Rehabilitation of a highly saline-sodic soil using a rubble barrier and organic amendments

The application of biochar and compost is a promising alternative to recover salt-degraded soils. However, in areas where the main source of salinity comes from the groundwater, it is also necessary to restrict the capillary rise of salts by means of a barrier. In this study, we show results of a field experiment, in which we tested the effect of a rubble barrier and the addition of biochar and compost on the establishment of a salt-tolerant grass (Distichlis spicata) in a highly saline-sodic soil. Our results showed that the capillary barrier: i) diminished the electrical conductivity and the CO2 fluxes by about one third to one half the values without barrier for both variables, ii) decreased the topsoil moisture (without barrier ca. 25-35%; barrier-zone ca. 15-25%), and iii) promoted the plant growth. Organic amendments did not show any effect. However, high-dose treatments had lower moisture content than the unamended ones (ca. 3-6% less water). Arrival of new plant species occurred preferably in the barrier-zone. We conclude that the barrier is an effective tool to decrease the soil salinity, but irrigation is needed to overcome smaller soil moisture during the dry season. Pyrochar was the most re-commendable amendment to be used. However, biochar and compost doses were insufficient for the rehabilitation of this highly saline-sodic soil. The natural emergence of plant species (Suaeda torreyana, Kochia scoparia and Sonchus oleraceus) can improve the rehabilitation activities in an effective and inexpensive way. Urban residues can effectively be used to establish a plant cover in saline-sodic soils.