水稻实地氮肥管理的氮肥利用效率及其生理原因

以代表性品种为材料，研究了水稻实地氮肥管理(SSNM)的氮肥利用效率及其生理机制。结果表明，SSNM的施氮量较常规施肥方法(FFP)降低了48.1%~63.0%，产量提高了0.1%~9.3%。SSNM的氮肥吸收利用率和农学利用率分别较FFP提高了31.4%~56.8%和143.6%~166.0%。水稻氮吸收高峰出现在穗分化期至抽穗期，此阶段SSNM处理氮的吸收量和其占最终总吸收量的比例均明显高于FFP。抽穗后SSNM水稻的吸氮量也明显高于FFP。自幼穗分化期开始，SSNM水稻根系重量和根系活力(尤其是单茎占有的根系活性)逐步超过FFP。SSNM 明显提高了幼穗分化期和抽穗期水稻叶片中谷氨酰胺合成酶、硝酸还原酶和Fd-谷氨酸合酶的活性。抽穗后SSNM处理水稻剑叶的光合速率高于FFP，上述结果表明SSNM有利于促进水稻中后期根系生长，提高物质生产和养分吸收，从而提高氮肥的利用效率。

Fertilizer-Nitrogen Use Efficiency and Its Physiological Mechanism under SiteSpecific Nitrogen Management in Rice

Nitrogen (N) fertilizer is one of the most important factors affecting grain yield in rice. High N inputs and low use efficiency is a main problem in rice production in China. Site-specific N management (SSNM) has been considered as a new technique which could increase N use efficiency in rice. However, its underlying mechanism is not understood. In this study, one indica hybrid Shanyou 63 and two japonica cultivars Wuyujing 3 and Yangjing 9538 were field-grown, and two treatments, SSNM and farmers’ fertilizer practice (FFP), were conducted. The results showed that SSNM reduced N rate by 48.1–63.0% and increased grain yield by 0.1–9.3% when compared with FFP. Recovery efficiency and agronomic efficiency of fertilizer-N under SSNM were increased by 31.4–56.8% and 143.6–166.0%, respectively, as compared with those under FFP. The peak of N uptake appeared during the peirod from panicle initiation to heading. The N uptake during this period and its ratio to total N uptake during the whole growth stage were significantly higher under SSNM than under FFP. The amount of N uptake after heading under SSNM was also much higher than that under FFP. From panicle initiation, root weight and activity (especially root activity per stem) under SSNM were higher than those under FFP. SSNM also significantly increased the activities of glutamine synthetase, nitrate reductase and Fd-glutamate synthase in leaves at the panicle initiation and heading stages. Photosynthetic rate of the flag leaves was also obviously greater under SSNM than under FFP. These results indicated that SSNM could promote root growth, increase matter production and nutrient uptake during the mid and late growth periods, leading to higher fertilizer-N use efficiency in rice.