不同灌溉方式下氢、氧同位素分布与小麦水分利用特征

目的]探明不同灌溉方式对小麦水分利用的贡献率及小麦根系吸水规律,可为合理应用灌溉用水提供科学依据。方法]利用稳定氢氧同位素示踪法,研究了防雨棚条件下常规灌溉(X)与滴灌(D)不同灌水量条件下(X₁,D₁:15 mm; X₂,D₂:30 mm; X₃,D₃:45 mm)冬小麦生长期间土壤水稳定同位素变化特征,以及土壤耗水强度、光合生理特征及水分利用特征。结果]随小麦生育期的推进,根系吸水逐渐加深。在拔节期小麦主要利用0—20 cm深度的土壤水; 在抽穗期X₂,D₁和D₂处理主要利用了0—20 cm土层的水分,但X₁处理主要利用了60—80 cm土层的水分,占53.9%,X₃处理主要利用了40—60 cm土层的水分,占77.0%。而D₃处理主要利用了0—60 cm土层的水分,占80.0%; 到灌浆期,X₁和X₂处理主要利用了0—60 cm土层的水分,分别占86.2%和90.6%,而X₃处理主要利用了40—60 cm土层的水分,占73.9%。而D₁和D₂处理不同土层的水分利用比例较均匀,分别介于7.1%～27.8%和13.0%～38.2%之间。D₃处理主要利用了20—40 cm土层的水分,占51.0%。除抽穗—灌浆期中水处理(D₂)及灌浆—收获期高水处理(D₃)外,滴灌均有效降低了小麦的日耗水量。与常规灌溉相比,滴灌D₂和D₃处理更利于提高小麦的光合速率和叶片水分利用效率。此外,滴灌处理在小麦抽穗期和收获期均有效提高了小麦的生物量。最终,滴灌较常规耕作小麦产量提高了21.6%～28.0%和水分利用效率提高了24.4%～36.7%,均以D₂处理最高。相关分析表明:小麦生长过程中,抽穗期0—20 cm土层水分贡献率和灌浆期80—100 cm土层的水分贡献率的提高对于其产量与水分利用效率的提高更为有利。结论]滴灌更利于提供均匀的水分供给作物,同时减少水分无效蒸发,提高作物产量和水分利用率。

Hydrogen and Oxygen Isotope Distribution and Water Use Characteristics of Wheat Under Different Irrigation Methods

Objective]Ascertaining the contribution rate of different irrigation methods to wheat water use and the water absorption law of wheat root system can provide a scientific basis for the rational application of irrigation water. Methods] Based on hydrogen-oxygen stable isotope tracing method, the characteristics of soil water stable isotope change during winter wheat growth under conventional irrigation(X)and drip irrigation(D)(X₁, D₁:15 mm; X₂, D₂:30 mm; X₃ and D₃:45 mm)were studied. Results] The absorption of water deepened with the advancement of the wheat growth period. Soil moisture in 0—20 cm depth was mainly consumed by wheat in the jointing stage under different treatments. In the heading stage, X₂, D₁, and D₂ treatments mainly used soil moisture in 0—20 cm layer, but X₁ treatment mainly used soil moisture in 60—80 cm layer, accounting for 53.9%, and X₃ treatment mainly used soil moisture in 40—60 cm, accounting for 77.0%. D₃ treatment mainly used soil moisture in 0—60 cm layer accounting for 80.0%. In the filling stage, X₁ and X₂ treatments mainly used soil moisture in 0—60 cm, accounting for 86.2%, and 90.6%, respectively, while X₃ treatment mainly used soil moisture in 40—60 cm layer, accounting for 73.9%. However, the water use ratio of different soil layers of D₁ and D₂ treatments were more uniform, ranging between 7.1%～27.8% and 13.0%～38.2%, respectively. The D₃ treatment mainly utilized the water in the 20—40 cm soil layer, accounting for 51.0%. Drip irrigation, except for D₂ and D₃ treatments, could effectively reduce the daily water consumption of wheat. Compared with conventional irrigation, D₂ and D₃ treatments were more beneficial to improve the photosynthetic rate and leaf water use efficiency of wheat. Moreover, drip irrigation treatment effectively improved the wheat biomass during both the heading and harvest periods. Finally, wheat yield and water use efficiency under the drip irrigation condition increased by 21.6%～28.0% and 24.4%～36.7%, respectively, compared with conventional irrigation conditions, and the D₂ treatment resulted in the highest among different treatments. The related analysis showed that during the growth process of wheat, the increment of water contribution rate of 0—20 cm layer in the heading growth stage and 80～100 cm layer in the filling growth stage was more conducive to improving the yield and water use efficiency. Conclusion] Drip irrigation is more conducive to providing uniform water supply to crops, and reducing ineffective evaporation of water and improving crop yield and water utilization.