Soil fertility evaluation and management by smallholder farmer communities in Northern Tanzania

Abstract

The role of the smallholder farmer community in soil fertility evaluation and management was examined from two ‘research for development’ projects in northern Tanzania. These are the African Highlands Initiative (AHI) and the Soil Water Management Research Group (SWMRG). Participatory approaches were applied by both projects. Farmers’ knowledge and experience were used in identifying soil fertility constraints using local indicators of soil quality and in generating resource flow maps. The farmers’ evaluation of soil fertility was compared with soil analytical data and with calculations of maize yields by the model QUEFTS. The use of farmers’ indigenous knowledge in soil fertility evaluation mostly agreed with laboratory analysis and model calculations by QUEFTS. Model calculations identified potassium as the most limiting nutrient in the highlands for yields less than 3 t ha-1 and phosphorus for yields higher than 4 t ha-1. Given that farmers’ evaluation of soil fertility is relative to what they see around them, there is a need to verify their observations, but also the interpretation of laboratory data by models like QUEFTS requires continuous and critical validation. Both projects have shown that there is scope to reverse the trends of declining soil fertility in smallholder farms in northern Tanzania.