Hydrogel agriculture
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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
loam Loam (in geology and soil science) is soil composed mostly of sand (particle size > ), silt (particle size > ), and a smaller amount of clay (particle size < ). By weight, its mineral composition is about 40–40–20% concentration of sand–sil ...
s. 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 Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and ...
, and leaching, and improve plant growth.
Desertification Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused by ...
and lack of water threaten agriculture in many arid and
semi-arid region A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-ar ...
s of the world; these may be mitigated with hydrogels.


Hydrogels

Hydrogel A hydrogel is a crosslinked hydrophilic polymer that does not dissolve in water. They are highly absorbent yet maintain well defined structures. These properties underpin several applications, especially in the biomedical area. Many hydrogels ar ...
s 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 Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
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 Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary ...
. * 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 Tragacanth is a natural gum obtained from the dried sap of several species of Middle Eastern legumes of the genus ''Astragalus'', including '' A. adscendens'', '' A. gummifer'', '' A. brachycalyx'', and '' A. tragacantha''. Some of these species ...
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
pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...
s (such as
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
s) 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 Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...
cypermethrin Cypermethrin (CP) is a synthetic pyrethroid used as an insecticide in large-scale commercial agricultural applications as well as in consumer products for domestic purposes. It behaves as a fast-acting neurotoxin in insects. It is easily degraded ...
and the
fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...
copper sulphate. Superabsorbent polymers can be used to release phosphate fertiliser slowly, by making an
ester bond In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
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.


See also

* Agriculture, Ecosystems & Environment * Farm water * Rainfed agriculture *
Swelling capacity The swelling capacity of a polymer is determined by the amount of liquid material that can be absorbed by it. This test can done by two methods: # Beaker test method # Tea bag test method Beaker test method In this method * A small amount of s ...
* Water conservation


References

{{reflist, 30em Agricultural technology