Li, F., China Agricultural University, Beijing, China, China Agricultural University, P.O. Box 295, 17 Qinghua Donglu, Beijing 100083, China
Keren, R., Institute of Soil, Water and Environment Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel

Efficient and sustainable reclamation of sodic soils is important to agricultural production. With the help of a peristaltic pump, laboratory-leaching experiments for sodic calcareous soils with exchangeable sodium percentage (ESP) of 1, 12.5, and 19 were conducted under atmospheric CO2 partial pressure to investigate native CaCO3 mineral dissolution and its contribution to the rehabilitation of moderate sodium-affected soils at the water flow velocities of 2 and 18 mm h-1, respectively. The electrical conductivity (EC), pH, and the Ca2+, Mg2+, Na+, K+, Cl-, and HCO3- concentrations in the leachates were measured. The exchangeable Na+ contents in the soils after leaching were measured and their ESPs were calculated. Results indicated that both soil sodicity and water flow velocity significantly affected native CaCO3 dissolution and sodic soil reclamation. Almost all of the Ca2+ to substitute the adsorbed Na+ came from the native CaCO3 dissolution. The CaCO3 dissolution rate decreased logarithmically with leachate volume and increased with the initial ESP level. The leachate EC increased with the initial soil ESP level and decreased with flow velocity. The total detected cation concentrations in the leachates within the first six pore volumes (PV) were greater than 3.0-4.6 mmolc L-1.Low flow velocity was favorable to the improvement of the reclamation rate and reclamation efficiency of sodic soils. After the leaching of six PV, 24.1-36.0% of the Na+ adsorbed in the soils with initial ESPs of 12.5 and 19 were removed. Without the aid of extraneous chemical amendments, the gradual reclamation of moderate sodic calcareous soils under suitable management is possible. Copyright © Taylor & Francis Group, LLC.