Abstract
The paddy rice variety used was Norin-8, which was grown in the paddy field under different levels of nitrogen supply and different density, changing the spacing at the begining of heading. The increased amount of dry matter production was measured by using growth-analysis during ripening period. Results obtained from this investigation briefly summerized as follows: 1) Relative growth rate (RGR) was completely controlled by the net assimilation rate (NAR) per unit leaf area, so far as the increment of top-dry-weight was expressed by RGR throughout ripening period. 2) The size of leaf area for maximum production of dry matter per unit field area (optimum L) was estimated nearly 2.3 m2/m2 field throughout ripening period. 3) The growth rate (G=dw/dt) during ripening period was controlled by leaf area per unit field area (L) in case the leaf area was restricted below the optimum L. 4) NAR in ripening period was closely related to both the nitrogen percentage and the chlorophyll percentage in leaf-blades. The relation was shown as a curve, usually showing the maximum value of NAR at 2.3% of total nitrogen content and 1.4% of chlorophyll content as fresh matter weight in leaf-blades, and rather decling NAR values at the higher percentages. 5) Forecasting of dry matter production in ripening period seems to be possible by determining the total nitrogen content in total leaf-blades per unit field area at the begining of ripening stage
