Evaluation of the medium- to long-term impact of Integrated Soil Fertility Management practices on soil productivity and other soil-based ecosystem services

Land degradation, and particularly soil fertility decline, poses a serious threat to crop production in Sub-Saharan Africa (SSA) because of an increasing pressure on land to meet the increasing demand for food caused by the growing population. In order to overcome the prevalent food insecurity and to eradicate poverty among smallholder farmers, there is a need for a paradigm shift in managing soil fertility by seeking options that optimize crop production per unit area through sustainable intensification (SI) in the face other drivers affecting productivity, including climate change. Sustainable intensification also includes the need to ensure that soil-related ecosystem services other than the production of food, feed, and fiber are retained. In recent years, Integrated Soil Fertility Management (ISFM) has formed the basis of many initiatives aiming at intensifying agriculture in Africa. ISFM is defined as a ‘set of soil fertility management practices that necessarily include the use of fertilizer, organic inputs, and improved germplasm combined with the knowledge on how to adapt these practices to local conditions, aiming at maximizing agronomic use efficiency of the applied nutrients and improving crop productivity. All inputs need to be managed following sound agronomic principles’. While ISFM has been shown to increase crop productivity and input use efficiency in short term trials, its longer term impacts on soil health and yield stability remain largely unknown. There is a need for long-term observatories to understand the processes associated with ISFM, its sustainability and identify the conditions for reversing soil degradation. Such long-term field trials also facilitate the optimization of ISFM across different cropping systems as affected by agro-ecological conditions and other drivers of change such as climate change. Various long-term ISFM trials are still on-going and a set of new ISFM trials in relation to grain legumes, maize, and cassava were initiated in 2014. This activity includes a set of on-going multi-locational ISFM trials focusing on restoring the soil organic matter pool and a set of new long-term trials thatwere be initiated in 2014.