Effect of wheat straw derived biochar on the bioavailability of Pb, Cd and Cr using maize as test crop oleh Muhammad Irfan, Farooq Ishaq, Dost Muhammad, Muhammad Jamal Khan, Ishaq Ahmad Mian, Khadim Muhammad Dawar, Asim Muhammad, Manzoor Ahmad, Shazma Anwar, Shamsher Ali, Fahim Ullah Khan, Bushra Khan, Hamida Bibi, Abid Kamal, Maria Musarat, Waheed Ullah, Muhammad Saeed