Study On Cotton Plant Growth And Soil Microbial Activity As Affected By Plastic Film Contamination In Soil

A experiment was carried out for studying the influence of plastic film in soil on the growth of shoot and root of cotton plant, soil physical property and soil microbial activitivities. The main results was as follows:1. There was stimulation of residual plastic film on growing of the cotton root in 0⁴0cm soil, root area(RA),root length density (RLD) and root dry weight (RDW) of cotton increased largely when residual plastic film rate was 900kg/hm², but there was hindrance on growing of the cotton root in 40¹00cm soil.2. Along with residual plastic film addition,cotton root activity first increased and then decreased ,MDA activity and POD activity increased,but SOD activity reduced.3. Dry matter weight of cotton plant and canopy/root ration reduced with adding residual plastic film, which distrubance thebalance of cotton root and shoot growth so that reduced the yield of seed cotton.4.Film-sphere microbial biomass C in June and July was reduced by 6.29% and 15.46% respectively as compared to the bulk soil in high film residue field (long-term cotton momocropping for over 15 years); The film-sphere microbial biomass N was 15.06 mg·kg^-1 and reduced by 14.04% compared to the bulk soil in July; Soil microbial biomass P reached most significance levels (p<0.01)between film-sphere and bulk soil in July. In the cotton fields of residual plastic film of 5 and 10 years, Soil microbial biomass C,N,P didn't reach significance levels between film-sphere and non-film-sphere in May^September.5. In the cotton fields of residual plastic film of 5 years, soil bacteria,actinomycetes and fungi didn't reach significant level between film-sphere and bulk soil in May^September. In the cotton fields of residual plastic film of 10 years, soil actinomycetes and fungi reached significance levels between film-sphere and bulk soil in July. In the cotton fields of residual plastic film of 15 years, the film-sphere soil bacteria reduced by 34.62% compared to the bulk soil,and soil actinomycetes respectively reached significance levels between film-sphere and bulk soil in June and July,and soil fungi respectively reached significance levels between film-sphere and bulk soil in June,July and August.6. In the cotton fields of residual plastic film of 5 years, soil ammonifyingbacteria,nitrobacteria and denitrobacteria didn't reach significant level between film-sphere and bulk soil in May^September. In the cotton fields of residual plastic film of 10 years,soil denitrobacteria respectively reached significant level between film-sphere and bulk soil in June and July. In the cotton fields of residual plastic film of 15 years, soil ammonifyingbacteria respectively reached significant level between film-sphere and bulk soil in June and July (p=0.0124,p=0.0248), soil nitrobacteria of the bulk soil was more than that of the film-sphere,and soil nitrobacteria respectively reached significant difference at 0.05 level between film-sphere and bulk soil in June and July, soil denitrobacteria respectively reached significant level between film-sphere and bulk soil in June,July and August.