Manual on integrated soil management and conservation practices : Manual based on the training course: Soil Management and Conservation - Efficient Tillage Methods for Soil Conservation, held at IITA, Ibadan, Nigeria 21 April-1 May 1997, organized by the Land and Plant Nutrition Management Service of the Land and Water Development Division and the Agricultural Engineering Branch of the Agricultural Support Systems Division, FAO, in cooperation with the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria