Bacteria can unlock phosphorus in the soil to help plants grow

In a study from the University of Washington, scientists have successfully introduced microbes into soil to make phosphorus more available to the roots of agricultural crops. The researchers collected the microbes from wild trees growing along the Snoqualmie River.

When phosphorus is applied in a fertilizer, chemical reactions with other minerals cause it to get locked up in the soil as phosphate, which makes it inaccessible to plants. To overcome this issue, farmers often use excessive fertilizer applications, leading to a buildup of chemicals that can pollute nearby waterways in agricultural runoff.

Phosphorus is one of the primary nutrients that is essential for plant growth, and it is needed for plants to complete their normal production cycle. 

“Crop productivity is constrained by the bioavailability of water-soluble nutrients, especially phosphorus in the form of phosphate,” wrote the study authors. “The efficiency of phosphorus acquisition, in which fine roots play a critical role, is important in addressing global food and bioenergy security issues that arise from increasing world population and climate change. In nutrient-limiting environments, plants are known to form associations with microorganisms capable of increasing the bioavailability of nutrients.”

Endophytes, which are bacteria or fungi that live inside a plant for at least some of their lifecycle, can be thought of as “probiotics” for plants, explained study senior author Professor Sharon Doty. Previously, her team demonstrated that microbes can help plants survive and even thrive in nutrient-poor environments.

In the current study, the researchers found that endophytic microbes collected from wild trees can unlock valuable phosphorus from the environment. The microbes simply break apart the chemical complexes that form phosphate.

“We’re harnessing a natural plant-microbe partnership,” said Professor Doty. “This can be a tool to advance agriculture because it’s providing this essential nutrient without damaging the environment.”

Using lab experiments, the team found that the microbes dissolved the phosphate complexes. In collaboration with multiple U.S. Department of Energy national laboratories, the researchers confirmed that the phosphorus unlocked by the microbes was successfully taken up by plant roots.

Advanced imaging techniques used in the national laboratories also showed that phosphorus gets bound up in mineral complexes within the plant. Endophytes living inside plants can re-dissolve these complexes, potentially sustaining the plant’s phosphorus supply.

The bacteria used in the experiments was obtained from wild poplar trees growing in western Washington. Despite a limited availability of nutrients like phosphorus on the rocky banks of the Snoqualmie River, poplar trees are thriving here because the microbes help them capture the nutrients they need.

The findings can be applied to agricultural crops, which are often planted in soil that has accumulated an abundance of phosphorus from years of fertilizer applications. According to the researchers, replacing fertilizers with endophytes could open the door to more sustainable food production.

The study is published in the journal Frontiers in Plant Science.

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By Chrissy Sexton, Earth.com Staff Writer