Occurrence Characteristics Of Farmland Soil Residual Film And Application Demonstration Of Biodegradable Film In Guizhou Province

Guizhou is located in the upper reaches of the Yangtze River and the Pearl River,which is one of the important ecological barriers in China.At present,the increase of plastic film residue is bringing serious plastic pollution in the basin,and the research on the present situation and occurrence characteristics of plastic film residue in this area is still limited.In this study,the use and residue of plastic film of main mulching crops（flue-cured tobacco,vegetables and pepper）in Guizhou Province were investigated and sampled by means of questionnaire survey and sampling monitoring,and the occurrence characteristics and influencing factors of soil residual film in the region were discussed.At the same time,a completely random experiment was designed to study the degradation characteristics,warming and moisture retention properties of four biodegradable films with no mulching（CK）and ordinary mulching（PE）as controls.The effects of film mulching on the growth and economic traits of flue-cured tobacco were studied,and the economic benefits after film mulching were analyzed and compared.The results indicate that:（1）The residual film content in the soil of 29 plots in this study ranged from 8.1 to 235.3 kg·hm^-2,with an average of 70.8 kg·hm^-2.With the increase of film mulching years,the fragmentation degree of residual film increases,and the quantity and proportion of residual film with length of <5cm and 5—10cm increased,and the quantity of residual film with length of 10—15cm and>15cmcm increased first and then decreased,and its proportion decreased.The average residual film quality of the three soil types was loam > clay > sand.Under the same film mulching years,the residual quality of different mulching crops was : vegetables > flue-cured tobacco > pepper.（2）The degradation degree of biodegradable film 2# is the largest,and the degradation degree of other biodegradable film is relatively small.With the increase of film mulching time,the mechanical properties of the four biodegradable mulch films were affected by the transverse and longitudinal tensile strength.Biodegradable film 1# and 4# had better effect on increasing temperature and preserving soil moisture during the growth period of flue-cured tobacco,which could increase temperature by 3.6—4.8℃,increase soil moisture by 3.4—3.8%,and achieve the effect of PE film.Biodegradable film 2 # and 3 # had a good effect of increasing temperature and preserving soil moisture in the rosette stage,but with the increase of time,the effect of increasing temperature and preserving soil moisture gradually deteriorated.Biodegradable film 1# and 4# in flue-cured tobacco growth period can promote plant height increased by 12.7—14.7cm,leaf area increased by 339.3—346.1cm²,leaf number increased by 2.0—2.7pieces.Biodegradable film 1# and 4# in the mature period can promote plant height increased by 22.3—23.4cm,leaf area increased by 376.1—441.0cm²,leaf number increased by 4.7—5.0,can achieve the effect of PE film.Biodegradable film 2# and 3# promoting had weak promoting effects.The yield of flue-cured tobacco covered with biodegradable film was 200.0—479.1kg·hm^-2 higher than that of CK treatment group,increased by 11.1—26.7%,the output value of flue-cured tobacco was 4.9—10.7thousand RMB·hm^-2 higher than that of CK treatment group,increasing by 8.2—18.0%,and the yield-increasing effect was obvious.The economic benefit of biodegradable film 1# and 4# was comparable to that of PE film,while the economic benefit of biodegradable film 2# and 3# was weaker than that of PE film.