As published in ACS Materials Letters , the equipment's atmospheric water irrigation system uses super moisture-absorbing gels to capture water from the air. When the soil is heated to a certain temperature, the gels release the water and make it available to the plants. When the soil distributes water, some of it returns to the air, which increases humidity and facilitates the continuation of the harvesting cycle.

"Enabling autonomous agriculture in areas where it is difficult to build irrigation and power systems is crucial to freeing agriculture from the complex water supply chain as resources become increasingly scarce," said Guihua Yu, associate professor of materials science in the Department of Walker. of Mechanical Engineering.

Each gram of soil can extract approximately 3-4 grams of water. Depending on the crops, approximately 0,1 to 1 kilogram of soil can provide enough water to irrigate about one square meter of farmland.

Soil gels draw water out of the air during the cooler and wetter periods of the night. Solar heat during the day activates the gels that contain water to release their content into the soil.

The team conducted experiments on the roof of the Cockrell School Engineering Teaching Center building at UT Austin to test the soil. They found that hydrogel soil was able to hold water better than sandy soils found in dry areas, and needed much less water to grow plants.

During a four-week experiment, the team found that their soil retained about 40% of the amount of water it started with. In contrast, the sandy soil only had 20% of its water left after just one week.

In another experiment, the team planted radishes in both types of soil. All radishes in the hydrogel soil survived a 14-day period without any watering beyond an initial round to make sure the plants took hold. The radishes on the sandy soil were watered several times during the first four days of the experiment. None of the radishes on the sandy soil survived more than two days after the initial irrigation period.

"Most of the soil is good enough to support plant growth," said Fei Zhao, a postdoctoral researcher in Yu's research group who led the study with Xingyi Zhou and Panpan Zhang. “Water is the main limitation, so we wanted to develop a soil that could collect water from the ambient air.”

The water-harvesting soil is the first major application of the technology that Yu's group has been working on for more than two years. Last year, the team developed the ability to use gel-polymer hybrid materials that work like "super sponges," drawing large amounts of water from ambient air, cleaning it, and rapidly releasing it using solar energy.

The researchers envision several other applications of the technology. It could potentially be used to cool solar panels and data centers. It could expand access to clean water, either through individual systems for households or larger systems for large groups such as workers or soldiers.