摘要:以水稻品种‘连粳7号’为试验材料进行盆栽试验，设置不施氮（0N，0 kg·hm-2）、中氮（MN，240 kg·hm-2）和高氮（HN，360 kg·hm-2）3种施氮水平及浅水层灌溉（0 kPa）、轻度干湿交替灌溉（-20 kPa）和重度干湿交替灌溉（-40 kPa）3种灌溉方式，研究不同水氮处理对水稻抽穗期根系分泌有机酸总量和组分变化、氨基酸含量及水稻氮肥农学利用率与偏生产力的影响及其耦合效应，探索水氮耦合机理，为水稻氮素高效利用及根际生态提供理论及科学依据。结果表明：轻度干湿交替灌溉增加了水稻根系酒石酸、柠檬酸、草酸、苹果酸、琥珀酸、总有机酸、氨基酸分泌量，分别较浅水层灌溉增加13.2%、8.7%、27.3%、40.0%、6.7%、6.3%及6.4%，水稻氮肥农学利用效率及偏生产力分别增加4.1%及1.7%，显著提高根系分泌有机酸及氨基酸含量；重度干湿交替灌溉减少水稻根系酒石酸、柠檬酸、草酸、苹果酸、琥珀酸的分泌量，显著降低根系分泌有机酸总量、氨基酸含量及水稻的氮肥利用效率。同一水分条件下，施氮显著促进根系酒石酸、乙酸、苹果酸、琥珀酸的分泌，降低了草酸和柠檬酸的分泌量。根系分泌的酒石酸和琥珀酸含量在MN与HN间差异较小。分析表明，根系分泌有机酸总量、氨基酸、苹果酸及琥珀酸的供氮效应为正效应，轻度干湿交替灌溉效应及与供氮的耦合效应为正效应，而重度干湿交替灌溉效应及其与供氮的耦合效应则为负效应。根系分泌的柠檬酸、草酸与氮肥利用率呈显著与极显著正相关，乙酸与氮肥利用间呈显著负相关。结果表明通过轻度干湿交替灌溉与中等施氮调控发挥水肥耦合效应，可以促进水稻根系酒石酸、苹果酸、琥珀酸及氨基酸分泌，提高氮肥利用效率，从而促进水稻高产。
关键词:水稻/
干湿交替灌溉/
水氮耦合/
根系分泌物/
有机酸/
氮肥利用效率
Abstract:Soil water and nitrogen conditions are the principal factors that affect crop growth and formation. Clarifying effects of soil water and nitrogen conditions and their coupling on grain yield of rice (Oryza sativa L.) have significant implications for high production efficiency and yield. There is extensive domestic and foreign research on the interactions of soil water and fertilizer. Specific focus has been put on ground parameters such as crop growth development, dry shoot formation, physiological function, hormone change, nutrient absorption and utilization, water use efficiency, etc. However, there is less work on the characteristics of root secretion, including changes in organic acids in roots. Research on the relationship between organic acid content and nitrogen utilization and the related interactions is also inconsistent and therefore inconclusive. The purpose of this study was to investigate the performance of root secretion under different nitrogen and water regimes and analyze the effect of the interaction of alternate wetting and drying irrigation and nitrogen levels. To that end, a pot-soil experiment was conducted using a mid-season japonica rice cultivar 'Lianjing 7' under different nitrogen rates[0N, MN (240 kg·hm-2) and HN (360 kg·hm-2)] and three irrigation regimes[keeping water (0 kPa), alternate wetting and moderate drying (-20 kPa) and alternate wetting and severe drying (-40 kPa)] in 2015 and 2016. The results showed that there was remarkable interaction between nitrogen rate and irrigation regime with the results similar for the two years. Under the same nitrogen rate, tartaric acid, citric acid, oxalic acid, malic acid, succinic acid, total organic acid and amino acid secretion of rice root at heading stage were higher (respectively by 13.2%, 8.7%, 27.3%, 40.0%, 6.7%, 6.3% and 6.4%) in treatment of alternate wetting and moderate drying than in treatment of keeping water flood irrigation. The nitrogen agronomic utilization and partial productivity of rice were increased by 4.1% and 1.7% respectively. The secretion amounts of tartaric acid, citric acid, oxalic acid, malic acid and succinic acid at heading stage decreased (respectively by 16.4%, 4.5%, 12.8%, 41.7% and 5.6%) under the treatment of alternate wetting and severe drying than under the treatment of keeping water. This also reduced total organic acid and amino acid in roots and overall nitrogen use efficiency. Under the same irrigation condition, nitrogen application accelerated the root secretion of tartaric acid, acetic acid, malic acid and succinic acid, but decreased the secretion of oxalic acid and citric acid at heading stage of rice. The differences in tartaric acid, acetic acid, malic acid and succinic acid secretion by roots were small between MN and HN treatments. Nitrogen application has positive effects on total organic acid, amino acid, malic acid, succinic acid secretion. Also its interaction effect with alternate wetting and moderate drying was positive, while the interaction effect with alternate wetting and sever was negative. Correlation analysis indicated that citric and oxalic acids secretion by rice roots was significantly positively correlated with nitrogen utilization. However, acetic acid was negatively correlated with nitrogen use efficiency. The results of the study suggest that increasing root secretion capacity through appropriate regulation of irrigation coupled with nitrogen rate increased nitrogen use efficiency and thereby promoted high yield of rice.
Key words:Rice/
Alternate wetting and drying irrigation/
Water and nitrogen interaction/
Root secretion/
Organic acid/
Nitrogen effi-ciency
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