Pasture and perennial crops in rotation help increase the organic matter in soil and provide a stable habitat for soil organisms. The increased diversity of plant species in pastures increases the diversity of soil organisms, which helps the cropping system adapt to environmental factors. Overgrazing of pastures can remove too much residue and trampling can compact the soil, reducing water and air infiltration. Overgrazing also reduces the root mass. Each soil organism has a role to keep the system functioning.
Bacteria are the prime colonizers of dead plants and roots.
The sticky secretions that come from bacteria as they move along bind soil particles. They transform ammonia to nitrogen so plants can take it up. Bacteria also produce growth-promoting compounds that stimulate plant growth from the roots. Fungi are often thought of as pathogens, but most have a valuable use in decomposing litter and binding soil particles together. When mycorrhizal fungi colonize a plant, they increase the amount of sugar that moves to the roots.