Sanjay-Swami and Mamta Phogat
Synthetic polymers in the form of crystals or tiny beads available under several trade names such as super absorbent polymers, root watering crystals, drought crystals and crystal soil are collectively known as hydrogels. Super absorbent polymers are synthetic compounds and are produced artificially. These materials are made from potassium Polyacrylate and Polyacrylamide copolymers and are capable of quickly absorbing water after contact with it and holding it up to many times of its volume and as the result increase water retention in the related soil. These materials are odorless and generally colorless, and do not pollute soil, water and plant tissues.
The Technology
The internationally patented technology is represented by a novel class of macro-molecular superabsorbent hydrogels, able to absorb more than 1.5 liters of water per gram of dry material, once in contact with liquid water or water solutions.
During the sorption process, the material turns from a glassy state to a gel-like material, able to store the water even under significant compression. The water can be released from the material under a diffusion mechanism, activated by a gradient of humidity between the inside and the outside of the material, or by phase inversion in a non-solvent for the polymer. The application of such a technology which has been tested is a ‘water reservoir’ in agriculture to be used in arid and desert regions of the world, where scarcity of water resources is a relevant issue. To this aim, the hydrogel is mixed, in the dry form, to the soil in the area close to the plant roots. The soil is watered and the water not absorbed by the plant roots is stored in the hydrogel which swells, and releases water to the cultivation as far as the soil is de-watered. This process allows high saving of water resources and a re-distribution of water available for cultivation in other human-related applications. Different classes of superabsorbent hydrogel have been developed. The last generation is a cellulose-based hydrogel cross-linked by citric acid, and using only ‘food grade’ reagents.
Applications of Super absorbents in Agriculture
In agriculture, Superabsorbent polymers are used as a soil additive, as reservoir of nutrients, and as water superabsorbent in the soil. Properties of this material are dependent on many factors, such as their chemical and compositional characteristics, soil texture, plant species and also environmental factors. Super absorbent polymers made from Polyacrylamide are of these materials and are used as water adsorbents for increased capacity of the soil to absorb and retain water and this property is very important to encounter the impacts of dehydration and reduce impacts of drought stress in crops. Biodegradation rate of super absorbent polymers in soil depends on the dimensions of soil particle and amount of organic matter. Also, with decreasing Oxygen in soil and in turn reducing activities of bacteria, biodegradation rate of super absorbent polymers will be reduced. Super absorbent polymers have influence on water infiltration rate in soil, bulk density, soil structure and the rate of evaporation from the soil surface. Moreover, the super absorbent polymers while raising water-holding capacity of light soils can address soil permeability problems of heavy soils and difficulties in washing fertilisers. Since that Super absorbents absorb water hundreds times of its own weight and being converted to long lasting gels, have a special place in agriculture, landscaping, erosion control and desert reduction. Quickly absorbing water and keeping it by super absorbents, raises absorption efficiency of water obtained from scattered rainfall. In the case of irrigating soil, they increase irrigation intervals. The amount of this increase depends on the physical conditions of the soil, climate of the region and the utilization amount of super absorbents in soil. According to their pH close to neutral, super absorbents have no adverse effect on the soil, and are not considered as toxic in soil. Also, after 4-7 years, depending on the type and composition of soil, they are destroyed by microorganisms and do not cause environmental
pollution.
