| Paspalum paspaloides (Michx.) Scribn. is a stolon-oriented breeding perennial weeds with strong adaptability to external environment condition, which does great harm to the rice growth when occurring in paddy. In this paper, in order to control P. paspaloides better in paddy, the effects of application of fertilizer, watering, water layer depth, soil layer on the growth and development of P. paspaloides, and the effects of water loss on single stem node germination and growth were studied, and the effects of water stress and salt stress on internodes germination and seedling growth were researched too. Moreover, the biological activities of nine kinds of herbicides for controlling gramineous weeds and the interaction of the cyhalofop-butyl mixed with fenoxaprop-P-ethyl to P. paspaloides were mesured. The chemical controlling tests above mentioned herbicides were conducted. The results are as follows:The experiments of the effects of fertilizer and/or watering on the growth and development of P. paspaloides showed that, it growed quickly, and the branche number and the total number of stem, length of stems and fresh weight were the biggest in treatment of both adequate water and fertilizer. The results of the water layer and soil layer depth showed that, the germination rate of the stem node was 100% in combination of soil depth 0 cm and water depth 0 cm(0 cm+0 cm treatment) after culture 30 days, the germination rate was 0% while 5 cm+5 cm treatment, the stem length was the longest and the fresh weight was the biggest in 0 cm+2 cm treatment in this trial. Water loss tests showed that single node stem section was dried in 40℃ for 10 minutes to 6 hours, the single internodes were completely lost germination ability. The node germination rates were less than 10% when stolons were dried in 40℃ for more than 2 hours. The internodes germination rate was only 3.3% when stolons were exposured to sunlight for 6 hours. In the experiments of water and salt stress, the internodes germination rate was below 35% in the water stress less than-0.5 MPa. The internodes could germinate at 0 g/L-20 g/L of salt concentration. The salt concentration greatly affected the seedlings height. The seedlings height of 1 g/L salt concentration were significantly lower than that of check treatment. While the salt concentration had little influence on root length and no significant difference between root length. Plant height of seedling and root length were decreased with the increase of value of water potential, when water potential value was -0.1 MPa, the seedlings height was 25.3 cm, which significantly lower than check treatment seedlings height,33.9 cm.In the bioassay tests including 11 foliage-treatment herbicides for controlling gramineous weeds, the results showed that the ED90 (dose for 90% efficacy of stem fresh weight) according to the order from high to low were clclethodim, quizalofop-p-ethyl and haloxyfop-P> pinoxaden >cyhalofop-butyl>clodinafop-propargyl>fenoxaprop-P-ethyl>metamifop>bispyribac-sodium >penoxsulam>pyribenzoxim.The combined action of mixing cyhalofop-butyl with pyribenzoxim to P. paspaloides was additive and synergistic effect. In herbicides control tests, the results indicated that the efficacies reached to 100% in 25℃ by foliage-treatment of cyhalofop-butyl with a dose of 120 and of 180 g a.i./hm2, metamifop with a dose of 120 and of 180 g a.i./hm2, bispyribac-sodium mixed with cyhalofop-butyl 30+60 g a.i./hm2, cyhalofop-butyl mixed with pyribenzoxim 75+18.75 g a.i./hm2, cyhalofop-butyl mixed with penoxsulam 75+15 g a.i./hm2. The efficacies of freesh weight were reached 95.45%,83.52% respectively in pot by cyhalofop-butyl 120 g a.i./hm2 and bispyribac-sodium mixed with cyhalofop-butyl 22.5+60 g a.i./hm2.The efficacyies were 95.37%,100%,100%,97.43%,97.64% respectively in barrel by bispyribac-sodium with a dose of 60 ga.i./hm2, cyhalofop-butyl with a dose of 120 and of 180 g a.i./hm2, metamifop with a dose of 120 and of 180 g a.i./hm2 at 45 days after treatment. They were significantly better than that of pyribenzoxim and penoxsulam. The efficacies were 100% at 45 days after treatment by 5 herbicides unregistered in paddy such as clclethodim, quizalofop-p-ethyl, haloxyfop-P, pinoxaden and clodinafop-propargyl. Simultaneously, these five herbicides were unsafe for rice and caused rice seedlings death. The efficacies against P. paspaloides and the safety to rice seedlings were similar by bispyribac-sodium mixed with cyhalofop-butyl 30+120 g a.i./hm2, fenoxaprop-P-ethyl mixed with cyhalofop-butyl 25.875+60 g a.i./hm2, clodinafop-propargyl mixed with cyhalofop-butyl 18+60 g a.i./hm2, clclethodim mixed with cyhalofop-butyl 45+60 g a.i./hm2, quizalofop-p-ethyl mixed with cyhalofop-butyl 15+60 g a.i./hm2 and pinoxaden mixed with cyhalofop-butyl 7.5+60 g a.i./hm2. The total percentage of stem control effect were 86.3%-87.3% and 90.6%-91.5% in fresh weight of fenoxaprop-P-ethyl against P. paspaloides. The phytotoxicity of rice treated by fenoxaprop-P-ethyl, fenoxaprop-P-ethyl mixed with cyhalofop-butyl appeared albinism symptom on central leaves of rice at 15 days after application, then the symptoms recovered after treatment 25 days. The seedling height, tillers and yield treated by fenoxaprop-P-ethyl alone or mixting were no significantely different compared to check treatment. |
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