One of the bases for establishing sustainable farming systems is to integrate nitrogen-fixing plants into the system, whether in the form of crop rotation or as perennial plants. In mountain areas, the most common farming approach is to use a mixed crop livestock agroforestry system. This can be made considerably more successful if nitrogen-fixing plants (NFPs), especially those that occur naturally in the environment, are deliberately incorporated into the system. NFPs are one of the cheapest and best sources of organic manure, they add nitrogen to the soil through the action of the microbes or microorganisms in their specialized root nodules and through the decay of their nitrogen-rich foliage. Generally, NFPs do not require extra fertilizer for growth; they are often pioneer species on degraded land and can be an important source of cash crops. Nitrogen-fixing herb, shrub, and tree species can be used to maintain soil fertility in agroforestry systems, to increase forest productivity, and to improve soils at degraded and eroded sites prior to introduction of other species. Both uses are demonstrated at the Knowledge Part at Godavari.