A rising chorus of investors and stakeholders, along with some farmers, are beginning to spread the message that the health of the soil is just as important as the health of the plants growing in it.

In honor of Earth Day, here are six startups working to improve the health of soil on farms and off.

The Soil Health Institute, created by the Noble Foundation, offers some clarity in describing its mission as safeguarding and enhancing “The vitality and productivity of soil.”

The Cocoon allows the trees to grow in soil that would otherwise not be conducive to growth and as it breaks down provides healthy microorganism life and an environment around the tree that is healthier for plant life due to the introduction of shade and increased water retention in the soil among other factors.

The company’s flagship technology Constructed Functional Microbiome produces microbial products for increasing crop yields and soil health with the goal of food safety.

The soil testing kit also allows farmers to gauge the health and productivity of their soil before they begin planting, allowing optimization of inputs and yields.

Wanda Organic is a Kenyan start-up providing organic bio-fertilizers to small and medium-sized farmers in order to improve their soil health and yields.