Non-exchangeable NH4-N in the subsoil:Significance for the N nutrition of plants (NitroNex)

该项目研究的是底土中不可交换的NH4-N对植物氮营养的贡献。全文分为两个主要部分：第一部分研究了不同作物条件下中央大田试验（CeFiT）底土中非交换性NH4-N含量及其影响因素。将特别考虑钻探圈，在那里容易矿化的有机物质被转移到更深的土层中，而矿化后形成的NH4+离子可能被特异性地结合在生物孔附近2:1粘土矿物的夹层中。此外，还将注意将转移到底土中的NO3-还原为NH4+，作为NH4+固定的来源。在第二部分中，将量化整个生长季节从地下土壤释放的非交换性NH4-N的量。将特别注意根系对粘土矿物中间层中NH4+离子动员的影响。部分粘土矿物夹层用15NH4+标记。在田间条件下，在中央微观实验（CeMiX）中，以及在特殊容器的模型实验中，允许从离根系一定距离的土壤样本中提取土壤样本，将创建非交换性NH4-N的枯竭曲线。

The project is dealing with the contribution of non-exchangeable NH4-N in the subsoil for the N nutrition of plants. It is divided into two main parts: In part 1 the content of nonexchangeable NH4-N in the subsoil of the Central field experiment (CeFiT) under different crops and influencing factors will be investigated. Special consideration will be given to the drilosphere, where easily mineralizable organic material is translocated into deeper soil layers and NH4+-ions, formed after mineralization may be specifically bound in interlayers of 2:1 clay minerals in the vicinity of biopores. Furthermore attention will be given to the reduction of NO3-, translocated into the subsoil, to NH4+ as a source for NH4+-fixation. In part 2 the amounts of non-exchangeable NH4-N released from subsoils throughout the growing season will be quantified. Special attention will be given to the influence of the root system on the mobilization of NH4+-ions from the interlayers of clay minerals. Partially interlayers of clay minerals will be labelled with 15NH4+. Under field conditions, in the Central microcosm experiment (CeMiX) as well as in model experiments with special containers, that allow to take soil samples from defined distances from the root system, depletion curves of nonexchangeable NH4-N will be created.