Effects of Irrigating Biochar- and Pectin-amended Soil with Treated Municipal Wastewater and Swine Wastewater on Soil Salinity and Sodicity

LIU Yuan; CUI Erping; LI Zhongyang; DU Zhenjie; GAO Feng; FAN Xiangyang

doi:10.13522/j.cnki.ggps.2017.0430

Abstract：[Objective]Reusing treated municipal wastewater and livestock-farm wastewater for irrigation can ameliorate the increased water scarcity and curtail their discharge to surface and subsurface watercourse, but inappropriate managements could result in soil salinization and sodification. The purpose of this paper is to experimentally investigate the impact of irrigating biochar- and pectin-amended soils with the aforementioned brackish water on soil qualities.[Method]The experiments were conducted in rhizoboxes and the control was without soil amendment. During the experiment, we measured soil pH, electricity conductivity (EC), concentration of typical ions and other indicators, from which the sodium adsorption ratio (SAR) and the exchange sodium percentage (ESP) were calculated.[Result]Compared with using swine wastewater, irrigation using treated municipal wastewater increased soil pH, EC, salt content, SAR and ESP, thereby risking secondary salinization and sodification; biochar and pectin addition did not have noticeable impact on soil pH. Compared to the control, biochar amendment did not alter the EC and salt content when irrigated with distilled water or treated domestic water, but led to an increase in EC and salt content by 34.9％ and 40.4％, respectively, when irrigated with swine wastewater. Pectin addition did not result in a noticeable change in EC and salt content, but increased the SAR and ESP compared to the control[Conclusion]Amending soil with biochar risked secondary soil salinization when irrigating with swine wastewater, while irrigating pectin-amended soil with treated municipal water or swine wastewater risked soil solidification. Irrigation with the above brackish water to soils amended by biochar or pectin should therefore be used with care.