Mixing superabsorbents, such as cross‐linked polyacrylamides (PAM), with sandy soils may decrease water percolation rates and increase water availability to crops. Four polymers were evaluated for their effects on water retention and hydraulic conductivity (HC) in the presence of either tap or distilled water and within sand mixtures. Water retained by the absorbents alone (at low suction) ranged between 200 and 500 kg kg−1 of polymer; water retained by the polymers when mixed with sand ranged between 40 and 140 kg kg−1 Water retained per kilogram of polymer increased with an increase in polymer concentration in the sand while undergoing desorption, but absorbed water decreased with polymer concentration during sorption, indicating an effect of hysteresis and absorption kinetics in the water absorption process. Applying a hydraulic head of tap water initially caused a decrease in the HC, explained by the decrease in the volume of the soil–absorbents mixtures, followed by a steady increase in HC ascribed to drainage of water from the swollen polymer granules that led to an increase in the size of pores available for water flow. Leaching the soil–absorbent mixtures with distilled water, simulating rainwater, increased the volume of the mixtures (due to polymer swelling) and decreased their HC due to pore blockage by the swollen polymer grains. Better understanding of the interaction among absorbents, soil, and water quality may produce an efficient and economic technology for improving the water management of sandy soils.

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., 2012. Regional spatial pattern of deep soil water content and its influencing factors. Hydrological Sciences Journal, 57 (2), 265-281.Abstract Plant root systems can utilize soil water to depths of 10 m or more. Spatial pattern data of deep soil water content (SWC) at the regional scale are scarce due to the labour and time constraints of field measurements. We measured gravimetric deep SWC (DSWC) at depths of 200, 300, 400, 500, 600, 800 and 1000 cm at 382 sites across the Loess Plateau, China. The coefficient of variation was high for soil water content (SWC) in the horizontal direction (48%), but was relatively small for SWC in the vertical direction (9%). Semivariogram ranges for DSWC at different depths were between 198 and 609 km. Kriged distribution maps indicated that deep soil layers became moister along northwest to southeast transects. Multiple statistical analyses related DSWC to plant characteristics (e.g. plant age explained >21% of the variability), geographical location and altitude (8-13%), soil texture and infiltrability, evaporation zone and eco-hydrological processes (P < 0.05). Regional land management decisions can be based on our DSWC distribution data to determine land uses and plant species appropriate for the soil type and location that would maintain a stable soil water balance. Maintaining infiltrability is of great importance in this and other water-scarce regions of the world.Key words spatial variability; land-use management; geostatistics; multiple linear regression; residual maximum likelihood analysis; Loess Plateau of China Répartition spatiale régionale du contenu en eau des sols profonds et des facteurs qui l'influencent Résumé Les systèmes racinaires des plantes peuvent utiliser l'eau du sol à des profondeurs de 10 m ou plus. Les données de répartition spatiale du contenu en eau des sols profonds (SWC) à l'échelle régionale sont rares en raison des contraintes de main d'oeuvre et de temps des mesures sur le terrain. Nous avons mesuré le contenu en eau du sol (CES) gravimétrique profond (CESP) à des profondeurs de 200, 300, 400, 500, 600, 800 et 1000 cm sur 382 sites à travers le plateau de loess, en Chine. Le coefficient de variation était élevé pour le CES dans le sens horizontal (48%), mais était relativement faible pour le CES dans le sens vertical (9%). Les gammes des semi-variogrammes pour le CESP à différentes profondeurs allaient de 198 à 609 km. Les cartes de répartition krigées ont indiqué que les couches profondes du sol devenaient plus humides le long de transects nord-ouest au sud-est. De multiples analyses statistiques ont relié le CESP aux caractéristiques des plantes (par exemple, l'âge des plantes expliquait plus de 21% de la variabilité), à la localisation géographique et à l'altitude (8-13%), à la texture et l'infiltrabilité du sol, à la zone d'évaporation et aux processus éco-hydrologiques (P < 0,05). Les décisions régionales de gestion foncière peuvent être basées sur nos données de distribution de CESP pour déterminer l'occupation du sol et les espèce...