Photosynthesis and productivity of rice at two levels of nitrogen

摘要

An experiment was conducted during the wet season of 1995 with an Indica variety, Takanari under two levels of nitrogen at the Tsukuba International Agricultural Training Centre, Tsukuba, Japan. In the early growing season, average temperature, sunshine hours and solar radiation were low. Later on, the weather conditions were highly congenial for rice growth and productivity. Higher N application increased the total leaf area and above ground dry matter production. Light extinction coefficient did not change between the treatments. Nitrogen absorption (g m~(-2)) pattern showed a parallelism with the rate of N application. Correspondingly, total carbon accumulation (g m~(-2)) was also higher in higher N plot. Net photosynthesis (mg CO_2 dm~(-2) h~(-2)) was always higher under the higher nitrogen condition. Photosynthetic activities (Pn) were more in upper leaves as compared to lower leaves. However, the increment of Pn was more in lower leaves. Higher grain yield was obtained when more N was applied.