Ammonium fixation in selected California decomposed granites
Ammonium fixation in selected California decomposed granites
复制标题
选定的加州风化花岗岩中的铵固定
作者：
D. Rider;Donald G. McGahan;V. Claassen
受干扰，有机质含量低，分解花岗岩（DG）基板上的植被受到植物有效水分和氮含量低的限制。来自美国北方加州的一个DG站点的数据表明，来自肥料或有机物矿化的铵的显著部分被固定到硅酸盐层间位置。为了评估NH 4+固定的更广泛的相关性，对加州其他11种受到严重干扰的DG基质的NH 4+固定能力进行了评估。基质的固定能力差异很大，并随着NH 4+施用量的增加而增加（124- 1，670 kg NH 4 + ha−1）。当用124 kg NH 4 + ha−1修正时，11种基质中的7种固定了14%至78%的添加NH 4+。一个典型的材料的粒度级的分析表明，非常细的砂级具有最高的固定能力和粘土和非常粗的砂具有最低的，在重量的基础上。整体固定能力没有表现出显着的关系，潜在的预测特征，包括提取的K+，NH 4+，或总N水平。三种方法的阳离子交换容量（CEC）的测量进行了测试，其预测NH 4+固定的能力。Ba法使用的指示剂阳离子不受层间固定的影响，因此不是NH 4+固定的可靠指示剂。在DG材料中，NH ~（4+）法与NH ~（4+）固定的关系最密切。NH 4+法和Ba法测得的CEC之间的差异被认为是最能预测NH 4+固定的。
Revegetation on disturbed, low organic matter content, decomposed granite (DG) substrates are limited by low plant-available moisture and nitrogen. Data from a single DG site in northern California, USA, showed that a significant fraction of the ammonium from fertilizers or organic matter mineralization was fixed into silicate interlayer positions. To evaluate the broader relevance of NH4+ fixation, the NH4+ fixation capacities of 11 other drastically disturbed DG substrates throughout California were evaluated. The fixation capacities of the substrates were quite varied and increased as added NH4+ application levels increased (124–1,670 kg NH4+ ha−1). When amended with 124 kg NH4+ ha−1, 7 of the 11 substrates fixed between 14 and 78% of the added NH4+. Analysis of particle size fractions of a typical material indicated that the very fine sand fraction had the highest fixation capacity and the clays and very coarse sands had the lowest, on a gravimetric basis. The overall fixation capacities showed no significant relation to potential predictive characteristics, including extractable K+, NH4+, or total N levels. Three methods of cation exchange capacity (CEC) measurement were tested for their ability to predict NH4+ fixation. The Ba method which utilizes an indicator cation that is not subject to interlayer fixation was not a reliable indicator of NH4+ fixation. The NH4+ method had the strongest relation to NH4+ fixation in the DG materials. The difference between the measured CEC of the NH4+ method and the Ba method was found to be most predictive of NH4+ fixation.