Agroclimatological enquiries

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1. Rainfall figures for the year 1974 and 1975 for Dodoma are as follows:- 1974 - 448 mm 1975 - 326 mm I also enclose a copy of graphical representation of the annual rainfall collected at Dodoma Meteorological station up to 1973/4 season. The dashed lines represent five year running means. 2. While we agree that soil, degradation is a major cause of low crop production and hence feminine in some semi-arid areas of Africa, this however is not the inherent cause of low crop production in areas of Central Tanzania. We are of the opinion that since all over the years these areas have been pastoral lands to the extent that very meager proportion of the land was put under cultivation, this has resulted in lack of experience on t part of the inhabitants there to adapt agricultural practices so to grow enough food to feed themselves. As meteorologists, we think that when these inhabitants of the semi-arid areas of Tanzania resorted to cultivation the following agrometeorological phenomena should naturally come into play. (a) The timing of sowing period is of vital importance in these areas due to the short rainfall season and the small amounts received annually. (b) Due to the short cropping period, selection of crops suitable to this particular type of enrironment is essential. For example, it is of little use, if any, to encourage farmers to grow a crop of a variety that will take more than four months to mature and whose water requirements is high. (c) Coupled with the low rainfall figures is the uneven distribution of the amounts during the growing period. On the average, the growing period in areas of Central Tanzania is from December to April. Experience has shown that about 50$ of the total annual figure of rainfall is collected by the end of January. However there have been seasons when well above 75% is collected during the first two months of the* cropping  season, leaving the period (when water is most required) barely dry. With the high rate of evaporation, the situation becomes even worse. / (d) Soil moisture require also plays an important role. Soil moist studies have shown that at time of onset of the rains, soil moisture present is so low that most of the first rains (which are quite vital agriculturally) go to replenish the lower layers and is hardly available to the plants. This being the case crops which have been sown in anticipation of the first rains take time emerge and hence develop to the size and state that would have been reached mu earlier had there been enough moisture at time of onset of the rains. The situation gets more alarming when rains set in late thus reducing the cropping period considerably. Hence, the effectiveness of rains (rather than the amounts), the right planting time and the right kind of crop to suit the environment both meteorologically and agronomical are some of the most important factors to be looked into whenever an agricultural project is being planned especially in are where cultivation has not been the order of the day. 3. With regard to publications on the meteorological aspects of the Central Plateau I would advice you to write to EAAFRO in Nairobi for copy of work done by Dr. Daag.
Available in Print form, East Africana Collection, Dr Wilbert Chagula Library, ( EAF FOS F78.A2)
Rainfall, Dodoma, degradation, Soil, pastoral
Fosbrooke, Henry A. (1976) Agroclimatological enquiries