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17 Pags.- 2 Tabls. 2 Supp. files. The definitive version, with Figs., is available at: https://onlinelibrary.wiley.com/journal/1099145x, In the early 20th century, when extensive areas of land were transformed from rainfed to irrigated agriculture, there was a severe lack of scientific and technical literature available on the effects of applying water to saline soils. This was the case of the Violada Irrigation District located in a semiarid region of NE Spain whose transformation started in the 1940s. We discuss the use of agronomical expertise and the limited knowledge of soils available prior to the transformation, the favorable and unfavorable scenarios encountered during the transformation, and the final success of irrigation despite the initial soil salinization and water logging. We attribute the technical success to the fact that gypsum is common in the soils and geological materials, and to the continued drainage efforts. Failures in the irrigation of saline lands are a frequent subject of discussion in the scientific literature; contrariwise, we present the history of a successfully irrigated district after 70 years., This work was funded by the Spanish Government under the research projects PCIN-2014-106 and CGL-2015-71360-P.

Summary Arid soil is common worldwide and has unique properties that often limit agronomic productivity, specifically, salinity expressed as soluble salts and large amounts of calcium carbonate and gypsum. Currently, the most common methods for evaluating these properties in soil are laboratory-based techniques such as titration, gasometry and electrical conductivity. In this research, we used two proximal sensors (portable X-ray fluorescence (PXRF) and visible near-infrared diffuse reflectance spectroscopy (Vis–NIR DRS)) to scan a diverse set (n = 116) of samples from arid soil in Spain. Then, samples were processed by standard laboratory procedures and the two datasets were compared with advanced statistical techniques. The latter included penalized spline regression (PSR), support vector regression (SVR) and random forest (RF) analysis, which were applied to Vis–NIR DRS data, PXRF data and PXRF and Vis–NIR DRS data, respectively. Independent validation (30% of the data) of the calibration equations showed that PSR + RF predicted gypsum with a ratio of performance to interquartile distance (RPIQ) of 5.90 and residual prediction deviation (RPD) of 4.60, electrical conductivity (1:5 soil : water) with RPIQ of 3.14 and RPD of 2.10, Ca content with RPIQ of 2.92 and RPD of 2.07 and calcium carbonate equivalent with RPIQ of 2.13 and RPD of 1.74. The combined PXRF and Vis–NIR DRS approach was superior to those that use data from a single proximal sensor, enabling the prediction of several properties from two simple, rapid, non-destructive scans.

7 Pags., 6 Figs., 4 Tabls., Soil scientists have long struggled with an effective method for quantifying gypsum content in soils. Several methods exist, but each is fraught with problems. Recent enhancements to portable X-ray fluorescence (PXRF) spectrometers have provided better detection limits especially for lighter elements such as S, a key component of gypsum. Thus, this research aimed to test the effectiveness of PXRF as a means of directly quantifying gypsum in soils. A total of 102 soil samples containing a wide variety of gypsum (∼2–95%) were subjected to both traditional laboratory analysis (thermogravimetry) and elemental analysis via PXRF. Simple linear regression and multiple linear regression were used to establish the relationship between the two datasets. Log transformation of some datasets was necessary to normalize the data. Using simple linear regression for Ca, laboratory data and PXRF Ca data produced an R2 of 0.8794. Similarly, simple linear regression for laboratory-quantified gypsum vs. PXRF S produced an R2 of 0.9120. Multiple linear regression of laboratory quantified gypsum vs. both PXRF S and Ca produced an R2 of 0.9127. No significant differences were observed between model generation and validation datasets. Overall, PXRF shows great promise for the direct quantification of gypsum in soils., Field and lab works in Spain were funded by the Spanish Government through the project AGL2012-40100. The contract of C. Castañeda is co-funded by ESF.

23 Pags., 3 Tabls., 8 Figs. The definitive version is available at: https://www.soils.org/publications/sssaj, Non-trodden soils free of human and livestock pedestrian activity occur on the floors of hypersaline playa-lakes in the Monegros’ inland wetlands in Spain. A soil surface vesicular crust (herein designed as A1v horizon) organized in decimetric polygonal plates is the main observable feature of these rare soils inhabited by the perennial halophyte shrub Arthrocnemum macrostachyum (Moric.) Moris (A.m.). The vesicular organization of the A1v, together with its discontinuity with the soil underneath, suggests the existence of two contrasting soil microenvironments. Thirty-three sites of seven wetlands inhabited by A.m. were sampled: the A horizon from 0 to 15 cm, that is, including A1v; and separately the A1v and the underneath A2 horizon up to 15-cm depth. Measurements included Munsell color, moisture, and salinity at different soil/water ratios, during both the dry and wet seasons along with determinations of gypsum content, calcium carbonate equivalent, and organic matter. Evidence of the mulching effect of A1v and its contrasting conditions against the underlying A2 is supported by the significant differences in 1:5 soil/water extracts electrical conductivity, with a July mean EC1:5 of 22.3 dS m−1 in A1v vs. 14.0 dS m−1 in A2, and by similar significant differences in all major ions, except Ca. In July, total dryness (0%) can be achieved by A1v whereas A2 retained some moisture (5% minimum). Significant moisture differences were found for A1v and A2 in December together with a homogenizing effect. These are significant traits to be considered both in halophyte germination and establishment studies, and in ecological and restoration plans., The first author was granted by INIA (Spanish Government). The article is a result of the Spanish projects AGL2009-08931, 2012GALC036, and PI200840I246.

37 Pags., 3 Tabls., 7 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145X