Influence of selected land use change and indigenous knowledge on soil quality in the Agro-pastoral Semi-Arid Karamoja-Uganda

Abstract

Karamoja agro-pastoral semi-arid zone of Uganda is characterised by rapid land use and land cover change (LULCC), and soil quality (SQ) decline. However, the extent to which these changes have occurred and their impacts on soil quality determinants remained undocumented. The main objective of this study was to contribute towards improved soil productivity in agro-pastoral semi-arid Karamoja, Uganda through integration of indigenous and scientific knowledge for sustainable ecosystem management. Specifically the study, (i) Assessed Land use change in agro-pastoral semi-arid Karamoja for the last 30 years (ii) Assessed the effect of selected land use change in agro-pastoral semi-arid Karamoja on soil physical, chemical and biological properties (iii) Assessed the soil quality indicators of selected Land use change in the semi-arid agro-pastoral region of Karamoja, Uganda. (iv) Evaluated indigenous knowledge-based soil quality parameters for building a local soil knowledge database. Thirty (30) soil samples were collected from all the selected land use (grassland, woodland and farmland) of the study Sub-Counties and analysed for soil physical, chemical and biological attributes. The results revealed pH as one of the major chemical parameter responsible for nutrient availability, hence pH is a key parameter in determining soil quality. Matany soils had the lowest score of soil quality, followed by Iriiri and Rengen. This implies that Rengen soil have intrinsically good soil quality for farming as compared with that of Matany and Iriiri. The percentage soil organic matter of all land uses were significantly different (p=0.05) across all sub-counties. The soil OM percentages were for Rengen (0.8, 2.8, and 3.3), Iriiri (2.3, 3.4, and 4.0) and Matany (3.4, 4.5, and 5.2) for farmland, grassland and woodland respectively. Rengen soil textural class was sandy loam while Iriiri and Matany were clay. The drainage rates across all land uses in Iriiri and Matany were not significantly different (p>0.05) unlike in Rengen Sub-County which was significantly different (p<0.05) with farmland having the lowest drainage rate (1.4) as compared to grassland (2.1) and woodland (2.1). Across all sub-counties studied, fungal and bacteria colony forming unit (cfu) means were significantly lower (p<0.05) in farmland top soil than the grassland and woodland. The general decrease in soil attributes values were linked to the soil degradation due to farming/tillage. In order to establish the soil quality index (SQI), the soil samples which were collected from the study sub-counties land use change were analysed for physical; Clay, sand, field capacity, Water saturation point, Available water, permanent wilting point, Drainage rate, soil bulk density and water stable aggregates, chemical; fungi, bacteria and actionomycetes cfus, soil respiration (CO2 mg g-1 of soil), AMF, and nematodes availability diversity and population properties were used. The SQI for different land uses for each Sub-County originated from the above soil attributes using minimum data set (MDS). In order to assess the influence of different land uses on soil soil quality, analysis of variance (ANOVA) was accomplished using SPSS (version 24). To separate the mean value significance and determine the strength of relationships among soil attributes, Duncan’s multiple range test and Pearson’s correlation coefficients, respectively were performed. Different land uses resulted into different soil quality indices. Hence, there were no universal soil quality index for all land uses. The study took into account the social demographic characteristics of the people, farming enterprises, methods of raising crops, crops yields trends, causes of the perceived yields trends, soil quality indicators. The soil quality perceived parameters derived from the survey were clustered into five categories namely; The relationship between age group and the perceived indicators of soil fertility varied significantly (p = 0.045) with the majority stating that they use either soil colour, soil depth or soil texture to rate the fertility of soil. Karamoja farmers use visible features that predict soil quality. In order to establish the relationship between the measurable soil properties and the perceived knowledge, both were compared. Whereas the farmers did not use empirical information, some attributes they use had good hints of soil quality as the measurable parameters. Conclusively, the soil quality in farmland deteriorated as compared to the wood and grasslands. Further, the results suggested that Land use change from woodland to grassland and farmland negatively influenced soil chemical, physical and biological properties in the study Sub-Counties of the agro-pastoral semi-arid Karamoja. The soil texture was more dependent on the soil inherent properties which are mainly determined by the soil forming factors.