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University of Nairobi (2019)

Simulating Impacts of Climate Change on Sorghum Production in the Semi-arid Environment of Katumani in Machakos County, Kenya

Bosire, Emily N

Titre : Simulating Impacts of Climate Change on Sorghum Production in the Semi-arid Environment of Katumani in Machakos County, Kenya

Auteur : Bosire, Emily N

Université de soutenance : University of Nairobi

Grade : Doctor of Philosophy in Meteorology 2019

Résumé partiel
Reduced agricultural production and food security continues to be pressing problems for the larger part of smallholder farmers in Sub-Saharan Africa (SSA), as well as semi-arid Eastern Kenya. The main objective of this study was to assess the potential impacts of climate change on sorghum production in the semi-arid environment of Katumani in Machakos County, Kenya. The study sought to determine the effect of current and future climate and agronomic practices on the growth, development and yield of two sorghum cultivars. It also evaluated different farm-level adaptation strategies that may improve the adaptive capacity of sorghum growing farmers in the face of climate change. The study was conducted in National Dryland Farming Research Centre at Katumani, in eastern parts of Kenya. The variability and trends of climate parameters and sorghum yields were determined using coefficient of variation, linear regression and Mann-Kendall test. The findings show that in the study area, the MAM season is characterized by high variations in seasonal rainfall compared to the OND season, but with low variability in both seasonal and annual temperatures. Additionally, higher variability (45%) in sorghum yield was noted. The results also showed insignificant trends for the intra seasonal rainfall characteristics. However, significant decreasing trends of rainfall at seasonal and annual scales were recorded at Iveti and Machakos DO station. Positive significant trends for maximum and minimum temperatures were noted at annual scale. Sorghum trend depicted positive insignificant trends. Field experiments were conducted to determine the effect of different cultivars, nitrogen and phosphorus levels on the growth, development and yield of sorghum. The experiments were laid out in a randomized complete block design with two replications over four seasons. The analysis of variance showed non-significant effect of nitrogen (N) and (P) on phenological parameters of sorghum, growth parameters (biomass) and yield. However, the parameters were influenced by cultivar effect. The interactive effect of N, P and cultivar in the four seasonal experiments were non-significant for all the parameters. The Agricultural Production Systems sIMulator (APSIM) model was calibrated and evaluated for growth, development and yield response of sorghum to inorganic nitrogen fertilizer. Modified index of agreement, coefficient of determination and root mean square error were used to determine the level of agreement between the observed values and model simulated values. Model evaluation results pointed out that APSIM has a propensity to slightly over estimate the phenology, growth and grain yield. However, the error in all the parameters was below 15%, which is judged acceptable.

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