Biophysical characterization was carried out in the mountain and oasis areas within the Northern Kenya Arid Lands with a view of identifying, soil constraints and opportunities for sustainable agricultural production in the area. The soil aspects were studied through desk-top analysis of the existing databases and collection of secondary data at regional scale, site evaluation surveys at site level and detailed soil survey at farm level. Based on biophysical data, the mountain and oasis area of the region was divided into three major eco-zones, namely (1) upper regions: mountains, hills and uplands, (2) middle level: footslopes and (3) low-lying areas: riverine, plains and bottomlands, which were found to occupy 20, 5 and 54% of the total land area of Kenya Arid and Semi-Arid Lands (KASALs) respectively. In these areas, soil structural degradation has taken place at varied rates through pulverization in the upper regions, compaction in the middle level and dispersion in the low-lying areas. The mean productivity index for the upper zone, middle slopes and the lowest zone was found to be 18.5, 19.6 and 1.3%, the most limiting factors being high acidity, increased compaction and high sodicity/salinity respectively. The opportunities for sustainable agriculture was found to be elimination of acidity and increased water saving for supplementary irrigation in the upper zone; harnessing run-off water and improving water holding capacity through subsoiling on the footslope; and precision and market oriented irrigated farming for improved water use efficiency in the lowest zone.
Key words: Biophysical characterization, soil quality and productivity index.
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