|Abstract or Summary
- Potato (Solanum tuberosum L.) is one of the most productive and nutritious food
crops. Due to its adaptability to cool climates, production in Sri Lanka has been restricted to
erosion-prone highlands. Vast potential exists for expansion of potato cultivation in the
lowlands while production areas in the highlands are limited by crop saturation. High soil
temperatures characteristic of lowland tropical areas strongly limit potato cultivation during
warmer months. Previous research, however, revealed that soil temperature can be reduced
by various techniques. Although soil temperature manipulation has been tried successfully,
the effect of these techniques on potato growth, dry matter partitioning, and tuber yield has
not been studied.
Experiment addressing these questions was conducted in two consecutive cropping
seasons from July to October of 1991 (Yala season) and December to March of 1991-1992
(Maha season) at the Regional Agricultural Research Center at Bandarawela (6° 5l'N
latitude, 80° 59' longitude, and 1300 m a.s.l.), Sri Lanka. The Yala season is warmer
while the Maha season is cooler. Treatments included various soil temperature suppression
systems such as rice straw mulching, interplanting, and hilling.
Rice straw mulch suppressed soil temperature by 1-6°C during the day. This system
hastened emergence and canopy development and increased potato plant height, leaf area
index (LAI), crop growth rate (CGR), and net assimilation rate (NAR) in both seasons.
LAI and CGR showed a quadratic relationship with time under rice straw mulch system.
Interplanting soybean (Glycine max L.), sweet potato (Ipomoea batatas L.) or double rows
of potato resulted in no appreciable effect on soil temperature suppression, or plant growth
in either season, except for emergence which improved under potato-soybean. Dry matter
partitioning to tubers was highest and showed a linear relationship with time under rice
straw mulch and rice straw-bridge systems while interplanting and hilling treatments did
not influence these factors substantially. Further, straw mulch improved total dry matter
(TDM) production, which showed a linear relationship with time. Tuber yield, individual
tuber weight, harvest index, and percentage of large tubers were improved under rice straw
mulching systems compared with interplanting and hilling.