In order to apply "pre-transplanting phosphorus application" (PTPA) to the lowland rice cultivation, we examined the effects of immersing the seedlings in potassium phosphate solution at different concentrations on the early growth and mineral absorption after transplanting using 15 varieties of rice. PTPA increased the total dry weight, leaf area and tillering number four weeks after transplanting. It increased the leaf area ratio (LAR) at two weeks after transplanting, by increasing allocation of assimilate to leaf blades, and raised the net assimilation rate (NAR) during the following two weeks (2-4 weeks). PTPA was supposed to shorten the rooting period, because it increased tillering number during the first two weeks after transplanting. Phosphorus (P) content per dry weight in each plant part two weeks after transplanting with increasing P concentration in the solution, but a varietal difference was observed in the extent of increase in the P content; it was high in the varieties that were bred in a tropical to subtropical region, such as Indica varieties. Total P content per plant was still increased by PTPA for at least four weeks after transplanting. These results suggested the possibility of lowland rice cultivation with reduced amount of phosphorus application by applying PTPA.
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