Use of either pumice or willow-based biochar amendments to decrease soil salinity under arid conditions

In order to alleviate salt- and water-stress in plants, innovative and economically-feasible techniques are needed. In this study, pumice and biochar (made from willow at 350 degrees C) of different particle sizes (1.5-, 3-, and 6-cm (sic)) were separately added at different rates (3, 6, and 12%, v/v basis) to a sandy soil and their effects on soil salinity and water retention were evaluated over time. Soils were drip irrigated with an artificial saline water under non-draining conditions. Pebbles applied at identical rates and sizes as pumice and biochar, were used as positive controls, whereas no amendment was the negative control. Treatments underwent 10 wetting and drying cycles at 35 degrees C at the end of which, the residual sandy soil (RS) was separated from the amendments. The electrical conductivity (EC) of RS followed the order pumice < biochar < positive control = negative control, with differences being significant at P < 0.05. The smallest EC and sodium adsorption ratio (SAR) values of the RS were achieved when applying 12% pumice, regardless of the particle size; the opposite pattern (12% > 6% > 3%) was observed in the pumice when analysed separately from RS. Pumice and biochar treatments also retained more water in the soil after each drying cycle (significant at P < 0.05). At the end of the experiment, the EC values of the leachates indicated that salts retained in pumice were more slowly mobilised than those in the biochar. The application of either pumice or biochar (made from willow at 350 degrees C) can contribute to decrease soil salinity, but pumice could additionally serve as a tool to remove salts from salt-affected soils. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Innovative and economically-feasible techniques are needed to alleviate salt- and water-stress in plants. The study found that adding pumice and biochar can improve soil salinity and water retention, with pumice performing better in reducing soil salinity and biochar better in water retention.