MANAGEMENT CONTROL OF SOIL ORGANIC-MATTER DYNAMICS IN TROPICAL LAND-USE SYSTEMS

Given the rapid conversion of tropical forests to crop and pasture lan d, the economic constraints to widespread fertilizer use, and the pote ntially negative ecological impacts of fertilizer misuse, there is an urgent need to improve the management of organic inputs and soil organ ic matter (SOM) dynamics in tropical land-use systems. One desirable g oal is the ability to be able to manipulate SOM dynamics via managemen t practices so as to promote soil conservation, to ensure the sustaina ble productivity of agroecosystems, and to increase the capacity of tr opical soils to act as a sink for, rather than a source of, atmospheri c carbon. Soil organic matter dynamics are affected by management acti vities such as: (1) manipulation of the soil environment via tillage, mulching, and application of organic or inorganic fertilizers; (2) var ying not only the quantity and quality of organic inputs, but also the placement and timing of application; and (3) manipulation of soil fau na. Although simulation models based on ecosystem concepts, such as Ce ntury, offer a dynamic conceptual framework to examine the effects of long-term management, the predictable management of SOM dynamics in tr opical agroecosystems is constrained by the lack of appropriate method ologies to isolate SOM pools that are responsive to management. (C) 19 97 Elsevier Science B.V.