ABSTRACT
The major cause of low productivity of agricultural crops, tree plantations, pastures, and natural habitats in the tropics is the extremely low fertility of most tropical soils. Low fertility results from the extremely rapid soil weathering, decomposition, erosion, and leaching of nutrients caused by high temperatures and high rainfall. This results in extremely acidic soils in which plant growth rates are far below their maximum potential due to lack of major soil nutrients (nitrogen, phosphorus, potassium), minor essential soil nutrients (magnesium, calcium, and trace essential metals such as zinc, manganese, copper, and molybdenum), high acidity, aluminum toxicity, and insufficient organic matter to retain nutrients and water in the soil. Addressing these problems through addition of chemical fertilizers is often too expensive to be practical, and unbalanced nutrient ratios in most chemical fertilizers frequently result in poor plant responses due to extremely inefficient uptake of fertilizers. Chemical fertilizers typically contain only N, P, and K, so if the other essential elements are missing, plants will be unable to utilize them, and most will be wasted.
