Agroclymatic characterization of Lesotho for dryland maize production
Moeletsi, Mokhele Edmond
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Agro-climatic characterization of Lesotho for dryland maize farming was performed using temperature and rainfall indices in a GIS environment. The temperature and rainfall meteorological parameters were patched for missing data using the UK method for the maximum and minimum temperatures. Missing daily rainfall data was patched using the inverse distance method. Statistical evaluation of the patching methods showed good performance. The spatial distributions of different temperature variables and indices were mapped. Important meteorological parameters were the frost occurrence (first day, last day and duration) and monthly and seasonal heat units. The onset of frost is early (March) over the highland areas while the low- lying areas onset can be as late as June. The last day of frost over the low- lying areas is mostly in August and on the other hand, the highlands last day of frost is in November/December at some places. Rainfall interpolation was done using the kriging method of the geostatistical analyst. Important aspects mapped include monthly averages, seasonal amounts, annual amounts and number of days of high daily rainfall. Wet season (October to April) rainfall was high (>800mm) over the north to northeastern parts of the country while some areas over the east and southern parts received less than 500mm of seasonal rainfall. Climatic potential of maize under dryland farming in Lesotho was investigated using five climatic suitability indices namely: probability of receiving heat units of greater than 1500GDD, probability of a frost-free growing season, probability of seasonal rainfall of more than 500mm, probability of 15-day dry spells during December to February and the slope of an area. For each of the above parameters a coverage layer was prepared in GIS environment and the layers were overlaid to obtain the agroclimatic suitability map of maize in Lesotho. The districts of Butha Buthe, Leribe and Berea are shown to have areas which are highly favorable for maize cultivation under dryland farming while the unsuitable areas are mostly over the high- lying areas (Mokhotlong, Thaba Tseka and Qacha’s Nek) together with other parts of the southern lowlands.