Super Absorbent Polymers, also known as SAP, hydrogel, absorbent polymers, absorbent gels, super soakers, super slurpers, water gel is a new type of macro molecular synthetic water absorbing polymer material that has a water uptake potential as high as 100,000% of its own weight in a short period of time by osmosis and form granules in soil to enhance soil properties. SAPs are generally white sugar-like hygroscopic materials that swell in water to form a clear gel made of separate individual particles and can retain moisture even under pressure without risk of conflagration or rupturing/blasting.
Super Absorbent Polymers used in agriculture are mostly prepared from acrylic acids and a cross-linking agent like potassium by solution or suspension polymerization. The polymer so formed is called a polyacrylate whose swelling capacity and gel modulus depends greatly on the quantity and type of cross-linker used. Polyacrylates are non-toxic, non-irritating and non-corrosive in nature and tested to be biodegradable with a degradation rate of 10%-15% per year. They demonstrate high water absorbance potential and can freely release 95% of the same under suction pressure by plant roots.
Application and Benefits:
The three most common soil conditions that hinder plant growth and crop yield are low water retention capability, high evapo-transpiration rate and soil moisture leaching. Apart from these, factors like unforeseen drought conditions, degradation & salination, overuse of synthetic fertilizers and pesticides and improper irrigation practices severely affect soil and plants, often rendering permanent damage to soil biota as well.
Hydrogel agriculture technology as it is popularly called can improve soil quality, preserve water and resist drought stress, it can increase seed sprouting and seedling development leading to better farm success. From the environmental aspects, it is non-polluting and biodegradable, helps in reducing irrigation frequency & water consumption and creates a simple cyclic process to provide water directly to roots and prevent soil compaction.
In agriculture and agroforestry, SAPs act as micro water reservoirs at plant roots. They absorb natural and supplied water 400-500 times their own weight and release it slowly on account of root capillary suction mechanism thus preventing water loss in soil by leaching and evaporation.
SAPs form a consistent cyclic process of absorption and release of water; the water so released can provide optimum moisture for quick germination and seedling maturation. Thus it reduces seedling mortality by several folds in nurseries.
In cold regions, death during germination and maturation is common due to moisture freezing in & around plant root tissue. Absorbed moisture in hydrogels does not freeze and makes easy accessibility to plants. It also regulates seedling growth temperature preventing death by freezing.
SAPs can help save water and labor by reducing irrigation frequency, help overcome drought conditions and act as soil conditioners, prevent leaching in sandy soils, runoffs in mountainous and sloping fields, improve virescence efficiency and restore soil biota.
SAPs can reduce overuse of fertilizers and pesticides in fields. The chemicals so absorbed with water are slowly released thus extending the operational life and uptake efficacy by root systems.
SAPs act as soil matter flocculants. They closely bind loose soil thus forming loams that can help better root latching. Simultaneously, the repeated absorb-release mechanism prevents over compaction of soil minerals and provides space for aeration and development of soil edaphon.
It has a wide area of application ranging from agriculture, forestry, industrial planting, municipal gardening, drought management, water conservation, It helps reduce soil erosion by surface run-offs, fertilizer and pesticide leaching to ground water, reducing cost of water and irrigation and success rate at growth and high yields of crops.
Super Absorbent Hydrogel Technology in India:
The National Research Development Corporation, an enterprise under the Department of Scientific & Industrial Research, MST, Govt. of India, agreed to commercialize a “Novel Superabsorbent Hydrogel Technology”. The prime features as stated under the agreement are:
Hydrogel can absorb minimum of 350 times its weight of pure water at 50°C.
Its high absorbency at high temperatures is suitable for semi-arid and arid regions.
Low rate application also improves soil physical properties like porosity, aggregate stability and hydraulic conductivity
No undesirable effect on crops and soil as reported by experimenters and farmers.
1.Less affected by the presence of salts in its immediate environment
2.Improves physical properties of soils and the soil less media
3.Improves seed germination and the rate of seedling emergence
4.Improves root growth and density
5.Helps plants withstand prolonged moisture stress
6.Reduces nursery establishment period
7.Reduces irrigation and fertilization requirements of crops with improved input use efficiency
SAPs have a multi-dimensional application aspect aimed at mitigating several problems associated with farming and environment.