Effects Of Degradable Film Mulching On Soil Hydrothermal Salt Distribution And Cotton Growth And Mechanism With Drip Irrigation In Typical Oasis Region

Object:By analyzing the effects of degradable film mulching on the growth and yield of drip cotton,soil temperature,salt and soil water use efficiency,this paper discusses the comprehensive effect of using degradable plastic film instead of ordinary plastic film,in order to reduce the increment of residual film into soil plough layer from the source and provide a scientific basis for the treatment of residual membrane pollution.Methods:On the basis of field test and combined with laboratory tests,the test cotton was widely used in Xinjiang area to popularize the dwarf,dense planting and early maturing variety"Xin Lu Zao 220".The degradable film was used in the local application of biodegradable film,photodegradation film and biodegradable film,and the plot test of degradable film covered under drip irrigation was carried out in 2015-2017.The water saving irrigation test station of the river university is carried out.Results:?1?Soil temperature has an important influence on the growth of cotton,especially in Xinjiang,the temperature of cotton seedling in the seedling stage is low,the meteorological disasters are frequent,and the film mulching has a significant influence on the growth of the crops.On the whole,the degradable film could effectively improve the soil temperature in the seedling stage of cotton,and the average temperature of 0²5cm in the seedling stage was significantly higher than that of no cover,but the temperature of four degradable mulching soil was 1.34 degrees lower than that of the ordinary plastic film,and the lowest decreased by 0.94?P<0.05?,but this effect gradually decreased with the growth of cotton.?2?In addition to film mulching has the function of heat insulation and another major role is moisture.Degradable mulching film will have different degrees of degradation with the increase of film mulching time during the mulching process,and at the same time,it will have an impact on soil moisture.In this experiment,the degradation of the degradable film from the film covered 60d in different degrees,the water retention effect of the degradable film on the soil was equivalent to that of the ordinary plastic film in the seedling stage.Through the study of the dynamic distribution of water in different soil layers,it was found that the film mulching effect mainly changed the soil moisture of soil 0⁴0cm depth soil,and this effect gradually weakened with the increase of the film mulching time.The water use efficiency of the four degradable mulching films was slightly lower than that of the ordinary plastic film,and the average water use efficiency was 12.25 kg·hm^-2·mm^-1.?3?The technology of drip irrigation under mulch is mainly applied to arid and semi-arid areas in Northwest China.This area has typical characteristics of less rainfall and strong evaporation,and the saline alkali land is widely distributed.The influence of degradable mulching film on salinity is one of the decisive factors of whether it can be widely promoted.The transport of salt is mainly affected by soil water.The model of film mulching and drip irrigation mainly changes the distribution of salt in shallow soil.The degradable film covers the soil salt effect similar to that of ordinary plastic film in the early and middle period of the growth of cotton,but in the later period of growth of cotton,the superposition of double action of soil evaporation without irrigation and degradable film degradation is degrading film salt.At about 30⁴0%high,ordinary plastic film mulching under salinity increased 15%.?4?The ultimate goal of mulching and drip irrigation is to promote crop growth,increase cotton production and increase economic benefits.Compared with the non-coverage,the growth process of cotton was significantly improved,especially the rapid emergence of cotton seedlings into the bud stage.3A test showed that cotton was about 15d in advance to enter the next growth process.The net photosynthetic rate of cotton under Mulched film was better because of the cumulative effect of growth,but the degradable film was slightly worse than the ordinary plastic film.The average yield of degradable plastic film is 5265 kg.hm^-2,which is lower than that of ordinary plastic film mulching.At the same time,the average net income and production ratio are not as good as ordinary plastic film,the average benefit and production ratio are 16485 yuan,hm^-2 and 1.7 respectively,and 10.3%and 6.1%lower than that of ordinary plastic film respectively.The cost of degradable plastic film is high,so its economic benefits are not ideal at present.?5?The actual degradation effect of degradable plastic film in the field determines whether it can solve the residual membrane pollution,and the ecological effect of the film is the decisive condition for its promotion.The 2a test showed that the film covered 60⁸0 d began to degrade,and the uniform fine lines were not completely degraded after covering180 d,and the BD3 degradable film mulching 180 d only appeared crack.The total degradation of the four-degradable plastic film during the period of application was not completely degraded.This is mainly related to the design degradation cycle of the film,which is to meet the requirements of large area mechanization planting in Xinjiang area.Conclusions:Degradable film mulching has a significant influence on soil temperature,water and salt,thus affecting the growth process,growth traits,yield,photosynthetic characteristics and soil water use of cotton.Under the present conditions,considering four types of degradable plastic film can improve crop yield and water use efficiency,comprehensive degradation characteristics of degradable film and analysis of environmental effects.The fully biodegradable film with PBAT material as masterbatch is more valuable in the long run,which provides a scientific basis for the extension of degradable film technology in arid and semi-arid areas.