Organic Amendments Modulate the Dissipation of Othello and Atlantis Herbicides in Wheat-Growing Soils

The present study investigated the effects of cow manure compost and biochar on the dissipation and half-life of Othello and Atlantis herbicides in wheat cultivation. A greenhouse experiment was conducted as a completely randomized design (CRD) with five treatments and four replications at the Faculty of Agriculture, Lorestan University, during the 2019–2020 crop year. The treatments consisted of a control without any organic amendment (NA), cow manure compost at 25 and 50 g kg−1 soil (CMC1 and CMC2), and cow manure-derived biochar at 25 and 50 g kg−1 soil (CMB1 and CMB2), all tested under the application of Othello and Atlantis herbicides in wheat cultivation. Soil samples were collected at 3, 15, 30, 55, and 110 days after herbicide application. Herbicide residues were determined using high-performance liquid chromatography (HPLC), while soil pH and plant growth parameters were also measured. The results showed that the addition of organic amendments significantly improved the growth and yield components of wheat compared to the control. The application of CMB2 produced the highest plant height at all growth stages. Soil pH gradually decreased over time, with the highest acidification observed in the CMB1 treatment. Herbicide residues decreased over time in all treatments, with biochar treatments showing the lowest residual levels compared to compost and control. The nutrient content (N, P, K, Ca, Mg, Fe, and Zn) of wheat tissues was significantly affected by the organic amendments, with their highest concentrations observed in the CMB2 treatment. Overall, the application of compost and biochar derived from cow manure reduced the persistence of herbicides in the soil and simultaneously improved nutrient uptake and wheat crop growth.