两种典型母质水耕人为土时间序列土壤黏粒矿物对铵离子与钾离子的吸附

Increasing ammonium adsorption is one of the effective alternatives in building an available N pool in soils to optimize crop recovery and minimize N losses into the environment. Currently, the effects of potassium on ammonium adsorption have been reported mostly for well-drained soils. Few studies have been made on Hydragric Anthrosols (paddy soils) characterised by long-term rice cultivation and a periodic redox process, and the underlying mechanisms for ammonium exchange are far less understood. Interactions between ammonium and potassium in paddy soils might be more complex than those in upland unflooded soils. This is because the amount of ammonium adsorption generally depends on the characteristics of the clay minerals present and therefore varies case by case. Moreover, the mineralogy changes of Hydragric Anthrosols are not only determined by parent materials, but also associated with fertilization. In order to utilize or make further study based on the current research, two representative Hydragric Anthrosols chronosequences, which were derived from purple sandy shale and Quaternary red clays will be selected to explore the dynamic changes in clay mineralogy during soil evolution and to understand interactions between ammonium and potassium in clay mineral transformation. This information will help establish guides for rational fertilization and increase the absorption and utilization ratio of N in establishing sustainable agricultural systems.

增强土壤对铵离子的吸附是优化土壤氮库、减少氮素流失的有效方法之一。已有关于施钾素对铵吸附的研究主要集中在排水良好的旱地土壤上，较少涉及到具有周期性氧化还原作用的水耕人为土。施钾素对水耕人为土铵吸附的影响可能要比旱地更为复杂，这使得在不同水耕人为土中施钾素对铵吸附的影响可能并不相同。而且已有研究大多缺少黏粒矿物方面的明确证据，也未考虑成土母质与水耕人为土发育的影响。因此研究不同母质水耕人为土时间序列土壤黏粒矿物对铵和钾的吸附与吸附过程中黏粒矿物的变化，不仅可对已有研究结果进行验证和补充，而且有助于系统理解在水耕人为土中施钾素对铵吸附的影响作用。基于此，选择紫色砂页岩和第四纪红黏土两种典型母质上发育的水耕人为土时间序列为研究对象，研究其黏粒矿物对铵和钾的吸附，以期明确成土母质和水耕人为土发育对铵离子和钾离子吸附的影响作用并揭示其黏粒矿物对铵离子和钾离子的吸附机制。

紫色水稻土是我国重要的种稻土壤之一，其肥力管理需要特别重视。近年来，化肥逐渐成为紫色水稻土最主要的肥料输入源。当地农民为了获得粮食高产，通常会根据作物长势加大化肥投入，极易导致施肥过量。提高肥效、保地节肥已成为当地农业可持续发展的重中之重。本研究以紫色水稻土时间序列为研究对象，重点研究紫色水稻土对NH4+和K+的吸附以及土壤的供钾能力与富钾矿物的关系，以期为紫色水稻土的施肥管理提供理论依据。研究结果表明紫色水稻土起源土壤（紫色土）全钾含量相对较高，种稻后黏粒和粉粒都存在一定程度的脱钾，并伴有矿物的显著变化。在黏粒部分，蒙脱石相对积累，而伊利石和绿泥石相对减少。在粉粒部分，石英和斜长石相对积累，而伊利石和钾长石相对减少。淹水稻作能促使紫色水稻土中的矿物钾向缓效钾转化，从而提高矿物钾的有效性。紫色水稻土有丰富的缓效钾和大量的富钾矿物（主要是钾长石和伊利石），缓效钾可以作为紫色水稻土长期稳定的钾素来源。从矿物类型和含量判断，伊利石可能是紫色水稻土缓效钾最主要的来源。淹水稻作可通过影响紫色水稻土的矿物组成和提高有机质（SOM）含量来影响土壤对NH4+和K+的吸附。在各种NH4+浓度范围内，SOM对NH4+的吸附都有明显的促进作用。当铵肥和钾肥混合施用时，低浓度的 K+ 更难被土壤吸附。而且会同时降低土壤对NH4+和K+的吸附，铵肥和钾肥最好分开施用。这为根据紫色水稻土本身的特点和水稻生长习性来设计更合理的施肥配方和施肥管理措施提供了理论依据。尽管如此，上述实验还停留在室内模拟阶段，已有的研究结果能否可用于实际水稻种植仍是当前需要解决的关键问题。这需要大量田间试验来验证。水稻土黏粒矿物变化的周期相对比较长，短期内很难被利用来提高土壤对NH4+的吸附。相比而言，提高有机质含量和改变施肥措施更容易实现。另外，如何有效利用紫色水稻土自身的缓效钾也是目前需要解决的关键问题。