Influence of plant spacing on potato (Solanum tuberosum L.) morphology, growth and yield under two contrasting environments

In experiments at a temperate (43oN) and a tropical (14oN) location, closer plant spacing decreased stem branching, root growth, and mean tuber size but increased tuber yields per ha. Closer spacing increased plant height at the temperate site but decreased it at the tropical site where canopy cover did not reach 100%. The increased branching at the wider spacing did not compensate for fewer plants/m2. Total and tuber weight per plant increased with wider spacing and was much greater under temperate than tropical conditions. Tuber yield/stem also increased with lower stem densities. Although these results provide initial data for modelling, the contrast between the two environments and interactions between spacing and cultivar suggest that further experiments need to be done with a range of cultivars at intermediate locations.