中文摘要：

摘要：以汕优63和连粳6号为材料，设置实地养分管理（SSNM，因地、因苗、因种施肥）和习惯施肥（FFP）处理，观察实地氮肥管理对水稻根系生长和产量的影响。结果表明：抽穗前FFP处理的根重大于SSNM处理，在抽穗及抽穗后SSNM处理的根重大于FFP处理。SSNM处理显著提高水稻整个生育过程的根冠比。SSNM处理的水稻根系氧化力自幼穗分化期开始（尤其是单茎占有的根系氧化力）均超过FFP处理。SSNM处理提高抽穗后水稻剑叶光合速率。与FFP处理相比，SSNM处理增加产量7．2％～9．4％，提高氮偏生产力38％～46％和氮农学利用率56％～77％。与FFP处理相比，SSNM处理在产量不降低甚至有所提高的前提下，可以较大幅度地降低施氮量，其重要原因在于促进了生育后期根系的生长。

英文摘要：

ABSTRACT.. Two rice cultivars of Shanyou 63 （indica） and Lianjing 6 （japonica） were grown in field experiments with two nitrogen （N） managements, site-specific N management （SSNM, N application according to soil fertility, leaf color and growth status, and cultivar types） and farmers＇ fertilizer practice （FFP）. Present investigation was aimed to deter- mine the effect of SSNM on roots growth and yield of rice. Results showed that the root dry weight in the FFP was higher as compared to that in the SSNM before heading, whereas it was lower at and after heading. During the whole growing season, SSNM significantly increased the root-shoot ratio. Compared with FFP, SSNM increased root oxidation activity （ROA） at and after panicle initiation, especially ROA per stem. SSNM also increased the photosynthetic rate of the flag leaves after heading. Compared with FFP, SSNM increased grain yield by 7.2% - 9.4%, N partial-factor productivity （grain yield/amount of N applied） by 38%-46%, and N agronomic efficiency by 56%-77%. The enhancement of root growth at the latter growing stage would account for the increase in grain yield and N use efficiency under SSNM.