Fenoxaprop-P-ethyl, a phenoxy herbicide of the aryloxy–phenoxy–propionic acid group, had a strong control effect when applied POST to weedy rice in this study, with the effective concentrations of 294 μM and 218 μM of herbicide causing 50% inhibition (IC50) in plant height and fresh weight values, respectively. However, fenoxaprop-P-ethyl caused phytotoxicity in cultivated rice. Isoxadifen-ethyl, a widely used herbicide safener in rice, can decrease the phytotoxicity caused by fenoxaprop-P-ethyl. Owing to the extremely similar morphological features and physiological properties of weedy and cultivated rice, it is not practical to spray isoxadifen-ethyl directly on cultivated rice plants to safen them. Applying the safener directly to cultivated rice seeds may be a practical alternative method. To improve the biological activity of isoxadifen-ethyl seed treatments, novel compounds were designed by splicing other groups, including amines, amino acids, and 2- methoxy-5-nitrophenol sodium salt, to the parental structure of isoxadifen-ethyl. Through hydrolysis, acyl chlorination, acyl amination, and esterification, a series of isoxadifen-ethyl derivatives were synthesized and their structures were determined by mass spectrometry and 1H nuclear magnetic resonance spectroscopy. The biological activities of five of the isoxadifen-ethyl derivatives, which possessed recovery effects similar to isoxadifen-ethyl, were able to relieve herbicide phytotoxicity. In pot experiments, isoxadifen-ethyl showed almost no activity as a seed treatment, while three derivative compounds, when used independently as seed treatments, were able to prevent the damage caused by fenoxaprop-P-ethyl. The results will help to develop a new control method for weedy rice, thereby decreasing production costs and increasing farmers’ incomes.

Imazapic is widely used in peanut production, and its residues can cause damage to succeeding crops planted in the following year. The planting area of peanut is large in Henan province. Inceptisol is the main soil type in Henan Province and was used in laboratory experiments that were conducted to investigate imazapic degradation in soil under various environmental conditions. The results indicated that the imazapic degradation rate increased with an increase in temperature, soil pH, and soil moisture, and decreased with organic matter content. The use of biogas slurry as a soil amendment accelerated imazapic degradation. The half-life of imazapic in sterilized soil (364.7 d) was longer than in unsterilized soil (138.6 d), which suggested that there was a significant microbial contribution to imazapic degradation. Imazapic adsorption was also examined and was found to be well described by the Freundlich isotherm. The results indicate that soil has a certain adsorption capacity for imazapic.

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