Biodegradable Mulch Films Research Articles

Degradability of biodegradable plastic films and its mulching effects on soil temperature and maize yield in northeastern China

Plastic film is an important resource in agricultural production, but it takes hundreds of years to degrade completely in natural environment. The large-scale use of plastic film will inevitably lead to serious environmental pollution. One way to solve the problem is to develop a substitutable mulching film, such as a biodegradable film that can ultimately be decomposed to water, carbon dioxide, and soil organic matter by micro-organisms. In this study, a 2-year experiment was conducted to determine the degradation properties of a biodegradable plastic film, including degradation rate, surface microstructure, tensile strength and elongation at break, and the effects of different mulching treatments on soil temperature and maize yield. The mulching experiment was conducted with three different biodegradable plastic films with different degradation rates, using a common plastic film and a non-mulched treatment as control. With the addition of the additives for degradation in the biodegradable plastic films, the degradation rates increased significantly, which were 7.2%-17.8% in 2017 and 18.1%-35.2% in 2018 after maize harvesting. However, the degradation occurred mainly on the ridge side. The decrease in tensile strength and elongation was proportional to the degradation rate of the degradable film. The SEM results indicated that the surface microstructures of the biodegradable films were loose and heterogeneous after maize harvesting. Biodegradable plastic film mulching increased the soil temperature at soil depths of 5 cm, 15 cm, and 25 cm, over the maize’s entire growth period, by 3.1°C-3.2°C in 2017 and 1.2°C-2.1°C in 2018 compared with the non-mulched treatment. The biodegradable plastic film increased the maize yield by 10.4%-14.3% in 2017 and 11.6%-24.7% in 2018. The soil temperature and maize yield increases were statistically significant; however, with respect to maize qualities, there were no statistically significant increases among the five treatments. This study shows that biodegradable plastic film can be used as a substitute for common plastic film. However, the ingredients in biodegradable plastic films should be improved further to ensure that they can be degraded completely after crop harvest. Keywords: biodegradable plastic film, film mulching, degradation properties, soil temperature, maize yield DOI: 10.25165/j.ijabe.20201302.5360 Citation: Zhang W W, Wang L H, Zhou J Q, Zhu K L, Sun S J. Degradability of biodegradable plastic films and its mulching effects on soil temperature and maize yield in northeastern China. Int J Agric & Biol Eng, 2020; 13(2): 146–153.

Appraisal of Biodegradable Mulching Films and Vegetal-Derived Biostimulant Application as Eco-Sustainable Practices for Enhancing Lettuce Crop Performance and Nutritive Value

Scientists, extensions specialists, and growers are seeking sustainable agricultural practices that are able to cope with these objectives in order to ensure global food security and minimize environmental damage. The use of mulching films and plant biostimulants in agriculture seems to be a valid solution for tackling these rising concerns. A greenhouse experiment was conducted in order to elucidate the morpho-physiological and nutritive characteristics of lettuce (Lactuca sativa L.) in response to foliar application of a tropical plant extract (PE) biostimulant and the use of plastic mulches. Two biodegradable mulch treatments (Mater-Bi® 1 and Mater-Bi® 2) were compared to black polyethylene (LDPE) and bare soil. Biodegradable mulch film Mater-Bi® 1 produced a comparable marketable fresh yield to the commercial standard polyethylene (LDPE), whereas Mater-Bi® 2 exhibited the highest crop productivity. When averaged over biostimulant application, lettuce plants grown with biodegradable film Mater-Bi® 2 exhibited superior quality traits in terms of K, Ca, total ascorbic acid, and carotenoids content. The combination of film mulching (LDPE, Mater-Bi® 1 or Mater-Bi® 2) with the tropical plant extract biostimulant exhibited a positive and significant synergistic effect (+30%) on yield. The PE-biostimulant induced higher values of SPAD index and total chlorophyll content when compared to untreated greenhouse lettuce. The mineral content of leaf tissues was greater by 10% and 17% (for P and Ca, respectively) when compared to the untreated lettuce (no PE application). Nitrate content was significantly reduced by 23% in greenhouse lettuce plants receiving PE as compared to the untreated control. The positive effect of Mater-Bi® 2 film on the ascorbic acid content has also been highlighted when combined with the biostimulant application, where a major amplification of total ascorbic acid (+168%) was recorded in comparison to the untreated lettuce. Overall, our work can assist leafy vegetables growers in adopting good agricultural practices, such as biodegradable plastic mulches and vegetal-derived biostimulants, to improve the sustainability of greenhouse production.

Biodegradable Mulch Film Technology and Harpin Protein for Quality Enhancement of Anna Apples During Cold Storage

Biodegradable Mulch Film Technology and Harpin Protein for Quality Enhancement of Anna Apples During Cold Storage

Biodegradable Mulch Based on Cellulose of Cornhusk with Addition Anti UV-Tinuvin

Plastics generally cause global-scale problems because they cannot be degraded into the environment and causing a build-up of plastic waste. Biodegradable plastic material can be an alternative to solve the problem because of its nature which is easily naturally degraded by microorganisms. One of the natural wastes that can be utilized to become fillers in plastic mulch so it is more easily degraded is cornhusk because its utilization is still limited and cornhusk has high cellulose content. In this study, the extraction of cellulose was carried out on cornhusk to obtain cellulose by the alkali method. There was a decreased in hemicellulose and lignin levels, which indicated that the extraction process was quite successful. Then in the process of making biodegradable mulch films, Tinuvin P was added as an anti-UV agent and oleic acid was carried out as plasticizer and with several variations. The results show that the addition of anti-UV agent P and addition of oleic acid reduces the mechanical properties of biodegradable mulch and can control the rate of degradation of the biodegradable mulch film.

Mechanical Property Deterioration of PBAT/PLA/ENR Mulching Films for the Cultivation of Fruit Trees and Flowers Under Real Field Conditions

The present study investigated the effect of different component ratios on the mechanical and biodegradable properties of the bio-based mulching film. Bio-based mulching films were prepared using blown film extrusion with extruder barrel temperature settings ranging between 167 to 170 ◦C and an extruder pressure of 119 bar. The blend composition consisted of Poly (Butylene Adipate-co-Terephthalate) (PBAT), Epoxidized Natural Rubber (ENR), and Polylactic Acid (PLA). The effect of real field conditions on the mechanical properties of the mulching films during the time of cultivation was investigated using a universal testing machine and the pendulum tear method. The mechanical property deterioration of the PLA/ENR mulching films under real field conditions was due to biodegradation caused by biological activity, temperature, and humidity. The results show that the performance of the biodegradable mulching films under actual user conditions for 6 months was still effective and the quality of the fruit trees and flowers improved when using the PLA/ENR mulching films.

Potential Use of Earthworms to Enhance Decaying of Biodegradable Plastics

Biosolid application, wastewater irrigation, and plastic mulching technologies are major sources of plastic pollution in agroecosystems. Microplastics may interact with soil physicochemical properties and organisms and negatively affect plant growth. To alleviate environmental plastic pollution, synthetic and biobased biodegradable polymers are replacing nonbiodegradable polymers, but their biodegradation rate in the field is frequently lower than that estimated from standardized biodegradation testing. Plastic polymer biodegradation is a multistep process that involves plastic deterioration, microbial colonization, production of polymer-degrading exoenzymes, and mineralization. However, these physicochemical and biological processes are not always efficient because of unfavorable environmental conditions (e.g., temperature, soil moisture). We propose to use earthworms to increase the biodegradable polymer biodegradation rate by creating optimal habitats for microbial proliferation. Earthworm-induced processes that lead to soil alteration (bioturbation) and solid organic wastes decomposition (vermicomposting) are described to understand how earthworms may favor biodegradable plastic mineralization. Therefore, we suggest two practical sustainable bioengineering strategies: (1) enhancing bioturbation by inoculating agricultural soils with soil-dwelling earthworms, which is viable for horticulture where using biodegradable mulching films increases plastic debris in the soil and (2) vermicomposting with blended biodegradable plastic debris and solid organic wastes, which is complementary to industrial or home composting of single-use biodegradable plastics.

An optimized model for simulating grain-filling of maize and regulating nitrogen application rates under different film mulching and nitrogen fertilizer regimes on the Loess Plateau, China

Grain-filling is a key stage allowing for the achievement of high grain yield. The ridge-furrow film mulching (RFFM) farming system has been widely adopted as a water saving and yield-improving planting pattern on the Loess Plateau of China. However, there is no convenient and effective model to understand the mechanism of maize grain-filling and effective nitrogen (N) management to obtain high grain yield under RFFM and N fertilizer. A two-year (2017–2018) field experiment was conducted on summer maize under RFFM (biodegradable film mulching (BM) and PE film mulching (PM)) and nitrogen fertilizer (0 (N0), 90 (N1), 180 (N2) and 270 (N3) kg N ha−1). The results showed that the 100-kernel dry weight was successfully simulated by the proposed model. After optimizing parameters, the model not only achieved minimum input requirements, but also successfully regulated N application. Moreover, characteristic parameters of grain-filling were significantly affected by the interaction of RFFM and N. N was beneficial for the improvement of the final 100-kernel dry weight (a) and grain-filling rate (Vmax, V¯) and was more improved under BM. The N1 with PM treatment reached the maximum grain-filling rate (Vmax) earlier. The maximum grain-filling rate (Vmax) and average rate of grain-filling (V¯) of PM was more sensitive to high N than BM. Parameters of the gradual-growing period were significantly affected by RFFM or N, but the interaction between RFFM and N had extremely significant effects on parameters of the fast-growing and slow-growing periods. For BM, N could improve the rate of three periods of grain-filling, and the N2 treatment was the best in the fast-growing and slow-growing periods. For PM, N could improve the rate of the gradual-growing period. According to the optimized model, the optimal nitrogen application rate of BM and PM was 205 kg ha−1 and 196 kg ha−1, respectively. Based on this optimized model, we could better understand the grain-filling process and achieve the appropriate nitrogen application rate.

Effects of different film mulches on photosynthetic characteristics and yield of summer maize (Zea mays L.) in the North China Plain

ABSTRACT Summer maize (Zea mays L.) is a globally essential food crop. To find the optimal mulch for summer maize, we explored the photosynthetic characteristics and yield of maize under different mulches. Four treatments were used during the 2016–2018 summer maize growing seasons: no mulch (CK), transparent film mulch (PF), biodegradable transparent film mulch (WF), and biodegradable black film mulch (BF). Thirty days after mulching, soil temperatures decreased in the order WF>PF>BF>CK. In all growing seasons, the chlorophyll content index (CCI) of maize was highest with BF. In 2016, the CCI with BF was 17.3%, 8.2%, and 13.2% higher than that with CK. At the flowering and filling stages, the net photosynthetic rate was highest with BF and lowest with PF. Meanwhile, the leaf water-use efficiency at the filling stage was 12.7% and 15.1% higher with BF than that with CK in 2017 and 2018, respectively. The 1000-kernel weight with BF was 8.9% and 2.5% higher than that with CK in 2016 and 2017, respectively, and the GY was 14.8% and 10.2% higher. These results indicate that biodegradable black film mulching is a feasible measure to improve the photosynthetic capacity and yield of maize in the North China Plain.

The effects of biodegradable and plastic film mulching on nitrogen uptake, distribution, and leaching in a drip-irrigated sandy field

Drip irrigation under plastic film mulching with applications of the N-fertilizer is an excellent agricultural strategy, resulting in saving irrigation water, improving N use efficiency, and increasing crop yield. However, the film residue and nitrate-nitrogen (NO3-N) losses are the leading cause of non-point pollution in agricultural fields. To promote the development of sustainable agriculture, the HYDRUS (2D/3D) model was first calibrated and then validated using experimental data from 2016 and 2017, respectively, collected in the drip-irrigated sandy field with plastic film mulching (PFM), biodegradable film mulching (BFM), and no film mulching (NFM). Additionally, the NO3-N spatial and temporal distributions, uptake, leaching, and use efficiency (NUE) under PFM, BFM, and NFM with 280 kg ha−1 of the N-fertilizer (the local recommendation) were evaluated using both observed and simulated data. These factors were also assessed under BFM with 210 (75 % of the recommended value) and 140 kg ha-1 (50 % of the recommended value) of the N-fertilizer. The results of numerical simulations were in good agreement with observations, with the RMSE, R2, and NSE during verification being 0.01-0.08 mg cm-3, 0.62-0.87, and 0.68-0.94, respectively. When the same amount of the N-fertilizer (280 kg ha−1) was applied in each treatment, there were no apparent differences in NO3-N concentrations in the soil profile, cumulative NO3-N uptake by corn (CNU), and cumulative NO3-N leaching (CNL) in the 100-cm soil depth between the BFM280 and PFM280 scenarios (the subscript indicates the amount of the N-fertilizer) during the early growing season (Day After Sowing [DAS] of 0–78 in 2016 and DAS of 0–92 in 2017). However, CNU and CNL were higher, and the NO3-N concentrations in the upper soil layer (0−40 cm soil layer) lower in these two scenarios than in the NFM280 scenario. The NO3-N concentrations in the topsoil layer (the 0−20 cm soil layer) in the BFM280 scenario were 3.9 % higher than in the PFM280 scenario during DAS 93–154 in 2017 due to the disintegration of the biodegradable film and 26.3 % lower during DAS 79–155 in 2016 because of intensive rainfall. Additionally, the highest NUE (50.9 kg kg-1, the average value for two years) was found when 75 % of the recommended N-fertilizer (210 kg ha−1) was applied. Therefore, an application of 210 kg ha−1 of the N-fertilizer in the BFM scenario can be recommended for sandy farmland to avoid plastic pollution, increase NUE, and effectively promote the development of sustainable agriculture.

The Effects of Biodegradable Mulch Film on the Growth, Yield, and Water Use Efficiency of Cotton and Maize in an Arid Region

Plastic residual film pollution in China is severe, and the use of degradable mulch film instead of plastic mulch can effectively alleviate this situation. The substitution of common polyethylene plastic mulch film with biodegradable mulch film in the agricultural production of cotton and maize in an arid region was investigated in the present study. Using bare soil as the control, we compared the effects of common polyethylene plastic film and biodegradable mulch film on crop growth, yield, and water use efficiency (WUE) in maize and cotton. The results indicated that: (1) the biodegradable mulch film in this region remained intact for 60 days after being laid down, significantly degrading after 120 days, and was associated with increased soil temperature, moisture conservation, and degradability in comparison to a bare soil control; (2) Both the biodegradable mulch film and the polyethylene plastic film significantly increased various physiological parameters, such as crop height, stalk diameter, and leaf area; (3) The biodegradable mulch film had a significant effect on crop yield by 69.4–76.2% and 65.2–71.9%, respectively, compared to the bare soil control. (4) Compared to the bare soil control, the biodegradable mulch film effectively increased WUE in the crops by 64.5–73.1%. In summary, biodegradable mulch film had comparable results to the common polyethylene plastic film in increasing crop growth, yield, and WUE. As the biodegradable mulch film causes no residual pollution, it is thus preferable to common plastic mulch film for agricultural applications in arid regions and supports the sustainable development of agroecosystems. Therefore, the use of degradable mulch films in agricultural production is more environmentally friendly and more conducive to the sustainable development of agricultural systems.

Quantification of Synthetic Polyesters from Biodegradable Mulch Films in Soils.

Soil biodegradable mulch films composed of the polyester polybutylene adipate-co-terephthalate (PBAT) are being increasingly used in agriculture. Analytical methods to quantify PBAT in field soils are needed to assess its soil occurrence and fate. Here, we report an analytical method for PBAT in soils that couples Soxhlet extraction or accelerated solvent extraction (ASE) with quantitative protonnuclear magnetic resonance (q-1H NMR) spectroscopy detection. The 1H NMR peak areas of aromatic PBAT protons increased linearly with PBAT concentrations dissolved in deuterated chloroform (CDCl3), demonstrating accurate quantitation of PBAT by q-1H NMR. Spike-recovery experiments involving PBAT addition to model sorbents and soils showed increased PBAT extraction efficiencies into chloroform (CHCl3) with methanol (MeOH) as cosolvent, consistent with MeOH competitively displacing PBAT from H-bond donating sites on mineral surfaces. Systematic variations in solvent composition and temperatures in ASE revealed quantitative PBAT extraction from soil with 90/10 volume % CHCl3/MeOH at 110-120 °C. Both Soxhlet extraction and ASE resulted in the complete recovery of PBAT added to a total of seven agricultural soils covering a range of physicochemical properties, independent of whether PBAT was added to soils dissolved in CHCl3, as film, or as particles. Recovery was also complete for PBAT added to soil in the form of a commercial soil biodegradable mulch film with coextractable polylactic acid (PLA). The presented analytical method enables accurate quantification and biodegradation monitoring of PBAT in agricultural field soils.

Optimization of Processing Parameters to Increase Thermal Conductivity of Rice Straw Fiber Film

Biodegradable mulching film (BMF) is a promising alternative to petroleum-based plastic mulching film. Thermal conductivity is an important quality factor of BMF that affects the heat transfer between ambient to soil and plant growth. The objective of this research was to enhance the thermal conductivity of fiber film through an environmentally friendly agent and optimized processing conditions. Response surface methodology (RSM) was used to optimize the processing conditions. With optimized process conditions of 70 g/m2 basis weight, 1.5% wet strength agent content, 0.5% neutral sizing agent content, 15% charcoal addition ratio, and 55 °SR beating degree, the films showed satisfactory thermal conductivity (0.0714 W/m·K) and high dry and wet tensile strengths (33.4 and 12.2 N). The addition of charcoal increased the thermal conductivity of the film by 34.31%. This promising result shows the biodegradable fiber film is able to increase soil temperature and meet the required temperature for crop growth.

Evaluating the effects of biodegradable film mulching on soil water dynamics in a drip-irrigated field

Drip irrigation with plastic film mulching (PM) is an important agricultural practice used to conserve soil water and produce higher crop yields worldwide. However, the plastic film is usually made from non-degradable polyethylene materials, which may lead to the incorporation of plastic into soils and cause a series of negative environmental effects. As such, biodegradable film mulching (BM) can represent a valuable alternative to PM. A two-year experiment was carried out during the 2014 and 2015 seasons to evaluate the effects of PM, BM, and no film mulching (NM) on the soil water balance in the corn field. The two-dimensional numerical HYDRUS-2D model was calibrated and validated using experimental data collected in 2014 and 2015, respectively, under BM, PM, and NM and then used to evaluate soil water contents (SWC), water fluxes, and soil water balances in two-dimensional soil profiles. The results of numerical simulations were in good agreement with measurements, with the mean relative errors for the calibration and validation periods for BM, PM and NM of 11.2%, 10.7%, and 11.7%, respectively. The results showed that SWCs were similar in the BM and PM scenarios during early and middle crop growth periods. Significant differences in SWCs were observed only after the average fraction of the disintegrated area of the biodegradable film was equal or higher than about 40% (during the late crop growth period). The results also showed that mulching mainly affects SWCs in the top 0–20 cm soil layer. There were significant differences in cumulative evaporation and water fluxes between different treatments, but an insignificant difference in root water uptake between PM and BM. Cumulative evaporation for BM increased by 30.5% compared to PM and decreased by 41.9% compared to NM. Corresponding cumulative water fluxes at the 80 cm depth increased and decreased by 6.6% and 48.8%, respectively. Two-dimensional simulations of soil water content distributions revealed that the “water stress” area in the soil profile (with SWCs lower than readily available water) before irrigation was 1.79 and 0.75 times larger for BM than for PM and NM, respectively. SWCs in the surface soil layer of BM also increased after rainfall during the late crop growth period, which improved the rainwater use efficiency by 8.2% compared to PM. Both experiments and simulations revealed that BM has more comparable soil moisture dynamics to PM than to NM.

Development and prospect of biodegradable mulch films in China

Development and prospect of biodegradable mulch films in China

Production of bio-degradable mulch film with innovating sowing solutions as the future for agriculture

Production of bio-degradable mulch film with innovating sowing solutions as the future for agriculture

Assessment of the Effect of Mulch Film on Crops in the Arid Agricultural Region of China under Future Climate Scenarios

Plastic mulch film is widely used in agricultural production. However, there are very few studies on degradable mulch film. In order to investigate the effects of using degradable mulch film in arid regions on crop yield and water use efficiency, we used fully biodegradable mulch films on both maize and bare land cultivation experimental areas. The DeNitrification-DeComposition (DNDC) model was used to analyze changes in maize biomass in the future under different climate scenario models. We found that using fully biodegradable mulch film in an arid region had a positive effect on biomass yields. In 2015–2017, the annual maize biomass yield increased by 24.5%, 28.9%, and 32.9%, respectively. Hence, this method has expansion and promotion value. A comparison of the DNDC model simulated biomass yields and actual measured values found that the ranges of R2, root mean square error (RMSE), and model efficiency (ME) were 0.98–0.99, 0.38–0.86 mg C ha−1, and 0.80–0.98. This result shows that the DNDC model can accurately simulate changes in maize biomass in this region. Under the premise of a good model fit, future climate scenario model data were used to drive the DNDC model. The results showed that the possible range of maize biomass yields in the future is −6.5% to 10.3%, with the most probable range being 0.2–1.5%. Using future climatic conditions, our work suggests that degradable mulch films can increase water use efficiency by an average of 9.5%. The results of this study can be used to promote the use of degradable mulch films in arid regions, significantly improving sustainable agricultural development.

Plastic scraps: biodegradable mulch films and the aesthetics of ‘good farming’ in US specialty crop production

Agriculture is a serious contributor to pollution and other environmental harms, making it an important site of action for the development of environmentally friendly products and practices. However, farmer adoption of such options is varied and dependent on a wide range of factors including the visual appeal (i.e., aesthetics) of sustainable farming. Recent studies have shown that negative aesthetics related to more environmentally friendly ways of farming can delay or prevent adoption of such practices. Drawing on the concepts of good farming, cultural capital, and the aesthetics of waste, this paper aims to assess the status of biodegradable plastic mulch (BDM) in relation to a range of alternative and conventional specialty crop growers’ aesthetic perceptions. BDM has the potential to significantly reduce non-biodegradable polyethylene (PE) mulch waste, thus addressing serious environmental and human health concerns. However, the aesthetics of BDM may present a challenge. BDM looks identical to PE plastic, and its degradation throughout the season results in scraps in the soil. To investigate aesthetics as a possible barrier to BDM adoption, we conducted five photo-elicitation focus groups with specialty crop growers in Washington State. Results indicate that alternative growers are slightly more adverse to the aesthetics of BDM, especially because of its ‘plastic’ appearance. Conventional growers had higher rates of BDM adoption, even though they felt a strong aesthetic aversion to the messy nature of BDM degradation. Confidence in the product, particularly as a result of education and experience, was believed to be the key to overcoming this negative aesthetic. Study participants offered a variety of ways to enhance the acceptability of BDM, such as making the mulch brown instead of black. These findings have wider implications for the acceptance and adoption of practices that, although environmentally friendly, have an unattractive visual element.

The role of mulching materials onLactuca sativaproduction – Brazil case study

In Brazil, the commonly used mulches in lettuce production are vegetable scraps or polyethylene film. In opposition, the use of biodegradable mulch films is increasing in Europe due to environmental problems associated to the conventional ones. Few studies regarding the application of these new mulches on horticulture crops in Brazil have been reported, which is a great barrier for the acceptance by producers. The main objective of this study was to fulfill this lack of knowledge, by the evaluation of the performance of different mulches on lettuce production. For this purpose we followed, throughout lettuce production cycle, the soil temperature, water volume and nitrogen content, mulch durability and deterioration, weed suppression, and crop yield. A full-scale field experiment was set up in the Taubate University Campus, to evaluate the suitability of three modalities for mulching application in lettuce production in comparison with bare soil. The experimental design used were randomized blocks with five replicates of all the treatments: (T1) bare soil, (T2) cover with rice husk, (T3) cover with polyethylene film and (T4) cover with biodegradable film. The variety used was crispa, with a cycle of 50 days and starting after the transplantation occurred on September 22, 2014. From results obtained, we observed that soil temperature and water volume content were higher on film modalities (T3 and T4). Regarding nitrogen soil content we observed that the lowest value was achieved on T2 modality. As expected, the weed control was higher in film modalities and the mulch films mechanical properties were kept along the crop cycle. Regarding average production of each modality, the highest values were obtained with T4 with 945 g plant‑1 followed by T3 with 823 g plant‑1, T2 with 733 g plant‑1, and T1 with 575 g plant‑1, respectively. Overall, we concluded that biodegradable mulch film, compared to polyethylene and rice husk, was more effective.

Evaluation of the biodegradation rate of mulch films

In Brazil in 2010 about 2,500 t of mulch films was used in horticulture. After the crop cycle, polyethylene mulches are often buried or burned with crop residues, as mulch films recycling is time-consuming and expensive due to high removal labour cost. Biodegradable mulch films appear as an alternative to polyethylene use, once they are incorporated in soil with crop residues at the end of the crop cycle. This study was performed in order to evaluate the biodegradation of different types of mulches in both real and laboratorial conditions, in tropical soils. The experimental design used was randomized blocks with five repetitions and four treatments: bare soil (BS), rice husk mulch (RHM), polyethylene mulch (PM), and biodegradable mulch (BM). In the laboratory a respirometric test was performed with the soil, at 70% of water holding capacity and 28°C. Carbon dioxide production was measured every 2 days, during a 20-days period. Microbial carbon was also determined by fumigation method, at the end of respirometric test. The results showed that the BM modality produced more carbon dioxide, 82.01 mg C-CO2 g soil‑1, than other modalities. Microbial carbon was higher on RHM modality with 21.56 µg Cmic g soil‑1, followed by BM with 19.60 µg Cmic g soil‑1 and lower values were found on BS and PM, with 12.18 and 13.57 µg Cmic g soil‑1, respectively. From the results obtained, RHM and BM higher CO2 verified were probably due to a synergetic effect between mulches carbon content and microorganism growth rate.

Impact of farmland mulching practices on the soil bacterial community structure in the semiarid area of the loess plateau in China

Farmland mulching is widely used to preserve soil moisture and increase crop yield in the semiarid region of the Loess Plateau. However, the effect of different farmland mulching on soil bacterial communities is not clear. Therefore, the impact of a 5-year field management practice (surface mulching) on the soil bacterial communities was studied in dryland farmland of the Loess Plateau by using Illumina sequencing of the 16S rRNA gene. The following treatments were investigated: (1) ridge-furrow mulching pattern; (2) flat plastic film mulching; (3) flat biodegradable film mulching; (4) flat straw mulching; and (5) control (CK), conventional flat planting without mulch. All farmland mulching increased the diversity of soil bacteria and the diversity was greatest under the plastic film treatment. The dominant phyla across all soil samples were Proteobacteria, Acidobacteria, and Actinobacteria. Cluster analyses showed that bacterial communities under mulching treatments were different from that of CK. The bacterial community composition of plastic film and straw mulching treatments, biodegradable film and ridge-furrow mulching treatments were similar at the phylum level. Spearman correlation analysis indicated that the response of bacterial alpha-diversity was mainly negatively associated with the soil organic carbon and total nitrogen. The Mantel test showed that the beta-diversity depended primarily on the soil total nitrogen and soil temperature. The changes of the bacterial community distribution were significantly related to the soil moisture, which varied significantly with a range of 9.8–17.3 between treatments. These results indicated that soil properties changed after long-term farmland mulching, and these changes were related to soil bacterial diversity and community structure. According to this study, flat plastic firm mulching was found to being a good option for increasing soil bacterial diversity and richness and thereby potentially stabilize functional stability of soil biological processes.