Tropical regions have the largest land area available for agricultural production to meet growing demand for food by the rapidly increasing world population. Tropical agriculture, however, is faced with a serious challenge of feeding about 70% of the world’s inhabitants and meeting other basic necessities of life for 75 to 80% of the population of the region that depends on farming. A significant portion of the population in tropical countries suffers from malnutrition. In addition to economic issues, intensification and extension of agriculture to marginal lands have created severe ecological problems (e.g., deforestation, soil degradation, pollution of water and the natural environment, and increased greenhouse gas emissions). In these situations, adopting sound practical measures to maintain and/or improve the nutrient-supplying capacity of tropical soils is the key factor to improving and/or sustaining the long-term crop production.