The role of indigenous knowledge in management of soil quality among farmers in Chuka and Gachoka Division, Central Kenya

Abstract

A field study was conducted in Chuka and Gachoka divisions, which fall in Meru South and Mbeere Districts, respectively, on a sample population of 60 farmers in the 2003 long rain season, to determine their perceptions of soil fertility and common soil management practices which influenced soil quality within farmers' fields. The study aimed at investigating use of indigenous knowledge in farming systems in Central Kenya. Farmers were asked to identify soil fertility indicators that theyv used to determine fertility status of their soils in the productive or non-productive fields within their farms. Farms were selected randomly in Kirege and Gachoka sub-locations in Chuka and Gachoka Divisions respectively. A list of villages was first obtained from divisional offices to constitute the sampling frame, from which the study farms were randomly selected. There were 6 villages in Chuka and 5 villages in Gachoka. Social data was collected first from all farms in the sample (60), after which top soils were sampled from both productive and non-productive plots within smallholdings in both divisions. Soil sampling was then conducted on fifteen farms selected in both divisions from the farms that were visited in the household survey. Two farms were then selected in each village, and sampled for topsoils (0-20cm) comprised of a composite from a minimum of 10 randomly selected sites on farmers' fields from which a subsample (500 g) was obtained. Soil chemical parameters that were determined included soil reaction (pH), exchangeable acidity, exchangeable bases (Ca and Mg), extractable phosphorus (Olsen), total organic carbon, available nitrogen, total nitrogen and total phosphorous, while physical parameters included soil texture and water aggregate stability. Throughout the chemical analyses, samples were randomly replicated within the batches for quality monitoring. The aim of the study was to determine farmers' soil fertility perceptions and common soil management practices that influenced soil quality within fields in Chuka and Gachoka divisions, Central Kenya. Results showed that farmers only used sensory information (soil tactile and visible characteristics) to distinguish within soil fertility categories. The most important indicators for characterising productive and non-productive fields included crop yield (86%) and performance (76%), soil colour (60%) and soil texture (40%) in Chuka division while in Gachoka, soil colour was the most important indicator (84%). A total of 18 indicator plant species were used to distinguish soil fertility status in both divisions. It was clear from the study that farmers used a comprehensive set of indicators to classify and assess the fertility of their soils. These included characteristics they could see, feel, or smell in their fields, based on their own historic experiences in cultivating their fields. Farmers had a clear understanding of physical soil characteristics, especially soil colour, texture, tilth, crop production potential and on-farm soil erosion risks. There was a tendency for farmers to place soil conservation structures on soils that they valued most. Regarding soils, there were significant statistical differences among soil fertility categories, using parametric techniques (ANOVA) for key soil properties (p <0.05), implying that the soils must have had different properties and that there was a qualitative difference in the soils that were characterised as different by farmers. In both sites, fertile soils had significantly higher pH (p<0.001), total organic carbon and exchangeable calcium (P<0.001), magnesium (p< 0.05) and available-N. Factor analysis conducted on measured physical and chemical soil properties identified 4 main factors that explained 65% of the total variance in soil quality and were linked to farmers assessment indicators such as crop yield and fertiliser response. The first factor grouped calcium, magnesium and soil pH, while the second component comprised of available nitrogen, organic carbon and total nitrogen. The third factor included plant nutrients mainly extractable phosphorous and available nitrogen, while the fourth factor comprised of soil physical properties (macroaggregates, micro aggregates, silt, clay). The four factors were designated as contrasts that described soil quality status on farmers fields. In conclusion, soil fertility and crop management practices that were investigated indicated that farmers understood and consequently utilized spatial heterogeneity and temporal variability in soil quality status within their farms as a resource to maintain or enhance agricultural productivity.