Tropical soil fertility research: towards the second paradigm

Soil management issues appear prominently in Agenda 21's priorities for sustainable land management, protecting the atmosphere, sustainable mountain development and combatting deforestation and desertification. Although major advances in managing soils of the tropics have taken place, a paradigm shift is emerging from the traditional soil fertility paradigm: overcome soil constraints to fit plant requirements through purchased inputs. A second paradigm addresses directly the issues in Agenda 21: rely more on biological processes by, adapting germplasm to adverse soil conditions, enhancing soil biological activity and optimizing nutrient cycling to minimize external inputs and maximize the efficiency of their use. Efficient nutrient management, therefore, is the basis for the second paradigm. An integrated strategy is proposed with 10 research components: 1) Analysis of farmer perceptions and policy constraints; 2) geographic depiction of soil-related constraints; 3) improving germplasm for soil constraint tolerance; 4) matching plant requirements to soil constraints; 5) strategic use of fertilizers; 6) nutrient budgeting and nutrient cycling; 7) biological control of soil erosion; 8) water harvesting; 9) controlling greenhouse gas emissions through improved soil management, and 10) policy design and implementation.