Assessing sustainability of low-external-input farm management systems with the nutrient monitoring approach: a case study in Kenya

In the search for Integrated Nutrient Management practices in response to t he widely observed soil fertility decline in Sub-Saharan Africa, the potent ial of low-external-input and organic farming remains to be systematically examined. The nutrient monitoring concept was used to assess the impact of technologies on nutrient flows and economic performance at activity and far m household level in Machakos district, Kenya. The nutrient flows and balan ces and economic performance indicators of farms practising low-external in put agriculture (LEIA) technologies for a number of years were compared wit h a group of farms practising conventional farm management. Based upon moni toring two farming seasons, it was concluded that both subsistence-oriented farm management systems result in serious N-depletion and that 60-80% of f arm income is based upon nutrient mining. No significant differences could be found between the LEIA and conventional farm management group. Only if L EIA farm management reduces nutrient losses through leaching and gaseous lo sses can a positive impact on nutrient balance be expected. Off-farm income plays a crucial role, especially in the conventional management group, in keeping farm household income levels above the poverty line. High-level com post application treatments in maize are attractive if labour and organic i nputs are available. (C) 2001 Elsevier Science Ltd. All rights reserved.