High productivity is an important aspect of agricultural sustainability in the humid tropics. However, most of the prevalent land uses and predominant agricultural systems in the humid tropics are characterized, with a few notable exceptions of silviculture and rice-based systems, by low crop and animal productivity, rapid decline in productivity with continuous use, and high rates of soil and environmental degradation. The principal objective of a sustainable land-use system is to maintain a high level of productivity, maintain or improve environmental and aesthetic attributes, and enhance soil quality. Inputs in Fig. 1 refer to additions of off-farm essential nutrients and amendments, while management refers to judicious use of on farm resources to minimize waste and the risks of soil and environmental degradation.
Soil quality depends on a range of soil properties and processes.
Soil properties important to its quality are soil structure, soil organic matter content, plant-available water and nutrient reserves, aeration, and rate and magnitude of nutrient cycling and transformations. Deterioration in soil quality affects the soils life-support processes. Soil processes important to soil quality include accelerated erosion, leaching soil organic matter, and fertility depletion leading to nutrient deficiencies and toxicities, and anaerobiosis. 1 Soil quality in relation to soil properties, soil processes, and environmental quality B. Sustainability and forest conversion Deforestation of TRF by unsuitable methods and conversion to agricultural land use with resource-based systems can adversely affect the soil properties and processes that lead to a rapid decline in soil quality with a negative impact on sustainability and environmental quality. The objective of using improved technology is to minimize the magnitude and rate of soil degradation set in motion by conversion of TRE to agricultural land uses, and to enhance soil quality and resilience so that productivity can be sustained with minimal adverse impact on soils and environment.