Image Credit: "Populus trichocarpa 05897" by Walter Siegmund © CC BY-SA 2.5

Poplar trees could help reduce the use of chemical fertilizers. Bacteria found on the tree branches help to convert nitrogen into a more useful form, giving nutrients to the tree. Nitrogen fixing, as it is called, is extremely important for all types of life. Before, it was widely believed that nitrogen fixing was only achieved in the roots of plants. When applying this bacteria from the branches of poplar trees to corn, tomatoes and peppers, less fertilizer was needed. This could eventually allow crops to grow in nutrient poor soil.[1]