Weed Communitiy Succession And It's Ecological Mechanism In Cotton Fields Under Different Planting Patterns

Drip irrigation under film is one of the most important cultivation techniques for cotton planting in Xinjiang province.Over the past 30 years,the continuous use of plastic film has led to the increasingly serious problem of residual pollution,which has severely restricted the sustainable development of agriculture.Removing the film will play an important role in controlling the increase of the residual film pollution.After the film is removed,the weed damage law and cotton growth will change under the original weed control system.In this study,four different planting modes were set,including film without weeding,filmless artificial weeding,filmless without weeding,and filmless chemical weeding.we analyzed their cotton field soil microenvironment,seasonal changes of weed communities,cotton growth,and indoor seed germination experiments,in order to clarify the occurrence of field weeds and environmental impact factors of dominant weed germination after unveiling and provide a scientific and technical basis for the construction of a weed control technology system in cotton fields.The main conclusions are as follows:(1)Within 90 days of sowing,the soil temperature of film without weeding was significantly higher than the other three non-film treatments,after which the gap gradually narrowed until there was no significant difference.During the cotton irrigation period,the moisture content on the soil surface(0 cm)of film without weeding was lower than that of the other three non-film treatments,and there was no significant difference in soil moisture in the four planting modes in 2019.The movement of salt follows the principle of“salt moves with water”.A salt accumulation zone is formed in a soil layer of 10-20 cm.The conductivity of the soil surface(0 cm)of the three non-film treatments is higher than that of the film without weeding.(2)A total of 11 weeds in 5 families appeared in cotton fields in 2018,and 15 weeds in 8 families appeared in 2019.Chenopodium glaucum,Cirsium setosum,Chenopodium hybridum,Chenopodium glaucum,Cynanchum cathayense and Phragmites communis is the dominant weed.In 2018,the damage degree of weeds in the four planting modes was low,and the total density of weeds was only 7.8 plants/m~2.Cotton field weeds occur as:film without weeding>filmless without weeding>filmless chemical weeding>filmless artificial weeding.In 2019,the degree of weed damage will increase,and the total density of weeds will be 81.6 plants/m~2.The occurrence of weeds is shown as:filmless without weeding>film without weeding>filmless chemical weeding>filmless artificial weeding.The species diversity of weed communities indicates that compared with the other three non-film treatments,the cotton field weeds of film without weeding are more abundant,with higher species diversity and more uniform species distribution.(3)In 2018,the plant height and the number of fruit branches with film without weeding were higher than the other three without film treatments.There was no significant difference between the three without film treatments,and the four planting modes had no significant effect on the stem diameter.In terms of plant height,stem diameter,and number of fruit branches in 2019,there was a law of film without weeding>filmless artificial weeding>filmless chemical weeding>filmless without weeding.Compared with the film without weeding,the yield of filmless without weeding decreased by38.54%,and there was no significant difference between filmless artificial weeding,filmless chemical weeding,and film without weeding.In terms of cotton fiber quality,compared with film without weeding,the three treatments without film increased the micronaire value of cotton,but reduced the fiber length.In addition,chemical weeding reduced the uniformity,specific strength and elongation of cotton fibers.(4)The temperature range for germination of perennial weeds,Chenopodium glaucum and Cirsium setosum in cotton fields under constant temperature conditions is 10?35?,with the temperature rising first and then decreasing,the optimum temperature range for germination is 20?25?.The annual temperature range for germination of the annual weeds Chenopodium glaucum and Amaranthus retroflexus in cotton fields under constant temperature is 15?40?,while the temperature of germination of Chenopodium hybridum is 20?40?.The optimum temperature range for germination of Chenopodium glaucum and Amaranthus retroflexus is 20?40?,and 30?40?is the optimum temperature for germination of Chenopodium hybridum.The germination rate of five weed seeds in cotton fields,such as Chenopodium glaucum,Cirsium setosum,Chenopodium glaucum,Amaranthus retroflexus,and Chenopodium hybridum,was negatively correlated with salt concentration and positively correlated with water potential.Five weed seeds in cotton fields could germinate at pH 5-10.