EFFECT OF COATINGS ON THE BEHAVIOR OF MANUFACTURED ZINC OXIDE NANOPARTICLES IN SOIL AND ZINC BIOAVAILABILITY TO PLANTS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1010358
• Project Start Date: Oct 1, 2016
• Project End Date: Sep 30, 2021
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF KENTUCKY
500 S LIMESTONE 109 KINKEAD HALL
LEXINGTON,KY 40526-0001

Performing Department
Plant and Soil Sciences

Non Technical Summary
This project will develop methods for synthesizing zinc oxide nanoparticle fertilizers with different coatings that are tuned to different types of soil. We will investigate the behavior of the particles in soils with a variety of different chemical characteristics including different pH values, phosphorus concentrations and organic matter amounts. We will then select particles to test as a fertilizer when growing wheat in a zinc deffeicient soil We will evaluate the effects of the fertilizer on plant growth and amounts of zinc in the leaves, stems, roots and grain.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

100%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	1549	2000	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
1549 - Wheat, general/other;

Field Of Science
2000 - Chemistry;

Keywords

wheat

nanotechnology

zinc

Goals / Objectives
The goals of this project are toExplore the influence of polymer and phosphate-based coatings on the aggregation, partitioning and dissolution of ZnO nanomaterials in natural soil of varying pH, organic carbon and phosphate content. Investigate the feasibility of fortifying wheat with Zn through the use of engineered ZnO nanocomposites used as either a seed coating or as a soil applied fertilizer.

Project Methods
Experiment 1) Investigation of the effect of coating on the colloidal stability and partitioning of ZnO MNPs to pore water.The experiment aims at testing hypotheses 1 and 3. To achieve this, silt loam soil of low phosphorous and organic matter content will be used (Sadler silt loam sub soil from near Princeton, KY). The pot experiment below will follow a 3-way factorial design were treatments, replicates and blocks are given in table 1. To identify most stable ZnO MNPs, the experimental setup will be performed 5 times each and will compare bulk ZnO to one ZnO NP at a time at two Zn and P levels. A pot experiment examining the effect of Zn-P relationships on wheat revealed that at exchangeable P concentrations higher than 25 mg/kg, Zn uptake by wheat was reduced even at high Zn fertilizer rates. Therefore, P will be added to pots at 0, 25, and 250 mg/kg soil on dry weight basis. Soil pH will be adjusted 6 and 8 by liming (natural pH of soil is 5.5). We will add Zn at a high rate that will enable application of analytical techniques to characterize the aggregation rate of the Zn (100 mg/kg). After 30d of incubation, we will extract the soil pore water and characterize the dissolution, aggregation and partitioning of the particles as described below in the materials and methods section.Experiment 2) Investigating the effect of coating, organic matter content and pH on the colloidal stability and partitioning of ZnO MNPs in and to pore water.The experiment aims at test hypotheses 1, 2 and 3. The following experiment will follow a 3-way factorial design treatments, replicates and blocks are given in the following table. Organic matter will be added at 1.5 and 3.0 on a (W/W) % (Carbon) basis. Soil pH will be adjusted 6 and 8 by liming (natural pH of soil is 5.5). Soils will be spiked to the maximum level of phosphate (250 mg/kg) to mimic poor Zn bioavailability to crops. We will use high Zn concentration (100 mg/kg) to allow for application of analytical techniques to characterize ZnO MNPs in the soil. After 30d of incubation, we will extract the soil pore water and characterize the dissolution, aggregation and partitioning of the particles as described below in the materials and methods section.Experiment 3) Investigate the bioavailability and bioaccessibility of ZnO MNPs to wheat and to humans.The experiment aims at investigating the hypothesis (4). To achieve this, the same silt loam soil of low organic matter and phosphorous content will be used. The experiment will be performed in pots following a completely randomized 2 way design were treatments, replicates and blocks are given in the following table, P and organic matter will be applied to mimic environments were P and NOM result in decreased Zn bioavailability (i.e. maximum level of P at 120 mg/kg will be added and maximum level of OM of 3 % (w/w) will be added). Spring wheat will be grown in the soil at pH 8. The Zn treatments will consist of ZnSO4, Bulk ZnO and a coated ZnO selected based on the results of the previous experiments. The Zn will either be added to the soil at a rate of 2.5 mg Zn/kg or it will be used to coat the seeds by soaking the seeds for 24 hours in solutions containing 2000 mg Zn/L prior to planting. Our previous research indicates that the maximum concentration should cause minimal effects on germination and shoot and root elongation. The logic behind seed treatment is that the Zn could be used more efficiently than adding to bulk soil, therefore reducing the costs. It has been shown to be a successful approach in crops such as peanut If successful in this experiment, further experiments could be done to develop ZnO MNP containing coatings for the seeds.

Progress 10/01/16 to 09/30/21

Outputs
Target Audience:The target audience includes researchers, companies, and farmers interested in the fortification of crops with zinc. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project trained PhD student, Zeinah El Haj Baddar, with a degree in soil science. Zeinah has gone on to a postdoc at the University of Georgia, Savannah River Ecology Laboratory How have the results been disseminated to communities of interest?Research results have been disseminated through peer reviewed journal articles, seminars, posters and platformed talks. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project demonstrated the beneficial use of polymer coated ZnO nanomaterials for increasing growth, yield, and zinc content of grain in wheat. We developed an understanding of how the interactions of ZnO nanomaterials differ from Zn ions in soil under different soil chemistry conditionsand in planta. We showed that soil water Zn concentrations can be increased using ZnO nanomaterials under conditions where Zn ions from conventional fertilizers are ineffective. Finally, we showed that treating seeds with ZnO nanomaterials is the most cost effective method with the lowest environmental impacts compared to soil ammendment.

Publications

• Type: Journal Articles Status: Published Year Published: 2021 Citation: Baddar, ZE and Unrine, JM. 2021. Effects of Soil pH and Coatings on the Efficacy of Polymer coated ZnO Nanoparticulate fertilizers in Wheat (Triticum aestivum). Environmental Science and Technology. https://doi.org/10.1021/acs.est.1c00443.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:The target audience for this project is sceintific researchers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A research analyst was trained to perform trace-element analysis. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?We plan to finish publishing our results and present them at a symposium on the sustainable use of nanomaterials in agriculture.

Impacts
What was accomplished under these goals? We worked on finishing up collection of data on a pot study comparing seed applicaiton of ZnO with soil applicaiton. We prepared a journal article for submission on the pot study, and we prepared a conference presentation which will be given in the next reporting period.

Publications

Progress 10/01/18 to 09/30/19

Outputs
Target Audience:Scientists working in the area of micronutrient delivery. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training for a PhD student was provided by the project. How have the results been disseminated to communities of interest?We have presented the results at two scientific conferences and published a peer review journal article. What do you plan to do during the next reporting period to accomplish the goals?We plan to complete publication of our pot studies showing Zn fortification in wheat when ZnO nanoparticles were used as a seed treatment.

Impacts
What was accomplished under these goals? During this project period we determined how coating properties affect the sorption and dissolution of ZnO nanoparticles in soil as a funciton of soil pH. We determined that the affinity of the coatings for natural organic matter dictated their sorption and dissolution behavior. We found that dextran coated ZnO nanoparticles had the highest affinity for soil organic matter and were therefore the most bioavailable due to their partioning to soil pore water. We also determined that wheat could be biofortified by adding dextran or dextran coated ZnO nanoparticles as a seed treatment at the time of planting. Direct ammendment of the soil with ZnO nanoparticles did not enhance Zn content in grain.

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Baddar, ZE; Matocha, C; Unrine, JM. 2019. Surface coating effects on ZnO sorption and dissolution in soil. Environmental Science: Nano, 6: 2495-2507

Progress 10/01/17 to 09/30/18

Outputs
Target Audience:The target audience is scientists and engineers researching ways to increase the zinc content of cereal crops for increased plant and human nutrition. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A PhD student was trained and has graduated. How have the results been disseminated to communities of interest?We have made presentations at the Soil Science Society of America Meetings, the Gordon Research Conference on Nanotechnology in Agriculture, and published our results. What do you plan to do during the next reporting period to accomplish the goals?We plan to finish writing manuscripts from this project and explore ways to use the particles to deliver ZnO NPsas a foliar application in wheat.

Impacts
What was accomplished under these goals? We developed a set of polymer-coated zinc oxide nanoparticles with varied coatings and surface chemistry. These coatings were tested as seed treatments and soil ammendments for winter wheat. We found that zinc oxide nanoparticles increased the growth and zinc content of wheat when used as a seed treatment. They were less effective as a soil ammendment. Particle coatings could be used to tune the particles to target specific plant tissues. We pubished one manuscript describing the use of these materials as a seed treatment (El Haj Baddar and Unrine, 2018) and we have another manuscript on their use as a soil ammendment in preparation.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: El Haj Baddar, ZW; Unrine, JM*. Functionalized ZnO nanoparticle seed treatments to enhance growth and Zn content of wheat (Triticum aestivum). 2018. Journal of Agricultural and Food Chemistry. DOI: 10.1021/acs.jafc.8b03277

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:The target audience of this proposal is plant and soil scientists involved in engineering nanofertilizers. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project provided training for a PhD student. How have the results been disseminated to communities of interest?Results have been presented at the SSSA meeting. Journal articles are in preparation. What do you plan to do during the next reporting period to accomplish the goals?We plan to finish writing three publications describing this year's accomplishments. We also plan to do an experiment where we spray the particles onto the leaves of wheat plants during anthesis.

Impacts
What was accomplished under these goals? During this reporting period, we completed studies investigating the partitioning and dissolution of ZnO nanoparticles (bare particles, dextran coated, phosphate coated, dextran phosphate coated) in a Zn defecient silt-loamsoil. We also completed two pot experiments investigating the uptake of Zn from these materials into wheat plants and into grain. The first pot experiment used seeds coated with the ZnO materials and the second used soils spiked with the ZnO materials with pH adjusted to either 6 or 8. We found that the ZnO nanoparticles have increased pore water Zn concentrations compared to ZnSO4 control, particluarly at pH 8. Follow up studies showed that the affinity of different ZnO nanomaterials for soil organic matter explained their partitioning to soil. For the pot studies, we found that ZnO nanomaterials were no more effective at increasing grain Zn concentrations than ZnSO4. We conclude that either Zn in ZnO form is not available for plant uptake until the ZnO dissolves, or we hit the physiological limit for Zn uptake.

Publications