Effects of Site-Specific Nitrogen Management on Yield and Dry Matter Accumulation of Rice from Cold Areas of Northeastern China

The effects of yield increase and mechanism of site-specific nitrogen management (SSNM) in five rice varieties from cold areas of northeastern China were studied. Plot experiment for critical SPAD value and experiments of two fertilization methods, SSNM and farmer's fertilization practice (FFP) were conducted to study their effects on the quality and dry matter accumulation of rice population, as well as N uptake. Compared with FFP, SSNM significantly decreased the average N rate by 33.8%, significantly increased average ear-bearing tiller rate and LAI for grain-filling stage by 12.3% and 14.1-27.6%, correspondingly, improved dry matter weight and N uptake after heading period by 4.3-29.1% and 11.8-55.1% (P<0.05), and heightened recovery efficiency and agronomic efficiency by 38.5-133.4% (P<0.05) and 39.8-194.3% (P< 0.05), respectively, as well as increased the average yield by 9.8% in 2004 and 2005. The results indicated that the accumulation rate of dry matter and N increased the rice yield and N use efficiency, because of improving rice population quality and increasing LAI after heading period.