Technical NoteEffect of gypsum content on soil water retention

- Scarce literature is available about the effects of gypsum on hydric soil behavior.
- We measured the water retention curve (WRC) of soils from gypsiferous lands.
- The measurements (0 to −1500 kPa) were fitted to the unimodal van Genuchten function.
- Gypsum content had specific effects on the WRC shape.
- A threshold of 40% gypsum was detected for the WRC α and n parameters.

SummaryMany gypsiferous soils occur in arid lands, where the water retention capacity of the soil is vital to plant life and crop production. This study investigated the effect of gypsum content on the gravimetric soil water retention curve (WRC). We analyzed calcium carbonate equivalent (CCE), equivalent gypsum content (EG), soil organic carbon content (SOC), and electrical conductivity of 43 samples collected from various horizons in soils in the Ebro Valley, NE Spain. The WRC of the fine earth was determined using the pressure-plate method (pressure heads = 0, −33, −100, −200, −500, and −1500 kPa), and the gravimetric water retention curves were fitted to the unimodal van Genuchten function. Soil gypsum content had a significant effect on water retention. Soils that had high gypsum content made WRC with higher water retention at near saturation conditions, and steeper WRC slopes. The EG threshold at which gypsum content had an effect on WRC was about 40%, and EG was positively and negatively correlated with the α and n parameters of the WRC, respectively.