AUSTIN, Texas – Worldwide, agriculture accounts for 70 percent of all water consumed annually. However, agriculture water use isn’t always efficient, with 40 percent of the water being lost to the environment from poor irrigation, inefficient application, and evaporation.

Guihua Yu, a professor of materials science at the University of Texas at Austin, and his team are pioneering an innovative solution for crops that uses water more efficiently: smart soil. Smart soil is an engineered soil that contains a specially designed hydrogel, a soft material made up of different types of polymers that absorb and hold liquids.

“The gels we make are very unique because they can self-water. That means they can extract water from ambient air,” Yu said. “The water is stored within the gel, doing the part of self-watering.”

Two chemical components in the hydrogel contribute to its self-watering abilities: calcium chloride and sodium acrylate. Calcium chloride is a salt often used in fertilizers as a plant nutrient. It also promotes water retention, and in the case of smart soil, it absorbs water from the air. Sodium acrylate is a super-absorbent material that is able to store the extracted water.

A third synthetic chemical component that is thermally responsive controls the release of water. At night, when temperatures are cooler, water is extracted and stored. During the day, when temperatures rise, the gel releases water to hydrate thirsty plants. Some of the water also returns to the air, which helps to continue the harvesting cycle.

“(The chemicals) are environmentally friendly and have been used in the biomedical field in tissue engineering,” Yu said, adding that the chemicals are also found in household items like diapers and that the gels are biodegradable.

Yu’s team developed the first version of the hydrogel used in smart soil about two years ago. Their latest version of smart soil can also manage a controlled release of fertilizer. Yu said incorporating the slow release of fertilizer will help producers avoid overfertilization, which can lead to land degradation. Yu estimates that the hydrogels have a shelf life of about a year, and he envisions a final product that will last a producer an entire season.

In scientific studies led by Yu’s team, plants rooted in hydrogel soil saw a 138 percent increase in stem length compared to plants grown in regular soil. Additionally, the smart soil achieved 40 percent water savings, reducing the need for frequent irrigation. Yu said plants grown in smart soil are healthier and stronger, although extensive testing in real-world applications is needed before the impact of smart soil can be fully understood.

Moving forward, the team is interested in commercializing smart soil, but their current limitation is cost. The synthetic polymer that is thermally responsive is expensive. Yu said switching to a cheaper material is crucial for applying it to large-scale farming. It allows the team to scale up their experiments, moving from the lab to the field to test the soil’s performance in more critical conditions. The team is searching for a replacement that is naturally occurring and organic.

Smart soil is beneficial in many ways. When Yu’s team began conceptualizing soil that could water itself, they imagined its use in unfarmable landscapes. In some parts of the U.S. and other countries worldwide, temperatures are very high, and the soil is too sandy to efficiently retain water. Smart soil could be used in these environments to make the land farmable, which is important for feeding a growing population, especially in areas where growing food is extremely difficult.

Additionally, if the hydrogel is cheaper, Yu said that smart soil will financially benefit the farming industry as a whole. Although he suspects that the upfront cost of incorporating smart soil into a large-scale farming practice will be high, the use of less water and less fertilizer over time will translate into savings and potentially higher yields.

“Moreover, using smart soil will be much more sustainable,” he said. “Overfertilizing causes the land to degrade to the point where it cannot be used. (Using smart soil) will become a healthier farming practice.”