Characteristics of Growth,Development and Nutrient Uptake in Rice under Site-Specific Nitrogen Management

With typical rice cultivars as materials,the growth and development characteristics and nutrient uptake in rice under site-specific nitrogen management(SSNM)were studied.SSNM could decrease N rate to a greater extent without any sacrifice in grain yield,when compared with farmers' fertilizer practice(FFP).Number of productive panicles under SSNM was a little lower than that under FFP,but productive tiller rate was much higher under SSNM.Leaf area index(LAI)and root weight were lower under SSNM than those under FFP before panicle initiation,but the results were reversed after heading stage.SSNM increased efficient and high efficient LAI rates at the heading stage,dry matter accumulation from heading to maturity stage,ratio of root to shoot,photosynthetic rate in flag leaves after heading stage and light transmission rate in rice population at the full heading stage.The uptake peaks of N,P,K under SSNM were all from panicle initiation to heading.During this period,the uptakes of N,P,K were about 45.6%-46.2%,39.6%-43.6%,and 44.2%-45.2% of total at maturity,which were all much higher than those under FFP.Reasons for yield increase and nutrient uptake laws in rice under SSNM were discussed.