1992 Volume 63 Issue 6 Pages 633-638
Under common cultivated conditions, silica contents in rice leaf blades correlated reversely with the nitrogen contents. The relation described a curve line throughout the life stage of rice plant. The relation curve shifted to the higher silica content side with the application of calcium silicate. The silica contents in soil solution in paddy field continued to be high with the application of calcium silicate. The silica contents in rice leaf blades cultivated without nitrogen lay over the relation curve at any life stage, while those in rice leaf blades cultivated with abundant nitrogen lay under the relation curve at panicle initiation stage. That is, when ammonia-formed nitrogen plowing soil remained at more than 4 mg/100g soil at the end of June and nitrogen contents in rice leaf blades at panicle initiation stage were more than 3.5×10^<-2> gg^<-1>, silica contents in rice leaf blades were less than 3×10^<-2> gg^<-1>. At heading and matured stage, dry weight of rice plant increased with its nitrogen uptake, but its silica uptake reached a peak of about 35 g m^<-2> at heading stage or about 60 g m^<-2> at matured stage. These results suggest that the main limiting factor of silica uptake by rice plant under abundant nitrogen cultivation is silica supply ability of paddy field at the later life stage. And at the earlier life stage a great deal of ammonia-formed nitrogen remaining in paddy soil and high nitrogen content of rice plant mainly limit the silica uptake by rice plants.
