Plastic biodegradable mulch (plastic BDM) is tilled after use, but there is concern about incomplete degradation and potential impact on subsequent crops, and we lack a reliable method to measure ...mulch degradation post soil-incorporation. We conducted two field experiments to (i) develop a sampling method to estimate the amount of mulch (fragments size >2.36 mm) in the field post soil-incorporation, and (ii) assess the amount of BDM in the soil after four consecutive years of mulch incorporation. In Expt. 1, we used the quartering method to reduce soil from a 1 m2 field sample area to a representative 19 L sample. In Expt. 2, we applied and tilled four plastic BDMs: BioAgri, Naturecycle, Organix AG, and an experimental mulch; and one paper mulch, WeedGuardPlus, in their respective plots for four consecutive years. Starting in year 2, we sampled soil with the quartering method each spring and fall to determine mulch recovery. With respect to the total amount of mulch applied, average mulch recovery in the fall for the three commercial plastic BDMs was 71%, 50%, and 35% after second, third and fourth applications, respectively. For the experimental mulch, the average recovery was 80%, 69%, and 54% in the fall after second, third, and fourth applications, respectively. Recovery was slightly lower in spring than in preceding fall all years. For WeedGuardPlus, average recovery was 14%–20% in each fall, and no recovery in any spring (complete degradation). The results show that the quartering method reliably estimates the amount of mulch in a field and BDMs degrade over time in the field even with repeated applications, but complete degradation takes >1 year. While a few standards (e.g., ASTM D5988) specify how to determine biodegradation of plastics in soil under controlled laboratory conditions, our sampling method assesses plastic degradation under diverse field conditions.
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•We developed a sampling method to quantify macro- and microplastics in soil.•The quartering method reliably quantifies plastics in field soil.•Biodegradable mulch does not accumulate in field even after repeated applications.•Full degradation of biodegradable plastic mulch takes >1 year in field conditions.•Biobased content does not determine the degradation rate of the mulch.
The global use of agricultural plastic films, which provide multiple benefits for food production, is expected to grow by 59% from 2018 to 2026. Disposal options for agricultural plastics are limited ...and a major global concern, as plastic fragments from all sources ultimately accumulate in the sea. Biodegradable plastic mulches could potentially alleviate the disposal problem, but little is known about how well they degrade under different environmental conditions. We quantified the degradation of biodegradable plastic mulches in compost and in soil at warm and cool climates (Tennessee and Washington). Mulch degradation was assessed by Fourier-transformed infrared (FTIR) spectroscopy, molecular weight analysis, thermogravimetric analysis (TGA), nuclear-magnetic resonance (NMR), and mulch surface-area quantification. Biodegradable plastic mulches degraded faster in compost than in soil: degradation, as assessed by surface-area reduction, in compost ranged from 85 to 99% after 18 weeks, and in soil from 61 to 83% in Knoxville and 26 to 63% in Mount Vernon after 36 months. FTIR analyses indicate that hydrolytic degradation of ester bonds occurred, and a significant reduction of molecular weight was observed. TGA and NMR confirmed degradation of biodegradable polymers. Our results indicate that biodegradable plastic mulches degrade in soil, but at different rates in different climates and that degradation occurs over several years. Faster degradation occurred in compost, making composting a viable disposal method, especially in cool climates, where mulch fragments in soil may persist for many years.
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•Biodegradable plastic mulches are a promising alternative to polyethylene mulches.•We evaluated degradation of biodegradable plastic mulches in compost and soil.•Degradation of biodegradable mulches in soil can take several years.•Thermal time is a useful predictor for degradation in soils.•Composting is a viable disposal method for biodegradable mulches.
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•We modeled moisture dynamics under different biodegradable mulch treatments.•Biodegradable mulch can be modeled with variable-flux boundary condition.•Infiltration and evaporation ...were affected by mulch treatments.•Deterioration of biodegradable mulch caused enhanced evaporation, but reduced runoff compared to polyethylene mulch.
Plastic mulch films are often used in agriculture to conserve soil moisture. Most of the plastic mulch currently used worldwide is made of non-biodegradable polyethylene, which has to be removed and disposed after harvest, incurring significant environmental costs. Biodegradable paper or plastic mulch could offer a valuable alternative to polyethylene. The objective of this study was to compare the effects of biodegradable mulches and standard polyethylene mulch on soil moisture dynamics during a growing season. A field experiment was carried out with pumpkin (Cucurbita pepo), which were irrigated and grown on raised beds covered with the following mulch treatments: no mulch, biodegradable paper, biodegradable plastic, and polyethylene. Soil moisture was measured at 10- and 20-cm depths. A numerical model (HYDRUS-2D) was used to simulate the moisture dynamics under the different mulch treatments, each represented by different boundary conditions at the soil surface. Polyethylene mulch, which created an impermeable surface layer, effectively reduced evaporation and maintained highest water content among the treatments. Biodegradable paper mulch, which was partially permeable to evaporation and rainfall throughout the growing season, resulted in soil moisture that was intermediate between that obtained for no mulch and polyethylene. Biodegradable plastic mulch, which was similar to that of polyethylene mulch initially in terms of effects on soil moisture, disintegrated during the growing season and allowed rainfall to penetrate and water to evaporate from the soil surface. Field data and model simulations both indicate that the biodegradable paper and plastic mulches provide comparable soil moisture dynamics as polyethylene mulch.
Plastic mulch is commonly used to produce many vegetable crops because of its potential to decrease days to harvest, control weeds, and improve soil moisture conservation. However, use of plastic ...mulch is relatively new for sweet corn ( Zea mays L.) in North America. We compared five plastic soil-biodegradable mulches BDMs; Bio360, Organix AG, Clear Organix AG, Naturecycle, and Experimental polylactic acid/polyhydroxyalkanoates (Metabolix, Inc., Cambridge, MA) and a paper mulch (WeedGuardPlus) against standard black polyethylene (PE; nonbiodegradable) mulch and bare ground cultivation for growth, yield, and quality of sweet corn cultivar Xtra Tender 2171. This field experiment was carried out in Mount Vernon, WA, which has a Mediterranean-type climate with an average air temperature of 16.1 °C during the 2017 and 2018 growing seasons. The experiment was drip irrigated; and in both years, preemergence herbicides were applied to the entire experimental area 1 to 2 days after seeding, and post-emergence herbicides were applied to alleys. While most mulches remained intact until the end of the growing season, Clear Organix AG started to split shortly after laying, resulting in significant weed pressure by midseason in both 2017 and 2018. Plant height toward the end of the season was lowest for plants grown on bare ground, intermediate for Clear Organix AG and WeedGuardPlus, and highest for the black plastic BDM and PE mulch treatments both years, except for Bio360 in 2018 where plant height was intermediate. Days to 50% tasseling and 50% silking were delayed 9 and 13 days, respectively, for bare ground and WeedGuardPlus compared with all other treatments in both years. Marketable ear yield was highest with the black plastic BDMs and PE mulch and lowest with bare ground, WeedGuardPlus, and Clear Organix AG treatments in both years. Total soluble solid content of kernels, and length and diameter of ears grown on the plastic BDM and PE mulch treatments were equal to or greater than, but never lower than, bare ground and WeedGuardPlus. These results indicate that growth, yield, and quality of sweet corn grown with black plastic BDMs are comparable to PE mulch, making black plastic BDMs an effective alternative to black PE mulch for sweet corn production in a Mediterranean-type climate.
Polyethylene mulch films used in agriculture are a major source of plastic pollution in soils. Biodegradable plastics have been introduced as alternative to commonly-used polyethylene. Here we ...studied the interaction of earthworms (Lumbricus terrestris) with polyethylene and biodegradable plastic mulches. The objective was to assess whether earthworms would select between different types of mulches when foraging for food, and whether they drag macroscopic plastic mulch into the soil. Laboratory experiments were carried out with earthworms in Petri dishes and mesocosms. The treatments were standard polyethylene mulch, four biodegradable plastic mulches (PLA/PHA polylactic acid/polyhydroxy alkanoate, Organix, BioAgri, Naturecycle), a biodegradable paper mulch (WeedGuardPlus), and poplar litter, which served as control. Four and three replicates for the Petri dish and mesocosm experiments were used, respectively. Macroscopic plastic and paper mulch pieces (1.5 cm × 1.5 cm and 2 cm × 2 cm) were collected from an agricultural field after a growing season, after being buried in the soil for 6 and 12 months, and after being composted for 2 weeks. We found that earthworms did not ingest polyethylene. Field-weathered biodegradable plastic mulches were not ingested either, however, after soil burial and composting, some biodegradable plastics were eaten and could not be recovered from soil any longer. Earthworms, when foraging for food, dragged plastic mulch, including polyethylene and biodegradable plastic, and poplar leaves into their burrows. The burial of macroscopic plastic mulch underground led to a redistribution of plastics in the soil profile, and likely enhances the degradation of biodegradable mulches in soil, but also can lead to leaching of plastic fragments by macropore flow.
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•Biodegradable plastic mulches may be a viable alternative to polyethylene.•Interaction of Lumbricus terrestris with plastic mulches was studied.•Earthworms dragged plastic mulch fragments into their burrows.•Lumbricus terrestris did not ingest polyethylene mulch.•Biodegradable plastic mulch was partially ingested, but only after weathering occurred.
Forest land affected by deforestation yields high soil and water losses. Suitable management practices need to be found that can reduce these losses and achieve ecological and hydrological ...sustainability of the deforested areas. Mulch has been found to be effective in reducing soil losses; straw mulch is easy to apply, contributes soil organic matter, and is efficient since the day of application. However, the complex effects of rice straw mulch with different application rates and lengths on surface runoff and soil loss have not been clarified in depth. The current paper evaluates the efficiency of rice straw mulch in reducing the hydrological response of a silty clay loam soil under high intensity and low frequency rainfall events (tap water with total depth of 49 mm and intensity of 98 mm/h) simulated in the laboratory. Surface runoff and soil loss at three lengths of the straw (10, 30, and 200 mm) and three application rates (1, 2, and 3 Mg/ha) were measured in 50 cm (width) × 100 cm (length) × 10 cm (depth) plots with disturbed soil samples (aggregate soil size < 4 mm) collected in a deforested area. Bare soil was used as control experiment. Runoff volume and erosion were significantly (at p < 0.05) lower in mulched soils compared to control plots. These reductions were ascribed to the water absorption capacity of the rice straw and the protection cover of the mulch layer. The minimum runoff was observed for a mulch layer of 3 Mg/ha of straw with a length of 200 mm. The lowest soil losses were found with straw length of 10 mm. The models developed predict runoff and erosion based on simple linear functions of mulch application rate and length, and can be used for a suitable hydrological management of soil. It is concluded that, thanks to rice straw mulch used as an organic soil conditioner, soil erosion and surface runoff are significantly (at p < 0.05) reduced, and the mulch protection contributes to reduce the risk of soil degradation. Further research is, however, needed to analyze the upscaling of the hydrological effects of mulching from the plot to the hillslope scale.
•Understanding the effects of rice straw mulch on surface runoff and soil loss is needed.•This study examines the effects of straw length and application rates on runoff and erosion rates.•Lowest and highest surface covers were measured in plots with 200-mm and 10-mm straw lengths, respectively.•200-mm straw length plots had the highest soil loss and the lowest runoff values.•10-mm straw mulch applied at 3 Mg/ha minimized soil loss.
•Weed management in organic orchard is contingent on the type of weeds present and soil fertility status.•Mulches (manufactured and organic) restrict nutrient management options on infertile ...sites.•Dead organic mulches alone are not adequate on sites with perennial rhizomatous weeds.•Living mulches are only appropriate on fertile sites with adequate moisture and intense mowing.•Tillage is the most appropriate option on sites with low fertility where amendments need to be applied.
Weed management is key component of establishing and sustaining a profitable organic orchard. Good site preparation is a critical part of an orchard establishment plan. Pre-plant weed control coupled with addressing soil fertility issues before planting can dramatically increase the options available to producer for weed management, while reducing the time to commercially viable levels of fruiting and harvest. Tillage may be the best option on sites with perennial rhizomatous weeds and low soil fertility, or where there is high risk of rodent damage to the crop. Dead organic mulches are best suited to sites with low presence of perennial rhizomatous weeds and sites where at least moderate levels of soil fertility are present. While living mulches tend to provide a desirable habitat in the orchard understory, they are competitive with the crop for water and nutrients, regardless of whether they are mowed or not. They should only be used on sites with good background soil fertility, with frequent mowing, and where climate or irrigation minimize risk of moisture stress. Most manufactured mulches can provide effective weed control for a longer period of time but reduce soil fertility management options. The use of biodegradable mulches under dead organic mulches poses interesting possibilities and should be studied further. Organic herbicides are presently not effective enough or too costly to be used as the primary means of weed control but would be a useful tool for spot and edge control of weeds in mulches.
•Plastic mulches generally have positive impacts on plant and soil.•There is no one-size-fits-all plastic mulch in perennial fruit production systems.•Mulch choice should be based on multiple factors ...such as crops and climates.
Perennial fruit crops are traditionally grown in systems without plastic mulch. However, there may be benefits to plastic mulch use and this review paper considers the use of plastic mulch in perennial fruit systems. Several studies have explored the use of non-biodegradable plastic mulches polyethylene (PE) and polypropylene (PP) in perennial fruit production systems and have demonstrated the positive impacts they can have on plants largely through modification of the soil environment. Unfortunately, PE and PP mulches are difficult to dispose of due to contamination and lack of recycling facilities and contribute to plastic waste generation. Soil-biodegradable plastic mulches (BDMs) are alternatives to PE and PP mulches and are designed to be tilled into soil and degrade by soil microbial activity. A few studies have evaluated BDM in perennial fruit production systems and have shown similar impacts on crop growth as PE and PP mulches. The choice of plastic mulch (PE, PP, and BDM) to use in a perennial fruit production system will impact plant growth and productivity, the soil environment, and management of pests and diseases, as well as other soil fauna. Overall, there is no one-size-fits-all plastic mulch in perennial fruit production systems, and mulch choice should be based on the specific crop, growers’ horticultural goals and philosophies, climatic and soil conditions, expected mulch longevity, affordability, commercial availability, and the type of production system (e.g., conventional versus organic). BDMs are presently not widely used in perennial fruit crop production but could be a more sustainable option relative to traditional plastic mulches. Future research should continue to explore different plastic mulch options and investigate long-term impacts of plastic mulches in perennial fruit cropping systems.
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