Assessment of Soil Organic Matter Molecular Characteristics Related to Hydrophysical Properties in Semiarid Soils (Central Spain).

The objective of this study is to analyze soil hydrophysical properties in addition to the molecular composition of the organic matter in semiarid Mediterranean cereal agroecosystems. Aggregate water-stability, total porosity, water holding capacity, andbandcparameters of the Kostiakov's equation for soil infiltration were determined using a double-ring infiltrometer. The soil humic acid (HA) was isolated and characterized mainly by analytical pyrolysis-gas chromatography mass spectrometry. Multivariate data treatments suggested favourable hydrophysical parameters associated to HAs with a substantial aliphatic domain. Soils with HAs consisting of condensed aromatic structures, often considered to correspond to advanced stages of humification and high resilience, do not coincide with those displaying favourable hydrophysical properties. The results discussed in this article provide support for moderate aliphatic hydrophobicity to be considered as a soil organic matter quality parameter positively influencing hydrophysical properties of semiarid soils. [ABSTRACT FROM PUBLISHER]