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Soil phosphorus dynamics along a loess–limestone transect in Mihla, Thuringia (Germany)

Weihrauch, Christoph, Opp, Christian
Zeitschrift für Pflanzenernährung und Bodenkunde 2017 v.180 no.6 pp. 768-778
agricultural land, aqua regia, hydrochloric acid, landscapes, phosphorus, soil horizons, soil profiles, soil sampling, solubility, Germany
The distribution of phosphorus (P) along a loess–limestone soil transect were investigated to delineate the spatial variation of the nutrient vertically in the soil profiles and laterally in the landscape. We hypothesized that spatial P patterns result from translocation caused by P mobilization, although P fixation would be expected along the slope. To depict this, three P fractions clearly differing in solubility were determined. Soil samples were treated with 0.1 M hydrochloric acid (HCl), with 12.1 M HCl, and with aqua regia (AR). In the profiles the spatial P distribution slightly corresponds to the occurrence of different bedrocks and substrata. Thus, a native “P loading” might not primarily explain the spatial P patterns. Especially the strong enrichment of the toeslope with easily soluble P indicates P translocation and prior mobilization. The enrichment is detectable throughout the profiles. Thus, superficial translocation (e.g., erosion) cannot sufficiently explain that pattern. Instead, underground processes must be the cause for this. They cause relatively high vertical and lateral variation in the spatial P distribution, e.g., within soil horizons and substratum layers. Hence, mixed sampling of soil sections might not produce data accurate enough for some kinds of P research and for P management. Also, the lateral P distribution should be detected more precisely prior to fertilization of agricultural land.