Self-watering soil powered by solar heat has been developed by a research group in Austin, Texas. Using absorbent gels, it draws moisture during cool and humid times at night, then solar heat during the day activates the water-containing gels to release their contents into soil.
When the soil is heated to a certain temperature, the gels release the water, making it available to plants. As the soil distributes water, some of it goes back into the air, increasing humidity and making it easier to continue the harvesting cycle.
Professor Guihua Yu leads the research group at the University of Texas in Austin, who believe the development will significantly improve food security in water limited regions of the world.
He spoke exclusively to Quota ahead of World Soil Day, on December 5th. Drylands account for 40% of the earth’s surface and 45% of agricultural land.
“Water is the basic environmental factor for agricultural production,” says Professor Yu. “Current freshwater production cannot meet the urgent demand for agriculture, especially for those drought regions facing severe water scarcity.”
Preliminary testing published in ACS Materials Letters showed that during a four-week experiment, the hydrogel soil retained approximately 40% of the water quantity it started with. In contrast, the sandy soil had only 20% of its water left after just one week.
In another experiment, the team planted radishes in both types of soil. The radishes in the hydrogel soil all survived a 14-day period and reached 15cm in length without any irrigation beyond an initial round to make sure the plants took hold.
Professor Yu hopes the novel soil will expand farmable land across the planet
Radishes in the sandy soil were irrigated several times during the first four days of the experiment. None survived more than two days after the initial irrigation period.
Each gram of soil can extract approximately three to four grams of water. Depending on the crops, approximately 0.1 to 1 kilogram of the soil can provide enough water to irrigate about a square metre of farmland.
Professor Yu hopes the soil will be able expand farmable land across the planet. But for now continued research and development is needed. Better water uptake can be achieved, he believes. And the system can be simplified for mass production.
“One issue is the relatively high cost of the chemical ingredients for our current materials,” says Professor Yu. So research into low-cost alternatives is needed.
The soil also needs to be tested in rural drylands for different crops and for longer test periods.
Professor Yu said, “We would be very glad to cooperate with other research groups and industrial partners for more scale-up studies of these gels/soils, as well as more system-wise designs to enable the commercialisation of this technology in the future.”