle size and temperature. subMPs embedding at 80 °C can be released sequentially according to their size (diameter D of 200 nm, 500 nm, 1 µm) when heated. The differences in their embedding extent are determined by the various subMPs sizes and result in their distinct release temperatures. Microparticles of the same size (D ≈ 1 µm) incorporated in films at different programming temperatures T_p (50, 65, and 80 °C) lead to a sequential release based on the temperature-memory effect. The change of apparent height over the film surface is quantified using atomic force microscopy and the realization of sequential release is proven by confocal laser scanning microscopy. The demonstration and quantification of on demand subMP release are of technological impact for assembly, particle sorting, and release technologies in microtechnology, catalysis, and controlled release.

The role of bacterial fertilizers in the formation of legume crops

The article presents the results of studies of the effect of bacterial fertilizers on the yield formation of grain legumes (soybean and lentil). The effect of root fertilization with Azotovite and Phosphatovite, fertilizers containing live cells and bacterial spores, on the structure of yield and yield capacity of legumes, the quality indicators of soybean and lentil grains were studied. The results obtained indicate that fertilizing with bacterial fertilizer Phosphatovite accelerates the maturation of legumes and increases the safety of plants for harvesting. Fertilizing plants with Azotovite and Phosphatovite contributed to an increase in soil microbiological activity. Bacterial fertilizers make it possible to obtain more seeds from soybean and lentil plants, while the content of crude protein, fat, and nitrogen in the grain increases. On average, over the years of research, fertilizing with bacterial fertilizers significantly increases the yield of legumes. It is noted that the efficiency of Azotovite is lower in conditions of insufficient precipitation during its use. In the conditions of the Chuvash Republic in legumes, fertilizing with Phosphatovite increases the productivity of plants.

Effect of clay colloid - CuO nanoparticles interaction on retention of nanoparticles in different types of soils: role of clay fraction and environmental parameters

The extensive application of metal oxide nanoparticles (NPs) in various sectors has raised concern about their subsequent release and potentially harmful impacts on the soil system. The present study has addressed the interaction of CuO NPs with bentonite clay colloids (CC) under varying environmental parameters as a model to represent the soil pore water scenario. Based on CuO - CC interaction in model and natural soil solution extracts (SSE), the role of clay fraction and their stability on CuO retention in various types of soils have been evaluated. Results suggested that increasing ionic strength (IS) in the system caused aggregation of CuO NPs, and in the presence of CC, critical coagulation concentration decreased drastically from 27.8 and 17.3 mM to 10.7 and 0.33 mM for NaCl and CaCl₂ respectively, due to heteroaggregation in the system. Interestingly, in the SSE, the dominating role of ionic valency, dissolved organic carbon (DOC), and CC was observed in colloidal stabilization over IS. No significant impact of temperature was observed on the stability of CuO NPs both in model and SSE. Further, stability studies in the SSE were correlated with NPs retention behavior in soils. Observations suggest that retention of CuO NPs in soils is a function of binding of the colloidal fraction to the soil, which in turn depends on the colloidal stability. The highest retention was observed in black and laterite soils, whereas lower binding of clay fraction in red soil caused the least retention. A decrease in K_d values after a certain application concentration provided maximum sustainable application concentration of CuO NPs, which may vary with soil properties. Results suggest that the binding of clay and organic matter with a sandy matrix of soil plays a prime role in deciding the overall fate of CuO NPs in the soils.

Fulvic–polyphosphate composite embedded in ZnO nanorods (FA–APP@ZnO) for efficient P/Zn nutrition for peas (Pisum sativum L.)

A nano-fertilizer (FA–APP@ZnO) was designed and prepared based on the copolymer of fulvic acid (FA) and ammonium polyphosphate (APP) with ZnO nanorods embedded, to tackle the antagonism between phosphorus (P) and zinc (Zn) in fertilization. FA–APP@ZnO was confirmed to revert the precipitability of H₂PO₄⁻ and Zn²⁺ into a synergistic performance, where FA and APP can disperse ZnO nanorods, and in return, ZnO catalyzes the hydrolysis of the absorbed APP. The hydrolysis rate constant of pyrophosphates consequently increased 8 times. The dry biomass of pea (Pisum sativum L.) under the FA–APP@ZnO hydroponics for 7 days increased by 119%, as compared with the situation employing the conventional NH₄H₂PO₄ and ZnSO₄ compound fertilizer. Moreover, the uptake of seedlings for P and Zn was enhanced by 54% and 400%, respectively. The accelerated orthophosphate release due to ZnO catalysis and the well-dispersed ZnO nanorods enabled by APP met the urgent demand for P and Zn nutrients for peas, especially at their vigorous seedling stage. This work would provide a new idea for constructing nano-platforms to coordinate the incompatible P and Zn nutrients for the improvement of agronomic efficiency.

Phyto-nanotechnology can improve the nutrient efficiency and alleviate the environmental stress caused by eluvial agricultural chemicals, contributing to sustainable agriculture.

New directions for agricultural wastes valorization as hydrogel biocomposite fertilizers

The tremendous amount of waste is an environmental and social problem worldwide. The agri-food sector is the largest producer of waste and requires the extensive use of fertilizers, which entails the need to look for innovative solutions in waste management. Properly recycled bio-waste can be reused as fertilizer. Polymer capsules with immobilized waste biomass can be applied as carriers for fertilizer nutrients. The amount of components exerts a certain influence on the effectiveness of copper ions binding. The most important physicochemical properties of biocomposites, such as swelling, SEM (Scanning Electron Microscopy) and FTIR (Fourier Transform Infrared Spectroscopy) were investigated. FTIR analyzes revealed that carboxyl and hydroxyl groups play a key role in Cu²⁺ ion binding. Morphology analysis showed that ion binding leads to homogenization of the composite surface, while coating the structure makes it more regular and cohesive. The sorption kinetics and the determination of the process's equilibrium parameters (Q_max = 29.4 ± 0.493 mg g^-1) play an important role. The study of Cu²⁺ ion release in different media showed that the chitosan layer slowed down the diffusion of cations by about 50% in NaNO₃ (1% m/m) solution. Preliminary studies of the applicability of the capsules in germination tests demonstrate that the biocomposites have no phytotoxic effects on the test plant. The chitosan coating slows the release of Cu²⁺ ions by about 20% compared to uncoated capsules. New fertilizer formulations containing chitosan-encapsulated hydrogel with biomass-immobilized micronutrients can be applied for precision agriculture to minimize the loss of fertilizer nutrients to the environment. These fertilizers could be used to cultivate houseplants and greenhouse crops.

A Bibliometric Network Analysis of Recent Publications on Digital Agriculture to Depict Strategic Themes and Evolution Structure

The agriculture sector is one of the backbones of many countries’ economies. Its processes have been changing to enable technology adoption to increase productivity, quality, and sustainable development. In this research, we present a scientific mapping of the adoption of precision techniques and breakthrough technologies in agriculture, so-called Digital Agriculture. To do this, we used 4694 documents from the Web of Science database to perform a Bibliometric Performance and Network Analysis of the literature using SciMAT software with the support of the PICOC protocol. Our findings presented 22 strategic themes related to Digital Agriculture, such as Internet of Things (IoT), Unmanned Aerial Vehicles (UAV) and Climate-smart Agriculture (CSA), among others. The thematic network structure of the nine most important clusters (motor themes) was presented and an in-depth discussion was performed. The thematic evolution map provides a broad perspective of how the field has evolved over time from 1994 to 2020. In addition, our results discuss the main challenges and opportunities for research and practice in the field of study. Our findings provide a comprehensive overview of the main themes related to Digital Agriculture. These results show the main subjects analyzed on this topic and provide a basis for insights for future research.

Uptake and Translocation of Mesoporous SiO2-Coated ZnO Nanoparticles to Solanum lycopersicum Following Foliar Application

Nanoparticles composed of ZnO encapsulated in a mesoporous SiO₂ shell (nZnO@SiO₂) with a primary particle diameter of ∼70 nm were synthesized for delivery of Zn, a micronutrient, by foliar uptake. Compared to the rapid dissolution of bare nZnO (90% Zn dissolution after 4 h) in a model plant media (pH = 5), nZnO@SiO₂ released Zn more slowly (40% Zn dissolution after 3 weeks), thus enabling sustained Zn delivery over a longer period. nZnO@SiO₂, nZnO, and ZnCl₂ were exposed to Solanum lycopersicum by dosing 40 μg of Zn micronutrient (in a 20 μL suspension) on a single leaf. No Zn uptake was observed for the nZnO treatment after 2 days. Comparable amounts of Zn uptake were observed 2 days after ZnCl₂ (15.5 ± 2.4 μg Zn) and nZnO@SiO₂ (11.4 ± 2.2 μg Zn) dosing. Single particle inductively coupled plasma mass spectrometry revealed that for foliar applied nZnO@SiO₂, almost all of the Zn translocated to upper leaves and the stem were in nanoparticulate form. Our results suggest that the SiO₂ shell enhances the uptake of ZnO nanoparticles in Solanum lycopersicum. Sustained and controlled micronutrient delivery in plants through foliar application will reduce fertilizer, energy, and water use.