Floating seedbed for preparing rice seedlings under unpredictable flooding occurrence at tropical riparian wetland

Preparation of rice seedlings on fl oating seedbed makes it possible for earlier rice growing season and more fl exible time for transplanting under unpredictable fl ooding condition. The objective of this research was to search for appropriate procedure for producing high quality rice seedlings using fl oating seedbed associated with three crucial factors, i.e. level of contact between substrate and water surface, seedling population density, and seedling age at time of transplanting. Seedbeds were constructed using 120 air-tight plastic bottles as fl oater. Surface dimension of the seedbed was 2 x 1 m with load capacity of 40 kg m-2; therefore, each seedbed can be loaded with 80 kg of growing substrate. Three experiments were sequentially carried out for optimizing knowledge on each of the three crucial factors. Seedling height, fresh weight, and SPAD value were used as primary indicators for seedling quality. Results of our experiments indicated that seedling height and weights were consistently lower in partially submerged substrate than those in no direct contact or with fi lm-thin contact setups. Seedling population density between seed application rates of 2 and 3 kg m-2 were not signifi cantly different, but these treatments were signifi cantly higher than that of application rate at 1 kg m-2. SPAD value was higher at denser seed application rates. Optimum seedling age was 21 DAP but acceptable range for transplanting was at ages between 14 and 28 DAP. Thus, open fl exibility for time of transplanting during fl oodwater receding process.