The GEMAS (geochemical mapping of agricultural soil) project collected 2108 Ap horizon soil samples from regularly ploughed fields in 33 European countries, covering 5.6 million km2. The <2 mm fraction of these samples was analysed for 53 elements by ICP-MS and ICP-AES, following a HNO3/HCl/H2O (modified aqua regia) digestion. Results are used here to establish the geochemical background variation and threshold values, derived statistically from the data set, in order to identify unusually high element concentrations for these elements in the Ap samples. Potentially toxic elements (PTEs),

Phosphorus availability is often a limiting factor for crop production around the world. The efficiency of P fertilizers in calcareous soils is limited by reactions that decrease P availability; however, fluid fertilizers have recently been shown, in highly calcareous soils of southern Australia, to be more efficient for crop (wheat [Triticum aestivum L.]) P nutrition than granular products. To elucidate the mechanisms responsible for this differential response, an isotopic dilution technique (E value) coupled with a synchrotron‐based spectroscopic investigation were used to assess the reaction products of a granular (monoammonium phosphate, MAP) and a fluid P (technical‐grade monoammonium phosphate, TG‐MAP) fertilizer in a highly calcareous soil. The isotopic exchangeability of P from the fluid fertilizer, measured with the E‐value technique, was higher than that of the granular product. The spatially resolved spectroscopic investigation, performed using nano x‐ray fluorescence and nano x‐ray absorption near‐edge structure (n‐XANES), showed that P is heterogeneously distributed in soil and that, at least in this highly calcareous soil, it is invariably associated with Ca rather than Fe at the nanoscale. “Bulk” XANES spectroscopy revealed that, in the soil surrounding fertilizer granules, P precipitation in the form of octacalcium phosphate and apatite‐like compounds is the dominant mechanism responsible for decreases in P exchangeability. This process was less prominent when the fluid P fertilizer was applied to the soil.

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Soil‐water properties vary widely with soil composition and texture, but measurements are often time consuming and expensive to determine using traditional laboratory methods. Mid‐infrared (MIR) spectroscopy is sensitive to soil composition, allowing multivariate calibrations to be derived between volumetric soil water retention and MIR spectra. Mid‐infrared partial least squares (PLS) models can be derived from the spectra of soils and reference data, and can be used to predict the water retention solely from the MIR spectra of unknown samples. Regressions between laboratory‐determined volumetric water retentions, θv, at matric suctions from 1 to 1500 kPa and values predicted by MIR PLS analysis are presented for a broad variety of surface soils from southern Australia. Cross‐validation produced coefficient of determination values ranging from 0.67 to 0.87 and standard error of cross‐validation in the range 4.1 to 3.2. Prediction robustness was tested using an independent set of samples for values of θv at field capacity (10‐kPa suction) and permanent wilting point (1500‐kPa suction). The prediction standard error for the test set was higher than for cross‐validation. This was attributed to a mismatch between spectra for the test set and those of the calibration samples, resulting in a reduced ability of the calibration samples to model the test set spectra. The MIR PLS prediction method performed at least as well as some pedotransfer functions and was shown to be a rapid and inexpensive method for the prediction of volumetric soil moisture content for a range of soil types at a range of matric suctions.

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