Phytotoxicity of vulpia residues: IV. Dynamics of allelochemicals during decomposition of vulpia residues and their corresponding phytotoxicity

The behavior and dynamics of 20 identified allelochemicals in vulpia residu es were both collectively and individually monitored, and their kinetic phy totoxicity was assessed. The total content of the identified allelochemical s in decaying vulpia residues increased from 0.31 to 1.24 mg/g dry residue over a 21-day decomposition period, while the total phenolic content increa sed from 1.86 to 2.16 mg/g dry residue. This corresponded to a phytotoxicit y increase from 42% to 82% of radical inhibition. Allelochemicals changed i n composition and quantity over the duration of the residue decomposition, Addition of soil to the residues reduced the total allelochemical contents extracted and altered the dynamic pattern. In the same period, the total co ntent of allelochemicals declined from 0.061 to 0.046 mg/g residue + soil, with the total phenolics reduced from 0.20 to 0.11 mg/g residue + soil, cor responding to a radical length increase from 53% to 109% of control. Only 1 4 of the identified allelochemicals were detected in the mix of soil and re sidues, in contrast to 20 present in the residues alone. The implications o f these findings are discussed.