Agronomic performances of biodegradable and non-biodegradable plastic film mulching on a maize cropping system in the semi-arid Loess Plateau,China

Hao ZHANG ,Mengqiong CHEN ,Ruiquan QIAO ,Fan DING ,Hao FENG and Rui JIANG,*

1Research Center for Cultural Landscape Protection and Ecological Restoration,China-Portugal Belt and Road Cooperation Laboratory of Cultural Heritage Conservation Science,Gold Mantis School of Architecture,Soochow University,Suzhou 215006(China)

2Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China,Ministry of Agriculture,College of Natural Resources and Environment,Northwest A&F University,Yangling 712100(China)

3College of Land and Environment,Shenyang Agricultural University,Shenyang 110866(China)

4Institute of Soil and Water Conservation,Northwest A&F University,Yangling 712100(China)

ABSTRACT Biodegradable plastic film mulch(PFM)is considered an alternative to non-biodegradable PFM to mitigate the negative impacts of residual film.However,the agronomic performance of biodegradable PFM in comparison to non-biodegradable PFM still needs to be tested.In this study,we evaluated the effects of biodegradable and non-biodegradable PFM on soil physicochemical properties,microbial community,and enzyme activities,as well as maize growth performance.Biodegradable and non-biodegradable PFM both increased soil temperature,water content,N content,and microbial biomass and maize yield by up to 30%,but decreased soil enzyme activities as compared to no mulching(control,CK).Most soil physicochemical properties,microbial community,and enzyme activities were similar under non-biodegradable and biodegradable PFM at the early stages of maize growth.However,at the late stages,soil temperature,water content,mineral N,,ammonia monooxygenase(AMO)activity,and total phospholipid fatty acids(PLFAs)decreased under biodegradable PFM owing to film fragmentation.White PFM increased soil temperature,water content,and total PLFAs at the early stages of maize growth but decreased soil mineral N and total PLFAs at the late stages,as compared to black PFM.As soil temperature and N availability were the major factors affecting soil microbial community,microbial activity decreased after the fragmentation of biodegradable PFM,owing to the decreased soil temperature,water content,and mineral N.Notably,biodegradable PFM could decrease accumulation in topsoil by decreasing N transformation due to the lower microbial and N-related enzyme(e.g.,AMO)activities,compared with non-biodegradable PFM,which may avoid negative environmental impacts,such as leaching or gas emission after harvest.Maize yield,height,aboveground biomass,and N uptake under biodegradable PFM were similar to those under non-biodegradable PFM during maize growth,implying that biodegradable PFM has no negative impact on crop growth and yield.In general,biodegradable PFM was equivalent to non-biodegradable PFM in terms of maize yield increase and N uptake,but was environmentally friendly.Therefore,biodegradable PFM can be used as an alternative to non-biodegradable PFM in semi-arid areas for sustainable agricultural practices.

Key Words: black plastic film mulching,enzyme activity,film fragmentation,microbial community,phospholipid fatty acid,white plastic film mulching

INTRODUCTION

Plastic film mulching in agriculture provides many benefits,such as increasing soil temperature,preserving water,reducing nutrient loss,promoting crop growth,and increasing crop yield (Zhou and Feng,2020).Owing to these benefits,plasatic film mulch(PFM)has been widely used in arid and semi-arid areas,particularly with crops that require high hydrothermal conditions like maize and cotton(Zhanget al.,2021).Agricultural plastic mulching films are mostly made of low-density polyethylene,which is not readily biodegradable and must be retrieved and disposed of after use.However,PFM disposal is expensive and timeconsuming(Yinet al.,2019).As a result,mulching films used are often not properly disposed of and sometimes even burned by farmers (Sintim and Flury,2017;Dinget al.,2022).Ineffective recovery of films from fields after crop harvest has led to soil pollution with plastics,particularly in China(Sintim and Flury,2017;Dinget al.,2022;Zhanget al.,2022).

The use of biodegradable plastic films instead of polyethylene is a promising way to mitigate the negative impacts of residual films or their burning on farmland.Biodegradable films can be tilled into soil after use and can be decomposed by microorganisms into CO2and H2O(Sintim and Flury,2017;Sintimet al.,2019),which effectively saves labor and disposal costs while reducing the adverse effects of residual films on crop root growth and soil(Yanget al.,2015).It also mitigates some negative effects caused by non-biodegradable plastic films,such as heat stress(Zhouet al.,2012),excessive use of soil nutrients(Chenet al.,2020),and reduction of soil organic matter content(Zhouet al.,2012).Therefore,biodegradable PFM has a great potential for agricultural production.

To be an appropriate alternative,biodegradable PFM must fulfill the agronomic effects of non-biodegradable PFM and have no adverse impact on the environment (Sintim and Flury,2017).Many studies have shown that the breakdown of biodegradable plastic films in laboratory is possible(Kasirajan and Ngouajio,2012);however,little is known about the effects of biodegradable plastic films on agronomic performance and soil quality in practical production(Liet al.,2014).Studies have shown that biodegradable PFM performs similarly to non-biodegradable PFM in weed prevention and improvement of crop yield and quality(Mileset al.,2012).Chenet al.(2021)showed that soil temperature and water content were similar under biodegradable PFM and non-biodegradable PFM,but other studies have shown that biodegradable PFM does not reach the extent of soil temperature under non-biodegradable PFM due to lower solar transmittance(Schettiniet al.,2007).Moreover,the breaking of biodegradable plastic films before harvest also affects soil temperature and water content(Chenet al.,2021).Furthermore,soil properties,such asandcontents,microbial community,and enzymatic activities,were also affected by PFM owing to changes in the soil microenvironment(Zhaoet al.,2020).Microorganisms are highly sensitive to environmental changes(Rutiglianoet al.,2004)and can be used to evaluate soil fertility and environmental quality (Chenget al.,2020).For example,higher soil water content,temperature,and N content under PFM will significantly improve soil microbial community and increase enzymatic activities.As biodegradable films are decomposed by microorganisms,soil microbial activities differ between biodegradable and non-biodegradable PFM(Brownet al.,2023),which in turn can affect N and C cycling(Liet al.,2014,Sintimet al.,2019).Although a few studies have reported on microbial and enzyme activities under PFM(Fanget al.,2020),it is not known how these activities change during the growing season under biodegradable PFM.Therefore,the potential environmental consequences of using biodegradable films have not been thoroughly studied.In general,agricultural mulching films are white or black.Studies have shown that the effect of mulching film color on crop yield is highly different based on seasonal conditions (Moreno and Moreno,2008).Black PFM can increase yields,decrease yields,or maintain yields similar to that of white PFM(Qinet al.,2018).However,there is little information on how black and white biodegradable and non-biodegradable PFM differ in terms of crop yield,soil physicochemical properties,and soil microbial activities.

The objectives of this study were to i) evaluate soil physicochemical properties and maize growth performance under non-biodegradable and biodegradable PFM and ii)quantify the effects of PFM on microbial and enzyme activities and explore the key factors controlling soil microbial activities.We hypothesized that biodegradable PFM had similar agronomic performance to non-biodegradable PFM,but with different effects on soil microbial and enzyme activities due to changes in soil hydrothermal and nutrient conditions.

MATERIALS AND METHODS

Experimental site

A field experiment was conducted at the Changwu Agro-Ecological Experimental Station of Chinese Academy of Sciences(35°12′N,107°40′E)in 2018.The study site is located on the Loess Plateau in northwestern China,which has a semi-humid monsoon climate.The average annual air temperature is 9.1°C,and the average annual precipitation is 584 mm,with more than 60%of total precipitation falling during the maize-growing season from April to October.The main cropping system in this area is a single crop of maize or wheat per year.According to the American system of soil classification,soil at the study site is Cumulic Haplustoll(Wanget al.,2016).

Experimental design

This study included five treatments:non-biodegradable PFM with white and black films(NonDeg-White and Non-Deg-Black,respectively),biodegradable PFM with white and black films(Degr-White and Degr-Black,respectively),and no mulching(control,CK).The five experimental treatments with three replicates each were arranged in a completely randomized design with a plot area of 18.06 m2(4.3 m×4.2 m).A ridge-furrow rainwater harvesting system was adopted in the mulching system,and ridges were covered with different films and planted with maize.The film width was 100 cm,and the film thickness was 0.01 mm.The ridges and furrows were made after fertilizer application.The widths of the ridges and furrows were 70 and 30 cm,respectively,and the ridges were 15 cm high.Fertilizers were applied during sowing.A total of 225 kg N ha-1,64 kg P ha-1,and 74 kg K ha-1was applied to each plot.Maize was planted at the end of April and harvested at the end of September in 2020.There was no irrigation during the maize-growing season,and field management was consistent with that of the local fields.The main raw material for the non-biodegradable white/black films was polyethylene,which showed no obvious degradation during the entire growth period.The main raw material for the biodegradable white/black films was a co-polymer of butylene adipate and butylene terephthalate,which began to degrade after 60 d and experienced further breakage after 75 d.

Soil samples were collected on June 8(jointing stage),July 18(tasseling stage),August 21(milk stage),and September 23(maturity stage),during the maize growth season in 2020.We used a soil auger to collect five intact soil cores(0-20 cm)at the middle between two crops;samples were taken randomly in each plot and mixed homogeneously to form one sample.Crop samples were collected at the same time as soil samples.Three maize plants were selected randomly from each plot.At harvest,all maizes in each plot were harvested to determine crop yield.

Soil and crop analyses

Soil temperature at 20 cm depth was measured in each plot with a digital thermometer at 9:00 a.m.for three consecutive days at each growing stage(jointing stage on June 8,tasseling stage on July 18,milk stage on August 21,and maturity stage on September 23).Soil water content was determined by oven-drying at 105°C for 12 h.Soil pH was determined using a pH meter at a soil:water ratio of 1:2.5(weight:volume).Organic C content was determined by K2Cr2O7oxidation (Bao,2020).Total N content was determined by Kjeldahl digestion.Nitrate nitrogen(N)and ammonium nitrogen()were extracted by 2 mol L-1KCl(1:10,soil:solution,weight:volume)and then measured using a continuous-flow analyzer.Mineral N was defined as the sum ofcontents.After measuring the crop height,the biomass of the crop was determined by drying at 105°C for 30 min and then maintaining at 75°C until a constant weight was reached.The crop N uptake was determined through Kjeldahl digestion.

Enzyme activities and microbial community

Activities of urease (URE),protease (PRO),and ammonia monooxygenase(AMO),which are related to N cycling,were measured using commercial kits(MultiSciences(Lianke) Biotech Co.,Ltd.,China).Soil microbial community structure was characterized using the phospholipid fatty acid (PLFA) method (Bossio and Scow,1998).The classification of the PLFAs detected in the present study was as follows:i14:0,i15:0,a15:0,i16:0,i17:0,a17:0,14:0,16:1 2OH,16:1ω9c,cy17:0,18:1ω5c,18:1ω7c,cy19:0,16:0,17:0,17:1ω8c,18:0,and 20:1ω9c indicate bacteria,and 16:1ω5c,18:1ω9c,and 18:3ω6c(6,9,12)indicate fungi(Frostegård and Bååth,1996).All analyses were completed within 3 weeks of sampling.

Statistical analyses

Data were log-transformed to meet the assumptions of normality and homogeneity of variance when necessary.One-way analysis of variance with Duncan’s test was used to evaluate the differences among treatments regarding soil properties,crop growth indices,enzyme activities,and microbial community (n=3) using SPSS 21.0.We performed redundancy analysis (RDA) using CANOCO 5.0,to evaluate relationships between soil microbial community and environmental factors.

RESULTS

Soil physicochemical properties

Compared with CK,soil temperature,water content,mineral N,were higher at each growing stage(P ＜0.05),whereas pH was lower at the late stages(milk and maturity stages)(P ＜0.05)under PFM(Fig.1).Most of the soil physicochemical properties were similar under the non-biodegradable and biodegradable PFM at the jointing stage,but soil temperature and water content,mineral N,andwere increased under non-biodegradable PFM at the late stages(P ＜0.05).At the milk and maturity stages,mineral N andwere higher under the black PFM than the white PFM(P ＜0.05).

Fig.1 Soil physicochemical properties under non-biodegradable and biodegradable plastic film mulching(PFM)at different stages of maize growth.Bars are standard errors of the means(n=3).Different letters above bars indicate significant differences among the treatments at each stage(P ＜0.05).CK=control with no mulching;NonDeg-White and NonDeg-Black=PFM with white and black non-biodegradable films,respectively;Degr-White and Degr-Black=PFM with white and black biodegradable films,respectively.

Soil microbial community and enzyme activities

Compared with CK,total PLFAs and PLFAs of bacteria and fungi during maize growth were increased under PFM(P ＜0.05)(Fig.2).They were similar among different PFM types at the jointing stage.At the tasseling stage,microbial PLFAs(including total PLFAs and PLFAs of bacteria and fungi)were higher under non-biodegradable PFM than under biodegradable PFM(P ＜0.05).At the late stages,microbial PLFAs under NonDeg-Black were higher than those under biodegradable PFM(P ＜0.05),but lower under NonDeg-White than those under other PFM treatments.At the early stages(jointing and tasseling stages),the soil under white PFM had higher microbial PLFAs than that under black PFM;however,the microbial PLFAs under black PFM were higher than those under white PFM at the late stages(P ＜0.05).

Fig.2 Total phospholipid fatty acids(PLFAs)(a),PLFAs of bacteria(b)and fungi(c),and activities of urease(d),protease(e),and ammonia monooxygenase(f)in soil under non-biodegradable and biodegradable plastic film mulching(PFM)at different stages of maize growth.Bars are standard errors of the means(n=3).Different letters above bars indicate significant differences among the treatments(P ＜0.05).U=unit;CK=control with no mulching;NonDeg-White and NonDeg-Black=PFM with white and black non-biodegradable films,respectively;Degr-White and Degr-Black=PFM with white and black biodegradable films,respectively.

Activities of URE and AMO were higher under CK than those under PFM at each growing stage,but PRO activity was lower under CK(except at the jointing stage)(P ＜0.05)(Fig.2).Under non-biodegradable PFM,the average AMO activity increased by 13.2%compared with that under biodegradable PFM.The average PRO activity was 18.1% higher under biodegradable PFM than that under non-biodegradable PFM.

Crop growth and yield

Compared with CK,crop height,aboveground biomass,and crop N uptake were increased under both nonbiodegradable and biodegradable PFM,with no significant differences between them(Fig.3).Aboveground biomass and crop N uptake under white PFM at the milk stage increased by 7.1%-16.0%and 6.5%-12.1%,respectively,compared with the black PFM.However,differences in aboveground biomass among different PFM types were not detected at the maturity stage.Crop yield increased by 30.0%-35.2%under PFM compared with CK(P ＜0.05).The highest crop yield was observed under Degr-Black,and there was no significant difference in crop yield among the four PFM treatments.

Fig.3 Crop height,aboveground biomass,and N uptake at different stages of maize growth and maize yield at maturity under non-biodegradable and biodegradable plastic film mulching(PFM).Bars are standard errors of the means(n=3).Different letters above bars indicate significant differences among the treatments(P ＜0.05).CK=control with no mulching;NonDeg-White and NonDeg-Black=PFM with white and black non-biodegradable films,respectively;Degr-White and Degr-Black=PFM with white and black biodegradable films,respectively.

Factors related tosoil microbial community

Redundant analysis showed that the major factors affecting soil microbial community were soil temperature(F=4.3,P=0.04),(F=33,P ＜0.01),(F=18.6,P ＜0.01),total N(F=4.6,P=0.02),and crop N uptake(F=5.6,P=0.02)(Figs.4 and S1,Table SI,see Supplementary Material for Fig.S1 and Table SI).These results indicated that soil microbial community were mainly affected by soil temperature and N content.

DISCUSSION

The four PFM treatments significantly increased soil temperature and water content compared with CK(Fig.1),particularly at the early stages of maize growth.Plastic film mulching also increased soil mineral N content during maize growth,indicating better hydrothermal and nutrient conditions under PFM than CK,as supported by many other studies(Zhou and Feng,2020;Wanget al.,2022).This is because the higher soil temperature and water content were beneficial for soil microbial growth(Figs.2 and S2,see Supplementary Material for Fig.S2),thus accelerating N transformation and increasing inorganic N content under PFM(Zhou and Feng,2020).Soil pH is a key factor affecting N transformation(Liuet al.,2020).The lower soil pH under PFM at the late stages due to the relatively highcontent may also have affected soil N transformation by affecting soil microbial factors,thus resulting in a different soil nutrient status between PFM and CK(Fig.1).However,URE,PRO,and AMO activities were higher under CK than those under PFM(Fig.2).This implies that N transformation is faster under CK than under PFM because these enzymes characterize the direction and intensity of N transformation(Van Oostenet al.,2019).However,highaccumulation in the topsoil also decreases the activities of these enzymes under PFM(Van Oostenet al.,2019).Therefore,although the N transformation processes were faster under CK,the mineral N andcontents were lower and the maize growth was poor compared to PFM (Fig.3).This implies that N is lost by leaching or gas emission from the soil with no mulching(the precipitation during this experimental period was 473 mm)but not taken up by crops(Guoet al.,2019).

Soil temperature,water content,and mineral N andcontents were not significantly different between the biodegradable and non-biodegradable PFM at the jointing stage,but significant changes were observed after the fragmentation of biodegradable films (Fig.1).At the middle and late growing stages,soil temperature,water content,and mineral N content decreased by 4.3%,4.2%,and 20.1%,respectively,under biodegradable PFM compared with nonbiodegradable PFM(Fig.1).This indicated that heating and moisturizing were decreased by biodegradable PFM owing to the fragmentation of biodegradable films at the late stages(Chenet al.,2021).There were no significant differences in soil organic C,total N,and pH between biodegradable and non-biodegradable PFM during maize growth since the study only lasted for 1 year.Therefore,biodegradable PFM affected soil available nutrients in the PFM planting system,but had no significant effect on soil organic matter and total N in the short term.

Unlike soil organic matter or total N,soil microbial indices were sensitive to PFM.The total PLFAs and PLFAs of bacteria and fungi decreased after fragmentation of biodegradable films(Fig.2)because of the decreased soil temperature,water content,and mineral N content (Fig.1).These results indicated that microbial activities were lower under biodegradable PFM than that under non-biodegradable PFM at the middle and late growing stages (Figs.2 and S2).Previous studies have suggested that microbial activity can characterize soil micro-environment conditions(Bünemannet al.,2018;Chenget al.,2020),and the RDA results obtained in the present study showed thatcontents along with soil temperature were the major factors affecting soil microbial community(Figs.4 and S1).Thus,compared with biodegradable PFM,non-biodegradable PFM provided a better and more stable micro-environment,which is conducive to increased N availability (especiallyN accumulation) in the topsoil at the late growing stages(Fig.4) (Wanget al.,2022).This is because biodegradable films begin to degrade and break up at the middle and late growing stages (Huanget al.,2019),and thus is not effective in preventing hydrothermal conditions(Wanget al.,2019).Thus,the better hydrothermal conditions of non-biodegradable PFM could accelerate N transformation and form a better soil micro-environment for microorganisms,leading to the improvement of microbial and enzyme activities(Huanget al.,2020;Brownet al.,2023).However,higher temperatures may reduce N utilization efficiency by microorganisms,improve N-related enzyme activities,and lead to the accumulation of mineral N(Daiet al.,2020).This might explain the much higheraccumulation under non-biodegradable PFM than under biodegradable PFM.Another reason foraccumulation was that the nitrification rate was lower because of the decreased AMO activity after the fragmentation of biodegradable films(Fig.3).This may also be explained by the carbonyl and hydroxyl functional groups in biodegradable films,which can adsorb cations (e.g.,) when biodegradable film changes to the form of microplastics,and thus may reduce nitrification(Menget al.,2022).However,accumulation under non-biodegradable PFM could cause negative environmental effects,and the rapid loss of soil organic N pool at the late stages would be detrimental to the growth of the next crop(Jianget al.,2018;Maet al.,2018).Biodegradable PFM could decrease microbial activity and N transformation at the late stages of crop growth and effectively reduceaccumulation in soil(Zhanget al.,2019).

Fig.4 Redundancy analysis(RDA)of soil microbial community(MC)with environmental factors(EFs).ST=soil temperature;SWC=soil water content;TN=total N;OC=organic C;CH=crop height;CNU=crop N uptake;CAB=crop aboveground biomass;TPLFAs=total phospholipid fatty acid(PLFAs);G+=Gram-positive bacteria;G-=Gram-negative bacteria;UB=unclassified bacteria;F=fungi;AC=actinomycetes;F/B ratio=the ratio of fungi to bacteria PLFAs;Iso/Ant ratio=the ratio of iso-to anteiso-PLFAs;Cy/Pre ratio=the ratio of cyclopropyl to precursor PLFAs;S/M ratio=the ratio of saturated to monounsaturated PLFAs.

Within the same PFM,PLFAs of bacteria and fungi were higher under white PFM than those under black PFM at the jointing and tasseling stages,but lower under white PFM than that under black PFM at the milking and maturity stages (Fig.2).These results indicated that white PFM increased microbial activity at the early stages,whereas black PFM increased microbial activity at the late stages of maize growth.However,bacteria and fungi PLFAs were lower under NonDeg-White than under other mulching treatments at the late stages of maize growth(Fig.2).This is caused by the plastic color refraction,reflection,and absorption of solar radiation,inducing different thermal effects in soil under PFM(Loughrin and Kasperbaueret al.,2002).At the early stages,white films exhibited a strong photothermal effect,and soil temperature was higher under white PFM compared with black PFM(Fig.1).Mineral N fertilization increased microbial activity and crop growth(Figs.2 and 3).The rapid growth of microorganisms and crops consumes more available N at the early stages of crop growth,and consequently,N depletion and premature aging can occur at the late stages(Steinmetzet al.,2016).In addition,black films have a low light transmittance,hindering the development of weeds and reducing the depletion of N availability compared to white films (Qinet al.,2018;Heet al.,2021).This is also explained by the higher nitrification due to increased URE and AMO activities under black PFM at the maturity stage.Therefore,the mineral N content was higher under black PFM than white PFM at the late stages(Fig.1),and this N excess was sufficient to increase microbial growth and activity.Thus,black PFM(no matter biodegradable or non-biodegradable)has more advantages than white PFM in maintaining the stability of soil ecosystem and the continuous use of farmland(Wanget al.,2021).

Crop height,aboveground biomass,and crop N uptake increased under PFM at all maize growing stages(Fig.3),indicating that PFM could improve crop growth and maize yield,as supported by previous studies(Jianget al.,2018).Although soil temperature and mineral N content were affected by mulching treatments,maize yield,and crop growth characteristics did not differ significantly among the four PFM treatments (Fig.3).These results showed that biodegradable films had no negative impact on crop growth and yield and thus could be used as an alternative to non-biodegradable films.This is because the early stages of maize growth usually suffer from drought and are crucial for maize production(Jianget al.,2018).Biodegradable PFM performs similarly to non-biodegradable PFM in terms of increasing soil temperature and moisture,weed prevention,and enhancement of crop growth at the early stages(Wanget al.,2021).After the early drought period,rainfall and temperature increased to meet maize growth requirements when biodegradable films began to degrade.Thus,there was no apparent effect of lower soil temperature and water content due to the fragmentation of biodegradable films on maize growth and yield.In the present study,the maize yield under black PFM was slightly higher than that under white PFM,but the difference was not significant(Fig.3),indicating that black PFM was more beneficial for increasing crop yield.Gupta and Acharya(1993)also found that black PFM had a better effect on crop growth than white PFM,which was explained by the prolonged crop growth time by black PFM.In addition,black PFM can improve maize quality indices,such as protein,N,and P contents(Fanet al.,2019;Wanget al.,2021).In conclusion,there is a great potential to replace non-biodegradable white films with biodegradable black films in semi-arid areas.However,we should note that the price of biodegradable films is 2-3 times higher than that of non-biodegradable films,which may be a limitation to the wide use of biodegradable films.Moreover,although biodegradable films are designed to degrade to CO2and H2O,they may break into microplastics to the same extent as non-biodegradable films or even more(Fanet al.,2022),and thus the long-term impact of biodegradable PFM on crop yield needs further study.

CONCLUSIONS

Non-biodegradable and biodegradable PFM both increased soil temperature,water content,N content,and total PLFAs and maize yield,but decreased soil enzyme activities as compared to no mulching.Most soil properties were similar under non-biodegradable and biodegradable PFM at the early stages of maize growth.However,soil temperature,water content,mineral N,and total PLFAs decreased under biodegradable PFM at the late stages when biodegradable films were fragmented.White PFM increased soil temperature,water content,and total PLFAs at the early stages,but decreased soil mineral N and total PLFAs at the late stages,as compared to black PFM.Soil temperature and N availability were the major factors affecting soil microbial community.Thus,soil microbial activity decreased after fragmentation of biodegradable films due to the decreased soil temperature,water content,and mineral N.Biodegradable PFM decreasedaccumulation in the topsoil due to the lower microbial and N-related enzyme activities,which may have avoided the negative environmental effects of non-biodegradable PFM.Maize yield and crop growth characteristics did not differ among the four PFM treatments,indicating that biodegradable films had no negative impact on crop growth and yield.Briefly,biodegradable PFM was equivalent to non-biodegradable PFM in terms of crop yield increase and N uptake,but it decreasedaccumulation and was environmentally friendly.Therefore,based on our short-term study,biodegradable films can be used as an alternative to non-biodegradable films in semiarid areas.However,the long-term effect of biodegradable film mulching requires further investigation.

ACKNOWLEDGEMENT

This study was funded by the National Natural Science Foundation of China(No.41877086),the Natural Science Basic Research Plan in Shaanxi Province of China (No.2020JZ-16),the UK Global Research Challenges Fund,and the UK Natural Environment Research Council Project(No.NE/V005871/1).

SUPPLEMENTARY MATERIAL

Supplementary material for this article can be found in the online version.