ABSTRACT
Many traditional farmers, such as those in China, India, Mexico, Papua New Guinea, Peru, ancient Rome, Spain, and South and Central America have added considerable quantities of organic material to the soil. Long-term soil fertility is often enhanced by the use of organic sources of nitrogen, although much of the nitrogen supplied by organic sources is not immediately available. The addition of large quantities of organic amendments does not always control soil pathogens. The combined practices of flooding fields for rice and using organic matter for fertilizers "are apparently key factors in the general absence of soilborne diseases in China." The practice of using green manure crops has important benefits, as they add organic matter to the soil, and play a role in the suppression of soilborne pathogens while improving the physical condition of the soil.
