Potato (Solanum spp.) in the hot tropics II. Soil temperature and moisture modification by mulch in contrasting environments

Abstract

Abstract In order to quantify the effects of mulch on soil temperature and soil moisture regimes during the growth of the potato crop, seven experiments were conducted at three contrasting hot tropical sites (latitude 5–12 °S) varying in altitude from 180 to 800 m. Mean maximum and minimum temperatures during the crop seasons ranged from 27° and 30° and 16° to 21°C respectively. Various mulches, mostly organic, were tested either singly or in combination with other agronomic practices, and in one experiment the interactions between mulch and three radiation levels (0, 50, and 75% reduction of incoming radiation) were studied. Mulch always enhanced soil moisture retention, but the improvement was less evident under increasing shade. Daily soil temperature fluctuations at tuber depth were damped by mulch, and maximum reduction of daytime soil temperature was recorded immediately following planting, before the crop emerged. Reductions of daytime soil heating and retention of heat within the soil at night by mulch were influenced by various edaphic and weather conditions. Maximum reduction during the day was achieved under conditions favouring soil heating (e.g. high irradiance, low soil moisture content, ridged soil, soil of low albedo) whereas heat retention at night by mulch, although greater in shaded than non-shaded plots, in general was relatively greater under conditions that favoured longwave re-radiation from the soil (e.g. ridged and dry soil).