Novel formulations of agrochemicals

(CRSs – Controlled-release systems)

There are several methods for agrochemicals application. Most often agrochemicals are sprayed by water solutions. This method is associated with high loss during application and short duration of action. Less than 5 % of pesticides target the pest1, 2 and only 30–50 % of fertilizers is used by the crops.3

Controlled-release systems (CRSs) enable agrochemicals last longer, thus elevate its effectiveness.4-7

CRSs advantages over standard formulation

CRSs advantages

CRSs impact

Higher effectivity

Lower agrochemicals consumption

Lower agrochemicals mobility

Lower costs

Lower mechanization and energy demand

Higher agrochemicals stability

Lower toxicity

Lower health risk

Better safety – lower occupation risk of exposure to agrochemicals

Lower risk for resistance development

Lower phytotoxicity

Fig 1: Theoretical concentration of CRSs and conventional formulation in soil. From ref 8

Some CRS types

Microencapsulation

Particles of agrochemicals are encapsulated into polymer shell. Microcapsules protect the agrochemicals from degradation and allow slow and continuous release of the active agent. Polymers can be both natural (starch, gelatin, cellulose) and synthetic (polystyrene, polyurethan, polyacrylamide).8-10
When non-biodegradable polymers are used, capsule suspension formulations are source of primary microplastics. ECHA plans to ban primary microplastics in agriculture. Thus, novel bio-degradable materials for microencapsulation are needed.

Nanoformulations

Nanomaterials are at least in one dimension of size 1-100 nm. Nanoformulations include: nanoparticles, encapsulated nanoparticles, nanoporous materials, nanocoating and nanoemulsions.11 These formulations allow slow release and better targeting (see Fig. 2). However, comprehensive knowledge about nanoformulated chemicals, their safety and behavior in natural ecosystems is missing.12-14 As well as microplastics, also nanoplastics are dangerous in the environment.

Degradable matrix

The active agent is in mixture with carrier (polymer) in the form of macroscopic pellets or granules. Agrochemicals release from the matrix is based on diffusion or biodegradability of the matrix. It can be used only for agrochemicals applied to soil.

Coating

Polymer coating can prolong active agent effect. Typically, coating is used for granulated fertilizer or to protect seeds. Biodegradable polymers like PHAs are of high interest for this application.

Research on PHAs-based controlled release systems

There is a high demand for biodegradable and non-toxic polymers for novel agrochemicals formulation. PHAs are fully biodegradable, biocompatible and non-toxic. They do not accumulate in soil environment. Moreover, they can be a source of organic carbon and positively impact soil microorganisms.15

PHAs for microencapsulation

In laboratory conditions, microencapsulation of pesticides into PHBV and P34HB co-polymers led to slower release of chemicals, higher photostability and higher effectivity compared to standard formulations.16-18 However, due to high demands of microencapsulation process and, so far, limited research results, we haven’t considered microencapsulation for further formulations development.

Fig. 2: Small particles spread more homogenously and target the pest with higher probability. From ref. 13

PHAs-based degradable matrix formulations

PHAs has been tested for degradable matrix slow-release formulations solo or in combination with other natural materials in laboratory conditions. The release of metribuzin from the P3HB matrix lasted for weeks or months (depending on the size of the matrix).3, 19-22 Effectivity of fungicide tebuconazole used in P3HB matrix formulation was comparable with commercial formulation even after 8 weeks of incubation.23 After 12 weeks, slow-release formulation of ammonium nitrate fertilizer was more effective than commercial formulation.3

P3HB

P(3HB)/clay

P3HB
P3HB

P(3HB)/wood flour

P3HB
P3HB

P(3HB)/peat

P3HB

Fig. 3: P3HB-based granules and pellets – formulations of agrochemicals with slow-release. Adopted from ref.24

Murugan et al. used PHBH co-polymer, palm fiber and NPK fertilizer in pellets. This fertilizer formulation improved growth of oil palms. Pellets elevated protebacteria population which might be beneficial for crops.15

PHBV co-polymer extruded pellets were also tested as CRS for DCD nitrification inhibitor. The slow release was based on precise engulfment of the active agent in the polymer and further biodegradability of the polymer.25

We test Hydal PHA in various formulations for agrochemicals.
We plan to be the first ones entering this segment with PHAs.

References

1 Pimentel, D. Amounts of pesticides reaching target pests: Environmental impacts and ethics. Journal of Agricultural and Environmental Ethics. 1995, 8(1): 17-29. doi: 10.1007/BF02286399.

2 Miller, G. T. Sustaining the Earth: An Integrated Approach: Brooks/Cole, 2004. 9780534496722.

3 Volova, T., E. Shishatskaya, N. Zhila, et al., Eds. New Generation Formulations of Agrochemicals. New York: Apple Academic Press, 2020.

4 Dhananjayan, V., S. Jayakumar and B. Ravichandran. Conventional Methods of Pesticide Application in Agricultural Field and Fate of the Pesticides in the Environment and Human Health. In: R. K. R, Thomas, S., Volova, T. and K, J. Controlled Release of Pesticides for Sustainable Agriculture. Cham: Springer International Publishing, 2020: 1-39. 978-3-030-23396-9.

5 Tian, C., X. Zhou, Q. Liu, et al. Effects of a controlled-release fertilizer on yield, nutrient uptake, and fertilizer usage efficiency in early ripening rapeseed (Brassica napus L.). Journal of Zhejiang University. Science. B. 2016, 17(10): 775-786. doi: 10.1631/jzus.B1500216.

6 Li, Z., Z. Liu, M. Zhang, et al. Long-term effects of controlled-release potassium chloride on soil available potassium, nutrient absorption and yield of maize plants. Soil and Tillage Research. 2020, 196: 104438. doi: https://doi.org/10.1016/j.still.2019.104438.

7 Sikora, J., M. Niemiec, A. Szeląg-Sikora, et al. The Impact of a Controlled-Release Fertilizer on Greenhouse Gas Emissions and the Efficiency of the Production of Chinese Cabbage. Energies. 2020, 13: 2063. doi: 10.3390/en13082063.

8 Anamika, R., S. Sunil, B. Jaya and B. Anil. Controlled pesticide release from biodegradable polymers. Open Chemistry. 2014, 12(4): 453-469. doi: https://doi.org/10.2478/s11532-013-0405-2.

9 Cao, L., Y. Liu, C. Xu, et al. Biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) microcapsules for controlled release of trifluralin with improved photostability and herbicidal activity. Materials Science and Engineering: C. 2019, 102: 134-141. doi: https://doi.org/10.1016/j.msec.2019.04.050.

10 Patil, D. K., D. S. Agrawal, R. R. Mahire and D. H. More. Synthesis, characterization, and controlled release study of polyurea microcapsules containing metribuzin herbicide. Russian Journal of Applied Chemistry. 2015, 88(10): 1692-1700. doi: 10.1134/S1070427215100225.

11 Chhipa, H. Nanofertilizers and nanopesticides for agriculture. Environmental Chemistry Letters. 2017, 15(1): 15-22. doi: 10.1007/s10311-016-0600-4.

12 Vryzas, Z. Pesticide fate in soil-sediment-water environment in relation to contamination preventing actions. Current Opinion in Environmental Science & Health. 2018, 4: 5-9. doi: https://doi.org/10.1016/j.coesh.2018.03.001.

13 Zhao, X., H. Cui, Y. Wang, et al. Development Strategies and Prospects of Nano-based Smart Pesticide Formulation. Journal of Agricultural and Food Chemistry. 2018, 66(26): 6504-6512. doi: 10.1021/acs.jafc.7b02004.

14 Garrigou, A., C. Laurent, A. Berthet, et al. Critical review of the role of PPE in the prevention of risks related to agricultural pesticide use. Safety Science. 2020, 123: 104527. doi: https://doi.org/10.1016/j.ssci.2019.104527.

15 Murugan, P., S. Y. Ong, R. Hashim, et al. Development and evaluation of controlled release fertilizer using P(3HB-co-3HHx) on oil palm plants (nursery stage) and soil microbes. Biocatalysis and Agricultural Biotechnology. 2020, 28: 101710. doi: https://doi.org/10.1016/j.bcab.2020.101710.

16 Lobo, F. A., C. L. de Aguirre, M. S. Silva, et al. Poly(hydroxybutyrate-co-hydroxyvalerate) microspheres loaded with atrazine herbicide: screening of conditions for preparation, physico-chemical characterization, and in vitro release studies. Polymer Bulletin. 2011, 67(3): 479-495. doi: 10.1007/s00289-011-0447-6.

17 Grillo, R., N. F. S. de Melo, R. de Lima, et al. Characterization of Atrazine-Loaded Biodegradable Poly(Hydroxybutyrate-Co-Hydroxyvalerate) Microspheres. Journal of Polymers and the Environment. 2010, 18(1): 26-32. doi: 10.1007/s10924-009-0153-8.

18 Suave, J., E. C. Dall’Agnol, A. P. T. Pezzin, et al. Biodegradable microspheres of poly(3-hydroxybutyrate)/poly(ε-caprolactone) loaded with malathion pesticide: Preparation, characterization, and in vitro controlled release testing. Journal of Applied Polymer Science. 2010, 117(6): 3419-3427. doi: https://doi.org/10.1002/app.32082.

19 Volova, T. G., N. O. Zhila, O. N. Vinogradova, et al. Constructing herbicide metribuzin sustained-release formulations based on the natural polymer poly-3-hydroxybutyrate as a degradable matrix. J Environ Sci Health B. 2016, 51(2): 113-125. doi: 10.1080/03601234.2015.1092833.

20 Volova, T., N. Zhila, E. Kiselev, et al. Poly(3-hydroxybutyrate)/metribuzin formulations: characterization, controlled release properties, herbicidal activity, and effect on soil microorganisms. Environ Sci Pollut Res Int. 2016, 23(23): 23936-23950. doi: 10.1007/s11356-016-7636-7.

21 Zhila, N., A. Murueva, A. Shershneva, et al. Herbicidal activity of slow-release herbicide formulations in wheat stands infested by weeds. Journal of Environmental Science and Health, Part B. 2017, 52(10): 729-735. doi: 10.1080/03601234.2017.1356668.

22 Kiselev, E. G., A. N. Boyandin, N. O. Zhila, et al. Constructing sustained-release herbicide formulations based on poly-3-hydroxybutyrate and natural materials as a degradable matrix. Pest Management Science. 2020, 76(5): 1772-1785. doi: 10.1002/ps.5702.

23 Volova, T. G., S. V. Prudnikova, N. O. Zhila, et al. Efficacy of tebuconazole embedded in biodegradable poly-3-hydroxybutyrate to inhibit the development of Fusarium moniliforme in soil microecosystems. Pest Manag Sci. 2017, 73(5): 925-935. doi: 10.1002/ps.4367.

24 Volova, T., S. Prudnikova, A. Boyandin, et al. Constructing Slow-Release Fungicide Formulations Based on Poly(3-hydroxybutyrate) and Natural Materials as a Degradable Matrix. J Agric Food Chem. 2019, 67(33): 9220-9231. doi: 10.1021/acs.jafc.9b01634.

25 Levett, I., M. Liao, C. Pratt, et al. Designing for effective controlled release in agricultural products: new insights into the complex nature of the polymer–active agent relationship and implications for use. Journal of the Science of Food and Agriculture. 2020, 100(13): 4723-4733. doi: https://doi.org/10.1002/jsfa.10531.