秸秆生物炭对稻田氨挥发的影响规律与机制研究

Ammonia volatilization from rice fields is an important way that leads to farmland nitrogen loss. Also it is detrimental to atmosphere environment (such as haze), eutrophication of surface water, etc. Hence, it has extremely significance to reduce ammonia volatilization from rice fields. In recent years, biochar was extensively investigated and applied in carbon sequestration and soil improvement, but few study focused on the influences of biochar on ammonia volatilization. The influence patterns and intrinsic mechanisms are unclear. Consequently, it is of great practical and scientific significance to investigate the influences of biochar application on ammonia volatilization from rice fields. .Both indoor culture experiments and pot experiments will be applied in this study. Straw-based biochar that produced under different temperature will be added to rice paddy soil that collected at Taihu Lake area. The patterns of ammonia volatilization will be monitored under different operating conditions. Meanwhile, the intrinsic mechanisms of the influences of biochar addition on ammonia volatilization will be investigated combined with various modern materials and microbiological analysis techniques, which mainly includes the following aspects: 1) the adsorption characteristics of biochar, 2) the influences of biochar on paddy soil properties, nitrification and denitrification, and 3) the influences of biochar on biofilm that exists on soil-water interface of paddy soil system. Based on a series of investigations, the appropriate biochar application amount will be proposed under the ammonia volatilization control–oriented purpose. This study will be helpful to obtain a more general understanding on the ecological environment effects of biochar, and provide theoretical guidance to production practices.

稻田氨挥发是农田氮素损失的重要途径，对大气环境（如雾霾的产生）、水体富营养化等皆有严重影响，减少稻田氨挥发意义重大。近年来生物炭被广泛用于固碳减排、土壤改良等研究和实践，但施加生物炭对稻田氨挥发产生的影响研究甚少，其规律和机制尚不清晰。因此，在规模化使用之前，考察生物炭对稻田氨挥发的影响规律和机制，具有重要的现实和科学意义。.为此，本研究拟分别通过室内培养和盆栽试验，将不同温度下制备的秸秆生物炭施入太湖地区水稻土中，研究不同条件下生物炭施加对稻田氨挥发的影响规律；并从秸秆生物炭本身吸附特性、对稻田土壤理化性质和硝化反硝化特征的影响，及稻田土水界面自然生物膜的影响等多角度入手，结合多种现代材料和微生物分析技术，阐释生物炭施加对稻田氨挥发影响的内在机制，并在此基础上，以氨挥发控制为导向提出生物炭适宜施加量。研究结果将有助于更加全面的理解施加生物炭产生的生态环境效应，为指导生产实践提供理论支持。

氨挥发是稻田最重要的气态氮素损失形式，而生物炭作为一种新兴的固炭减排环境材料近年在农业应用领域得到广泛关注。但是生物炭影响稻田氨挥发的研究尚不充分。基于此，本研究围绕生物炭施加影响稻田氨挥发的排放规律和内在机制进行了探索，以期为实践提供理论支持。主要研究内容和重要结果如下：.1）生物炭的应用没有改变氨挥发通量模式，某些条件下增加了氨挥发累积量，而且生物炭施加量较高时（3wt%）更加显著。氨挥发增排效应主要归因于生物炭添加提高了田面水和表层土壤pH。此外，生物炭降低了硝化速率，导致NH4+-N含量处于较高水平，不利于氨挥发减排。从生物炭事宜施加量角度分析，考虑到氨挥发这一问题，未来将生物炭应用于大田时应选用相对较低添加量（如0.5wt%）。.2）不同生物炭处理及施加方式对稻田田面水氨硝动态及表土氨硝含量会产生影响，进而可能影响氨挥发的排放。结果表明，生物炭不同施加方式均降低了田面水氮素损失风险。其中，田面水NH4+-N的控制效果更为显著，在基肥期效果更佳，且高施加量（3.0%）和高温烧制（700℃）生物炭优于低施加量（0.5%）和较低温（500℃）烧制的生物炭。此外，生物炭表施较混施更能降低田面水氨氮损失风险。这将为氨挥发的调控产生积极影响。.3）控制氨挥发排放需要从更全面的视角进行审视，不应为了减少氨挥发而以牺牲其他优良特性（如温室气体减排）为条件。结果表明，添加生物炭后，两种温室气体排放通量模式均未发生变化。但是累积CH4和N2O排放量会减少。较高施加量和较高温度制备生物炭是温室气体减排的有利因素，但对氨挥发减排有负面作用。因此从总氮减排的角度，需要控制生物炭施加量。.4）不同种类的生物炭对稻田土水界面生物膜和微藻的毒性效应不同。本研究常规热解生物炭对微藻的毒性效应并不突出，且显著低于水热生物炭的藻毒性。因此，常规热解生物炭通过抑制土水界面微藻进而影响光合作用和氨挥发的可能性不大。