Salk Institute Trials Deep-Root Soybeans to Trap Carbon and Beat Drought

Scientists at the Salk Institute are field-testing soybean plants engineered to grow deeper, steeper root systems, in an effort to store more carbon underground while making crops more resilient to drought.

The work, supported by an $18 million grant from the Bezos Earth Fund, is being carried out at a research field in Champaign, Illinois, and in laboratories in La Jolla, California. Researchers say the modified plants could offer a dual benefit: pulling carbon out of the atmosphere and locking it into deeper soil layers, while also helping crops reach moisture that remains underground when the surface dries out.

Wolfgang Busch, director of the institute's Harnessing Plants Initiative, said the team has spent six years developing root systems that grow further down. "Deeper root structure will be able to reach deeper layers of the soil," he said. Because soil dries from the top during a drought, plants with roots that reach deeper are often better able to access remaining moisture.

Ordinary soybean plants grown by farmers have shallow roots that spread sideways and slope down only gently. The engineered plants, by contrast, have many more roots that descend far more sharply. The scientists identified 347 genes linked to carbon storage and root growth, then edited the plant's DNA to direct it to build larger root structures that grow downward.

According to Busch, those deeper roots also deposit carbon in soil layers that are less likely to be disturbed. Because the roots penetrate below the depth affected by tilling, planting and harvesting, conventional farming practices may not release as much of the stored carbon back into the air. The soil, he said, can act as a carbon bank, holding carbon that plants have drawn down through photosynthesis.

Todd Michael, also of the Salk Institute, said the steeper roots may have an additional advantage: allowing farmers to plant crops closer together. Noting that smaller plants grown in tighter rows were a hallmark of the Green Revolution, he said denser planting could translate into higher yields. "We think that these steeper roots both give us deeper roots that can fight off drought problems, store more carbon, but also potentially enable us to put more plants in a smaller area," he said.

Based on earlier laboratory results, the researchers estimate the deeper-rooted soybeans could store one metric ton of carbon dioxide per hectare per year. Busch said the team has calculated that the approach could potentially achieve carbon drawdown and sequestration in the gigaton range, which would address a substantial share of the problem. The scientists also believe deeper roots could help with excess nitrogen in farm fields.

How long the carbon remains stored will depend on how deep the roots grow and on conditions in the surrounding soil. Initial results from the field trial are expected this autumn. Busch described the field test as the real measure of the technology, where unexpected problems can arise, but said the sight of green soybeans in the test plots and early preliminary results had eased some of that anxiety.