ANALYSIS OF THE FACTORS OF HIGH-YIELDING ABILITY FOR A JAPONICA TYPE RICE LINE, 9004, BRED IN CHINA .3. THE EFFECTS OF STAGE AND AMOUNT OF NITROGEN APPLICATION ON YIELD FORMATION

Japonica type rice line 9004, high yielding glutinous rice developed i n Jiangsu Province, China, was cultivated with and without nitrogen at early tillering (ETS), spikelet differentiation (PFS I), spikelet deg eneration (PFS II) or heading (HS) stage; and including ETS in stages 2-4, to analyze the effects of application stages and amounts (0-30.0g N/m(2)) of nitrogen on yield formation. 1) Winnouwed paddy yield range d from 804 to 1081g/m(2), and the ranges for number of spikelets, perc entage of ripened grains and 1000 kernel weight were 3.14-5.06x10(4)/m (2), 79.6-93.7% and 25.2-29.0g, respectively. 2)The yields in ETS, PFS I and II plots were increased due to an increased number of spikelets per area owing to the increase in the number of panicles and spikelet s per panicle, respectively The yield in HS plot increased due to an i ncreased percentage of ripened grains and 1000 kernel weight when less nitrogen was aplied before heading. Higher yields were obtained in th ose plots to which a higher amount of nitrogen was applied, and the in creasing trend was PFS I>PFS II>ETS>HS. 3) Yield was affected by the n umber of spikelets per area and dry matter production during the ripen ing period. The number of spikelets per area had a significant correla tion to the number of grains per panicle, and the dry matter productio n during the ripening period also had a significant correlation to LAI , the amount of absorbed nitrogen and the number of spikelets per area . 4)The results mentioned above suggest that the increments of nitroge n absorption from the panicle initiation stage to heading and dry matt er accumulation before and after heading play very important roles to ensure the number of spikelets per area and the dry matter distributed for each spikelet, respectively, in the panicle weight type variety b red in China recently.