Comparative effects of different types and doses of biochar on soil quality indicators and arugula growth under saline conditions

Population and food demand increased rapidly so to face this increment; we must dramatically increase food crop production to ensure global food security. Hence, saline agriculture is a possible solution for producing food in salt-affected soils using saline water for irrigation. The objectives of this study were to investigate the effects of applying different types and doses of biochar to saline soil under irrigation by saline water on soil quality indicators and growth parameters and yield of arugula plant. Four types of biochar: banana leaves biochar (BLB), rice straw biochar (RSB), sorghum stalks biochar (SSB), and wood chips biochar (WCB) were applied to the soil in the pots at levels of 1%, 3%, and 5% (w/w). This pot experiment was cultivated by arugula under irrigation with saline water (6.2 dS m^{- 1}). Total available nitrogen increased significantly relative to the control treatment (unamended soil) by 41%, 34%, 43%, 34%, 33%, 24%, 41%, and 44% under adding 3%WCB, 5%WCB, 1%BLB, 3%BLB, 5%BLB, 5%SSB, 1%RSB, and 5%RSB treatments, respectively. Results showed significant increases in available potassium (K) over the control treatment by 48%, 125%, 410%, 738%, 137%, 352%, 632%, 158%, 576%, and 849% for 5%WCB, 1%BLB, 3%BLB, 5%BLB, 1%SSB, 3%SSB, 5%SSB, 1%RSB, 3%RSB, and 5%RSB treatments, respectively. Cation exchange capacity increased significantly relative to the control treatment by 26%, 22%, 30%, 58%, 31%, 54%, 28%, and 48% for 3%WCB, 5%WCB, 3%BLB, 5%BLB, 3%SSB, 5%SSB, 3%RSB, and 5%RSB, respectively. Relative to the control treatment, the fresh biomass of the arugula plant significantly improved by 97%, 143%, 76%, 129%, 103%, 146%, 81%, 57%, 121%, and 97% for 3%WCB, 5%WCB, 1%BLB, 3%BLB, 1%SSB, 3%SSB, 5%SSB, 1%RSB, 3%RSB, and 5%RSB, respectively. The highest value of fresh biomass, nitrogen uptake, and phosphorus uptake of arugula plant were observed at 3%SSB applications. According to the results obtained from our study, we recommend adding sorghum stalks biochar at 3% which is a promising approach to rehabilitate saline soil and use saline water for sustainable crop production, this is attributed to the effective improvement of the nutrient uptake, productivity, and growth of arugula plant under saline conditions as it enhances the tolerance of plants under salt stress as well as improved nutrient supply and soil quality. Also, adding 3% sorghum stalks biochar saves the costs of addition and production compared to adding 5% dose. This study also provided useful information about the optimal quantities and types of biochar used to improve the productivity of saline soils.