Abstract
Four experiments were planted June 1982-November 1983 in the Philippines to evaluate the effects of season and soil mulches on Solarium potato growth and yield in a location where monthly mean minimum temperatures did not go below 20ºC. Rice straw, rice hulls and sugarcane bagasse were compared with no mulch using the cvs Cosima, Desiree and Red Pontiac. All mulches reduced the daily maximum soil temperature by 2-4°C depending on the season and the phase of crop production, resulting in faster emergence and canopy development, earlier tuber initiation, significantly higher tuber yields, slightly higher tuber dry weight concentration during the hottest season. The mulches all improved yields during all seasons, with the greatest effect during the January-April and June-September seasons when yields were increased by at least 50%, from 4-10 to 8-15 t ha-1. During the cooler months yield improvements were smaller. Red Pontiac appears to have higher heat tolerance than Cosima and Desiree, with all producing yields of over 20 t ha -1 with mulch. The physiological age of the seed is a major consideration in heat tolerance, as older seed gave faster early growth but a decrease in tuber weight due to respiration 60 days after planting if temperatures were high.
