Integrative use of biochar and biostimulants improves cadmium detoxification and yield in cotton

Dealing with abiotic stress is a challenge to maintaining sustainable agricultural productivity, especially for the dual stress of soil salinity and heavy metal contamination. A field experiment was conducted in a completely randomized factorial design to assess the combined effects of biochar (BC), plant growth-promoting microorganisms (PGPM), and seaweed extract (SWE) in mitigating cadmium (Cd) toxicity while promoting cotton growth in saline soils. The study included eight treatments: control (CK), single applications of SWE, PGPM, or BC, dual applications of BC + SWE, BC + PGPM, and PGPM + SWE, and a triple application (BC + PGPM + SWE). Results showed that the BC + PGPM + SWE treatment significantly improved soil quality by reducing the Na and Cd bioavailability by 31 % and 34 %, respectively, while enhancing soil organic matter, microbial biomass carbon, and soil enzymatic activity. Antioxidant defense mechanisms in cotton leaves were significantly induced, as indicated by enhanced activity of SOD, APX, DHAR and GR from 1.8-folds in SOD to 3.4-folds the control in GR. Multivariate analysis revealed that enzymatic and non-enzymatic antioxidants of the ascorbate-glutathione cycle seemed to play a key role in oxidative stress mitigation with maintenance of redox homeostasis and chelation of Cd, resulting in a reduction of 18 % and 56 % in Cd translocation factors from root to shoot, and from shoot to bolls, which contributing to a 65 % increase in cotton seed yield. This study demonstrates an integrative approach to enhancing the resilience of the soil and its productivity, thereby offering a scaling-up, eco-friendly strategy toward sustainable agriculture in degraded and stress-prone ecosystems.