Soil heatflux under coconut (Cocos nucifera Linn) in an humid tropical oxisol

Abstract

The heatflux into an oxisol under coconut in an humid tropical climate was analysed.            

The peak daily solar radiation and air temperature during dry period (December-May) in this region goes upto 1050 Wm-1 and 35° C respectively. The maximum surface soil (2,5 cm depth) temperature observed in an open field was 62° C on a summer day. The diurnal variation of soil temperature in the open field was between 33° and 45°C at 5 cm depth and it was reduced by 2-7° C due to coconut canopy and by 1-7° C due to natural mulch material.

The heat capacity and diffusivity values of the soil were 0.4315 cal cm^{-2 o}C^-l and 0.596 x l0^-3sec^-1 respectively at PWP (permanent wilting point) moisture content. The diurnal heat flux into 5-10 cm layer of soil was between +0,412 and -0,165 cal cm-1 h~ in the open field, whereas it ranges between +0,494 and -0.296 cal cm-1hr-l in the coconut garden. The maximum surface heat flux into 2.5-5.0cm depth was 6.42 cal cm-1 hr-l.

Mulching around the basin of the coconut tree causes heat flow to be either at equilibrium or negative.

The maximum heatflow into 5-10 cm layer (1430 IST) was up to 0.849 cal cm-. hr-1 in different seasons and it is not related to soil moisture content.