Phytotoxicity of MBOA on Tested Plants and the Changes in Its Concentration in Soil

Abstract

This study of phytotoxicity of MBOA (6 methoxy-2benzoxazolinone) on some tested plants and the changes in its concentration in soil, was carried out in the laboratory of Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Sean campus, Nakhon Pathom province and Institute of Life and Environmental Sciences, University of Tsukuba, Japan during January, 2007- September, 2008. The efficacy of various concentrations of MBOA by plant bioassay in Bidens pilosa, Ageratum conyzoides and Oryza sativa cv. RD 6 were evaluated. The results showed that MBOA at 1 mM ingibited the growth of all tested plants especially in root length. The phytotoxicity of various concentrations of MBOA in the soil was determined using plant bioassay in Oryza sativacv. Nipponbare. The results indicated that the phytotoxicity of MBOA was the highest in sea sand, followed by Ryugasaki and Tennodai soil, respectively. Inaddition, the changes in its concentration of MBOA in the soil was investigated at 0, 1, 2, and 3 days after application. By centrifugation method using double tubes, the soil water was separated from the applied-soil were measured by high performance liquid chromatography (HPLC). The results indicated that MBOA concentration in the soil water in Ryugasaki soil was higher than Tennodai soil. However, the amount of MBOA adsorbed in Tennodai soil was higher than that of Ryugasaki soil. It was closely related with the different phytotoxicity of MBOA Ryugasaki soil and Tennodai soil. These results indicated that MBOA activity in the soil ws induced substantially by its concentration in plant available soil water which was primarily determined by its adsorption in soil, mostly in soil organic matter.