Biodegradable Mulch Films Research Articles

Biodegradable mulching vs traditional polyethylene film for sustainable solarization: Chemical properties and microbial community response to soil management

Soil solarization is usually performed with polyethylene plastic films, which are often disposed of by taking them to landfills, burying them in soil, burning them or occasionally recycling them, and these approaches have a great impact on the environment. Therefore, the use of biodegradable films seems to be an interesting eco-sustainable alternative to traditional films. The effect of soil solarization carried out by using biodegradable mulch or traditional polyethylene plastic film was determined under greenhouse conditions. The response of the soil was assessed by chemical determinations and microbiological culture-dependent and culture-independent approaches to evaluate the microbial biodiversity, biological status and quality of the soil. The biodegradable film avoided a high ammonia concentration in the soil, thanks to both lower soil water content and slightly lower temperature than polyethylene film, and these conditions probably have been optimal for growth of nitrifying bacteria, which were more efficient in BIO, as highlighted not only by lower ammonia value but also by higher nitrate value. Both films did not affect organic matter and total nitrogen content. Moreover, the modifications of the environmental and ecological conditions associated with the different film covers applied to the soils affected prokaryotic and eukaryotic populations, leading to the establishment of a new dominant microbial community. Interestingly, microbiological analyses highlighted a different behavior modulated with the two films indicating different times of recovery post stress.Overall, the results highlighted the potential of biodegradable film that appears to be a suitable replacement for traditional polyethylene plastic film for soil solarization, with great environmental benefits.

Agricultural, Ecological, and Social Insights: Residual Mulch Film Management Capacity and Policy Recommendations Based on Evidence in Yunnan Province, China

Mulch film contaminates the environment while increasing agricultural yield. As such, the factors that impact the residual film management capacity of farmers must be identified, which would also be helpful for the sustainable development and security of agriculture. We investigated 10 counties across nine cities (states) by surveying 1284 households. The improved entropy-weighted composite index and the grey correlation analysis model were employed to measure the residual film management capacity from five dimensions: human capital, use behavior, management skills, public policy, and willingness. The entropy-weighted composite index results showed that residual film being harmful to the environment had the highest overall rate of 0.0745, followed by the effectiveness of mulch film, which was 0.0715. The results of the grey correlation analysis model showed that willingness to use biodegradable mulch film had the highest correlation of 0.8960, followed by educational level of the laborers, which was 0.8824. We found that residual film being harmful to the environment, effectiveness of mulch film, willingness to use biodegradable mulch film, and educational level of the laborers were the major factors influencing the residual mulch film pollution knowledge of households. Based on this finding, the government should increase subsidies for promoting biodegradable mulch film and publicize the hazards of residual films using diversified means in multiple channels.

Effective and Sustained Control of Soil-Borne Plant Diseases by Biodegradable Polyhydroxybutyrate Mulch Films Embedded with Fungicide of Prothioconazole.

Soil-borne diseases and plant rhizosphere nematode have caused many crop yield losses. Increased environmental awareness is leading to more restrictions on the use of certain fumigants and root irrigation methods due to their impact on human health and soil system. Therefore, it is necessary to find alternative treatments to maintain crop economic yields and environmental sustainability. In the present work, biodegradable antifungal mulches were prepared by blending poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (PHB) with fungicide of prothioconazole (PRO), which were used for effective and sustained control of soil-borne plant diseases. To reveal the application prospect of the PHB/PRO composite films in the management of soilborne plant diseases, some physical and biological properties were evaluated. The proper mulch film of PHB/PRO was assessed based on its mechanical and optical properties, while water solubility and the film micromorphology was further characterized. The release patterns of composite films under different pH levels were investigated. Moreover, the in vitro antifungal bioassay and pot experiment showed satisfactory bioactivity of the PHB/PRO films against Sclerotium rolfsii Sacc., a soil-borne disease in peanut fields. This study demonstrated that the biodegradable mulch films containing PRO fungicide are capable of inhibiting soil-borne plant pathogenic fungi effectively, and this facile but powerful strategy may find wide applicability in sustainable plant and horticulture protection.

全生物降解地膜对南疆玉米产量及土壤理化性质的影响

全生物降解地膜对南疆玉米产量及土壤理化性质的影响

Field test on the biodegradation of poly(butylene adipate-co-terephthalate) based mulch films in soil

The use of plastic much films has been fundamental to promoting food production in many regions of the world. However, concern is growing about the progressive accumulation of plastic residues in soil after crop harvest and its subsequent impact on soil health and potential to enter the food chain. Although biodegradable films have been developed to prevent these problems, it is still unclear whether they are environmentally benign. Here we evaluated the physical and chemical breakdown of four commercial poly(butylene adipate-co-terephthalate) based biodegradable mulch films (BMF1, BMF2, BMF3 and BMF4) in an agricultural soil over a 26-month period. Based on visual examination, degradation followed the series BMF4 > BMF1, BMF2 > BMF3. Importantly, microplastic residues (fragments <5 mm) still remained in the soil of all 4 plastic types after 2 years, suggesting that they are likely to accumulate over time if used on an annual basis. Viscosimetry, Fourier transform infrared (FTIR) spectroscopy and Thermogravimetric Analysis (TGA) were used to characterise the breakdown process. Our results indicated that the degradation of the mulch film after burial in agricultural soil may be linked to the nature of the polymer but also to its manufacturing formulation. Although the peak changes of polyester in the infrared spectrum were not distinct, the plastic films showed other signs of degradation including a reduction in intrinsic viscosity after burial in soil. The different degradation rates of BMF1 and BMF2 at the molecular level may be due to the different CaCO3 contents. In conclusion, under field conditions, we show that slight variations in the formulations of commercial biodegradable mulch films leads to very different persistence rates in soil. Further, we conclude that their slow rate of degradation will ultimately lead to their progressive accumulation in soil if used repeatedly.

Modeling maize evapotranspiration and associated processes under biodegradable film mulching in an arid dripped field

Plastic-film mulching in arid fields under drip irrigation has widely been replaced by biodegradable film mulching (BFM) to avoid plastic-film residue pollution. However, existing ET models are not able to accurately represent field evapotranspiration (ET) under BFM due to the disintegration of biodegradable film. Therefore, this study proposed an improved ET model considering BFM (BSW) based on the Shuttleworth-Wallace model (SW), and the performance of the model was compared with those of the SW, Penman-Monteith (PM) and modified Shuttleworth-Wallace models considering plastic-film mulching (MSW). In addition, the models were validated against observed data from a two-year (2018–2019) maize field experiment under high, medium and low drip irrigation with the depths of 30, 22.5, and 15 mm, respectively. The BSW model performed well with a normalized root mean square error (NRMSE), normalized mean absolute error (NMBE) and index of agreement (IA) for ET under different irrigation depths of 0.12, 0.25, and 0.96, respectively, and 0.10, 0.22, and 0.95 for evaporation (E) under different irrigation depths, respectively. During the early growing stage (elongation and tasseling stage), the BSW model obtained MBEs of cumulative ET (MBECET) and cumulative E (MBECE) of 2.1 and 5.6 mm, respectively, similar to those of the MSW model under high irrigation, but with MBECET estimation accuracy improved by 95.3% and 97.7% compared with the SW and PM models, respectively. The BSW model showed further improvements in estimation accuracy during the middle and late growth seasons (filling and maturation stages) with average MBECET and MBECE of 1.5 and 0.8 mm, respectively for both years. In addition, the E/ET under BFM was decreased with increasing of irrigation depth, while E/ET was positively correlated with the disintegrated area of biodegradable film.

Development of microwave-assisted extraction and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry for the determination of organic additives in biodegradable mulch films

Organic additives are extensively used as ingredients in biodegradable mulch films. They are swiftly released into the environment, which may have an ecotoxicological impact on plant growth and development, as well as on soil microbial community abundance and function. Herein, a method based on the application of microwave-assisted extraction (MAE) and dispersive liquid–liquid microextraction (DLLME) was developed to analyze eighty organic additives by gas chromatography-mass spectrometry in poly(butylene adipate terephthalate) (PBAT) biodegradable mulch films. This was a comprehensive study, including the identification of organic additives, optimization of MAE and DLLME methods, analysis of isocyanate conversion, and evaluation of the matrix effect (ME). Under the optimized experimental conditions, this method exhibited excellent detection capabilities for organic additives, except for 5 kinds of isocyanates and their reaction products, with coefficients of determination R2 > 0.999 and lack of fit P > 0.05 in linear regression parameters. A negligible ME was observed. The relative recoveries were 93.0–109.8%, and the repeatability and reproducibility varied within the ranges of 2.06–8.76% and 2.38–10.23%, respectively. The limits of detection and limits of quantitation were 0.0008–0.0586 μg g−1 and 0.003–0.195 μg g−1, respectively. The developed method was further successfully applied to the analysis of organic additives in PBAT biodegradable mulch films from four different manufacturers. Interestingly, the Venn diagram and principal component analysis showed that different manufacturing origins display obvious characteristic differences in the organic additive types and concentrations.

Incorporating DNA-level microbial constraints helps decipher methane emissions from Chinese water-saving ground cover rice production systems

• Relating CH 4 fluxes to methanogens and methanotrophs under GCRPS remains unclear. • GCRPS reduced CH 4 emissions and the yield-scaled CH 4 emissions. • GCRPS decreased the abundance of mcrA gene while stimulated that of pmoA gene. • Microbial parameters are useful to better predict CH 4 emissions from rice paddies. While water management has been documented to regulate CH 4 emissions from rice paddies, the mechanisms behind the association between CH 4 emissions and functional microbes remain unclear under water-saving ground cover rice production systems (GCRPS). In GCRPS, the soil is kept aerobic by maintaining 80 %–90 % of the water holding capacity but without standing water over the entire rice-growing season, and the soil surface is covered with rice straw or plastic film to reduce water evaporation. A split-plot field experiment was conducted to examine the effects of various GCRPS-related water-saving regimes on CH 4 emissions by linking to CH 4 -related microbes over the 2015 and 2016 rice growing seasons in a typical Chinese rice field. Methane fluxes and related functional genes [methanogens ( mcrA and methanogenic archaeal 16S rRNA ) and methanotrophs ( pmoA )] abundances were simultaneously measured using the closed chamber method and molecular techniques, respectively. The results showed that relative to the conventional waterlogged control (WRPS), GCRPS-related water-saving practices consistently reduced CH 4 emissions, which was largely attributed to the decreased relative abundance of the methanogenic functional gene mcrA while the methanotrophic functional gene pmoA increased. When averaged over the two rice seasons, the grain yield was 17.38 % and 12.22 % greater under the GCRPS -straw and GCRPS -film water-saving systems relative to WRPS, respectively. Water-saving regimes decreased the yield-scaled CH 4 emissions as compared with the WRPS, especially under GCRPS -film . The CH 4 fluxes showed a positive correlation with the relative abundance of mcrA and its ratio to pmoA , but a negative correlation with the relative abundance of pmoA . The performance of CH 4 -simulated models could be improved by incorporating microbial parameters to predict CH 4 emissions from rice fields. Overall, this study updates our understanding of the microbial mechanisms underlying CH 4 emissions from water-saving GCRPSs. We proposed the GCRPS regime with biodegradable film mulching as a desirable water-saving strategy to reconcile high yields and low CH 4 emissions in rice production.

Preparation and characterization of black biodegradable mulch films from multiple biomass materials

In this work, high strength and eco-friendly black biodegradable mulch films (BMF) were prepared via a simple and low-cost process. Cellulose was dissolved in NaOH/humic acid/urea solvent and the base films were formed via a phase inversion process, then chitosan/nepheline solution with glycerol as the additive was coated on both sides to obtain the BMF. The influences of composition with different concentration on mechanical properties were studied, and the optimal composition of the BMF was found. The characteristics of the BMF were researched by means of polarized optical microscope, scanning electron microscopy, diffuse reflectance infrared fourier transform spectroscopy, thermogravimetric analysis, light transmittance property, contact angle, water vapor permeability, soil temperature analysis, and degradation test. These results showed that the BMF had good mechanical properties, thermal stability, light transmittance performance, water resistance, soil moisture retention, and great biodegradation. These results indicated that the BMF exhibited superior properties, which could facilitate the utilization of biomass materials and the replacement of traditional polyethylene mulch films.

Benchmarking the Agronomic Performance of Biodegradable Mulches against Polyethylene Mulch Film: A Meta-Analysis

Growers are interested in biodegradable alternatives to petroleum-based polyethylene mulch film (PEM). However, many growers cite limited knowledge about biodegradable mulch films (BDMs) as a significant barrier to adoption. Agronomic field tests of BDMs are often limited temporally or spatially, and the variability of performance results relative to PEM may be contributing to this perceived knowledge gap. Our objective was to use data available in the scientific literature to provide the first quantitative performance benchmark of BDMs against PEM. We extracted data from 66 articles for meta-analysis. Response ratios were calculated for comparison of BDMs relative to black PEM, and differences among categorical groups were determined using 95% bootstrap confidence intervals. Overall, BDMs reduced soil temperature by 4.5% ± 0.8% (±one standard error) compared to PEM, and temperatures were coolest beneath paper-based BDM. Starch-polyester BDM was less effective than PEM for weed control, but paper-based BDM reduced weed density and biomass by 85.7% ± 9.2%. Paper-based BDMs were particularly useful for controlling Cyperus spp. weeds. Despite differences in soil temperature and weed suppression, crop yields were not different between BDMs and PEM. Future research should focus on reducing costs, adding functional value, and increasing the biodegradability of BDMs.

An alternative to polyethylene film mulch: Field evaluation of biodegradable film mulch on winter potato in the south of China

AbstractPolyethylene (PE) film mulching (PM) contributes to the increase of crop yields and farmer incomes at the expense of environment. We performed a 2‐yr field experiment to evaluate the possibility of replacement of PM with poly(butylene‐adipate‐co‐terephthalate)‐based biodegradable film mulching (BM) for winter potato (Solanum tuberosum L.) in the south of China. Both PM and BM treatments showed higher soil temperature and water content than no mulching (NM), and there was no significant difference between PM and BM before 60 d after sowing (DAS). Because of the breakdown of biodegradable film, reduced soil temperature and water content were observed in the BM treatment when compared to PM after 60 DAS, whereas no significant difference was observed in potato yield as well as marketable yield between PM and BM treatments, leading to higher water use efficiency in PM than BM. The net revenues of treatments BM and PM were increased by $1,015 and $1,720 ha−1 in growing season 2015–2016, and $967 and $1,295 ha−1 in 2016–2017, respectively, compared to NM. The PE film was barely degraded, whereas biodegradable film residue was reduced to an extremely low level with less than 5 kg ha−1 on field at 330 DAS. Therefore, BM is a viable and eco‐friendly alternative to PM for increasing yield of winter potato in the south of China.

Soil hydro-thermal characteristics, maize yield and water use efficiency as affected by different biodegradable film mulching patterns in a rain-fed semi-arid area of China

The farming practice of fully mulched double ridge-furrow with polyethylene (PE) film has been widely used to improve productivity of many staple crops in arid and semi-arid regions of northwest China. However, the residual PE film has caused many environmental problems such as “white pollution” and land degradation. Biodegradable film might be a good substitute for PE film in agriculture production, but the evidence for the appropriate biodegradable film mulching pattern for maize is lacking. A 2-year field experiment was carried out to identify a suitable biodegradable film mulching pattern for maize at a typical rain-fed semi-arid site on the Loess Plateau. The local widely cultivated maize variety ‘Luodan 9′ was sown in five planting patterns: 1) conventional flat planting without film mulching (CK); 2) flat planting with full mulching with biodegradable film (FB); 3) ridge-furrow planting with biodegradable film mulching on ridges (RFB); 4) double ridge-furrow planting with full biodegradable film mulching (DRFB) and with full transparent PE film mulching (DRFP). The results indicated that biodegradable film mulching patterns (including FB, RFB and DRFB) significantly increased soil hydrothermal conditions, improved leaf area index, shoot and root biomass, and thus enhanced maize yield and water use efficiency (WUE) in comparison to CK (P < 0.05). Among the three biodegradable film mulching patterns, maize yield and WUE in DRFB (average across two growing seasons) were 9.7% and 11.7% significantly greater than FB, and were 9.9% and 12.2% significantly greater than RFB. In addition, maize yield and WUE in DRFB did not differ significantly from those in DRFP, except that the maize yield was 5.2% (P < 0.05) lower than DRFP in 2013 (a warm and dry season). Present field demonstration clearly indicated that DRFB could serve as a promising option to ameliorate soil hydrothermal conditions, improve maize growth and yield performance, boost WUE, and simultaneously reduce environmental risks such as “white pollution” in rain-fed semi-arid regions of northwest China.

An Appraisal of Biodegradable Mulch Films with Respect to Strawberry Crop Performance and Fruit Quality

Fragaria × ananassa is a fruit grown all over the world, appreciated for its organoleptic and nutraceutical properties. Together with other berry fruits, it is rich in bioactive molecules that make it a beneficial fruit for human health. However, strawberry cultivation is influenced by pre- and post-harvest factors. Being a small plant, its fruit comes into direct contact with the soil and, as such, can quickly decompose. To reduce this inconvenience, farmers have used different strategies to mulch the soil, and the most useful method is polyethylene mulch films that are not biodegradable. The focus on environmentally sustainable agriculture can be represented by a transition to biodegradable mulch films. In our study, ten biodegradable mulch films were used to understand their effectiveness in covering the soil during the cultivation cycle of strawberry cv. Rociera. Polyethylene film was considered the control. The best yield and the highest number of fruits with greatest size and quality were obtained on polyethylene, BioFlex® (P2), Bio 6, and Bio 7 films. On BioFlex® (P2) and Bio 3 biodegradable films, strawberries showed a higher calcium and magnesium content, respectively. These results may encourage growers toward the use of eco-sustainable agricultural practices, such as biodegradable mulch films.

Characterization of a mesophilic actinobacteria that degrades poly(butylene adipate-co-terephthalate)

An aliphatic aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT) is a chemically synthetic and biodegradable polymer that exhibits good mechanical properties, similar to those of low-density polyethylene (LDPE), and can be a replacement for LDPE as biodegradable mulch films in the agricultural field. Biodegradability of PBAT is stable at high temperature conditions (50 – 60 ˚C) such as compost environments compared to mild temperature conditions (25 – 37 ˚C) such as soil environments. Considering that PBAT could be used in biodegradable agricultural applications such as mulching film, it is important to investigate the biodegradation mechanism at mild temperatures. In this study, a PBAT-degrading bacterium isolated from a soil environment, designated as strain NKCM 2511, was studied in detail. Genetic and biochemical analysis revealed that the strain belongs to the genus Rhodococcus in the phylum Actinobacteria. The strain grew only in aerobic conditions and formed a clear zone on a PBAT containing plate in the temperature range of 20 ˚C to 30 ˚C. Based on biochemical oxygen demand (BOD) biodegradation testing, among 3 PBAT components, adipicacid and terephthalic acid resulted in low growth rate of the strains (5 % and 7 %, incubated at 25 °C for 20 days), whereas 1,4-butanediol resulted in good growth of the strains (55 %). The low BOD biodegradation rate of PBAT by this strain (7 %) may be due to such low rates of terephthalic and adipic acid. Additionally, the PBAT degradation rate was proportional to the growth rate in the presence of various carbon sources. Therefore, the strain was an aerobically mesophilic PBAT-degrading bacterium that expressed the PBAT-degrading enzyme constitutively. To our knowledge, this is the first report on a PBAT-degrading actinobacterial strain in mild conditions. This study provides information to better understand the biodegradation mechanism of PBAT under mild conditions such as in fields.

Disintegration and mineralization of mulch films and leaf litter in soil

Biodegradable mulch films are used in agriculture for controlling weeds. The intrinsic biodegradability and safety of the films is proven by using standard test methods in the laboratory. On the other hand, the degradation that occurs in fields after use can be followed by observing the fragmentation and disappearance over time. The disintegration that occurs after use is a relevant process, because persistent shreds can interfere with the subsequent crop and disrupt the agricultural cycle in the long term. Disintegration is not proof of biodegradation. If fragmentation is not followed by ultimate biodegradation, it is just a shift of the pollution from a visible to an invisible state, which is ultimately the source of microplastics. In this article we followed both the “disappearance” of pieces of a conventional mulch film, a biodegradable one, filter paper, and dried maple leaves and their parallel conversion into CO2. The results showed that there was a clear correlation between the visual disappearance of the tested material and the mineralization level. The final mineralization of the biodegradable mulch film was similar to the level reached by filter paper and dried leaves, while the conventional mulch film showed neither fragmentation nor mass loss nor mineralization.

Fully biodegradable film to boost rainfed maize (Zea mays L.) production in semiarid Kenya: An environmentally friendly perspective

Abstract Conventional polyethylene plastic film mulching has been widely used, but its subsequent plastic residue pollution received widespread concern. Fully biodegradable film mulching is viewed as a potential substitution solution, however, it is generally thought not to be efficient as conventional plastic film mulching in field productivity and economic harvest. A two-year field experiment using a newly produced fully biodegradable film was conducted in semiarid Kenya in 2016 and 2017 respectively. Five treatments were designed as: 1) ridge-furrow mulching (RFM) with transparent plastic film (RFMT), 2) RFM with fully biodegradable film (RFMD), 3) RFM with black plastic film (RFMB), 4) RFM with grass straw (RFMG) and 5) traditional flat planting without mulching (FP) as CK. We found that RFMD achieved the similar evaporation-restricted, yield-increased and water-saving effectiveness as RFMT and RFMB did across two growing seasons. The RFMD lowered evaporation by 58.1 mm, while increasing grain yield by 70.16 %, above-ground biomass by 77.7 % and water use efficiency (in reference to grain yield) (WUEG) by 131.8 % in comparison with CK respectively. Furthermore, RFMD increased net economic income by 49.8 % in 2016 and 42.0 % in 2017 respectively relative to CK, as RFMT and RFMB did. It is noted that the degradable film used in this experiment is a non-polyethylene material and still can be maintained for 60 days in a fine physical state. Also, average soil temperature was significantly elevated by 1.6 °C in 2016 and 1.8 °C in 2017 in RFMD respectively, in comparison with CK, which was beneficial to crop growth and grain filling particularly in relatively cool long rainy season. Considering residual film pollution, the biodegradable film showed reliable advantages in environmental friendliness and field productivity. Therefore, it might be a promising farming solution to boost rainfed maize production and environmental sustainability in east African Plateau.

PBAT biodegradable mulch films: Study of ecotoxicological impacts using Allium cepa, Lactuca sativa and HepG2/C3A cell culture

Biodegradable mulch films are an alternative to polyethylene films used in agriculture for weed control, improving crop productivity. This change could minimize the residue production and costs related to the final disposal. Nevertheless, the environmental safety of these biodegradable products is scarcely investigated. In this work, samples of poly(butylene adipate-co-terephthalate)-PBAT mulch films, with and without UV stabilizer additives, were prepared. Aqueous extracts of soil samples, where mulch films were disposed, were investigated using bioassays with Lactuca sativa, Allium cepa, and cell culture HepG2/C3A. As PBAT is expected to suffer photodegradation and biodegradation, soil samples mixed with films before and after these processes were evaluated. Soil aqueous extracts promoted root grown (mainly hypocotyl) of L. sativa, probably due to presence of nutrients. So, to evaluate toxicity potential, in this case it was necessary to use aqueous extract prepared with soil instead of ultrapure water as the control. After doing this analysis it was observed that no adverse impacts due to PBAT films occurred. No chromosomal abnormalities were observed in A. cepa bioassay for any of tested samples. The absence of genotoxic potential was confirmed by comet assay and micronucleus test using human hepatocarcinoma cell line HepG2/C3A. These results showed that the soil did not induce damage to the tested organisms, before and after degradation of PBAT films.

Effects of residual plastic-film mulch on field corn growth and productivity

Plastic-film mulching has played an important role to promote agricultural production in arid areas; however, due to its inefficient recycling capacity, large amounts of residues have been accumulated in soils, causing negative impacts on crop growth and on the environment. To investigate these effects on water use efficiency, a two-years field experiment was carried out, applying different levels of plastic-film residues, from 0 to 600 kg ha−1. Results show that these residues have a negative impact on root and shoot growth at several growth stages of corn crop, particularly if above 300 kg ha−1. Root length and weight density decrease with the amount of residues throughout the majority of crop season. Plastic-film residues of about 600 kg ha−1 are responsible for the decrease of the biomass root to shoot ratio during the tasseling stage. Moreover, during physiological maturity, root and shoot revealed the highest sensitivity, and the least negative effects on the root system. Results also show that crop water consumption has a slight decrease with the plastic-film residues, though there was also a significant decrease of the yield and the water use efficiency reduction. This information allows to state that it is determinant to learn how to deal with the problem, adjusting the irrigation and crop management to avoid yield impacts. It would also be important to find an efficient procedure to mechanically collect the residues in the soil, and to apply new biodegradable film mulching.

Metrics for quantifying the circularity of bioplastics: The case of bio-based and biodegradable mulch films

The concept of circularity and its quantification through the Material Circularity Indicator (MCI) is well established for traditional plastic products. In this paper a methodological approach for calculating the circularity of bio-based and biodegradable (BB) products is proposed and applied to BB mulch films. BB products are different from traditional products in as much as they are sourced and regenerated (recycled) not through technical cycles but the biological loop. The suggested method is an adaptation of the MCI where two major changes were made: (i) the mass of the bio-based component corresponds to the recycled material in input and (ii) the mass of the bio-based component leaving the system through composting or biodegradation in soil is accounted as recycled. The modified MCI supports the eco-design of innovative BB products and allows for the comparison of their circularity taking into account the biological source and the expected end of life process such as biodegradation. To demonstrate the adaptation, the method has been applied to BB mulch films. Results showed that the MCI of a biodegradable mulch film, characterized by an average bio-based feedstock content of 30% is 0.37 ± 0.04 in a 0–1 scale. For BB mulch film, the amount of bio-based feedstock is the most sensitive factor and controls linearly the value of the MCI.

Effects of biodegradable plastic film mulching on soil microbial communities in two agroecosystems.

Plastic mulch films are used globally in crop production but incur considerable disposal and environmental pollution issues. Biodegradable plastic mulch films (BDMs), an alternative to polyethylene (PE)-based films, are designed to be tilled into the soil where they are expected to be mineralized to carbon dioxide, water and microbial biomass. However, insufficient research regarding the impacts of repeated soil incorporation of BDMs on soil microbial communities has partly contributed to limited adoption of BDMs. In this study, we evaluated the effects of BDM incorporation on soil microbial community structure and function over two years in two geographical locations: Knoxville, TN, and in Mount Vernon, WA, USA. Treatments included four plastic BDMs (three commercially available and one experimental film), a biodegradable cellulose paper mulch, a non-biodegradable PE mulch and a no mulch plot. Bacterial community structure determined using 16S rRNA gene amplicon sequencing revealed significant differences by location and season. Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA where differences were observed between BDMs and no-mulch plots. Extracellular enzyme assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDMs and PE treatments. Overall, BDMs had comparable influences on soil microbial communities to PE mulch films.