To generalize data it is recommended to use more than one biochar type, differing for their properties. Even biochars prepared from the same material at different temperatures
@ Saba, I think wheat straw biochar is the best for saline-alkali soils as I have seen they are working well under coastal saline-alkali soils in India.
Biochars of most plant materials are naturally alkaline because of the excess of permanent cations. Straw or wood char typically have low base contents otherwise Adil is correct about acid modification.
If you use acidified Hydrochar instead of biochar it will work very well you can make it from wheat straw, rice husk or maize stover. The reason that i want to suggest you that Hydrochar has more carbon sequestration, organic matter, soil organic carbon and also some nitrogen as compared to biochar and i did experiment on Hydrochar and Farmyard Manure in my Masters.