| During the Dec. 2005 to July 2007, an experiment was conducted to investigate distribution of the field weeds and their control in Quzhou citrus orchard, which represents the typical condition of soil fertility, topography, geomorphology and climate in Southwest of Zhejiang province. The main results are as the follows:In the investigated area, there were 80 species of weeds, belonging to 27 families respectively, among which the Gramineae had the biggest population containing 20 species, occupying 25% of the total weeds. Following was the Asteraceae, 11 species, occupying 13.7% of the total weeds. The most densely growing weed was Kentucky bluegrass, with the density of 302s/m~2. The frequency of weeds almost reached 100% were crabgrass, little fleabane, copperleaf and drought water grass. The dominant species in spring and winter were Kentucky bluegrass, bedstraw- bovine-Chickweed. The dominant ones in summer and autumn were crabgrass, copperleaf, goose grass, little fleabane and E. hispidula.There were 71 species in the differently managed citrus orchard (H, M and L; high, medium and low levels of management), classified into 26 families. Gramineae were 17 species and occupied 23.9% of the total weeds. Compositae were 11 species and occupied 15.5% of them. There were 26 species in H orchard, 52 species in M orchard, and 67 species in L orchard. The dominant species in L orchard were more complex than H orchard and M orchard. The density was analyzed by SPSS10.0 through comparison between H and L orchards, H and M orchards. The density showed significant difference. The height of the weeds was also compared among the H, M and L orchards, and the height of little fleabane, copperleaf, drought water grass and praticola ohwi showed great differences.Under the same concentration, with the comparison of 7d and 15d, 7d and 30d, applying 60 and 20ml/667m~2 of Hydrolysis Bispyribac-sodium showed significant difference in the preventing effect. With different concentrations, the preventing effect to copperleaf, green bristle grass, little fleabane, Malachium aquaticum was significantly different. The experiment of the preventive effect of Glyphosate with the concentration of 200, 300 and 400 ml/667m~2 showed that 300 ml/667m~2 had the greatest effect on copperleaf, attaining the preventive effect of 100%, and the concentration of 400 ml/667m~2 showed a better effect on copperleaf, green bristlegrass, little fleabane and goose grass. The experiment also showed that the Glyphosate with the concentration of 300 ml/667m~2+300 ml/667m~2 Paraquat had a better effect on copperleaf, green bristle grass, little fleabane and goose grass than the pure Glyphosate with the same concentration. There appeared no significant differences of preventive effect on Malachium aquaticum, asteraceae and capsella by using 70 or 50 ml /667m~2 of Benazolin-ethyl.During the same period, the Glyphosate (30d treatment) with the concentration of 150 ml/667m~2 had no significant effects on fresh weights of crabgrass, green bristlegrass and little fleabane, while it showed significant effects on fresh weights of copperleaf, goose grass when treated for 15d. It was better to spray Glyphosate at the early period of the weed. Compared to the Glyphosate with the concentration of 400, 300, and 200 ml/667m~2, the Glyphosate with the concentration of 50 and 100 ml/667m~2 had significant effects on copperleaf, goose grass, green bristlegrass of fresh weight for 30d treatment, and so did the Glyphosate with concentration of 50 ml/667m , and 400, 300, 200, 100 ml/667m~2.An integrated management system with various measures should be adopted to control the citrus orchard weeds, for the single measure especially the use of a single chemical herbicide will lead to the development of a harder prevented "super weed", which will obviously damage the biological diversity. |
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