Characterization of land uses and Soilphysico-chemical properties in farmer’s categorized fields in Kamuganguzi subcounty,Kabale district, south-western Uganda.
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There is limited understanding about integrated soil fertility management (ISFM) and soil and water conservation practices among small holder farmers in Uganda. The smaller holder farmers have resolved on using local knowledge to assess soil productivity based on soil physical properties instead of combined approach of local knowledge and scientific measures hence low yields. This study was therefore aimed at characterisation of land use and physiochemical properties in farmer‟s categorised field on Ferralsols in Kamuganguzi subcounty, south-western Uganda. The treatments were farmer and soil fertility status. The study was arranged in a randomized completely research design (RCBD) with field category and farmers as blocking factor. Random method of sampling was used to collect soil samples for the chemical analysis in each field. The soil was then mixed well in the basin and quartering was done to obtain the representative soil sample and this was repeated to obtain the 3 samples from each field category under farmer making 30 samples. Chemical analysis involved determination of SOM, Soil PH, N, P, K, CEC, Ca, and Na. The laboratory results on different parameters were entered in an Excel spreadsheet and the data subjected to analysis using the GenStat 14th Edition Statistical software and significant component means of Variance, standard error obtained using (LSD) at 5% probability levels, confidence interval. A two-way analysis of variance (ANOVA) was performed to determine significant differences. There was a significant (P<0.05) effect of farmer on all the physical and chemical parameters of the soil investigated in this study (Table 4.2; Appendix 1). For pH, the highest average (5.6± 0.02) was from field of farmer named Kinosi Rodah whereas the lowest (4.7± 0.02) was from farmer named Mugisha (Table 4.3, Table 4.1).Average pH of productive soils was significantly higher (5.7 ± 0.01) than that of soils categorised as unproductive (5.3± 0.01). . There was a significant (P<0.05) effect of farmers on total nitrogen of the soil (Table 4.2; Appendix 1, A4) . All the values of total nitrogen observed ranging from 0.88 ± 0.23% to 1.85 ± 0.23% from the study were above the 0.2%N threshold for crop production (Fairhurst 2012) and 0.25% from (Okalebo et al.,2002). The high concentrations of total nitrogen observed in the study was not expected for both the productive and unproductive soils because tropical soils have inherently low N levels attributed to high rates of mineralization (Ojeniyi 2010) and unabated soil nutrient mining (Olupot et al., 2020). The available phosphorous contents in the study lie within the recommended range of phosphorous in the soil (15-25ppm) from (Okalebo 2002; xi Fairhurst 2012; Gourley 2013) except for sweet potatoes field (7.9± 3.598ppm) and eucalyptus (10.1± 3.598ppm).The high available phosphorous content from unproductive soil under bare land (28± 3.598ppm) above the critical limit was not as expected from the study because this field was located on hilltop and was exposed to erosive factors. Both the productive and unproductive soils had low potassium content below the critical limit (0.4 cmol/kg) (Fairhurst 2012). It may be attributed to the utilization and nutrient uptake by food crops grown like sweet potatoes, maize, and banana alongside the basic cations (Singh 2020). On the other hand average calcium contents ranged from 16.3 ±3.425Cmol/kg to 38 ±3.425Cmol/kg. All the values of calcium observed were above the critical limit (10ppm) (Okalebo et al., 2002; Fairhurst, 2012). The farmers of Kamuganguzi subcounty use local knowledge to characterize the soil properties basing on their experience, the farmers uses soil physical properties like soil depth, and soil colour, topography and vegetation distribution and others to characterize the soil as productive and unproductive. The farmer‟s local knowledge regarding soil properties has been utilized in allocation of land for different uses for example food crops like banana, maize, sweet potataoes are allocated to productive soil located in valley bottom. The local knowledge and scientific methods relate/in consistency when it comes to some soil physical and chemical properties and farmers have different field management practices they do to maintain soil fertility and this affect soil properties. Soil pH and potassium levels were the major limiting factor for crop production in Kamuganguzi subcounty, Soil organic matter and organic carbon, total nitrogen, calcium were most favorable factors that support crop production. Phosphorous levels were also high except for some fields like (sweet potatoes with soils characterized as productive and eucalyptus in unproductive soil), Soil texture was favorable (clay loam class) for crops like maize according to the textural class. Combined use of local knowledge and scientific methods reduces on high costs involved in soil characterisation compared to using only scientific methods, Intensive cultivation on steep hills in Kamuganguzi subcounty should be discouraged to ensure increased crop production since it increases the rate of depletion of soil fertility especially exchangeable basic cations and soil organic matter. Crops like sweet potatoes contribute to decline in soil pH, available phosphorus and exchangeable bases. Practices like organic matter use, cover cropping, minimum tillage, mulching, fallowing, terracing and more other soil conservation practices are critical in hilly areas.