A super-absorbent polymer that can soak up more than 500 times its own weight of water could provide a solution to the well-known problems of afforestation and agriculture in arid and marginal soils, according to agronomist Doctor Alicia Chacalo of Mexico's Universidad Metropolitana.

Doctor Alicia Chacalo of Mexico's Universidad Metropolitana.

When water is added to a powdered form of the polymer, it forms a viscous gel that dries slowly, releasing water over a long period. If the powder is mixed with soil and packed around the roots of a plant or tree, any water added is first stored in the gel, and then released over time directly to the roots, providing maximum targeted benefit to the plant.

The key advantage of the polymer, called solid rain by its inventor, is its much more economical use of water. Experiments conducted by the Universidad Metropolitana show that using the product consumes just one eighth the amount of water required by conventional watering and irrigation techniques. Dr Chacalo said solid rain can deliver major cost savings as well as making more effective use of scarce water resources.

Another benefit is that pollutants present in the soil are not washed down to the water table as they often are by conventional irrigation and watering techniques. The polymer itself is non-polluting according to Dr Chacalo.

Once in the soil, the polymer can be replenished up to ten times. If replenished by seasonal rains, for example, this would give it a useful life of up to ten years. Alternatively it can be replenished by adding water manually or mechanically.

According to Doctor Chacalo, a major benefit is that solid rain can guarantee the survival of a plant through the critical period following planting. She said the product has many other potential applications, for example, buried in a trench in a forest it can act as an effective firebreak.

Many major afforestation programs across the world have failed due to inadequate water resources. Dr Chacalo said that Mexico has recently drawn up a plan that calls for 28 million trees to be planted each year, many of which, on past experience, will die. She said solid rain could make some doubtful afforestation projects viable. The same applies to agriculture on marginal lands.

Solid rain is a polymer, potassium polyacrilate, which is being marketed by Mexican company, Silos de Agua, established by the product's inventor, Sergio Rico.

The publicity material for the product states that “for the first time in the history of humankind you can have in your hands solid rain, and store it in sacks”. It goes on to claim that solid rain will contribute to solving the problems of hunger, poverty and migration.

Dr Chacalo presented the findings of her experiments to the sixth International Conference on Landscape Ecology and Forest Management which was held in Chengdu, capital of China's southwestern Sichuan Province, from September 16-22, 2008. Over two hundred scientists attended the conference including over 80 from overseas.

(China.org.cn by John Sexton, September 22, 2008)