Effect Of Climate Variability On Pearl Millet (penn/setum Glaucum} Productivity And The Applicability Of Combined Drought Index For Monitoring Drought In Namibia

Abstract

Climate variability has been one of the most important determinants of crop productivity in the world. Pearl millet farmers in the northern parts of Namibia always encounter poor pearl millet yields due to intra-seasonal characteristics and climate variability. Specifically, the dry spells that always occur across pearl millet growth stages and recurrent droughts adversely affect crop productivity. The overall objective of this study was to assess the effect of climate variability on pearl millet (Pennisetum glaucum) productivity and explore the usefulness of the Combined Drought Index for agricultural drought detection in Namibia. The specific objectives of the study were to determine the effect of the length of growing period, the length of dry spells that occur during pearl millet growth stages and rainfall anomaly on pearl millet yields. The study also evaluated the possibility of using the Combined Drought Index (CDI) as an indicator for early agricultural drought detection in Namibia. The study used correlation analysis to determine the degree of association between the study parameters. Instat Statistical Analysis Software was used to perform climatic analysis, whereby soil water balance was used to determine season length and the occurrence of dry spells (dry days) during the pearl millet three major growth stages. Monthly rainfall and temperature for fourteen years (1998- 2012) as well as the Normalized Difference Vegetation Index (NDVI) data were used in the analysis. Estimated daily rainfall for Ondangwa, Outapi and Ongenga were also used in the analysis of this study. The study revealed that the effect of length of growing period, dry spells and rainfall anomalies on pearl millet yields varies from region to region and also with pearl millet growth stages. There was also significant influence of lengths of dry spells that occur at growth stage one (GS1) in Oshana and Ohangwena, growth stage two (GS2) in Omusati and growth stage three (GS3) in Ohangwena on pearl millet yields. The Combined Drought Index (CDI) was able to capture the historical drought events experienced in Namibia. The study, therefore recommends the use of the Combined Drought Index as a third agricultural drought monitoring and detection indicator in Namibia.