我国典型红壤潜在酸化的过程及机制

Acidification in the upland of red soil in southern China is occurring extensively and significantly in recent 30 years, and it has threatened national food security and sustainable development of agriculture. The decrease in soil pH is often used as an indicator to assess the extent of acidification. However, in a long-term fertilization experiment in the typical red soil in Hunan province, our previous study showed that soil pH decreased rapidly after applying N fertilizer in the first ten years, but remained stable at pH 4.2 in the following years. Protons are accumulated in soils during the acidification process without pH drop, it was referred as soil potential acidification, but little is known about its processes and mechanisms. To advance our understanding of soil potential acidification, I propose to use soil samples after 0, 5, 10, 15, 20, 25, 30 years of fertilization in long-term experiment for potentiometric titration and determination of soil chemical indicators and principal component analysis and so on, in order to analyze the three key processes of kaolinite weathering and protonation of iron and aluminum oxides and dissolution of iron and aluminum oxides, to quantify the change of red soil acidification and potential acidification in particular, and to illuminate its dominant factors at different stages. The research will deepen our understanding of the processes and mechanisms of red soil acidification in China, and provide theoretical support for the scientific evaluation of red soil acidification and the remediation of acidified soil.

近30年来我国南方红壤旱地大面积快速酸化，严重威胁国家粮食安全和农业可持续发展。酸化表征最常用的指标是土壤pH的下降程度。但是，申请者课题组在湖南典型红壤上的长期施肥试验检测结果表明，施用化学氮肥的土壤pH在前10年迅速下降，之后基本稳定在4.2左右。这种pH没有明显下降但土壤中有质子累积的酸化（本文称其为潜在酸化），其过程与机制人们尚不清楚。针对这一科学问题，本项目通过采集该长期试验的历史及项目期间的土壤样品，形成红壤施肥0、5、10、15、20、25、30年的时间序列，采用电位滴定、土壤化学指标测定和主成分分析等方法，解析红壤酸化过程中矿物高岭石风化、铁铝氧化物质子化、铁铝氧化物溶解等三个关键过程的相对贡献大小，定量红壤酸化特别是潜在酸化变化的趋势，阐明酸化不同阶段的主导因素。研究结果将丰富我国红壤酸化的基础理论，为红壤酸化的科学评估及酸化土壤的改良提供理论依据。

近30年来我国南方红壤旱地大面积快速酸化，严重威胁国家粮食安全和农业可持续发.展。本项目通过采集该长期试验的土壤样品和收集文献资料，采用土壤样品检测分析和数据分析等方法，解析红壤酸化过程中关键过程的相对贡献大小，定量红壤酸化特别是酸化变化的趋势，阐明酸化不同阶段的主导因素。研究结果将丰富我国红壤酸化的基础.理论，为红壤酸化的科学评估及酸化土壤的改良提供理论依据。.