Impact of Biochar Amendment and Brackish Water Irrigation on Water and Salt Movement in Saline-alkaline Soil

【Objective】 Biochar amendment has been widely used to improve soil quality and remediate soil contamination. The objective of this paper is to elucidate the impact of its combination with brackish water irrigation on water flow and salt transport in saline-alkaline soils in the Yellow River Delta. 【Method】 The experiment was conducted using soil columns. Soil taken from the delta was amended with biochar of wheat or maize straw respectively. There were 10 treatments by applying 10 t/hm2 (X1) and 20 t/hm2 (X2) of wheat biochar (X1), or 10 t/hm2 (Y1) and 20 t/hm2 (Y2) of maize biochar. The control was irrigation with deionized water (CK). The concentration of the brackish water was 3 g/L. In each treatment, we measured the movement of water, salt and soil pH. 【Result】 Amending soil with biochar combined with brackish water irrigation improved soil infiltration capacity and water retention in the soil. The wheat straw biochar worked better in improving infiltration than the maize straw biochar. Biochar amendment combined with brackish water irrigation also facilitated salt leaching, reducing salt content in the soil by 7.3% to 10.44%, compared to the CK. Wheat straw biochar worked better in de-salinizing the soil than maize straw biochar, especially the X1 whose desalination rate was 53.74%. The addition of biochar combined with brackish water irrigation increased soil pH, albeit not significantly, especially the maize straw biochar in X2 which affects soil pH most. 【Conclusion】 Amending the soil with 10 t/hm2 of wheat straw biochar combined with brackish water irrigation was effective to improve the quality of the saline soils in the Yellow River Delta region. Results of this study provide guidance to sustainably utilize brackish water and biochar to improve productivity of the saline-alkaline soils in Yellow River delta and areas with similar conditions.