Flaveria bidentis decomposition and residual body regeneration in soils

Flaveria bidentis invasive plant is a malignant weed in cultivated lands and ecotones in the North China Plain (NCP). Herbicides used to eliminate this weed leave chemical residues on vegetables that have human healthy risks. This study investigated regeneration ability of cut/remaining parts of F. bidentis after hand weeding. Soil incubation was conducted to explore the degradation of dry F. bidentis straw containing 12.2 g·kg^-1 of nitrogen and compared with that of Trifolium repens green manure plant containing 23.3 g·kg^-1 of nitrogen. The aim was to learn the possibility of artificially weeded F. bidentis as a green manure. The results showed that regeneration percent of different parts of F. bidentis shoots was 10%~80%, and that of different remaining parts of the weed was 70%~100%. It was therefore recommended to remove F. bidentis residues (including left roots) from the fields. During 60 days of the soil incubation experiment, treatments with both F. bidents and T. repens straws showed the highest apparent daily net CO₂-C release in the first 10 days after incorporation. Thereafter, the apparent daily net CO₂-C release dropped and stabilized. Apparent net CO₂-C release in soils with F. bidentis straw was lower than that in soils with T. repens straw. Microbial biomass nitrogen content of F. bidentis straw treated soil was higher than those of T. repens straw treated and control soils. Also microbial biomass carbon content of F. bidentis straw treated soil was lower than that of T. repens straw treated soil, but similar to that of control soil. Within 20 days of soil incubation, F. bidentis straw exhibited mineral nitrogen fixation and mineral nitrogen re-release after 40 days. In conclusion, F. bidentis enhanced soil nitrogen and microbial biomass, which in turn improved soil fertility. Artificially weeded F. bidentis was usable as a form of green manure after inactivated treatment.