蔗渣生物质炭和DMPP对岩溶区石灰性土壤氮素迁移转化的影响及其环境效应

Calcareous soils developed by carbonate rock with rich calcium and magnesium are characterized by the relatively low available nutrients, water- and fertilizer-retaining capacity but high nitrate production potential in karst region, which can obviously impede soil quality. In this study, we will use sugarcane bagasse-derived biochar as an improvement material for calcareous soil. The field and laboratory experiments will be conducted using In-situ monitoring and 15N trancing technique to investigate the effect of sugarcane bagasse-derived biochar with different application rates and nitrification inhibitor (DMPP) on the temporal and spatial variation in the transportation, transformation and utilization of nitrogen (N) and N loss (i.e., NH3 volatilization, nitrogenous gas emissions, surface runoff and leaching) in “sweet corn-sweet corn-vegetable” cropping system, and to propose the suitable application rate of sugarcane bagasse-derived biochar for crop growth. In addition, we will also determine the rates of N transformation process involved in the production and consumption of inorganic N in calcareous soil to elucidate the underlying mechanisms and influencing factors of N transportation change caused by sugarcane bagasse-derived biochar and DMPP. These results will provide the theory basis for sugarcane bagasse resource utilization, increasing N use efficiency and reducing the negative environmental effect in calcareous soil under agricultural cultivation in karst region.

岩溶区石灰性土壤富钙镁偏碱，导致养分有效性低、保肥和保水性能差、硝态氮产生潜势高等问题，限制着地力水平提高。本项目利用岩溶区甘蔗制糖过程中产生的蔗渣生物质炭改良石灰性土壤，以甜玉米-甜玉米-蔬菜连作系统为背景，通过大田模拟和实验室培养试验，结合原位监测和15N同位素标记技术，研究蔗渣生物炭用量水平和硝化抑制剂(DMPP)对岩溶区石灰性农田土壤质量变化、氮素迁移和利用率的影响；定量土壤氨挥发、氮氧化物气体、地表径流和淋溶等途径的氮损失量；同时测定土壤氮的内在转化过程速率，与氮利用率和各途径损失氮量耦合，阐明蔗渣生物炭和DMPP影响石灰性土壤氮素迁移变化的机制与影响因素；提出适合研究区域作物生长的蔗渣生物炭施用水平。项目结果可为岩溶区蔗渣资源化利用、提高石灰性土壤氮肥利用率和减少负面环境效应提供科学依据。

针对岩溶区石灰土“粘瘦”可能制约土壤无机氮供应能力而导致区域地力低下问题，本项目系统调查了岩溶区农田土壤氮转化过程特点，评估了岩溶区土壤无机氮供应能力及其影响因素，结果发现岩溶区长期农业种植能够显著减低土壤无机氮供应能力，土壤粘重和有机质含量下降是制约土壤无机氮供应的关键因子；蔗渣生物质炭能够显著提高退化农田土壤平均重量直径，改善土壤结构，促进铵态氮周转，并降低硝态氮产生，有利于土壤无机氮的保持，但这种效应对于未退化农田土壤并不明显。蔗渣生物质炭联合DMPP施用显著减少N2O排放（减少65.4%），提高了作物产量（增加4.5%）。本项目研究结果表明，蔗渣生物质炭联合DMPP施用能够促进岩溶区退化石灰土无机氮周转和供应，提高作物氮利用效率且减低负面环境效应。