Superabsorbent polymer for plants – Potassium polyacrylate

*This page is about superabsorbent polymer for the plant, potassium polyacrylate, water-retaining agent/gel.

Potassium polyacrylate – the superabsorbent polymer for plant

Potassium polyacrylate is a potassium salt of polyacrylic acid with the chemical formula [−CH2−CH(CO2K)−]n.

As a type of superabsorbent polymer for plants, potassium polyacrylate is a unique superabsorbent granule, which acts to provide increased moisture availability to plants.

It mixes with soil to increase the soil’s capacity for holding water and making it available to plants. This improved soil readily releases moisture, along with water-soluble nutrients, to plant roots on demand.

Just like a “mini-reservoir”, soils treated with potassium polyacrylate granules don’t ‘bind’ water tightly, and release water in response to a plant’s root suction. It can repeatedly hydrate and release captured moisture, on-demand, as plants need it for months or more.

What can it do?

  • Absorbs more than hundreds times its weight in water, then releases up to 95 percent of that held moisture as the plants demand it;
  • Rehydrates over and over again during the growing season;
  • Increase soil porosity and structure;
  • Can be applied in a variety of ways: Preplant, Post plant, Postemerge/side-dress, Seed coating, Root dip, Potting/soil mix.

How does it work?

Absorbing plenty water

Potassium polyacrylate works similarly to a sponge under the soil surface. It is composed of a set of polymeric chains,

which are linked together chemically to become a water-insoluble, net-like matrix that gently attracts and holds hydrogen molecules. The immense size and weight of its molecular structure allow each potassium polyacrylate granule to absorb over 500 times its original weight in purified water.

Auto to release water for plants

It does not ‘bind’ water tightly. The potassium polyacrylate granules release just the right amount of water in response to a plant’s root suction. There are no waterlogging or other ill effects caused by ‘free’ water filling air cavities in the soil.

Tip: the specific retention of Ag-SAP is 1.3-1.4 MPa and the specific retention of roots is about 1.6-1.7 MPa.

Improving soil

Potassium polyacrylate maximizes plant growth by reducing plant stress. It also absorbs and releases soil nutrients, water-soluble fertilizer, and chemicals in the same manner as water, creating a healthy microenvironment in the plant root zone. The result is faster germination, quicker emergence of seeds, consistent growth, and higher, better-quality yields of edibles with less water and fewer inputs.

Test of it

A. Lab test

1. Water holding capacity test


soil: 500 ml; water: 750 ml; SAP: 5 grams

2. The wilting point test

It can increase the water holding capacity of soils and delay the wilting point.

A sandy soil treated with 2 grams of potassium polyacrylate per kg of soil holds water twice as long as untreated soil.

B. Field test

1. Lettuces in Japan

Result: The lettuces in SAP pot have increased by 64.13% in yield.

Citation: Potassium polyacrylate field test: lettuce

2. Oats in Argentine

Result: “These last pictures are from last week, and are to reap almost. After we move the machine to harvest, the yields of oats with your SAP increased almost 60%, which is far excited than we expect.”

Citation: Potassium polyacrylate field test: oat

3. Dry beans in America

Result: +13. 9% yield/acre.

Citation: Potassium polyacrylate field test: dry beans

4. Onions in America

Result: +5.13% yield/acre.

Citation: Potassium polyacrylate field test: onion

5. Potatoes in America


How to use Ag-SAP?

Seed coating

1. Make Ag-SAP water gel;
2. Mix water gel with seeds (2:5);
3. Wait for 1-8 hours before sowing the seeds.

Grow seedlings

1. Make Ag-SAP water gel;
2. Mix water gel with soil (1:5);
3. Grow seedlings with the mixed soil.

Planting crops

1. Make Ag-SAP water gel;
2. 50-150 kg water gel per acre dosage, along with seeds hole application or ditch application to the soil around the seed.
3. Cover seeds with soil.

Topdressing for crops

1. Dig a 10-20cm deep ditch beside the crops
2. Make Ag-SAP water gel;
3. Fill ditch with water gel (50-150 kg water gel per acre);
4. Cover ditch with soil.

Planting/transplanting trees

1. Make Ag-SAP water gel in a big plastic drum (or another nonmetallic container).
2. Dipping roots in the drum before planting.
3. Mix water gel with soil (2:5);
4. Planting trees in the hole after laying the soil mixed with water gel.

– Avoid metal containers;
– Protect from light and moisture.

How to choose SAP for plants?

There might be 3 types of Ag-SAP you’d meet:

1. Fake type – Never purchase

For more money, some profiteers would sell defective SAP or industrial purpose SAP as fake type “Ag-SAP”.

This type of SAP’s main composition is sodium polyacrylate.

And it:

  • won’t repeatedly absorb & release water in soil;
  • would break down into sodium which causes soil salinization.

2. Common type

As we know, common Ag-SAP’s main composition is potassium polyacrylate.

There are two types of common Ag-SAPs:

a. Potassium polyacrylate with acrylic amide.

  • advantage: a long period of validity (available in the soil for 3-6 months);
  • disadvantage: acrylic amide’s a kind of cancerogenic substance.

b. Potassium polyacrylate without acrylic amide.

  • advantage: no acrylic amide and totally harmless;
  • disadvantage: a short period of validity (available in the soil for 1-3 months).

3. improved type

There are some types of Ag-SAPs improved on some side like:

  • Starch-based SAP – which is totally biodegradable in soil and brings nutrient to plants;
  • Minerals-based SAP – which is available in the soil for years.

Further Reading

Does potassium polyacrylate physically change the amount of water a plant needs for optimum growth?

Plants require a specific amount of water for optimal growth. Potassium polyacrylate doesn’t change that amount, but It does manage water more efficiently. Instead of water being dispersed into the soil or evaporating, it is absorbed by potassium polyacrylate and held for the plant to use as needed. This “bound water” more effectively and efficiently nourishes the plant.

Does potassium polyacrylate change the nature of the moisture it absorbs?

No, it triggers no chemical reactions. Potassium polyacrylate merely absorbs moisture and any water-soluble nutrients it contains, and remains suspended in the plant root zone, storing the moisture and nutrients in plant-available form.

Did will increase moisture near the root structure cause root rot?

Potassium polyacrylate granules will expand to many times their original volume, then contract and repeatedly expand based on the water available. This action forces soil particles apart, increasing aeration-the key element required to prevent root rot. Once the granules reach their maximum absorption, excess water is allowed to move deeper into the soil profile. This combination of idea water availability and good aeration promotes faster plant growth and minimizes the potential for root rot.

Is potassium suitable for only one type of soil?

No, it provides benefits to all soil types. Soil particles in sandy soils are relatively large and have the poor water-holding capability. Potassium polyacrylate holds water, preventing it from moving past plant roots where it is needed most. Clay soils, which are more compacted, benefit from the increased aeration created as Potassium polyacrylate expands and contracts, which increases oxygen levels and water percolation.

Can I mix fertilizer with it?

Yes. By combining potassium polyacrylate and nutrients, your plants have the best advantage – both food and water.

How often do I apply it?

In general, we recommend a fresh application of potassium polyacrylate with each new planting. This ensures that it is in close proximity to the seeds (to increase germination) and roots.

How do seed furrow treatments help increase uniformity in crop maturity across the field?

By applying potassium polyacrylate in seed furrows at planting, the germinating seed and seedlings have a constant supply of moisture and nutrients available for a more complete, consistent germination and seedling emergence. Potassium polyacrylate removes variances caused by dry spots in the field for more uniform stand and crop development.

  References: Potassium polyacrylate: Sum up all knowledge about it