Legume Symbiotic Nitrogen Fixation: Agronomic Aspects

Abstract

The Earth’s population, increasing exponentially (Figure 1), is expected to reach 10 billion, nearly double its present status, by 2035 (Bockman et al., 1990). Of this projected population, 90% is expected to reside in tropical and subtropical regions of the developing countries in Asia, Africa, and Latin America (Waggoner, 1994). Plant sources currently provide 80% of the caloric and dietary protein needs for tropical countries, and this is not expected to change in the near future. In 1910 human beings used about 10% of the total carbon fixed through photosynthesis (Golley et al., 1992). Currently humans use 40% of that carbon, and it is estimated that by 2030 humans will require 80%. Individual protein and caloric consumption of the Earth’s current 5.7 million people averages 70 g.protein.d⁻¹ and 2,400 calories-d, respectively (Waggoner, 1994). The range of protein consumption varies from 38 to 125 g protein.d^ℒ1, while the range of caloric intake varies from 1, 800 to 3, 500.d⁻¹, with the low range values associated with developing countries (Bongaarts, 1994). The anticipated doubling of Earth’s population will exacerbate the current inequalities in nutritional intake. Clearly, to maintain the current level of protein and caloric intake over the next 40 years will necessitate unprecedented increases in crop production. This enhanced production will need to be achieved despite a significant deterioration of much prime agricultural land and will require the utilization of large areas now considered marginal.