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Although the Green Revolution dramatically increased food production, it led to non- sustainable conventional agricultural practices, with productivity in general declining over the last few decades. Maintaining food security with a world population exceeding 9 billion in 2050, a changing climate, and declining arable land will be exceptionally challenging. In fact, nothing short of a revolution in how we grow, distribute, store, and consume food is needed. In the last ten years, the field of nanotoxicology in plant systems has largely transitioned to one of sustainable nano-enabled applications, with recent discoveries on the use of this advanced technology in agriculture showing tremendous promise. The range of applications is quite extensive, including direct application of nanoscale nutrients for improved plant health, nutrient biofortification, increased photosynthetic output, and greater rates of nitrogen fixation. Other applications include nano-facilitated delivery of both fertilizers and pesticides; nano-enabled delivery of genetic material for gene silencing against viral pathogens and insect pests; and nanoscale sensors to support precision agriculture. Recent efforts have demonstrated that nanoscale strategies increase tolerance to both abiotic and biotic stressors, offering realistic potential to generate climate resilient crops. Considering the efficiency of nanoscale materials, there is a need to make their production more economical, alongside efficient use of incumbent resources such as water and energy. The hallmark of many of these approaches involves much greater impact with far less input of material. However, demonstrations of efficacy at field scale are still insufficient in the literature, and a thorough understanding of mechanisms of action is both necessary and often not evident. Although nanotechnology holds great promise for combating global food insecurity, there are far more ways to do this poorly than safely and effectively. This review summarizes recent work in this space, calling out existing knowledge gaps and suggesting strategies to alleviate those concerns to advance the field of sustainable nano-enabled agriculture. 

Phosphorus (P) is critical for crop production but has a high nutrient use inefficiency. Tomato was grown in soil amended with five P-sources, used as-is, or embedded within a biodegradable polymer, polyhydroxyalkanoate (PHA). Correlation analysis identified treatments that maintain plant growth, improve bioavailable soil P, and reduce P loss. Three performance classes were identified: (i) micro- and nanohydroxyapatite, which did not increase bioavailable P, plant P-uptake, or change P in runoff/leaching compared to controls; (ii) monocalcium phosphate (MCP), dicalcium phosphate (DCP), calcium pyrophosphate nanoparticles (CAP), and PHA-MCP that increased P-uptake and/or bioavailable P but also increased P loss in runoff/leaching; and (iii) PHA-DCP and PHA-CAP, where increased bioavailable P and plant P-uptake were achieved with minimal P loss in runoff/leaching. In addition to identifying treatments that maintain plant growth, increase bioavailable P, and minimize nutrient loss, correlation plots also revealed that (i) bioavailable P was a good indicator of plant P-uptake; (ii) leached P could be predicted from water solubility; and (iii) P loss through runoff versus leaching showed similar trends. This study highlights that biopolymers can promote plant P-uptake and improve bioavailable soil P, with implications for mitigating the negative environmental impacts of P loss from agricultural systems. 

Limited data exist on how surface charge and morphology impact the effectiveness of nanoscale copper oxide (CuO) as an agricultural amendment under field conditions. This study investigated the impact of these factors on tomatoes and watermelons following foliar treatment with CuO nanosheets (NS-) or nanospikes (NP+ and NP-) exhibiting positive or negative surface charge. Results showed plant species-dependent benefits. Notably, tomatoes infected with Fusarium oxysporum had significantly reduced disease progression when treated with NS-. Watermelons benefited similarly from NP+. Although disease suppression was significant and trends indicated increased yield, the yield effects weren't statistically significant. However, several nanoscale treatments significantly enhanced the fruit's nutritional value, and this nano-enabled biofortification was a function of particle charge and morphology. Negatively charged nanospikes significantly increased the Fe content of healthy watermelon and tomato (20–28 %) and Ca in healthy tomato (66 %), compared to their positively charged counterpart. Negatively charged nanospikes also outperformed negatively charged nanosheets, leading to significant increases in the content of S and Mg in infected watermelon (37–38 %), Fe in healthy watermelon (58 %), and Ca (42 %) in healthy tomato. These findings highlight the potential of tuning nanoscale CuO chemistry for disease suppression and enhanced food quality under field conditions. 

Abstract Although silicon-based nanomaterials (Si-based NMs) can promote crop yield and alleviate biotic and abiotic stress, the underlying performance mechanisms are unknown. In the present study, the effect of the root application of Si-based NMs on the physiological responses of cherry radish (Raphanus sativus L.) was evaluated in a life cycle experiment. Root exposure to 0.1% (w/w) Si-based NMs significantly increased total fresh weight, total chlorophyll and carotenoids by 36.0%, 14.2% and 18.7%, respectively, relative to untreated controls. The nutritional content of the edible tissue was significantly enhanced, with an increase of 23.7% in reducing sugar, 24.8% in total sugar, and 232.7% in proteins; in addition, a number of nutritional elements (Cu, Mn, Fe, Zn, K, Ca, and P) were increased. Si-based NMs exposure positively altered the phytohormone network and decreased abscisic acid content, both of which promoted radish fresh weight. LC-MS-based metabolomic analysis shows that Si-based NMs increased the contents of most carbohydrates (e.g., α-D-glucose, acetylgalactosamine, lactose, fructose, etc.) and amino acids (e.g., asparagine, glutamic acid, glutamine, valine, arginine, etc.), subsequently improving overall nutritional values. Overall, nanoscale Si-based agrochemicals have significant potential as a novel strategy for the biofortification of vegetable crops in sustainable nano-enabled agriculture. 

The addition of biochars and nanoparticles with adsorbed Azotobacter vinelandii and Bacillus megaterium alleviated damage from Fusarium infection in both tomato (Solanum lycopersicum) and watermelon (Citrullus lanatus) plants. Tomato and watermelon plants were grown in greenhouse for 28 and 30 days (respectively) and were treated with either nanoparticles (chitosan-coated mesoporous silica or nanoclay) or varying biochars (biochar produced by pyrolysis, gasification and pyrogasification). Treatments with nanoparticles and biochars were applied in two variants – with or without adsorbed plant-growth promoting bacteria (PGPR). Chitosan-coated mesoporous silica nanoparticles with adsorbed bacteria increased chlorophyll content in infected tomato and watermelon plants (1.12 times and 1.63 times, respectively) to a greater extent than nanoclay with adsorbed bacteria (1.10 times and 1.38 times, respectively). However, the impact on other endpoints (viability of plant cells, phosphorus and nitrogen content, as well antioxidative status) was species-specific. In all cases, plants treated with adsorbed bacteria responded better than plants without bacteria. For example, the content of antioxidative compounds in diseased watermelon plants increased nearly 46% upon addition of Aries biochar and by approximately 52% upon addition of Aries biochar with adsorbed bacteria. The overall effect on disease suppression was due to combination of the antifungal effects of both nanoparticles (and biochars) and plant-growth promoting bacteria. These findings suggest that nanoparticles or biochars with adsorbed PGPR could be viewed as a novel and sustainable solution for management of Fusarium wilt. 

Plastics have become an integral component in agricultural production as mulch films, nets, storage bins and in many other applications, but their widespread use has led to the accumulation of large quantities in soils. Rational use and reduction, collection, reuse, and innovative recycling are key measures to curb plastic pollution from agriculture. Plastics that cannot be collected after use must be biodegradable in an environmentally benign manner. Harmful plastic additives must be replaced with safer alternatives to reduce toxicity burdens and included in the ongoing negotiations surrounding the United Nations Plastics Treaty. Although full substitution of plastics is currently not possible without increasing the overall environmental footprint and jeopardizing food security, alternatives with smaller environmental impacts should be used and endorsed within a clear socio-economic framework. Better monitoring and reporting, technical innovation, education and training, and social and economic incentives are imperative to promote more sustainable use of plastics in agriculture.

 

Phosphorus (P) loss from agro-ecosystems impinges upon P use efficiency by plants and thereby constitutes both agronomic and environmental nuisances. Herein, we report on the potential for controlling P leaching loss and application in crop fertilization through repurposing and nano-functionalizing tripolyphosphate (TPP) as a sole P source. The developed TPP-Chitosan and TPP-Chitosan-ZnO nanofertilizers exhibited positive surface charges, 5.8 and 13.8 mV, and hydrodynamic sizes of 430 and 301 nm, respectively. In soil, nanoformulations of TPP-Chitosan and TPP-Chitosan-ZnO significantly reduced cumulative P leaching during 72 h, reaching 91 and 97% reductions, respectively, compared to a conventional fertilizer, monoammonium phosphate (MAP). Cumulative P leaching after 72 h from these nanofertilizers was, respectively, 84 and 95% lower than from TPP alone. TPP-Chitosan-ZnO was, overall, 65% more effective in reducing P leaching, compared to TPP-Chitosan. Relative to MAP, the wheat plant height was significantly increased by TPP-Chitosan-ZnO by 33.0%. Compared to MAP, TPP-Chitosan and TPP-Chitosan-ZnO slightly increased wheat grain yield by 21 and 30%, respectively. Notably, TPP-Chitosan-ZnO significantly decreased shoot P levels, by 35.5, 47, and 45%, compared to MAP, TPP, and TPP-Chitosan, respectively. Zn release over 72 h from TPP-Chitosan-ZnO was considerably lower, compared to a control, ZnO nanoparticles, and averaged, respectively, 34.7 and 0.065 mg/L, which was 534 times higher for the former. Grain Zn was significantly higher in the TPP-Chitosan treatment, relative to MAP. TPP-Chitosan also significantly mobilized the resident K, S, Mg, and Ca from soil into the plant, helping to improve the overall nutritional quality and supporting the role of chitosan in nutrient mobilization. Taken together, our data highlight the potential for repurposing a non-fertilizer P material, TPP, for agricultural and environmental applications and the effect of applying nanotechnology on such outcomes. Broadly speaking, the reduction in P loss is critical for controlling the eutrophication of water bodies due to nutrient overload and for sustaining the dwindling global P resources. 

Enhancing the delivery efficiency of NPK fertilizers benefits both crops and the environment through moderating the supplied dosage of nutrients in the soil, avoiding side reactions, maximizing absorption by the plant, and minimizing leaching and runoff. Bio-based materials such as cellulose are ideal scaffolds for nutrient delivery due to their inherent biocompatibility, biodegradability, and significant water uptake. In this work, nanocellulose-based hydrogels were regenerated from mixed softwood in acidic media and loaded with NPK by immersion in varied concentrations of an NPK-rich fertilizer solution. High loading of NPK was achieved within the hydrogel, but immersion in the matrix provided only slight slowing of nutrient release compared to rapid solubility of conventional formulations. Densification, crosslinking, and coating of the hydrogels with beeswax were ineffective strategies to further slow NPK release. Following these results, both gas and solution-phase esterification reactions of the cellulosic matrix with hexanoyl chloride were performed after NPK loading to introduce a hydrophobic surface layer. While solution-phase modification led to phosphorus leaching and was overall ineffective in altering nutrient release, the gas-phase modification slowed the release of P and K by more than an order of magnitude. Moreover, it was found that varying both the properties of the hydrophobic surface layer and the nutrient loading provide a means to tune release rates. Overall, this work demonstrates the potential of nanocellulose-based hydrogels to be used as an environmentally safe and sustainable vehicle for the controlled release of nutrients in agricultural applications. 

Increasing the capacity of biological nitrogen fixation (BNF) is an effective strategy to enhance food security while simultaneously reducing the carbon and nitrogen footprint of agriculture. Nanotechnology offers several pathways to enhance BNF successfully.