Comparison of Rice Plant Development with Different Transplanting Density under SRI Practices in the Lysimeter

Abstract

Transplanting a single young rice seedling is one of the common methods in SRI practices. However, farmers in some lowland areas hesitate to apply this method due to the threats such as seasonal floods, birds and pests. Most of the farmers are more comfortable with transplantation of two or more seedlings per hill. Thus, an experiment was conducted in the lysimeter at the rooftop of the University of Tokyo in 2015 to compare the rice plant development with different transplanting density. As an experimental design, two sets of single seedling transplantation were applied with alternative wetting and drying irrigation as replications; the same irrigation condition was applied to other transplantations with two, three and four seedlings per hill. The plant height, number of leaves and tillers, dry biomass, and grain yields were selected as the main factors for the comparison of rice plant development. As a result, no difference was observed for the development of height across all transplantation density treatments during the vegetative phase. However, during the reproductive and ripening phases, single-seedling transplantation reached greater height. For the development in number of tillers and leaves, three and four seedlings produced more tillers and leaves than one and two seedlings. We found that the grain yield is significantly higher in three and four seedlings rather than one seedling.