ABSTRACT
This study assessed the effects of Land use/Land cover change on soil quality in the semi arid area of northern Katsina state. This study employed an integrative methodology that comprised of five major components (i) digital image processing of Landsat Thematic Mapper image covering the study area for 1 986, Enhanced Thematic MapperETM for 1 996 and Enhanced Thematic Mapper PlusETM+ for 201 1 in IL WIS 3 .3 Academic software environment (ii) post classification comparison change detection and analysis which generated change statistics for 1 986, 1 996, 2006 and 20 1 1 , subsequent upon which change scenario (CS) areas were developed (iii) collection of 50 soil samples each (25 top soil and 25 sub soil) from the seven identified (CS) in the study area (iv) laboratory analysis of the collected soil samples for (texture, Ph, total Nitrogen, organic carbon, exchangeable cations, available Phosphorous and CEC using standard analytical procedures. The results obtained revealed that (i) there were changes in LULC across the study area between 1 986 and 20 1 1; (ii) between 1 986 and 1 996, riparian vegetation, scrubland and woodland decreased while reservoir/water body, bare sand surface/rock out crop, scattered cultivation and settlement/builtup areas increased (iii) three LULC types manifested continuous decrease while four have appreciated over spatial and temporal scales. (v) seven CS patterns discovered includes (1) Scrubland to Scattered Cultivation, 2) Woodland to Settlement/Built-up areas, 3) Riparian Vegetation to Scattered Cultivation, 4) Woodland to Bare sand surface, 5) Scrubland to Bare sand surface, 6) Woodland to Scattered Cultivation, 7) Scrubland to Settlement/Built-up areas. Soil fertility rating discovered that CSs 7, 3 and 5 maintained the best soil fertility while CS 2 maintained the lowest soil fertility at the surface layer of the soil. In the sub surface soil layer, the study revealed that CSs 5 and 4 exhibited the best soil quality levels while CS 2 portrayed the lowest soil fertility. It was concluded that (i) Satellite imageries provided a good source of information for detecting changes in LULC;(ii) during the study period, tree/shrubs cover decreased by 77.71% while reservoir/water body increased by 72.28%, bare sand surface/rock out crop increased by 68. 1 0%, scattered cultivation increased by 1 27.28% and settlement/built-up areas increased by 1 62.95%; (iii) the study also concluded that there were generally high levels of conversion of the predominantly savannah grassland (scrubland (77.71 %) and woodland 7 1 .78%) community into either permanent cultivation, settlements (built-up) or bare surfaces in the area, (iv) CSs involving conversion of lands into permanent cultivation are in general having lowest levels of most of the soil quality parameters in the area (vii) soils were generally low in organic matter and this can have an overall negative effect on their productivity level. In order to address the problem of rapid LULC transformation and address the problem of soil fertility loss on a sustainable basis in the study area, it was recommended that (i) sustainable and coordinated Land use planning should be instituted at local, state and country levels; (ii) awareness campaigns with a view to ensuring that the people understand the negative effects and consequences associated with land use/land cover change; (iii) re-introduction of cattle tracks/route way (Burtali); (iv) development of a computerized RS/GIS database at local, state and country levels for coordinated and continuous monitoring of environmental changes, (v) there is need for frequent assessment of the spatio-temporal consequence of changes;( vi) farmers should be encourage to consider avoiding continuous cropping among others.
