水分管理对水稻生长与根际激发效应的影响特征

Effect of Water Management on Rice Growth and Rhizosphere Priming Effect in Paddy Soils

作物根际沉积碳输入而引起的根际激发效应,对农田土壤碳排放通量和碳平衡起到关键的调控作用.在稻田生态系统中,由于频繁的干湿交替,土壤CO2和CH4排放以及根际激发效应明显有别于其他自然生态系统.因此,明确稻田生态系统干湿交替过程中水稻根际激发效应的方向与强度,对于减缓稻田温室气体排放具有重要意义.本研究采用^(13)C-CO2连续标记法,结合盆栽试验,研究干湿交替和持续淹水条件下,水稻生长以及根际激发效应的响应特征.结果表明,相对于持续淹水处理,干湿交替处理使水稻地上部和根系生物量以及根冠比显著提高,并增加了土壤微生物生物量.持续淹水条件下,13CO2和13CH4排放通量随水稻生长由10.2μg·(kg·h)^(-1)和2.8μg·(kg·h)^(-1)(63 d)增加到16.0μg·(kg·h)^(-1)和3.2μg·(kg·h)^(-1)(75d).而在干湿交替条件下,经过12 d的落干处理13CO2和13CH4排放通量分别降低了57.5%和88.1%.持续淹水条件下,CO2和CH4的根际激发效应表现为正激发效应,而且随水稻的生长而增加.而干湿交替处理下,经过12 d的落干处理,CO2和CH4的根际激发效应分别由0.29 mg·(kg·h)^(-1)和12.3μg·(kg·h)^(-1)(63 d)降低到-0.39 mg·(kg·h)^(-1)和0.07μg·(kg·h)^(-1)(75d).因此,干湿交替处理,能有效促进水稻生长和降低CH4的累计排放量.合理地田间水分管理对于提高水稻产量和降低温室气体排放具有重要意义.

The rhizosphere priming effect(RPE)caused by carbon inputs from crop rhizodeposits plays a key role in regulating the carbon emission flux and carbon balance of farmland soils.Due to frequent alternations between dry and wet conditions,CO2 and CH4 emissions and the RPE in paddy field ecosystems are significantly different to those of other ecosystems.Therefore,it is of great significance to determine the direction and intensity of the rice RPE under alternations of dry and wet to limit greenhouse gas emissions.In this study,using a13C-CO2 continuous labeling method combined with a pot-based experiment,the response of rice growth and the RPE under alternating dry and wet and continuous flooding conditions was examined.The results showed that,compared with the continuous flooding treatment,the alternating dry and wet treatments significantly increased aboveground and root biomass and the rootto-root ratio,and also increased soil microbial biomass.Under continuous flooding conditions,fluxes of13CO2and13CH4 increased with rice growth from 10.2μg·(kg·h)^(-1)and 2.8μg·(kg·h)^(-1)(63 d)to 16.0μg·(kg·h)^(-1)and 3.2μg·(kg·h)^(-1)(75 d),respectively.During the 12-day drying process,the emissions of ^(13)CO_(2)and^(13)CH_(4)derived from rhizosphere deposited C decreased by57.5%and 88.1%.Under continuous flooding conditions,the RPE for CO2and CH4 were positive and increased with the growth of rice.Under the alternating dry and wet treatment,after 12 days of drying,the RPE for CO2 and CH4 was reduced from 0.29mg·(kg·h)^(-1)and 12.3μg·(kg·h)^(-1)(63 d)to-0.39 mg·(kg·h)^(-1)and 0.07μg·(kg·h)^(-1)(75 d).Thus,alternating wet and dry treatment can effectively promote rice growth and reduce the cumulative emissions of CH4.Therefore,adopting appropriate field water management is of great significance for increasing rice yields and mitigating greenhouse gas emissions.