INTRODUCTION In present era, crop production is negatively affected due to abiotic stresses including heavy metals and salinity (Murtaza et al., 2015; Rizwan et al., 2016a). Soil contamination with cadmium (Cd) has affected the production of good quality food worldwide (Gallego et al., 2012; Rizwan et al., 2012). Crop plants could absorb Cd easily via roots which can translocate to the aerial parts even in plants grown in moderately Cd-contaminated (Rehman et al., 2015; Rizwan et al., 2017). Excess of Cd not only had negative effects on the quality of foods but also reduces the growth and yield of plants through different mechanism such as reduction in nutrient uptake, photosynthesis and overproduction of reactive oxygen species (ROS) (Nagajyoti et al., 2010). Soil salinization is another adverse environmental factor involved in limiting the growth and productivity of crops across the globe (Hussain et al., 2015; Abbasi et al., 2016; Mohamed et al., 2017). Agricultural soils mainly irrigated with wastewater and applied with sewage sludges may simultaneously be contaminated with toxic metals and salinity (Bauddh and Singh 2012; Rehman et al., 2018). Previous studies showed that salinity increased the Cd uptake in plants whereas reduced the plant growth (Shafi et al., 2009; Rady et al., 2016). It was also observed that both Cd toxicity and salinity caused oxidative stress in crops (Abbasi et al., 2016; Zhang et al., 2016; Abbas et al., 2017a). Rice is one of the main cereals and is the staple food for over 50% of the world population (Rizwan et al., 2016b). Available evidences have shown that the rice plant has the ability to accumulate Cd which negatively affects the rice growth and quality (Gao et al., 2016; Rehman et al., 2017). Therefore, minimization of Cd in edible parts of the crops is necessary mainly to reduce its negative effects on humans. Different amendments could be used for the purpose of reducing Cd stress and salinity in crops (Ok et al., 2015; Rizwan et al., 2015). Biochar, a product of organic material under lower O2 environment, as soil amendment has been increasingly used to improve the soil fertility, heavy metal toxicity and salt stress in plants (Akhtar et al., 2015a; Bian et al., 2016; Rizwan et al., 2016c; Abbas et al., 2017a). Biochar could also improve the plant growth by increasing the Pak. J. Agri. Sci., Vol. 56(1), 197-204; 2019 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/19.7546 http://www.pakjas.com.pk RESIDUAL EFFECT OF BIOCHAR ON GROWTH, ANTIOXIDANT DEFENCE AND CADMIUM (Cd) ACCUMULATION IN RICE IN A Cd CONTAMINATED SALINE SOIL Farhan Hafeez 1 , Muhammad Rizwan 2, *, Muhammad Saqib 3 , Tahira Yasmeen 2 , Shafaqat Ali 2 , Tahir Abbas 2 , Muhammad Zia-ur-Rehman 3 and Muhammad Farooq Qayyum 4 1 Department of Environmental Sciences, COMSATS University Islamabad, Abbottabad Campus, Tobe Camp University Road Abbottabad 22060 Pakistan. 2 Department of Environmental Sciences and Engineering, Government College University, Allama Iqbal Road, 38000 Faisalabad, Pakistan. 3 Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan. 4 Department of Soil Sciences, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan. *Corresponding author: mrazi1532@yahoo.com Both salinity and cadmium (Cd) contamination of soils are the most critical issues of global food security. Soil application of biochar could decrease toxic metal and sodium (Na) uptake by plants in the season, but its long-term residual effects on metal uptake in latter crops need evaluation. A pot experiment with rice was conducted under ambient conditions in a Cd- contaminated soil which was used in an earlier experiment on wheat where soil was treated with different rates of biochar (0, 3, and 5% w/w) and irrigated with water having different salinity levels (0, 25, and 50 mM). Further treatments were not applied in the current study. The results revealed that plant growth and photosynthesis reduced while Cd and Na concentrations and oxidative stress were increased in plants under combined Cd and salinity. Biochar application reduced the Cd and Na concentrations and increased the potassium (K) concentrations in plants while diminished the oxidative stress in salt-stressed rice. Biochar positively affected the plant growth and physiology in a soil treated with 0, and 25 mM salt stress. However, plant growth and photosynthesis were reduced with biochar amendments under 50 mM NaCl stress. Soil AB-DTPA extractable Cd was higher in salinized soil without biochar addition, while biochar reduced the Cd extractability. It can be concluded that all biochar amendments had a significant residual effect on decreasing Cd and Na uptake while plant growth was negatively affected at higher biochar and salinity levels. Keywords: Biochar, residual effect, heavy metal stress, salinity, physiology.