水热炭减少稻田氨挥发损失的效果与机制

作为生物质水热碳化的产物,水热炭因其丰富的孔隙结构和官能团等良好的表面特性,在稻田氨(NH_3)挥发减排方面有着良好的应用前景.本研究将水热炭作为一种土壤调理剂施加到稻田土壤中,通过水稻全生育期土柱试验,考察其对稻田氨挥发的影响.试验通过设置3个处理:CKU(不施加水热炭对照)、SHC(锯末水热炭)和W-SHC(水洗锯末水热炭),研究了不同水热炭对田面水pH、田面水NH_4~+-N浓度、氨挥发排放通量和累积量及单位产量氨挥发排放累积量的影响.其中水热炭和水洗水热炭施加量为0. 5%(质量分数).结果表明,SHC处理显著降低了NH_3挥发累积排放量和单位产量NH_3挥发累积排放量(P 0. 05),相比CKU分别减少了32. 42%和47. 61%. W-SHC处理氨挥发减排效果稍弱,NH_3挥发累积排放量和单位产量NH_3挥发累积排放量相比CKU分别减少了10. 14%和27. 71%.氨挥发减排可能与水热炭的施用导致的田面水pH变化和NH_4~+-N浓度的降低有关.与CKU相比,SHC和W-SHC处理均降低了田面水pH和NH_4~+-N浓度,且在水稻基肥期(BF)和蘖肥期(SF1)影响较明显.土壤脲酶活性受到水热炭施加的显著抑制(P 0. 05),同时土壤氨氧化基因(AOA和AOB)丰度也显著增加(P 0. 05),导致土壤氨氧化作用增强,这对于田面水NH_4~+-N浓度有削减作用.本研究将为实现稻田氨挥发减排背景下的水热炭农业环境应用提供理论和数据支持.

Effect of Applying Hydrochar for Reduction of Ammonia Volatilization and Mechanisms in Paddy Soil

Hydrochar, as a product of the hydrothermal carbonization of biomass, has good application prospects for the NH₃ volatilization reduction in rice fields due to its rich pore structure and functional surface. In this study, hydrochar was applied as a soil conditioner to paddy soil. A soil column experiment was conducted to investigate the effect of hydrochar on NH₃ volatilization throughout the growth period of rice. The experiment was conducted with three treatments:CKU (control without hydrochar); SHC (sawdust hydrochar); and W-SHC (water-washed sawdust hydrochar). The application rate of SHC and W-SHC was 0.5% (w/w). The study investigated the effects of different hydrochars on the pH and concentrations of NH₄⁺-N in floodwater, the flux and accumulation of NH₃ volatilization, and the yield-scale cumulative emission of NH₃ volatilization. Results show that the SHC treatment significantly reduces cumulative emissions of NH₃ volatilization and the yield-scale cumulative emissions of NH₃ volatilization (P<0.05), which were 32.42% and 47.61% lower than CKU, respectively. The effect of W-SHC on ammonia volatilization reduction was slightly weaker, as the cumulative emissions of NH₃ volatilization and the yield-scale cumulative emissions of NH₃ volatilization decreased by 10.14% and 27.71%, respectively, compared with CKU. The NH₃ volatilization reduction was possibly related to the disturbance of pH and the decrease in NH₄⁺-N concentrations in the floodwater because of the application of hydrochar. Compared with CKU, both SHC and W-SHC treatments reduced the pH and NH₄⁺-N concentration in the floodwater. The impacts were more obvious in the rice base fertilizer period (BF) and the first supplemental fertilizer period (SF1) than in the second supplemental fertilizer period (SF2). The soil urease activity was significantly inhibited by hydrochar (P<0.05), and the abundance of soil ammonia-oxidizing gene (AOA, AOB) also significantly increased after application of SHC (P<0.05). This resulted in the enhanced efficiency of ammonia-oxidizing, which had an effect on the reduction of the NH₄⁺-N concentrations in the floodwater. This study provides theoretical and experimental data support for the application of hydrochar in agro-environments with regard to ammonia volatilization reduction in paddy fields.