Chemical herbicides are the most common method of weed control in crops, but they can also negatively affect the host crops, such as wheat (Triticum aestivum L.). The damage caused to the crop plants is often temporary and minor, but sometimes, it can be more substantial, requiring remedial measures. Salicylic acid (SA) is a plant hormone widely used to promote plant growth and to mitigate oxidative stress through its exogenous application. We evaluated the role of exogenously applied SA (as a pre-treatment) in ameliorating the oxidative damage caused by the herbicide mesosulfuron-methyl + iodosulfuron-methyl in wheat plants. The herbicide disrupted the physiological function of plants by affecting several enzymatic antioxidants. The hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents increased at herbicide concentrations higher than 18 g ai ha−1 compared with the untreated control. However, the SA decreased the H2O2 and MDA contents compared with plants that were not treated with SA prior to the herbicide application. The activity of superoxide dismutase (SOD) and polyphenol oxidase (PPO) enzymes increased with increasing rates of the herbicide, as well as over time, regardless of the SA treatment. The activity of catalase (CAT) increased up to the herbicide rate of 18 g ai ha−1 and then decreased at the higher rates, while SA pre-treatment enhanced the CAT activity. The activities of ascorbate peroxidase, peroxidase, and glutathione-S-transferase enzymes generally increased in response to the herbicide application and SA pre-treatment, but fluctuated across different days of sampling following the herbicide application. Herbicide stress also induced high levels of proline production in wheat leaves as compared with the untreated control, while SA pre-treatment decreased the proline contents. Overall, the pre-treatment with different concentrations of SA mitigated the herbicide damage to the physiological functions by regulating the enzymatic antioxidants.

Using adjuvants to optimize and increase the efficacy of herbicides is an acceptable manner to reduce herbicides undesirable impact on the environment in sustainable agriculture. In this study, it was demonstrated that the application of 0.1% of the non-ionic surfactant (NIS, Contact) and 0.5 L ha-1 of a crop oil concentrate (COC, Renol) did not improve the efficacy of rimsulfuron on Amaranthus retroflexus. In contrast, the same treatments enhanced performance and rainfastnes of rimsulfuron in Chenopodium album in pot expriments. Increasing non-ionic surfactant concentration to 1 L ha-1 increased rimsulfuron performance around 11-fold for Amaranthus retroflexus compared to around 3-fold for Chenopodium album. The same treatment, also reduced the rainfastness of rimsulfuron on Amaranthus retroflexus while improving the rainfastness of rimsulfuron on Chenopodium album. Measured ED50 and ED90 values of rimsulfuron indicated that the addition of the 0.2 L ha-1 of NIS improved the recommended (60 g ai. ha-1) and the reduced (30 g ai. ha-1) of rimsulfurom in field. The highest potato yield measured (60 tons per ha) when 60 g ai. ha-1 rimsulfuron was applied at three stages (S1, S4, and S7) without using a NIS; not significant differences were measured when the same dose of rimsulfuron was applied at the three (S1, S4, and S7) and two (S1, S4) stages with NIS.