生物炭和沼液配施底肥对土壤水氮吸附及缓释的影响机理

The study on the influence mechanism of base fertilizer being biochar and biogas slurry combination on water-nitrogen adsorption and slow release in soils is proposed by employing the good absorption characteristics of biochar which is used as the carrier of biogas slurry for the problems such as biogas slurry low in ratio of solid to liquid and high in nitrogen loss because of nitrogen infiltration and volatilization. First of all, the influence of biochar on the water holding capacity of soils will be studied to obtain the key parameters of water holding capacity and the soil-water characteristic curve. What’s more, the adsorption characteristics of ammonia nitrogen and nitrate nitrogen of different concentration in soils and the influence laws of physical- chemical property of soils and main chemical composition of biogas slurry on the nitrogen adsorption under the conditions of biochar and biogas slurry combination will be studied to obtain the adsorption model and the key adsorptive parameters. The influence mechanism of biochar and biogas slurry combination on nitrogen adsorption in soils will be revealed. Finally, the characteristics of ammonia volatilization, water and nitrogen transport and nitrogen conversion and the influence laws of leaching on it under the conditions of biochar and biogas slurry combination will be studied to obtain the slow release model and the key combination parameters. The mutual influence laws of biochar, biogas slurry and soils will be explored by synthesizing physical- chemical property of soils. The influence mechanism of base fertilizer being biochar and biogas slurry combination on water-nitrogen slow release in soils will be revealed. The controllable parameters to realize the efficient use of nitrogen slow release of biogas slurry will be proposed. The nitrogen loss problem of biogas slurry used as fertilizer will be solved. This research can provide basic theory for technology development of biochar and biogas slurry combination.

针对沼液固液比低，农用过程中存在氮素渗滤及挥发损失大等问题，利用生物炭良好的吸附特性，将生物炭作为沼液的载体，提出生物炭和沼液配施底肥对土壤水、氮吸附及缓释的影响机理研究。首先，研究生物炭对土壤持水性能的影响，获得关键持水性参数和土壤水分特征曲线。然后，研究生物炭和沼液配施条件下，土壤对不同浓度的铵态氮、硝态氮的吸附特性及土壤理化性质和沼液中主要化学成分对氮素吸附的影响规律，获得吸附模型和关键吸附性参数，揭示生物炭和沼液配施对土壤氮吸附的影响机理。最后，研究生物炭和沼液配施条件下，土壤氨挥发、水氮迁移、氮转化的特征及淋溶对其的影响规律，获得缓释模型和关键配施参数，综合土壤的理化性质，探明生物炭、沼液和土壤之间的相互影响规律，揭示生物炭和沼液配施底肥对土壤水、氮缓释的影响机理，提出沼液氮素高效缓释利用的可控性参数，解决沼液农用中的氮损失问题，为生物炭和沼液配施技术的发展提供理论基础。

沼液是优质的液体有机肥料，但在施用过程中容易降低土壤粘性，加速氮素向深层土壤的迁移及氨挥发损失。课题组系统研究了生物炭和沼液配施条件下，土壤对水、氮的吸附及缓释机理，完成了任务书的全部研究内容，取得的成果如下：. 1、生物炭和沼液配施对土壤水、氮吸附的影响机理分析。根据生物炭对土壤持水能力及土壤吸附沼液氮素特性的影响规律，分析生物炭和沼液配施对土壤氮素吸附的影响机理。结果表明，生物炭能显著提高土壤的持水能力；生物炭对土壤吸附沼液氮素特性的影响均随着生物炭添加量的增加而增加，随生物炭粒径的减小而增加。. 2、生物炭和沼液配施对土壤氮素缓释的影响机理分析。根据生物炭和沼液配施条件下，土壤氨挥发和水、氮的迁移转化规律，以及淋溶对土壤水、氮分布特征的影响规律，分析生物炭和沼液配施对土壤氮素缓释的影响机理。结果表明，深施沼液和添加生物炭可以有效控制土壤的氨挥发损失，且氨挥发量和氨挥发持续时间均随着沼液施用深度和生物炭添加量的增加而减少。土壤垂直剖面上的氨态氮和硝态氮含量沿着沼液施用点向上向下逐渐降低，沼液施用点处的氮素含量最大，但硝态氮相对于氨态氮下渗的更深；淋溶条件下，生物炭的添加对延缓氨态氮和硝态氮的淋失速度，以及减少氨态氮和硝态氮的淋失量均具有显著的积极作用，10cm的沼液施用深度和10%的生物炭添加量最优。. 3、生物炭对秸秆和沼液同步还田时秸秆腐解特性及土壤氮素分布特征的影响研究。根据生物炭配施条件下，秸秆和沼液同步还田过程中秸秆的腐解特性，探索加快秸秆腐解速度的高效方法。结果表明，生物炭对混施沼液秸秆还田的腐解具有显著的促进作用，且生物炭在一定程度上能够抑制秸秆腐解过程中氮素向硝态氮的转化及向深层土壤的下渗，从而减少了氮素损失。