Movement of allelopathic compound coumarin from plant residue of sweet vernalgrass ( Anthoxanthum odoratum L.) to soil

This study investigated the movement of coumarin, an allelopathic compound, from the plant residue of sweet vernalgrass ( Anthoxanthum odoratum L.) to soil, as well as the dynamics of coumarin in soil. The level of coumarin dissolved from sweet vernalgrass plant residue in both Andosols and Cambisols, which were watered every day, peaked on the fifth day after the beginning of watering, and fell gradually thereafter. Specifically, the coumarin content in Cambisols on the fifth day was 14.2 p.p.m., which is four times the coumarin level found in Andosols. The recovery percentage of coumarin extracted with MeOH from the soil‐treated coumarin water solution was approximately 70% in Cambisols and 35% in Andosols. As the days continued, the recovery rate of coumarin tended to decrease, but not in the disinfected soils. The recovery rate of coumarin in Andosols at temperatures of 25°C and 15°C rapidly decreased on the sixth and 10th days, respectively. These results indicate that the coumarin of sweet vernalgrass plant residue will move into soil easily after rainfall, and that both soil type and the presence of microorganisms are related to the disappearance of coumarin in soil.