Opportunities and challenges for nanotechnology in the agri-tech revolution

ArticleinNature Nanotechnology 14(6):517 · June 2019with 325 Reads 
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Abstract
Nanotechnology offers a range of opportunities for sustainable agriculture. Successful developments will need a systems approach to designing proposed nanotechnologies.

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    The need for appropriate science and regulation to underpin nanosafety is greater than ever as ongoing advances in nanotechnology are rapidly translated into new industrial applications and nano-enabled commercial products. Nevertheless, a disconnect persists between those examining risks to human and environmental health from nanomaterials. This disconnect is not atypical in research and risk assessment and has been perpetuated in the case of engineered nanomaterials by the relatively limited overlap in human and environmental exposure pathways. The advent of agri-nanotechnologies brings both increased need and opportunity to change this status quo as it introduces significant issues of intersectionality that cannot adequately be addressed by current discipline-specific approaches alone. Here, focusing on the specific case of nanoparticles, we propose that a transdisciplinary approach, underpinned by the One Health concept, is needed to support the sustainable development of these technologies. The development of nano-enabled agriculture will require proper safety regulations. This Perspective outlines the need for a combined approach to regulate health and environmental risks under the same framework.
  • Article
    The underground root–soil–microbe interactions are extremely complex, but vitally important for aboveground plant growth, health and fitness. The pressure to reduce our reliance on agrochemicals, and sustainable efforts to develop agriculture makes rhizosphere interactions’ research a hotspot. Recent advances provide new insights about the signals, pathways, functions and mechanisms of these interactions. In this review, we provide an overview about recent progress in rhizosphere interaction networks in crops. We also discuss a holistic view of the root–soil–rhizomicrobiome interactions achieved through the advances of omics and bioinformatics technologies, and the potential strategies to manage the complex rhizosphere interactions for enhancing crop production.
  • Article
    There are a wide variety of synthetic and naturally occurring nanomaterials under development for nanoscale cargo-delivery applications. Viruses play a special role in these developments, because they can be regarded as naturally occurring nanomaterials evolved to package and deliver cargos. While any nanomaterial has its advantage and disadvantages, viral nanoparticles (VNPs), in particular the ones derived from plant viruses and bacteriophages, are attractive options for cargo-delivery as they are biocompatible, biodegradable, and non-infectious to mammals. Their protein-based structures are often understood at atomic resolution and are amenable to modification with atomic-level precision through chemical and genetic engineering. Here we present a focused review of the emerging technology development of plant viruses and bacteriophages targeting human health and agricultural applications. Key target areas of development are their use in chemotherapy, photodynamic therapy, pesticide-delivery, gene therapy, vaccine carriers, and immunotherapy.
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    Neonicotinoid insecticides are widespread in surface waters across the agriculturally intensive Midwestern United States. We report for the first time the presence of three neonicotinoids in finished drinking water and demonstrate their general persistence during conventional water treatment. Periodic tap water grab samples were collected at the University of Iowa over 7 weeks in 2016 (May–July) after maize/soy planting. Clothianidin, imidacloprid, and thiamethoxam were ubiquitously detected in finished water samples at concentrations ranging from 0.24 to 57.3 ng/L. Samples collected along the University of Iowa treatment train indicate no apparent removal of clothianidin or imidacloprid, with modest thiamethoxam removal (∼50%). In contrast, the concentrations of all neonicotinoids were substantially lower in the Iowa City treatment facility finished water using granular activated carbon (GAC) filtration. Batch experiments investigated potential losses. Thiamethoxam losses are due to base-catalyzed hydrolysis under high-pH conditions during lime softening. GAC rapidly and nearly completely removed all three neonicotinoids. Clothianidin is susceptible to reaction with free chlorine and may undergo at least partial transformation during chlorination. Our work provides new insights into the persistence of neonicotinoids and their potential for transformation during water treatment and distribution, while also identifying GAC as a potentially effective management tool for decreasing neonicotinoid concentrations in finished drinking water.
  • Article
    The agro-ecosystem is under enormous pressure due to rapid population growth, increasing global food demand, increasing fresh water withdrawals and energy consumption, excessive food waste, inefficient use of agrochemicals, environmental degradation and climate change. Nanotechnology offers opportunities to make food production more sustainable by providing better sensors for monitoring physical, chemical, or biological properties and processes; technologies for controlling pathogens to increase food safety and minimize food waste; improved membranes and sorbents for distributed water treatment and resource recovery; novel materials for timed and targeted delivery of agrochemicals; and, new materials for monitoring and improving animal health. This tutorial review provides an overview of the nanotechnology opportunities of greatest potential determined through an NSF-funded interdisciplinary workshop of ∼50 experts from the U.S. and the EU in the areas of nanotechnology, energy, water, agriculture, systems engineering, data integration and analysis, and social science. This paper also presents examples of selected specific opportunities and the remaining scientific and engineering challenges that must be overcome to realize the benefits of nanotechnology across the farm to fork continuum.
  • Article
    Engineered nanoparticles (ENPs) are introduced to the soil environment mainly via wastewater biosolids applied to soils and their targeted delivery in agricultural applications. The impact of ENP size and surface coating on the activity of extracellular enzymes and bacterial community composition of an agricultural soil was examined using model gold nanoparticles (nAu). These endpoints were chosen as indicators of the soil's response to external disturbances. The activity of five extracellular enzymes important in nutrient-cycling was measured in soils treated with commercially available 50 nm citrate-coated nAu and polyvinylpyrrolidone (PVP)-coated nAu of three different nominal diameters: 5, 50, and 100 nm. At low particle concentration (0.1 mg nAu kg⁻¹ soil), decreasing the size of PVP-nAu resulted in an increased stimulation of soil enzyme activity. No correlation between size of PVP-nAu and soil enzyme activity was observed at a higher dose (100 mg nAu kg⁻¹ soil). At a fixed size of 50 nm, citrate-coated nAu generally resulted in significant increases in soil enzyme activity at 30 days of exposure compared to PVP-coated nAu. Data from 16S rRNA gene sequencing showed that the community composition of soil spiked with citrate-coated nAu clustered significantly away from soil spiked with PVP-nAu at higher concentration (100 mg nAu kg⁻¹ soil), showing the effect of type of nAu surface coatings. Abundance of bacteria annotated to operational taxonomic units (OTUs) from important soil bacterial groups, including Actinobacteria and Proteobacteria, increased following exposure of soil to nAu and more substantially following exposure to citrate-coated nAu for 30 days. This study shows that release of nanomaterials such as nAu to soils may have significant effects on soil enzyme activities and microbial communities and thus impact nutrient cycling in soils. Moreover, this study provides baseline knowledge that may be useful in customizing nanoparticle size and surface coating for their potential use as nutrient delivery agents in agriculture.
  • Article
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    Losses at every stage in the food system influence the extent to which nutritional requirements of a growing global population can be sustainably met. Inefficiencies and losses in agricultural production and consumer behaviour all play a role. This paper aims to understand better the magnitude of different losses and to provide insights into how these influence overall food system efficiency. We take a systems view from primary production of agricultural biomass through to human food requirements and consumption. Quantities and losses over ten stages are calculated and compared in terms of dry mass, wet mass, protein and energy. The comparison reveals significant differences between these measurements, and the potential for wet mass figures used in previous studies to be misleading. The results suggest that due to cumulative losses, the proportion of global agricultural dry biomass consumed as food is just 6% (9.0% for energy and 7.6% for protein), and 24.8% of harvest biomass (31.9% for energy and 27.8% for protein). The highest rates of loss are associated with livestock production, although the largest absolute losses of biomass occur prior to harvest. Losses of harvested crops were also found to be substantial, with 44.0% of crop dry matter (36.9% of energy and 50.1% of protein) lost prior to human consumption. If human over-consumption, defined as food consumption in excess of nutritional requirements, is included as an additional inefficiency, 48.4% of harvested crops were found to be lost (53.2% of energy and 42.3% of protein). Over-eating was found to be at least as large a contributor to food system losses as consumer food waste. The findings suggest that influencing consumer behaviour, e.g. to eat less animal products, or to reduce per capita consumption closer to nutrient requirements, offer substantial potential to improve food security for the rising global population in a sustainable manner.
  • Article
    While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in situ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.
  • Article
    Full-text available
    While slow release of chemicals have been widely applied for drug delivery, little work has been done on using this general nanotechnology based principle for delivering nutrients for crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent bio-compatibility while acting as a rich phosphorous source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in-situ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with nitrogen (N) weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.
  • Article
    An aqueous colloidal dispersion (∼230 nm average size) of the copper (Cu) nanoparticle (NP)-grown carbon nanofibers (CNFs) was used as a stimulant for crop yields. The Cu-CNFs (average diameter = 95 nm), separately prepared on an activated carbon microfiber substrate using chemical vapor deposition, were dispersed in Cicer arietinum seed-containing water. The CNFs served as a carrier for the Cu micronutrient, with a controlled release of the Cu NPs. The CNFs also served as a growth stimulant by increasing the water uptake capacity of the plants. The scanning electron microscopy images, elemental (Cu/C) mapping, and atomic absorption spectrometry data corroborated the effective translocation of the Cu-CNFs from the root to the shoot of the plants. The water uptake capacity, germination rate, shoot and root lengths, and chlorophyll and protein contents significantly increased in the plants using the Cu-CNFs. This is the first study showing the use of the Cu-CNFs as a carrier of micronutrients in plants, with an effective translocation ability.
  • Article
    Nitric oxide (NO) is a signaling molecule involved in plant response to various abiotic stresses. However, the application of NO donors in agriculture is hampered by the instability of these compounds. Despite the successful uses of NO-releasing nanoparticles for biomedical purposes and the variety of nanomaterials developed as carrier systems of agrochemicals, the potential applications of nanocarriers for NO delivery in plants have not yet been tested. Herein, we report the synthesis and characterization of chitosan nanoparticles (CS NPs) containing the NO donor S-nitroso-mercaptosuccinic acid (S-nitroso-MSA). The efficiency of these NO-releasing NPs in mitigating the deleterious effects of salinity on maize plants was compared to that of the non-encapsulated NO donor. The NPs were synthesized through ionotropic gelation process, and mercaptosuccinic acid (MSA), the NO donor precursor, was encapsulated into CS NPs (91.07% encapsulation efficiency). Free thiol groups of MSA-CS NPs were nitrosated, leading to S-nitroso-MSA-CS NPs (NO-releasing NPs). The incorporation of S-nitroso-MSA into CS NPs allowed a sustained NO release. Treatments of salt-stressed maize plants with S-nitroso-MSA-CS NPs resulted in a higher leaf S-nitrosothiols content compared to that of free S-nitroso-MSA. Moreover, S-nitroso-MSA-CS NPs were more efficient than was the free NO donor in the amelioration of the deleterious effects of salinity in photosystem II activity, chlorophyll content and growth of maize plants because the protective action of the nanoencapsulated S-nitroso-MSA was achieved at lower dosages. Overall, these results demonstrate the positive impact of S-nitroso-MSA nanoencapsulation in increasing NO bioactivity in maize plants under salt stress.
  • Article
    Nanoparticles (NP) have great potential in agriculture. For example, micronutrients have poor mobility in plants and poor availability in neutral soils, yet they play pivotal roles in root health. We investigated whether foliar sprays of micronutrient NP could affect plant health in disease infested soils. In the greenhouse, NP of AlO, CuO, FeO, MnO, NiO, and ZnO were sprayed on tomatoes and grown in soilless medium infested with the Fusarium wilt fungus. NP of CuO, MnO, or ZnO reduced disease estimates [area-under-the-disease-progress-curve (AUDPC)] by 31%, 28%, or 28%, respectively, when compared to untreated controls. When NP of CuO, MnO, or ZnO, their bulked equivalents, or their sulfate salts were compared to untreated eggplants and held in the greenhouse in soilless medium infested with the Verticillium wilt fungus, NP of CuO increased fresh weights by 64%, reduced AUDPC values by 69%, and had 32% more Cu in the roots. These same amendments were sprayed onto the foliage of tomato and eggplant transplants and set in field plots in soil heavily infested with the Verticillium wilt fungus. Compared to untreated controls, yields of tomato were 33% or 31% greater with NP of CuO or the bulked MnO, respectively. NP of CuO or ZnSO4 increased eggplant yields by 34% or 41% when compared to controls, respectively. In vitro studies found NP of CuO were not inhibitory to the Fusarium wilt fungus, suggesting host defense was being manipulated.
  • Article
    A circular economy will look to chemistry to provide the basis of innovative products, made from renewable feedstocks and designed to be reused, recycled, or the feedstock renewed through natural processes. The substances that products are made of will increasingly be treated as a resource equal to the raw materials, and not just disposed of. This perspective discusses the role of chemists in a world without waste.
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    Fluoride and nitrate contamination in drinking water sources have been a major problem in many countries. The long term health hazards and increasing levels of fluoride and nitrate in drinking water through natural and anthropogenic sources have been challenging and warrants the need for advanced technologies for abating these contaminants. Various technologies have been reported so far for fluoride and nitrate removal from drinking water. Recent advances in nanotechnology and nanomaterial synthesis have showed significant impact on fluoride and nitrate removal when compared to other conventional adsorbents and process. The present review discusses the recent advances in nanotechnology and nanomaterials synthesis, modification in process parameters and use for composite nanomaterials for enhanced removal of fluoride and nitrate from contaminated water.
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    The use of lower concentrations and fewer applications of herbicides is one of the prime objectives of the sustainable agriculture as it decreases the toxicity to non-targeted organisms and the risk of wider environmental contamination. In the present work, nanoparticles were developed for encapsulation of the herbicides imazapic and imazapyr. Alginate/chitosan and chitosan/tripolyphosphate nanoparticles were manufactured, and their physicochemical stability was evaluated. Determinations were made of the encapsulation efficiency and release kinetics, and the toxicity of the nanoparticles was evaluated using cytotoxicity and genotoxicity assays. The effects of herbicides and herbicide-loaded nanoparticles on soil microorganisms were studied in detail using real-time polymerase chain reactions. The nanoparticles showed an average size of 400 nm and remained stable during 30 days of storage at ambient temperature. Satisfactory encapsulation efficiencies of between 50 and 70% were achieved for both types of particles. Cytotoxicity assays showed that the encapsulated herbicides were less toxic, compared to the free compounds, and genotoxicity was decreased. Analyses of soil microbiota revealed changes in the bacteria of the soils exposed to the different treatments. Our study proves that encapsulation of the herbicides improved their mode of action and reduced their toxicity, indicating their suitability for use in future practical applications.
  • Article
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    Sustainable use of nanotechnology for agricultural practice requires an understanding of the plant’s life cycle and potential toxicological impacts of nanomaterials. The main objective of this study was to compare the impact of TiO2 and ZnO nanoparticles of similar size (25 ± 3.5 nm) over a range of concentrations (0 to 1000 mg/kg) on translocation and accumulation of nanoparticles in different plant sections; as well as to establish physiological impact on tomato plants. The results indicated that there is a critical concentration of TiO2 and ZnO nanoparticles upto which the plant’s growth and development are promoted; with no improvement beyond that. Aerosol mediated application was found to be more effective than soil mediated application on the uptake of the nanoparticles was in plants. A mechanistic description of nanoparticle uptake, translocation and resultant plant response is unraveled. The present investigation demonstrates the concept of nanoparticle farming by understanding plant – nanoparticle interaction and biodistribution.
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    Nanotechnology has the potential to innovate the agricultural, feed and food sectors (hereinafter referred to as agri/feed/food). Applications that are marketed already include nano-encapsulated agrochemicals or nutrients, antimicrobial nanoparticles and active and intelligent food packaging. Many nano-enabled products are currently under research and development, and may enter the market in the near future. As for any other regulated product, applicants applying for market approval have to demonstrate the safe use of such new products without posing undue safety risks to the consumer and the environment. Several countries all over the world have been active in examining the appropriateness of their regulatory frameworks for dealing with nanotechnologies. As a consequence of this, different approaches have been taken in regulating nano-based products in agri/feed/food. The EU, along with Switzerland, were identified to be the only world region where nano-specific provisions have been incorporated in existing legislation, while in other regions nanomaterials are regulated more implicitly by mainly building on guidance for industry. This paper presents an overview and discusses the state of the art of different regulatory measures for nanomaterials in agri/feed/food, including legislation and guidance for safety assessment in EU and non-EU countries. Copyright © 2015. Published by Elsevier Inc.
  • Article
    Nitrogen fertilizer tends to migrate into the environment through runoff, leaching and volatilization, causing severe environmental pollution. In this work, a high-performance water and nutrient loss control fertilizer (WNLCF) was developed by adding high-energy electron beam (HEEB) dispersed attapulgite (HA)-sodium polyacrylate (P)-polyacrylamide (M) complex to traditional fertilizer. Therein, HA-P-M was used as the water and nutrient loss control agent (WNLCA) which could self-assemble to form three-dimensional (3D) micro/nano networks in aqueous phase. Thus water and nutrient could be effectively combined and held in the networks which could be then retained in the soil via the filtering effect of soil, resulting in low loss of water and nutrient. Pot experiments of 15N-labeled fertilizer indicated that WNLCF could effectively improve the amounts of fertilizer nutrients in the stem of corn and facilitate the growth of corn. Therefore, this work provides a promising approach to enhance the utilization efficiency of water and nutrient, and lower the pollution risk of fertilizer.
  • Article
    A laboratory study was undertaken to regulate the release of zinc (Zn) to the soil-plant system using a nano-sized manganese hollow core shell. The manganese carbonate core was used as a template to produce hollow shells like capsules, using cationic and anionic charged polymer electrolytes through electrostatic interaction. After achieving the nano-dimension hollow shell, Zn was fortified by loading zinc sulfate (ZnSO4). The hollow core shell was characterized using a particle size analyzer, Fourier Transform Infra Red Spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) before and after loading of Zn. The characterization studies clearly indicated that the hollow core shell was successfully loaded with Zn to a level of 10%, and the presence of Zn was confirmed using Energy-dispersive x-ray spectroscopy (EDAX). The sorption and desorption pattern of the Zn-loaded hollow core shell was examined using a percolation reactor. The results showed that the Zn-fortified core shell released Zn for more than 696 h while Zn release ceased after 408 h in ZnSO4-fertilized soil. These data indicated that the hollow core shell can be used to regulate Zn release. Rice (Oryza sativa L.) plants fertilized with a Zn-fortified core shell had a higher Zn uptake of 5.66 and 3.47 mg hill−1 under submerged and aerobic moisture regimes, respectively. The data suggest that the encapsulation of Zn using a manganese hollow core shell improves Zn use efficiency by rice while reducing the loss of nutrients and minimizing environmental pollution.
  • Article
    The Twelve Principles of Green Chemistry were first published in 1998 and provide a framework that has been adopted not only by chemists, but also by design practitioners and decision-makers (e.g., materials scientists and regulators). The development of the Principles was initially motivated by the need to address decades of unintended environmental pollution and human health impacts from the production and use of hazardous chemicals. Yet, for over a decade now, the Principles have been applied to the synthesis and production of engineered nanomaterials (ENMs) and the products they enable. While the combined efforts of the global scientific community have led to promising advances in the field of nanotechnology, there remain significant research gaps and the opportunity to leverage the potential global economic, societal and environmental benefits of ENMs safely and sustainably. As such, this tutorial review benchmarks the successes to date and identifies critical research gaps to be considered as future opportunities for the community to address. A sustainable material design framework is proposed that emphasizes the importance of establishing structure-property-function (SPF) and structure-property-hazard (SPH) relationships to guide the rational design of ENMs. The goal is to achieve or exceed the functional performance of current materials and the technologies they enable, while minimizing inherent hazard to avoid risk to human health and the environment at all stages of the life cycle.
  • Article
    Increase in demand for our primary foodstuffs is outstripping increase in yields, an expanding gap that indicates large potential food shortages by mid-century. This comes at a time when yield improvements are slowing or stagnating as the approaches of the Green Revolution reach their biological limits. Photosynthesis, which has been improved little in crops and falls far short of its biological limit, emerges as the key remaining route to increase the genetic yield potential of our major crops. Thus, there is a timely need to accelerate our understanding of the photosynthetic process in crops to allow informed and guided improvements via in-silico-assisted genetic engineering. Potential and emerging approaches to improving crop photosynthetic efficiency are discussed, and the new tools needed to realize these changes are presented. Copyright © 2015 Elsevier Inc. All rights reserved.
  • Article
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    Engineered nanomaterials (ENMs) enable the control and exploration of intermolecular interactions inside microscopic systems, but the potential environmental impacts of their inevitable release remain largely unknown. Plants exposed to ENMs display effects, such as increase in biomass and chlorophyll, distinct from those induced by exposure to their bulk counterparts, but few studies have addressed the mechanisms underlying such physiological results. The current investigation found that exposure of Arabidopsis thaliana to nano zero-valent iron (nZVI) triggered high plasma membrane H+-ATPase activity. The increase in activity caused a decrease in apoplastic pH, an increase in leaf area and also wider stomatal aperture. Analysis of gene expression indicated that the levels of the H+-ATPase isoform responsible for stomatal opening, AHA2, were 5-fold higher in plants exposed to nZVI than in unexposed control plants. This is the first study to show that nZVI enhances stomatal opening by inducing the activation of plasma membrane H+-ATPase, leading to the possibility of increased CO2 uptake.
  • Article
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    Since humans worldwide obtain more than 99.7% of their food (calories) from the land and less than 0.3% from the oceans and aquatic ecosystems, preserving cropland and maintaining soil fertility should be of the highest importance to human welfare. Soil erosion is one of the most serious threats facing world food production. Each year about 10 million ha of cropland are lost due to soil erosion, thus reducing the cropland available for world food production. The loss of cropland is a serious problem because the World Health Organization and the Food and Agricultural Organization report that two-thirds of the world population is malnourished. Overall, soil is being lost from agricultural areas 10 to 40 times faster than the rate of soil formation imperiling humanity’s food security.
  • Article
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    Nanofertilizers may be more effective than regular fertilizers in improving plant nutrition, enhancing nutrition use efficiency, and protecting plants from environmental stress. A hydroponic pot experiment was conducted to study the role of foliar application with 2.5 mM nano-silicon in alleviating Cd stress in rice seedlings (Oryza sativa L. cv Youyou 128) grown in solution added with or without 20 μM CdCl2. The results showed that Cd treatment decreased the growth and the contents of Mg, Fe, Zn, chlorophyll a, and glutathione (GSH), accompanied by a significant increase in Cd accumulation. However, foliar application with nano-Si improved the growth, Mg, Fe, and Zn nutrition, and the contents of chlorophyll a of the rice seedlings under Cd stress and decreased Cd accumulation and translocation of Cd from root to shoot. Cd treatment produced oxidative stress to rice seedlings indicated by a higher lipid peroxidation level (as malondialdehyde (MDA)) and higher activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and a lower GSH content. However, those nano-Si-treated plants had lower MDA but higher GSH content and different antioxidant enzyme activities, indicating a higher Cd tolerance in them. The results suggested that nano-Si application alleviated Cd toxicity in rice by decreasing Cd accumulation, Cd partitioning in shoot and MDA level and by increasing content of some mineral elements (Mg, Fe, and Zn) and antioxidant capacity.
  • Article
    Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture.However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns.It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees.Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals.Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.