Linking local and scientific indicators of soil quality to agroforestry contributions in maize-based production systems

Abstract

Soil fertility decline is a major limiting factor for achieving household food security in sub Saharan Africa and has led to increasing concern on agricultural sustainability. Development of indicators of soil quality to monitor changes resulting from land use and soil management have been proposed to address the issue. To better understand the soil fertility problem in the study area, we hypothesized that local farmers can detect differences in soil quality within their farms by using local soil quality indicators which would in return assist in highlighting changes in soil resulting from agroforestry trees. Forty-seven (47), smallholder farmers were interviewed on local soil classes, biological indicators of soil quality and agroforestry tree attributes influencing soil quality. In addition, they were asked to orally describe the characteristics of the local soil classes that occurred in their farm. This was followed by soil sampling guided by local soil classes and soil qualities recognized for each farm. Twenty-seven (27) out of 117 fields were classified as intermediate (transitional) between productive (good) and non-productive (poor) soil. To substantiate farmers’ perception of soil quality we carried out common soil chemical analyses on samples collected from local soil classes identified by local farmers. Results shows farmers had detailed knowledge of plant species they use as bio indicators of soil quality and their influence on farming activities. Plant species such as Sesbania spp, Acacia abyssinica, Bidens pilosa, Digitaria scalarum, Tagetes minuta and Galinsoga parviflora were named by different farmers as bio-indicators of productive soil. Farmers associated invading species and grasses with unproductive soils. Most of the farmers in the study area were found to be aware of macrofauna as bio-indicators and their activities whereby earthworms and beetle larvae were indicators of productive soil. In contrast, majority of interviewed farmers attributed ants to destruction of crops and regard them as detrimental in the soil. Lastly, laboratory tests results of soils corroborated respective farmers’ perceived soil qualities. The study conclude that farmers hold complex ecological or local knowledge on indicators of soil quality and contribution of agroforestry tree in their farms. They can also recognize the tradeoffs underlying a biodiverse agroforestry system and their creative capability in the utilisation of local knowledge was demonstrated. It is therefore necessary to find a realistic and common ground between scientific and local knowledge in order to implement a sustainable agricultural program