Study On The Occurrence And Integrated Management Of Weeds In Turf

The occurrence and distribution of the weed communities in turf in Nanjing and the other cities in Jiangsu Province were studied. The principal factors affecting the occurrence of the weeds were observed. The effect of meteorological factors on emergence of several worst weed species was studied and the optimal time for control was set up. The allelopathic potential of extract of Trifolium repens was assessed. Then the ecological reason was given to explain the phenomenon of Trifolium repens infesting grossly to bermudagrass turf.With line intercept method, forty-two sampling plots in Nanjing and thirty-three ones in the other nine cities in Jiangsu province were surveyed in order to find out weed species, infestation and distribution in turf. The obtained data were analyzed with principal component analysis. 162 weed species in turf, belonging to 37 families, including 121 winter-spring weed species and 85 summer-fall weed species were recorded in Jiangsu Province. According to the indexes of important value, frequency, Cyperus rotundus, Digttanasanguinalis, Poa annua, Alternanthera philoxeroides, Oxalis corniculata Were the WOrst turf Weeds.By studying thirty-three sampling plots, it was found that multitude factors affected on the infestation and distribution of weed species. The infestation of weed species evolved in all directions. The factor of frequent artificial interference replaced the factors of discrepancy of zone and climate among cities becoming the most important factor in determining the weed infestation. According to the infestation and distribution of weed species, thirty-three sampling plots were divided into 3 groups. By studying forty-two samples in Nanjing, it found that the most important factor affected on the infestation and distribution of weed species was the level of turf management. And the soil moisture of turf played the secondary effect on the weeds. According to these two factors, forty-two turf sampling plots were divided into 4 groups. The characteristic of each group was studied and the dominant weed species in each group were listed.The emergence of nine turf weed species in Nanjing was studied from October 2000 to 2002. The date and soil temperature in the stages of beginning, peak and end of occurrenceof every weed species were identified. The effect of meteorological factors on weed emergence was analyzed with partial correlation analysis and path analysis. The results of partial correlation analysis showed that the soil temperature was the principal factor affecting the emergence of weeds. Soil evaporation was a negative factor affecting the emergence of five summer-fall weed species. The correlation between weed emergence and the other three meteorological factors like air humidity, rain falling and sunshine was not significant. The results of path analysis showed that the indirect effect of soil temperature and soil evaporating on weed emergence were stronger than direct effect. However the other three factors mainly directly affected. The interaction between soil temperature and soil evaporation was the greatest in indirect effect.Pingcaolong No.3 WP, a preemergence herbicide, was applied to control the weed species in winter-spring season in Dichondra repens at the middle of September. When applied at 30g(ai)/mu, the emergence rate of Poa annua and Stellaria media were reduced and the turf quality was not affected. Two preemergence herbicides, Pingcaolong No.6 WP and Pingcaolong No.7 WP, were applied to control Poa annua in bermudagrass at the beginning of November. When applied at 100g(ai)/mu, the emergence was reduced 81.84% and the hurt to turf was slight 60 days later. By evaluating the efficacy of the mixtures of preemergence and postemergence herbicides for the control of Digitaria sanguinalis in bermudagrass at the end of April. When applied at 20g+25ml/mu, Pingcaolong No.7 WP plus Pingcaolong SC, the infestation of Digitaria sanguinalis reduced 88.34%. When applied at 25ml+15g/mu, SC plus Pingcaolong No.3 WP, the infestation of Digitaria sanguinalis r...