Biochar increased photosynthetic and accessory pigments in tomato (Solanum lycopersicum L.) plants by reducing cadmium concentration under various irrigation waters.

Fresh surface water supplies are gradually becoming insufficient in arid and semi-arid regions of the world. Thus, farmers in these areas are being forced to use poor quality sewage water. Irrigating vegetable crops with sewage water having high metal concentration may affect growth and biochemical processes of plants. Biochar (BC) can sorb these metals and may reduce their toxic effects on plants. Thus, a greenhouse experiment was conducted to study the influence of cotton stalks derived biochar (CSDB) at control (0%) and 1%; ground water (GW; 0.01 ppm Cd); cadmium-contaminated water (CCW; 2 ppm Cd); and sewage water (SW; 0.13 ppm Cd) on growth and biochemical processes of tomato (Solanum lycopersicum) plants. On an average, additions of 1% BC significantly (p ≤ 0.05) enhanced dry weight of roots (36%) and shoots (52%) of plants as compared to without BC application. Biochar (1%) decreased shoot Cd concentration by 33% at SW and 100% at CCW. The Cd uptake was increased by 33% with the BC + CCW treatment. Soil organic matter (SOM) was increased 1.2 times while pH and EC were increased by 5 and 47%, respectively, in 1% BC amended soil. Biochar application alleviated toxic effects of Cd and improved growth as well as productions of photosynthetic and accessory pigments in tomato plants.