Plants' ability to use carbon dioxide as fertilizer is significantly affected by how much water and soil nutrients are available to the plants, a new study from the University of Minnesota shows.

The study, published in the journal Nature Geoscience, is the result of a 5-year field experiment in which researchers tested how plants responded to a variety of scenarios using different combinations of carbon dioxide, nitrogen and water availability.

Past studies have shown that increased levels of carbon dioxide in the Earth’s atmosphere can act as fertilizer and enhance plant growth. But what hasn’t been known is what role other factors in plant growth — water and soil nutrients — may play in that process. The work by the Minnesota team uses realistic state-of-the art experiments available at only a handful of sites around the world.

The authors used unique open-air techniques with grassland plots at a research site in Minnesota to possible combinations of rainfall, carbon dioxide and soil nutrients. They found that plants in poor soils and with less-than-average rainfall lost their ability to use any extra carbon dioxide they were exposed to.