Hydrogel agriculture
# Hydrogel agriculture

Common hydrogel agriculture's ingredient is potassium polyacrylate or sodium polyacrylate. As a superabsorbent material, it can absorb plenty of water and turn water to gel to store water.

Hydrogel agriculture technology uses insoluble gel-forming polymers to improve the water-holding properties of different soils, such as clays and sandy loams. This can increase water-holding and water use (up to 85% for sand), improve soil permeability, reduce the need for irrigation, reduce compaction, soil erosion, and leaching, and improve plant growth.

Desertification and lack of water threaten agriculture in many arid and semi-arid regions of the world; these may be mitigated with hydrogels.

## Hydrogels

Hydrogels are hydrophilic crosslinked polymers that form three-dimensional molecular networks which can absorb and hold great amounts of water.

### Different type of hydrogels in agriculture

Different types may be suitable for agricultural use.

* A starch-based (grafing) hydrogel is biodegradable and cheap, and can be modified to adjust its ability to hold water. Cross-linked acrylic acid polymer hydrogels are commercially available; they are effectively insoluble but slowly break down releasing toxic acrylamide.
* Mineral grafing type potassium polyacrylate.
* None grafing type potassium polyacrylate.
* Mineral grafing type sodium polyacrylate.

## Potential uses in agriculture

Hydrogels of different kinds could be useful in agriculture, reducing drought stress in plants, making better use of irrigation water and fertilizer.

Superabsorbent hydrogel polymers can in principle influence soil permeability, density, structure, texture, evaporation and infiltration rates of water through soils. They can also allow pesticides to be released slowly over a long period, increasing effectiveness and reducing side-effects such as pesticide runoff. There has therefore been considerable research interest into the possible use of hydrogels in agriculture. For example, a hydrogel based on gum tragacanth increases the water content of clay soil by up to 5.35% and of sandy loam by up to 5.5%; it could also be used to release calcium chloride slowly over a prolonged period.

Suitably prepared hydrogels can simultaneously supply and slowly release pesticides (such as herbicides) in the soil, and increase a sandy soil's retention of water. Hydrogels developed for this purpose include polymers of oligooxyethylene methacrylate, linked by ionic and covalent bonds to a herbicide such as 4-chloro-2-methylphenoxyacetic acid (CMPA). Other hydrophilic polymers studied have been made from a variety of different acrylate monomers to release the pesticides 2,4-D and CMPA. These offer different combinations of pesticide release rate and soil water retention. Hydrogels can also be used to encapsulate the insecticide cypermethrin and the fungicide copper sulphate. Superabsorbent polymers can be used to release phosphate fertiliser slowly, by making an ester bond between polyvinyl alcohol and phosphoric acid. A polymer/clay superabsorbent composite material made by attaching acrylamide to finely powdered attapulgite (a fuller's earth clay) shows promise for its excellent water retention and low cost compared to polyacrylamide hydrogel.

## Commercialization

In 2015, The Indian Agriculture Research Institute (IARI) reported the development of a novel hydrogel for agricultural use. It was intended to help farmers to cope with drought, making efficient use of water in arid and semi-arid regions of India. the product is to be commercialized by the Ministry of Science and Technology's National Research Development Corporation (NRDC) in collaboration with a company based in Chennai, Reliance Industries Limited.

In 2016, a water absorbing material named Alsta hydrogel was introduced in the India agriculture market after testing from NTC Pune with a potential to absorb water 400 times of its own weight. It is a potassium polyacrylate based granular non-toxic polymer and soil conditioner that is compatible with all kind of soils and crops to greatly reduce irrigation frequency and loss of soil moisture by leaching and evaporation.

Alsta hydrogel, as many others, does not present any internationally recognised certificate about its non-toxicity on human, animal or microorganisms naturally present in soils, neither on its biodegradability or its transfer of elements to the plants growing with it. Statements remain to be measured by an independent certified laboratory.

