Assessment of soil fertility depletion in Mozambique

In this study soil fertility loss is determined by combining land units (based on soil fertility, precipitation and erosion) and land use types (characterized by crops, scale and occupation percentage of the land) into land use systems. Three nutrient balance-related parameters were derived: (1) nutrient depletion calculated for cultivated fields, (2) nutrient depletion averaged per land use system (including non-cultivated areas) and (3) nutrient balance compared with the soil nutrient resources in order to assess the rate at which the soil nutrient buffering capacity is affected in a land use system. At field level the cropping systems with the highest nutrient depletion are maize/cassava, both in small scale and in large scale cropping systems. The land use systems with the highest nutrient depletion on cultivated fields are those receiving more than 1000 mm of annual precipitation, having a high soil fertility and an annual erosion of 25 t ha(-1). Buffering capacity breakdown is negligible in the largest part of Mozambique. The spatial distribution of these three parameters is presented in three maps. Each indicator has its own value for planners at different scales. (C) 1998 Elsevier Science B.V. All rights reserved.