TRENDS OF RAINFALL AND MAIZE PRODUCTIVITY IN MALAWI

Abstract

Daily rainfall data between 1966 and 2005 across all Agricultural Development Areas (ADDs) in Malawi wasinvestigated to determine changes in selected rainfall characteristics and their impact on Maize productivity. Rainfallindices analyzed included rainfall amounts (annual and seasonal), onset, cessation, dry spells and length of rainy season.Man Kendal ' s trend test was applied to the time series of these indices to detect any trends in the time series. WaterRequirement Satisfaction Index (WRSI) for maize crop was used to study the spatial-temporal variation of maizeproductivity and thus its linkage to rainfall. Definition of onset and cessation adopted from the Department ofMeteorological Service (DMS) Malawi was used in demarcating seasons to extract seasonal rainfall amount, length andother parameters. The results of the study indicate that with the exception of Karonga ADD located at the Northern tip ofthe country there were no significant trends in all variables related to crop productivity including onset, cessation,rainfall amount and dry spells. The spatial and temporal variability of maize production in Malawi was captured quitewell by the WRSI. The relationship between long-term average WRSI and maize yield (tonnes/ha) for different stations inMalawi had a correlation coefficient of 0.82 while the relationship of countrywide average WRSI and maize yield had acorrelation coefficient of 0.75. Areas with low long term average WRSI like Shire valley also showed low productivitywhile those with higher WRSI like Mzimba and Salima ADD had a good yield. On average Malawi has sufficient rainfallto sustain rain-fed maize crop as most of the time (67%) rain-fall is enough to give an average yield. It was also foundout that Malawi experience droughts and hence food shortages when WRSI value is close to or below 60%.