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

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 a ¹³C-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 root-to-root ratio, and also increased soil microbial biomass. Under continuous flooding conditions, fluxes of ¹³CO₂ and ¹³CH₄ increased with rice growth from 10.2 μg·(kg·h)^-1 and 2.8 μg·(kg·h)^-1 (63 d) to 16.0 μg·(kg·h)^-1 and 3.2 μg·(kg·h)^-1 (75 d), respectively. During the 12-day drying process, the emissions of ¹³CO₂ and ¹³CH₄ derived from rhizosphere deposited C decreased by 57.5% and 88.1%. Under continuous flooding conditions, the RPE for CO₂ and 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 0.29 mg·(kg·h)^-1 and 12.3 μg·(kg·h)^-1 (63 d) to -0.39 mg·(kg·h)^-1 and 0.07 μg·(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.