轻度干湿交替灌溉协调水稻根冠生长、提高产量及氮肥利用效率

徐国伟; 赵喜辉; 江孟孟; 陆大克; 陈明灿

doi:10.11674/zwyf.2021034

轻度干湿交替灌溉协调水稻根冠生长、提高产量及氮肥利用效率

Alternate wetting and moderate drying irrigation harmonize rice root and shoot growth, improves grain yield and nitrogen use efficiency

摘要

摘要:
目的干湿交替灌溉是水分高效利用的有效措施，但是适宜的干湿程度受多种因素的影响。因此，研究不同干湿交替灌溉下水稻根系及地上生长发育的差异，以探讨干湿交替灌溉对水稻产量及氮肥利用效率的影响及其机理。
方法以‘徐稻3号’为材料进行盆栽试验，设置传统灌溉 (保持2～3 cm浅水层，CI)、轻度干湿交替灌溉 (−20 kPa，AWMD) 和重度干湿交替灌溉 (−40 kPa，AWSD) 3种灌溉方式，研究干湿交替灌溉对水稻 (Oryza sativa L.) 根长、根重、根冠比、根系伤流量、根系细胞分裂素含量、地上部重量、叶片光合速率、非结构性碳水化合物 (NSC) 运转及籽粒中ATP酶活性的影响。
结果轻度干湿交替灌溉显著增加了根长、根重、根冠比、根系伤流量、根中细胞分裂素含量，如抽穗期比传统灌溉分别提高13.3%、6.7%、10.8%、8.1%、7.4%；茎鞘中NSC向籽粒运转率提高23.3%，同时提高籽粒中ATP酶活性16.3%～18.4%、提升主要生育期叶片硝酸还原酶活性10.9%～44.0%，增加成熟期植株的吸氮量。最终水稻产量及氮肥利用效率显著增加，重度干湿交替灌溉则显著减少根长、根重，抑制根系活性及合成细胞分裂素的能力，如抽穗期分别比传统灌溉降低30.1%、20.8%、40.5%、34.4%，降低地上部的生长，显著降低主要生育期叶片的光合速率，抽穗期降低26.4%，虽促进NSC的运转，但是较低的花后干物质积累与籽粒库活性，导致水稻产量降低32.8% (2018年)与31.6% (2019年)；同时重度干湿交替灌溉下，植株吸氮量显著减少，叶片硝酸还原酶的活性降低19.2%，氮肥吸收利用率、农学利用率及偏生产力分别降低18.0%、34.7%及31.8%。
结论轻度干湿交替灌溉能够改善根系形态，提高根系代谢功能，协调地上部生长，提高水稻产量及氮肥利用效率。重度干湿交替灌溉不利于水稻根系生长，抑制代谢，不宜采用。

Abstract:
Objectives Alternate wetting and drying (AWD) irrigation, one of the most efficient water use technologies, is widely adopted in rice production worldwide. However, its effects on grain yield and N-use efficiency varies with cultivation method, soil and climate. In this study, we investigate rice root and shoot trait response to AWD to understand the mechanism underlying the beneficial effect of the technology.
Methods A pot experiment was conducted using a mid-season japonica rice cultivar of Xudao 3 in 2018 and 2019. Three irrigation regimes were set up, namely, conventional irrigation (CI), alternate wetting and moderate drying (−20 kPa, AWMD) and alternate wetting and severe drying (−40 kPa, AWSD). Rice root morphology and physiological indexes were recorded.
Results AWMD significantly increased root length, root weight, root-shoot ratio, root bleeding sap, and cytokinin content by 13.3%, 6.7%, 10.8%, 8.1%, and 7.4% at heading stage, respectively. AWMD increased the dry matter accumulation from heading to maturity, promoted NSC transport from stem and sheath to grains, and improved grain ATPase activity by 16.3%−18.4%. Also, leaf nitrate reductase (NR) activity increased by 10.9%−44.0% in the main growth stages, N uptake of plants at maturity increased, and the grain filling rate, 1000-grain weight, and grain yield increased as well. Meanwhile, the N absorption and utilization efficiency, agronomic utilization efficiency, and partial productivity increased by 17.2%, 21.6%, and 8.4%. AWSD significantly reduced root length by 30.1%, root weight by 20.8%, inhibited root activity by 40.5%, and the ability to synthesize cytokinins by 34.4% at heading stage. Aboveground growth and leaf photosynthesis rate across the main growth stages were thus decreased, such as reduction of 26.4% at heading stage in photosynthesis rate. Although pre-stored NSC remobilization from stem to grains was enhanced, less post-anthesis dry matter accumulation and grain sink activity resulted in lower rice yield. The plant N uptake (P < 0.05) reduced under AWSD, and NR activity of rice leaf decreased by 19.2%. The N use efficiency (P < 0.05) decreased compared with conventional irrigation. The N use efficiency, agronomic use efficiency, and partial productivity decreased by 18.0%, 34.7%, and 31.8%.
Conclusions Alternate wetting and moderate drying irrigation effectively improves root morphology, increases root metabolism, promotes aboveground growth, and enhances rice yield and N use efficiency. Alternate wetting and severe dying irrigation is not recommended.

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