The enhanced mineralization of simazine and bentazon in soil after plant uptake

[triazine-ring-¹⁴C] simazine and [benzene-ring-¹⁴C] bentazon were added to the epipedon of a Luvisol from loess with and without maize shoots or roots (2 g/100 g soil) and mineralization proceeded in accordance with the standardized BBA degradation method at 50% of the maximum water holding capacity of the soil and at 22°C. The same degradation study was conducted using maize shoots (simazine) and maize roots (bentazon) which had taken up either ¹⁴C-simazine or ¹⁴C-bentazon from soil application. After 93 days of incubation 6.6% (simazine) or 7.2% (bentazon) of this plant incorporated ¹⁴C was mineralized to ¹⁴CO₂. This was 4–10 times greater than the mineralization of active ingredients applied to the soil and 4–6 times higher when compared to variants which in addition received maize shoots (simazine) or roots (bentazon) as an additional energy source for microbial development. Apparently as a consequence of the more intensified degradation processes, the bound residue fractions were higher by a factor of 2 when the residual radiocarbon reached the soil already incorporated into plant material.