Microbes (left) in the soil are able to increase the rate at which phosphorus is bound and unbound to particles in the soil. Imagine that the soil is a mixture of particles and water (as shown on the right), and this mixture is like a solution (like when you mix salt or sugar with water). The phosphorus in that solution is typically bound to the particles and in this state the phosphorus isn’t available for plants to use. But microbes (left) are able to use various mechanisms (center) to increase the rate at which the phosphorus becomes available for plants to use (right).