Isotopic Studies of Azolla and Nitrogen Fertilization of Rice: Report of an FAO/IAEA/SIDA Co-ordinated Research Programme on Isotopic Studies of Nitrogen Fixation and Nitrogen Cycling by Blue-Green Algae and Azolla

Nitrogen is the most limiting element for crop production. Traditionally, expensive commercial fertilizers are used to correct soil nitrogen deficiencies. Indeed, 50% of the increase in rice yields after World War II can be attributed to increased fertilizer nitrogen use. Although an increased rate of fertilizer nitrogen application has been advocated to meet the growing demand for food, it is unrealistic to advise the farmers to apply fertilizers they could hardly afford, and whose prices ...