The early summer sky is reflected in rice paddies after planting.
Small white particles float on the water. They may look like fragments of polystyrene, but they could be the empty plastic shells left behind after nutrients have been released from coated fertilizer granules.
Plastic-coated fertilizers gradually release nutrients according to the growth of the crop. Because they can be applied once during rice planting and reduce the need for additional fertilization later in the growing season, they are often marketed in Japan as “one-shot fertilizers.”
For Japanese agriculture, which faces an aging workforce and severe labor shortages, the labor-saving benefits are significant.
However, some of the empty coating shells may leave rice paddies through drainage channels, enter rivers, and eventually reach the sea.
Is it possible to develop fertilizers that use no plastic without increasing the burden on farmers?
The problem cannot be solved by simply replacing one material with another.
Why Did Plastic-Coated Fertilizers Become So Widely Used?
Plastic-coated fertilizers consist of fertilizer granules covered with resin or another coating. This structure allows nitrogen and other nutrients to be released gradually in response to temperature and moisture.
Because the nutrients become available as the rice grows, these fertilizers can reduce the amount washed away all at once and may also lower the total quantity of fertilizer required.
They can also be applied during rice planting, reducing the need for farmers to enter the paddies during the hot summer months to apply additional fertilizer.
Plastic-coated fertilizer is therefore more than a convenient agricultural product.
It is also a technology that has helped Japanese agriculture respond to structural challenges such as an aging farming population, expanding farm sizes, and labor shortages.
In a fiscal 2023 survey conducted by Japan’s Ministry of Agriculture, Forestry and Fisheries, 79.7 percent of the 1,195 rice farmers who responded said they used plastic-coated fertilizers.
This figure shows how deeply the technology has become embedded in agricultural practice.
For that reason, simply arguing that farmers should stop using it immediately because it harms the environment fails to reflect the realities of the field.
From Rice Paddies to Rivers—and from Rivers to the Sea
Even after the fertilizer has dissolved, its outer plastic coating remains.
Because these empty shells are lighter than water, they can float on the surface and leave paddies with drainage water during soil puddling or around the time of rice planting.
Once they travel from agricultural drains into rivers and eventually reach the sea, recovering them becomes extremely difficult.
According to the Ministry of Agriculture, Forestry and Fisheries survey, 42.4 percent of farmers using plastic-coated fertilizers said they implemented measures to prevent the shells from escaping during the puddling period.
By contrast, 57.2 percent said they had not taken such measures.
Awareness of the problem is growing, but preventive action in the field remains insufficient.
This is not only because of the additional time and cost involved. Farmers have also found it difficult to determine which fertilizers contain plastic coatings, while runoff-prevention methods have not yet become established throughout every farming region.
Option 1: Slow-Release Fertilizers Without Plastic
One possible alternative is to use fertilizers that release nutrients gradually through mechanisms that do not rely on plastic coatings.
Examples include fertilizers coated with sulfur and urea-formaldehyde fertilizers that release nutrients slowly through chemical processes.
These products have the advantage of leaving no plastic coating shells behind.
However, they cannot necessarily be used in exactly the same way as conventional coated fertilizers.
The rate at which nutrients are released changes according to air temperature, water temperature, soil conditions, rice variety, and planting season.
In some regions or cultivation systems, the timing of nutrient release may not match the growth of the rice, potentially affecting crop yield or quality.
What is needed is not an immediate nationwide transition to a single alternative, but repeated field trials adapted to individual regions.
A fertilizer cannot become a technology that farmers can use continuously if it is evaluated only by whether it is plastic-free.
Yield, crop quality, price, and labor requirements must also be considered.
Option 2: Applying Only What Is Needed, When It Is Needed
Another approach is to move away from applying all fertilizer at once and instead apply only the necessary amount at the appropriate stage of crop growth.
Traditionally, additional fertilization required farmers to carry heavy fertilizer into the paddies, creating a considerable physical burden.
Today, however, several alternatives are being developed and tested.
These include:
- Applying fertilizer from the air using agricultural drones
- Introducing dissolved fertilizer into paddies with irrigation water
- Placing fertilizer beside the roots during planting
- Depositing fertilizer at an appropriate depth in the soil
- Using sensors and satellite imagery to identify areas where crops require additional nutrients
Precision fertilization could make it possible to apply fertilizer only where growth data indicate that it is needed.
This approach does not simply replace plastic-coated fertilizer with another product.
It changes the fertilization system itself.
Drones and specialized machinery, however, require significant investment. Skilled operators are also necessary.
In some areas, introducing this equipment independently may be unrealistic for small-scale farmers.
Regional systems will therefore be essential, including shared machinery, cooperative arrangements, and contracted agricultural services provided by Japan Agricultural Cooperatives, local governments, or agricultural corporations.
Option 3: Can Biodegradable Materials Solve the Problem?
Research is also progressing on fertilizer coatings made from materials designed to break down in the natural environment.
Under certain conditions, microorganisms can decompose biodegradable plastics into water, carbon dioxide, and other substances.
If adequate degradation can be achieved, such materials may reduce the long-term persistence of conventional plastic coating shells.
However, a material labeled “biodegradable” does not necessarily disappear quickly in every environment.
Conditions such as temperature, microbial activity, and oxygen availability differ among agricultural soil, rivers, and the ocean.
A material may decompose effectively in farmland but take much longer to break down if it enters the marine environment.
The coating must also meet two seemingly conflicting requirements.
It must remain durable enough to protect the fertilizer until nutrients are needed, yet begin to decompose after its function has ended.
Biodegradable materials are a promising option, but their use does not eliminate the need to prevent runoff.
The important questions are not limited to what the material is made from.
We must also determine where it decomposes, how long that process takes, and what substances remain after decomposition.
The Immediate Priority Is to Keep the Shells Inside the Paddy
It will take time for alternative technologies to become available throughout the country.
In the meantime, measures are needed to prevent the plastic shells currently in use from leaving rice paddies.
Possible actions include:
- Using less water during soil puddling
- Allowing water levels to fall naturally instead of immediately draining paddies
- Installing collection nets at drainage outlets
- Recovering floating coating shells from the water surface
Some measures can be introduced without major equipment or infrastructure.
Yet asking individual farmers to collect escaped shells does not address the problem completely.
Questions remain about where the collected material should be taken and who should pay for its treatment and disposal.
Responsibility should not fall on farmers alone.
Fertilizer manufacturers, distributors, agricultural cooperatives, local governments, and the national government must share responsibility for preventing, collecting, and properly treating the waste.
Moving from “Replacing the Material” to “Changing the System”
Japanese fertilizer-related organizations have set out the goal of creating agriculture that no longer depends on plastic-coated fertilizers by 2030.
An interim progress report published in February 2026 described several developments, including:
- Commercialization of non-plastic slow-release fertilizers
- Field testing of fertilizer application through irrigation water
- Trials using agricultural drones
- Wider adoption of coated fertilizers containing less plastic
However, no single technology is yet capable of immediately replacing conventional coated fertilizers across every region and rice variety.
Different solutions must be combined according to local conditions.
This may involve:
- Transitioning to fertilizers that do not use plastic
- Reducing labor through drones or irrigation-based fertilization
- Using soil analysis to prevent excessive fertilizer application
- Keeping coating shells from leaving rice paddies
- Sharing the costs of collection and disposal across society
The environmental challenges surrounding agriculture are too complex to be solved by introducing a single new material.
A Solution Cannot Last If It Only Increases the Burden on Farmers
Does the price we pay for rice adequately reflect the labor and expense required to protect the environment?
If lower-impact fertilizers cost more than conventional products and also require additional work, farmers cannot be expected to bear the entire burden.
Consumers can support environmentally responsible agriculture by paying fair prices for lower-impact products.
Government policy can help finance the adoption of alternative technologies.
Manufacturers can accept greater responsibility for what happens to their products after use.
Communities throughout a watershed can monitor and recover material before it reaches rivers and the sea.
Because this problem connects rice paddies with the ocean, its solution cannot be confined to farmland alone.
Labor-Saving Rice Farming and a Healthy Marine Environment Can Coexist
Plastic-coated fertilizers were developed to reduce the physical burden on farmers.
Blaming the farmers who have relied on this technology will not solve the problem.
The real question is how to provide the functions these fertilizers have performed—releasing nutrients when crops need them and reducing additional fertilization work—through a different system that does not allow plastic to escape into the environment.
Change the material.
Change the method of fertilization.
Share machinery across the community.
Stop runoff before it leaves the paddy.
And avoid concentrating all the costs and responsibility on farmers.
An alternative technology is more than an alternative product.
It requires us to reconsider labor-saving agriculture, food production, regional water environments, and the future of the ocean as parts of a single connected system.
The small coating shells flowing out of rice paddies pose a question to us:
Can we preserve the convenience that supports farmers while updating it into a form suited to the next era?
References
- Ministry of Agriculture, Forestry and Fisheries, Japan: Preventing the Runoff of Plastic Coating Shells from Coated Fertilizers
- Ministry of Agriculture, Forestry and Fisheries, Japan: Survey on Preventing the Runoff of Plastic Coating Shells from Slow-Release Fertilizers
- Ministry of Agriculture, Forestry and Fisheries, Japan: Continued and Strengthened Measures to Prevent the Runoff of Fertilizer Coating Shells, February 2026
- National Agriculture and Food Research Organization: Development of Smart Deep Fertilization Machinery
Article Excerpt
Plastic-coated fertilizers reduce the need for farmers to apply additional fertilizer, but their empty shells may travel from rice paddies through rivers and into the sea. Can non-plastic fertilizers, drone application, and biodegradable materials provide a solution? This article explores how agriculture can reduce environmental impacts without sacrificing the labor-saving technologies that support farmers.
