长三角设施蔬菜地土壤演变机制与板结复退途径研究

Because human activities are very intensive in greenhouse vegetable cultivated land, researches on soil dynamics in its soils are significantly important for revealing mechanisms of human impacts. Paddy soils with clayey texture are converted to greenhouse vegetable cultivated land in Yangtze River delta to meet the needs of urbanization. However, soil dynamic mechanisms of these greenhouse vegetable cultivated lands are unclear and soil compact degradation of them is serious with no effective restoration measures at present. This program plans to choose the conventional and organic greenhouse vegetable farms with converted from paddy soils for 0, 3, 6, 9, 12 years in Nanjing as research areas and time dynamic scale and to use industrial computed tomography scan imaging technology to characterize the three-dimensional pore structure of the soils. The researches will include (1) to determine the response of soil dynamics to cropping patterns with convention and organic greenhouse vegetable cultivation by means of the greenhouse vegetable cultivated soils with >100 years of cultivations in city of Yixing, Jiangsu Province as the quantitative characterization benchmark of soil compact degradation evaluation, (2) to explore the mechanisms of soil compact degradation in conventional greenhouse vegetable cultivated land through comparing to the changes of soil organic matter content and the dynamics of three-dimensional soil structure between conventional and organic greenhouse vegetable cultivated lands, and (3) to quantify the relations between varying additive amounts of ameliorants such as inorganic porous foaming sand, bamboo charcoal, and humus acid and the efficiency of soil compact restoration in order to identify the optimal restoration approach for compacted soils. The results might reveal the mechanisms for soil compact degradation in conventional greenhouse vegetable cultivated lands and provide feasible restoration approaches.

人为作用强烈的设施蔬菜地，其土壤演变研究对揭示人为作用机理具有重要意义。为满足城镇化发展需求，长三角地区把质地粘重的水稻田改成设施蔬菜地，目前其土壤演变机制不清，土壤板结退化严重，且尚无有效修复措施。本项目以南京常规和有机设施蔬菜基地为研究区，选择水稻田及其转为设施蔬菜地3年、6年、9年和12年的大棚为演变时间序列，利用工业CT扫描成像表征土壤三维孔隙结构技术，首先研究土壤演变对常规和有机设施种植模式的响应，并以宜兴市上百年种植历史的老蔬菜地为基准定量表征土壤板结状况；其次，比对常规与有机设施蔬菜地土壤有机质含量变化和土壤三维结构演变趋势，研究常规设施蔬菜地土壤板结的发生机制；第三，研究无机多孔泡沫砂、竹炭和腐殖酸三种改良剂不同添加量与土壤板结复退效率间的量化关系，明确板结退化土壤最优恢复途径。研究结果可揭示常规设施蔬菜地土壤板结退化机制，并为土壤复退提供切实可行的改良途径。

人为作用强烈的设施蔬菜地，其土壤演变研究对揭示人为作用机理具有重要意义。为满足城镇化发展需求，长三角地区把质地粘重的水稻田改成设施蔬菜地，目前其土壤演变机制不清，土壤板结退化严重，且尚无有效修复措施。本项目以南京常规和有机设施蔬菜基地为研究区，选择水稻田及其转为设施蔬菜地3年、6年、9年和12年的大棚为演变时间序列，利用工业CT扫描成像表征土壤三维孔隙结构技术，首先研究土壤演变对常规和有机设施种植模式的响应，并以宜兴市上百年种植历史的老蔬菜地为基准定量表征土壤板结状况，结果表明，水田改为常规设施蔬菜地后土壤容重增大，土壤CT孔隙度降低，土壤各项异性增加，土壤明显退化，但随着种植年限的延长退化可能会逐渐趋缓，且在有机种植模式下设施蔬菜地土壤结构的退化会受到抑制。其次，比对常规与有机设施蔬菜地土壤有机质含量变化和土壤三维结构演变趋势，研究常规设施蔬菜地土壤板结的发生机制，研究发现，有机质每增加1%，容重下降0.038 g cm3，总孔隙度增加2.45%，CT孔隙度增加1.49%，且由于有机质增加的难度较大，改良效率低；第三，研究无机多孔泡沫砂、竹炭和腐殖酸三种改良剂不同添加量与土壤板结复退效率间的量化关系，结果表明，泡沫砂的改良效果最佳，每施用1%体积比泡沫砂，CT孔隙度增加0.69%。本课题研究结果揭示了常规设施蔬菜地土壤板结退化机制，并为土壤复退提供切实可行的改良途径，为土壤结构改良提供了重要的指导意义和实践应用价值。