Integrated use of sewage sludge and chemical fertilizers enhances growth, biochemical traits and stress tolerance in the rice-wheat cropping system

Sewage sludge (SSL), historically regarded as an environmental challenge, is increasingly recognized as a nutrient-rich organic amendment with considerable potential for sustainable agricultural use. This study evaluated the combined effects of SSL and chemical fertilizers (CF) on the growth, physiological performance and biochemical characteristics of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) cultivated under a rice-wheat cropping system. The experiment, conducted over two consecutive cropping seasons, demonstrated that integrated nutrient management involving SSL and CF significantly improved plant height, tiller number, chlorophyll concentration, protein and starch contents, membrane stability index (MSI) and chlorophyll stability index (CSI). The most pronounced improvements were observed under the treatment comprising 30 t ha-1 SSL in combination with 100 % of the recommended dose of fertilizer (RDF). Furthermore, stress-associated metabolites such as proline, phenolics and malondialdehyde (MDA) were significantly lower under SSL-CF treatments, indicating reduced oxidative and abiotic stress and enhanced physiological resilience. These findings reveal that SSL not only supplies essential nutrients but also enhances physiological efficiency and stress tolerance in cereal crops. Nonetheless, the potential risks associated with heavy metal accumulation underscore the need for systemic monitoring and regulated application strategies. Collectively, the study provides robust evidence that the integration of SSL with CF improves soil fertility, maintains crop productivity and supports environmentally sound nutrient management for long-term agricultural sustainability in intensive cereal-based systems.