University of Texas engineers have created a new type of soil that can absorb water from the air and distribute it to plants. This new soil type could expand the map of farmland around the globe. According to the University of Texas, it can also reduce agricultural water use during worsening droughts.
The "atmospheric water irrigation system" developed by the engineers uses super-moisture-absorbing gels to capture water from the air. When the soil is heated to a certain temperature, the gels release water, making it available to plants. As the soil distributes water, some of it is released back into the air, increasing moisture and making it easier to continue the harvest cycle.
“The ability to farm autonomously in areas where it is difficult to build irrigation and power systems is critical to freeing crop production from the complex water supply chain as resources become increasingly scarce,” said Guihua Yu, assistant professor of materials science at Walker University, Department of Mechanical Engineering.
Each gram of soil can extract approximately 3-4 grams of water. Depending on the crops, about 0,1 to 1 kg of soil can provide enough water to irrigate about a square meter of farmland, the engineers say.
Gels in the soil draw water out of the air during cooler, wetter night periods. The heat of the sun during the day activates the water-containing gels to release their contents into the soil.
A team of researchers conducted experiments on the roof of the Cockrell Engineering Training Center building at UT Austin to test the soil. They found that hydrogel soil was able to hold water better than sandy soils in dry areas and needed much less water to grow plants.
During the four-week experiment, the team found that the soil retained roughly 40% of its water content. On the contrary, only 20% of water remains in sandy soil after a week.
In another experiment, a team of researchers planted radishes in both types of soil. All plants in the hydrogel soil survived the 14 day period without any irrigation. Radishes in sandy soil were watered several times during the first four days of the experiment. None of the radishes in the sandy soil survived more than two days after the initial watering period.
"Most of the soil is good enough for plant growth," said Fei Zhao, a PhD researcher in Yu's research group, who led the study along with Xinyi Zhou and Panpan Zhang. "The main constraint is water, so we wanted to develop soil that can collect water from the surrounding air."
Harvesting water from soil is the first major application of the technology, and a team of scientists has been working on it for more than two years.