The role of plant residues in soil productivity: farmers'knowledge and practices in Embu District, Kenya

Plant residues from trees, crops or weeds play an important role in determining the soil fertility status in smallholder farmers of the central highlands of Kenya region. A study was conducted in Embu district of Kenya, located in the densely populated windward side of the south-eastern slopes of Mount Kenya, to document farmers knowledge and practices in the prevalence and utilisation ofthese residues. A total of 134 small-scale . farmers cutting across five major agro ecological zones of the 30 kIn transect were interviewed. Farmers indicated that trees, Degraded soils are a major constraint to crops or weed residues found in their farms agricultural production and food security in were associated with generation of plant the central highland of Kenya region residues which either improve or impoverish (Smaling, 1997; Hudgens 1996). The the farm niches where they are found. Plant traditional residues that were associated with soil Long term experiments provide some fertility enhancement included: Zea mays, insights in the consequences of land Physeolus vulgaris, Grevillea robusta, management strategies that cannot be Combretum molle, Cordia africana, Ficus obtained through other means. For instance, sycomorous, and Camellina sinensis. On the trials established at Kenya Agricultural other hand, the residues of Eucalyptus Research Institute land at Kabete near saligna, Macadamia integrifolia, Cupressus Nairobi have shown that the soil organic lusitanica, Croton megalocarpus, Acacia matter declined from 2.1 % (in the original meamsii, Sorghum bicolour and Mangifera coffee estate) to 1.2% C after planting a indica continued to impoverish the soil in the maize-beans rotation over a period of twenty farm fields where they occur. The farmers years (Kapkiyai et al., 1999). Swift and attributed the good or poor crop Woomer (1993) state that it is not the loss performance in farm sections with certain of the soil carbon which poses the threat to types of plant residues to the decomposability the smallholder livelihood, but rather the assocated decline in crop yields resulting from degraded soils. Th euse of plant residues play a crucial role in the long-term improvement of soil physical and chemical properties.