Research On Control Technology And Allelopathy Of Miscanthus Floridulus

Miscanthus floridulus is a perennial herbaceous plant of Gramineae, which has strong exclusiveness and usually become monodominant communities in some areas. In recent years, some major fast-growing timber trees, e.g. Cunninghamia lanceolata and Pinus massoniana, using clear-cutting as main harvest method. M. floridulus becomes one of the major malignant weed in forest of southeast China; which seriously influenced seedling’s gownth, and reduced progress of afforestation in difficult site. In order to rapid control M. floridulus, the mechanism of M. floridulus invaded into seedling’s plantation and its control measures were studied. We provided theoretical basis and application of technology for controlling M. floridulus.The control measures, environmental influence and allelopathy of M. floridulus were studied in this paper.(1) Control effect and cost of two control modes were compared in eastern and southwestern Zhejiang, the optimal control mode was selected out: mow and burn M. floridulus, twice applied Glyphosate(9 L·hm-2) with surfactant C12BE(0.14%). The control effect of this mode was higher than CK 35.76%; The cost of this mode was less than other control mode 42.8% and traditional manual control 36.1%. This mode can be widespread applied in M. floridulus intrusion areas.(2) Different physical measures effect on nutrition loss of run-off and soil. There had no siginificant difference on TN and TP of surface soil between burning, mowing and digging roots treatments; burning significantly impacted on the TK, which increased than mowing and digging roots treatments by 56.55% and 43.81%. Burning treatments significant effected runoff loss of TN, TP and TK; the loss content were higher than CK 29.62, 24.7 and 21.35 times. Runoff loss of TN, TP and TK in mowing and digging roots treatments were similar, higher than CK 9.6-11.7 times. Burning has a great influence on soil and run-off nutrition loss,according different site conditions need choose suitable physical measures.(3) The Glyphosate residues in runoff and soil were changed with differet treatments.The Glyphosate residues of treatments 9、18、36 L·hm-2 were 0.032、0.048、0.66 mg·kg-1 in soil after 1 month spray. The residues in soil were completely degraded after 6 months. The Glyphosate residues of treatments 9、18、36 L·hm-2 were 0.21、0.16、1.89 mg·L-1 in runoff after spraying 17 d; The runoff residues on 36 L·hm-2 treatment 2.7 times higher than maximum limit, the residues decreased to 0.037 mg·L-1 after 1 month.(4) The various control measures effect on soil microbe. The amount of 5-15 cm soil bacteria and fungi were dramatically decreased, and 0-5 cm soil actinomycetes were significantly promoted in burning treatments. Glyphosate more significantly effected microorganism on 0-5 cm soil layer than 5-15 cm soil layer. With spraying concentration variation, amount of soil microorganism were not showed regular changing. Glyphosate( 9 L·hm-2) has little influence on soil microbe, can be using widely.(5) Allelopathy effect of M. floridulus.Allelopathy of aqueous extracts from leaves and stems effected on radicle and blade length, blade width, seed germination and fresh biomass of L. sativamuch morethan roots in winter; allelopathy of roots and rhizospheric soil enhanced on grown seasons; the least allelopathy season was summer. The 10% aqueous extracts from leaves significantly decreased radicle length growth of L. sativa. Main allelopathic chemicals which suppressed L. sativa growth were organic acids by isolated and identifiedallelochemicals. Allelopathy index of cradled M. floridulus increased 2-8 times than CK. The relative content of allelochemicals for inhibiting other plants(palmitic acid, linoleic acid, stigmasterol) and allelochemicals for inhibiting natural enemies(trans-aconitic acid) were increased more than other allelochemicals, hence these allelochemicals in leaves of M. floridulus might be dominant factor of inhibiting L. sativa growth. Allelopathy effect was increased by cradled M. floridulus, it was a disadvantage factor for afforestation seedling survival. So should be clear that weeding before afforesting, to ensure the survival rate of afforestation seedlings reach the standard.