DEVELOPMENT OF SOIL CLIMATE REGIMES OF KENYA USING SPATIAL JAVA NEWHALL SIMULATION MODEL

Abstract

Climate change is a fundamental threat to food security, development and the fight against poverty. Identification of strategies to alleviate its impacts on agriculture is essential. One such strategy is making future climate predictions which help to develop ways to fight possible outcomes such as food shortages. Unfortunately, there is limited available information on biophysical data (especially up-to-date soil maps) required for multipurpose and specific land use planning. Soil maps production has for long relied on expert knowledge and manual delineation which has several limitations. This has led to low soil map production, a process that requires tremendous amounts of time and resources. Unlike paper maps, digital maps are accurate and can be updated easily with new information. However, use of current digital soil mapping techniques and models such as spatial Java Newhall simulation model and is not common in Kenya due to, among other factors, lack of expert knowledge and resources to undertake the soil survey procedures. The purpose of this study was to develop a digital soil climate map of Kenya illustrating the water and temperature constraints for agriculture, both for present and future conditions. Soil temperature and moisture regimes were estimated from the Newhall simulation model, using present (1971-2000) atmospheric climate records and future (2050) projected climate scenarios (precipitation and air temperature) from World Climate- Global Climate Data (Version 1.4). Records of temporal monthly patterns of the soil moisture and temperature regimes were then digitally mapped using ArcGIS for Desktop software. A relationship between the different soil temperature and moisture regimes and some of the current major crops was then explored. Spatial comparisons, in percent change units, was done to detect changes in soil climate between present and future conditions using subtraction method. The spatial comparison maps created were also used against crop spatial distributions, and a relationship derived. The output showed that Kenya is dominated by isohyperthermic, isothermic and isomesic soil temperature regimes both for current and future conditions. The aridic, ustic and udic soil moisture regimes also dominate the country in both conditions. Over 80% of the country will not experience changes in soil temperature in future global climate change scenarios expected in year 2050, but about half of it is expected to experience increases in soil moisture according to the model. Although the cryic temperature regime is present in both times, it covers less area in the future climate conditions where it is completely absent in the Aberdare Mountain Ranges of central Kenya. Thermic temperature is absent in current conditions but is expected to occur in the future while this is the reverse for pergelic temperature regime. Soil climate-crop relationships showed possible suitable soil moisture conditions for diversity in crop growth in the arid and semi-arid parts of Kenya. It was concluded that the variations in rainfall and temperatures due to climate change are likely to impact on Kenyan agriculture. To take advantage of the expected increases in soil moisture in the arid and semi-arid parts of Kenya, policies on land use need to be aligned to this. Overall, the techniques adopted for estimating the soil climate regimes in this study shows promising results, but field measurements and more expert knowledge are still needed for validation and fine tuning of the process.