外来入侵植物黄顶菊残体的恢复再生能力和在土壤中的分解特性

在华北平原, 外来入侵植物黄顶菊[Flaveria bidents (L.) Kuntze]是一种农田和生态环境中的恶性杂草, 使用除草剂清除势必威胁到农业生产尤其是蔬菜生产的安全性。本课题研究了黄顶菊的不同部位离体茎段和残留部分的恢复再生能力; 并采用土壤培养试验, 研究了含氮量为12.2 g·kg^-1的黄顶菊烘干残体和含氮量为23.3 g·kg^-1的白三叶草残体在土壤中的分解过程及矿质氮的供应能力, 探讨人工拨除的黄顶菊作为绿肥的可能性。试验表明, 黄顶菊不同部位离体茎段的再生能力达10%~80%, 不同大小的残留部分再生能力达70%~100%。因而人工除草后必须将拔除的黄项菊残体带出田间以防其再生。在整个60 d的土壤培养期间, 黄顶菊和白三叶草残体均表现为施入土壤的前10 d内表观CO₂-C日释放量最大, 以后趋于平稳; 但黄顶菊残体处理土壤的CO₂-C日释放量一直低于白三叶草。黄顶菊残体处理的土壤微生物量氮高于白三叶草残体处理及土壤对照; 微生物量碳则为黄顶菊残体处理低于白三叶草残体处理, 且与土壤对照相近。在培养的前20 d, 黄顶菊残体分解过程中显著固定了土壤矿质氮素, 培养40 d后的表现为矿质氮释放。黄顶菊残体具有提高土壤氮素营养和微生物量, 增肥土壤的作用, 人工拨除的黄顶菊经灭活处理后可以作为绿肥施入田间。

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.