Soil temperatures near Nairobi

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McCulloch J. S. C.
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Continuous records of soil temperature at Muguga, Kenya, (1 0 13'S, 36° 38'E) under bare soil at nominal depths of one, three and six inches and one, two and three feet were taken for the period 1954-1955. The form of the temperature wave proved remarkably constant from day to day and the diurnal variation was measurable down to about one foot. The mean of maximum and minimum temperature is a good approximation to the daily mean temperature, as obtained by numerical integration, at depths of 6 in. and over. Nearer the surface, however, the mean of maximum and minimum gives an overestimate of the daily mean temperature. The annual soil temperature wave was not sufficiently marked to justify a mathematical analysis, but the mean diurnal wave for selected ten-day periods was analysed and values of thermal diffusivity were computed for the depth ranges 1-6 in. and 6-14 in. Despite seasonal changes in soil moisture content, diffusivity values proved remarkably constant with mean values of 0'0020 and 0•0015 cm~ sec-1 respectively for the two depth ranges. There was no obvious correlation with soil water changes.
East African Agricultural And Forestry Journal, 85 (363), p. 51-56