environmental impacts associated with Polyethylene and Biodegradable Plastic the use and disposal of low-density Mulches for Strawberry Production in the polyethylene plastic mulch films for crop production (He et al., 2015; United States: Experiences and Opinions of Kasirajan and Ngouajio, 2012; Liu et al., 2014; Steinmetz et al., 2016). Growers in Three Regions PE mulch offers many benefits to farmers, such as improved weed man- Jessica R. Goldberger1, Lisa W. DeVetter2, agement, moderated soil temperature, 3 increased soil moisture, higher yields, and Katherine E. Dentzman improved crop quality, and higher profits (Freeman and Gnayem, 2005; ADDITIONAL INDEX WORDS. environment, Fragaria ·ananassa, grower survey, Garwood, 1998; Lamont, 1993, matted row, mulch disposal, plasticulture, sustainability 2005). Because PE mulch does not biodegrade, disposal options include SUMMARY. Although agricultural plastic mulches can have significant horticultural recycling, incineration, on-farm burn- Fragaria ·ananassa benefits for specialty crops such as strawberry ( ), there can also ing, and landfilling (Hempill, 1993; be significant economic and environmental costs. In particular, polyethylene (PE) plastic mulch requires labor and financial investments for removal and disposal. Moore and Wszelaki, 2016). The num- Micro- or nanoparticles may persist in soil and negatively affect microbial activity, ber of recycling facilities that accept PE physical soil properties, and nutrient availability. A possible alternative to PE mulch mulch is limited because of contamina- is biodegradable plastic mulch, which has similar horticultural benefits but does not tion with soil and/or vegetation (up to need to be removed from the field at the end of the growing season. Biodegradable 50% by weight) (Kasirajan and Ngoua- plastic mulch can be tilled into the soil, where it is converted by soil microorganisms jio, 2012). Moreover, the labor and into water, carbon dioxide, and microbial biomass. Although horticultural and transport costs associated with recy- environmental research into the impacts of PE and biodegradable plastic mulch is cling, burning, and landfilling force ongoing, it is also important to understand farmers’ practices and perceptions re- some farmers to stockpile, bury, or lated to these mulches. We conducted a survey of strawberry growers in three illegally dump their spent PE mulch. growing regions of the United States: California, the Pacific Northwest, and the Mid-Atlantic. Our results indicate several regional differences, with California Plastic fragments and additives can ac- farmers being more likely to have used biodegradable plastic mulch, and growers cumulate in soil, thus altering soil phys- from California and the Pacific Northwest being more likely to perceive negative ical properties, nutrient availability, and impacts of PE mulch compared with growers in the Mid-Atlantic. Regardless of microbial activity (Bandopadhyay et al., region, a majority of growers were interested in learning more about biodegradable 2018; Steinmetz et al., 2016). plastic mulch. We conclude with several suggestions for biodegradable plastic mulch Introduced in the 1990s, bio- development and outreach that may promote strawberry growers’ adoption of this degradable plastic mulch is a potential technology. alternative to PE mulch (Kasirajan and Ngouajio, 2012; Miles et al., he widespread use and disposal threats to wildlife via entanglement and 2017; Sintim and Flury, 2017). Made of plastics are associated with ingestion (Thompson et al., 2009a, from starch and other biodegradable Tsignificant environmental im- 2009b). Of the 6.3 billion tonnes of polymers, biodegradable plastic pacts, such as accumulation in land- plastic waste generated since the 1950s, mulch is designed to perform compa- fills and the natural environment, and an estimated 79% has accumulated in rably to PE mulch while also biode- landfills and the natural environment grading in soil or composting Received for publication 30 Apr. 2019. Accepted for (Geyer et al., 2017). Plastic pollution in environments at the end of its useful publication 9 July 2019. marine environments has been well lifetime (Miles et al., 2017). The Published online 21 August 2019. documented (Law, 2017; Worm long-term environmental impacts of 1Department of Crop and Soil Sciences, Washington et al., 2017). More recent research biodegradable plastic mulch require State University, P.O. Box 646420, Pullman, WA 99164 has focused on the contamination of further investigation (Bandopadhyay 2Department of Horticulture, Northwestern Wash- terrestrial ecosystems, including agro- et al., 2018; Brodhagen et al., 2017; ington Research and Extension Center, Washington ecosystems, by microplastic particles Li et al., 2014; Razza and Cerutti, State University, 16650 SR 536, Mount Vernon, WA (<5 mm) and nanoparticles (<0.1 mm) 2017; Sintim et al., 2019). Neverthe- 98273 (Machado et al., 2018a, 2018b; Ng less, biodegradable plastics are one 3Department of Agricultural Economics and Rural Sociology, University of Idaho, 875 Perimeter Drive, et al., 2018; Rillig et al., 2017; possible way to mitigate global agri- Moscow, ID 83844 Rodr ıguez-Seijo and Pereira, 2019). cultural plastic pollution (Cassou, This work was supported by the U.S. Department of Of particular concern are the 2018). Agriculture (USDA) National Institute of Food and Agriculture (NIFA) Specialty Crop Research Initiative (award no. 2014-51181-22382) and USDA NIFA Hatch funds (accession no. 1014754 and 1014919). Units J.R.G. is the corresponding author. E-mail: jgoldberger@ To convert U.S. to SI, To convert SI to U.S., wsu.edu. multiply by U.S. unit SI unit multiply by This is an open access article distributed under the CC 0.4047 acre(s) ha 2.4711 BY-NC-ND license (https://creativecommons.org/ 25.4 inch(es) mm 0.0394 licenses/by-nc-nd/4.0/). 1 micron(s) mm1 https://doi.org/10.21273/HORTTECH04393-19 0.9072 ton(s) tonne(s) 1.1023
• October 2019 29(5) 619 RESEARCH REPORTS
Although polymer scientists, soil Table 1. Strawberry production in the United States and selected states. Data scientists, toxicologists, and related from the 2012 Census of Agriculture (USDA, 2014). scientists conduct research on the U.S. rank U.S. rank environmental impacts of plastic Farms for no. of Total area for total Mean area mulching practices, it is instructive State (no.) farms (acres)z area (acres) also to study the human dimensions California 995 2 40,926 1 41.1 of plastic use and disposal in agricul- Pacific Northwest ture. For example: What are farmers’ Oregon 399 9 2,121 3 5.3 perceptions of the advantages and Washington 614 3 1,514 4 2.5 disadvantages of PE mulch? How do Mid-Atlantic farmers typically dispose of PE mulch? New York 588 4 1,220 5 2.1 Is biodegradable plastic mulch per- Pennsylvania 1,015 1 1,049 6 1.0 ceived to be a viable alternative to PE U.S. Total 10,388 67,467 6.5 mulch? What is the likelihood that z farmers would consider using biode- 1 acre = 0.4047 ha. gradable plastic mulch? To answer these and related questions, we sur- North Carolina), Mid-Atlantic (New do not incur the removal and disposal veyed strawberry growers in Califor- York, Pennsylvania), Pacific North- costs associated with PE mulch. Eco- nia, the Pacific Northwest (Oregon west (Oregon, Washington), and nomic research has shown that U.S. and Washington), and the Mid- Midwest (Ohio, Michigan, Wiscon- consumers are willing to pay more for Atlantic (New York and Pennsylvania) sin). Globally, the largest producer of strawberries grown with biodegrad- in 2016 to explore regional differ- strawberries is China, followed by the able plastic mulch, which may in part ences in strawberry growers’ experi- United States, Mexico, Egypt, Tur- offset the higher upfront cost of the ences and opinions related to the use key, and Spain (Food and Agriculture mulch (Chen et al., 2018). of PE and biodegradable plastic Organization of the United Nations, Our human dimensions study, mulches. Strawberry growers were 2017). which focuses on farmers’ experiences chosen as the study population be- U.S. strawberry production and and opinions related to PE and bio- cause of their widespread use of plas- marketing practices vary by region degradable plastic mulch, is part of tic mulch, high crop value, and (Samtani et al., 2019). For example, a larger project, ‘‘Performance and potential interest in biodegradable most California strawberries are an- Adoptability of Biodegradable Plastic plastic mulch products. Two hundred nual plantings for fresh market (Fen- Mulch for Sustainable Specialty Crop andnineteenstrawberrygrowers nimore, 2017); the Pacific Northwest Production,’’ funded by the USDA completed the survey, for a response is known for the production of high- National Institute of Food and Agri- rate of 21%. Our study not only quality processing fruit in a perennial culture’s Specialty Crop Research Ini- contributes to the nascent literature matted row system (Finn, 2017); and tiative program (award no. 2014– on farmers’ adoption of biodegradable the Northeast and Mid-Atlantic states 51181–22382). The survey was con- plastic mulch (Cowan et al., 2015; exhibit a combination of perennial ducted by the project’s Technology Goldberger et al., 2015; Scaringelli matted rows and raised-bed plasticul- Adoption Working Group with guid- et al., 2016) but also meets the call ture for fresh-market strawberries ance from a transdisciplinary team of for more research on stakeholders’ (Pritts, 2017). Plastic mulch is in- scientists, Extension personnel, perceptions of the environmental im- creasingly popular across all U.S. farmers, mulch manufacturers, and pacts of agricultural landscapes un- strawberry production regions be- other stakeholders. der plastic mulch (Steinmetz et al., cause of its ability to suppress weeds, 2016). moderate soil temperature, conserve Materials and methods In 2017, the United States pro- water, and protect plants (DeVetter The population for this study in- duced 3.6 billion pounds of straw- et al., 2017; Fernandez et al., 2001; cluded growers in three strawberry pro- berries, valued at $3.5 billion [U.S. Freeman and Gnayem, 2005). Bio- duction regions: California, the Pacific Department of Agriculture (USDA), degradable plastic mulch has been Northwest (Oregon, Washington), 2018]. Fresh market strawberries shown to perform comparably to PE and the Mid-Atlantic (New York, accounted for 83% of total strawberry mulch for strawberry production in Pennsylvania). These five states were production, and processing straw- terms of weed suppression (Andrade ranked in the top 10 U.S. states for berries (i.e., frozen, freeze-dried, or et al., 2014), soil moisture retention number of strawberry farms and straw- included in strawberry-based food (Costa et al., 2014), fruit quality berry acres according to the 2012 U.S. products) accounted for the remain- (Bilck et al., 2010), crop yield Census of Agriculture (Table 1). The ing 17% (USDA, 2018). According to (DeVetter et al., 2017), and material three regions were selected for this the 2012 U.S. Census of Agriculture, functionality from planting to har- study because of their known differ- 10,388 farms grew strawberries on vesting (Kapanen et al., 2008). Bio- ences in farm scale, production char- a total of 67,467 acres in 2012 degradable plastic mulch costs two to acteristics, and marketing practices. (Table 1). California produced 91% three times more than PE mulch These regional differences were hy- of the strawberry crop in 2017 (Velandia et al., 2018; Zhang et al., pothesized to influence growers’ ex- (USDA, 2018). The other top 10 2018); however, because it does not periences with and opinions about the strawberry-producing states are lo- need to be removed and discarded at use of PE and biodegradable plastic cated in the South Atlantic (Florida, the end of its useful lifetime, farmers mulches for strawberry production.
620 • October 2019 29(5) Other top 10 U.S. states for straw- and biodegradable plastic mulches, Apr. 2016. The phone calls indicated berry production (e.g., Florida, Mich- strawberry production and marketing a higher proportion of ineligible igan, North Carolina, Wisconsin) practices, fumigation practices, deci- names on the mailing list than antici- could have been included in our study; sion-making and sources of agricul- pated. The sample disposition was however, limited research funds pre- tural information, farm characteristics, adjusted based on the prevalence of vented us from administering the sur- and demographics. Growers could opt ineligibles, resulting in a final response vey to growers in all production to complete the survey on paper or rate of 21%. regions. Future research should focus online. FARM CHARACTERISTICS. Survey on the U.S. South and Midwest. ANALYSIS. The primary objective results indicate that strawberry oper- The majority of the grower names of this study is to compare strawberry ations vary in acreage, production and postal addresses were purchased farm characteristics, as well as characteristics, and marketing prac- from Meister Media (Willoughby, growers’ experiences and opinions tices by region. California growers OH), a corporation that publishes pe- about PE and biodegradable plastic had more strawberry acreage (125.4 riodicals on fruit and vegetable pro- mulches, across three U.S. produc- acres per grower on average) than duction. Because the Meister Media tion regions. Because the data set growers in the Pacific Northwest list included relatively few names in contained continuous and categorical (15.0 acres) and Mid-Atlantic (3.2 the Pacific Northwest, the list was variables, two tests for statistical sig- acres) [F(2, 213) = 21.78, P £ supplemented with addresses from nificance were employed to assess re- 0.001]. Nearly all Mid-Atlantic straw- Oregon Tilth, the Oregon Strawberry gional differences: analysis of variance berries (99.8%) were produced for the Commission, the Washington State was used for continuous variables, fresh market compared with 93.3% in Department of Agriculture Organic and Pearson’s chi-square was used California and 74.3% in the Pacific Program, and the Washington Straw- for categorical variables. Some of the Northwest [F(2, 219) = 30.12, P £ berry Commission. The survey was categorical variables were recoded 0.001]. Given that our mean acreages conducted by the authors in association into fewer categories for the purpose are higher than the USDA averages with staff at Washington State Univer- of analysis. Pairwise comparisons of (Table 1), larger scale growers were sity’s (WSU’s) Social and Economic column proportions were examined likely overrepresented in our survey Sciences Research Center. The survey using the Bonferroni correction. All sample. project (‘‘2016 Survey of Strawberry statistical analyses were conducted Table 2 presents additional pro- Growers’’) received exemption status using IBM SPSS Statistics (version duction and marketing characteristics by the WSU Institutional Review Board 25.0 for Macintosh; IBM Corp., for survey respondents in the three (IRB) in Feb. 2016 (IRB no. 15010). Armonk, NY). regions. Respondents in California Following the tailored design and the Pacific Northwest were more method (Dillman et al., 2014), a pre- Results and discussion likely to grow at least some certified notification letter and questionnaire Two hundred and nineteen organic strawberries compared with (titled ‘‘Use of Plastic Mulch Films strawberry growers completed the sur- Mid-Atlantic respondents. Respon- in U.S. Strawberry Production: vey: 32 in California, 30 in Oregon, 28 dents in California and the Pacific Growers’ Experiences and Opin- in Washington, 41 in New York, and Northwest were also more likely to ions’’) were sent to 1497 strawberry 88 in Pennsylvania. After accounting report that strawberries were their growers in Feb. 2016. A reminder for ineligibles (i.e., individuals who did primary agricultural product in terms postcard and replacement question- not grow strawberries or no longer of value of sales. California respon- naire were sent to nonrespondents in farmed) and bad addresses, the initial dents were more likely to use the hill Mar. 2016. The survey consisted of response rate was 16%. Because of the system of strawberry production (i.e., 60 questions related to growers’ ex- low response rate, 300 nonrespon- raised beds with or without plastic periences with and opinions about PE dents were contacted by phone in mulch), and matted rows were more
Table 2. Production and marketing characteristics of strawberry farms in California, Pacific Northwest (Oregon, Washington), and Mid-Atlantic (New York, Pennsylvania). Data from 2016 survey of U.S. strawberry growers. California Pacific Northwest Mid-Atlantic Farm characteristic (% respondents)z N x2y df P Certified organic—some or all acres 61.2 a 41.1 a 4.7 b 214 60.97 2 <0.001 Strawberry—primary farm product 50.0 a 29.3 a 7.8 b 218 33.36 2 <0.001 Hill system 71.4 a 44.4 b 42.7 b 206 7.75 2 0.021 Matted row system 25.0 a 55.6 b 64.5 b 206 14.58 2 0.001 Fumigation of strawberry fields 62.1 a 7.1 b 7.0 b 213 60.95 2 <0.001 Wholesale marketing 69.0 a 26.8 b 18.0 b 213 31.04 2 <0.001 Direct-to-retail marketingx 69.0 a 32.1 b 21.9 b 213 24.57 2 <0.001 Direct-to-consumer marketingw 37.9 a 64.3 a 92.2 b 213 47.43 2 <0.001 U-pick operation 6.9 a 39.3 b 46.1 b 213 15.28 2 <0.001 zEach subscript letter denotes a subset of region categories whose column proportions do not differ significantly from each other (P £ 0.05, Bonferroni correction). yPearson’s chi-square. xDirect-to-retail marketing includes direct to conventional supermarket, food cooperatives, natural foods stores, restaurants, schools, or hospitals. wDirect-to-consumer marketing includes farmers markets, community supported agriculture schemes, roadside stands, and farm stores.
• October 2019 29(5) 621 RESEARCH REPORTS prevalent in the Pacific Northwest (EPA) by active ingredient, and PE mulch among California respon- and Mid-Atlantic. Runners are re- currently no biodegradable plastic dents include the use of day-neutral/ moved in a hill system to encourage mulches are approved for this appli- remontant cultivars in annual hill the production of large plants and cation (DeVetter et al., 2018; EPA, systems on raised beds, larger opera- berries, whereas runners spread freely 2019). However, a grower could tions, prevalence of certified organic and root within the row in a matted choose to remove a tarp after fumiga- production, and the practice of drip row system (Strik, 2017). California tion is complete and transition to or bed fumigation in conventional respondents were more likely to fu- using a biodegradable plastic mulch, systems combined with the use of migate their strawberry fields com- particularly in situations where a field approved tarps that can function as pared with respondents in the other is broadcast fumigated and the tarp mulches later in the life of the plant- two regions. Wholesale and direct-to- needs to be removed before bed ing (Bolda et al., 2017; EPA, 2019). retail marketing channels were more formation. Fourth, farmers engaged PE mulch use is less common in the common in California, and U-pick in on-farm marketing activities [e.g., other two regions because of farmers’ operations were more prevalent in U-pick, community supported agri- preference for the matted row system the Pacific Northwest and Mid-Atlantic. culture (CSA)] may not be interested of strawberry production with June- Mid-Atlantic respondents were much in plastic mulch because of fear that bearing cultivars and use of direct more likely to use direct-to-consumer customers could rip or otherwise dis- marketing practices. marketing channels compared with re- turb the plastic mulch films while Survey respondents were also spondents in California and the Pacific visiting the strawberry fields. More- asked about PE mulch use for crops Northwest. over, U-pick and CSA customers may other than strawberry (Fig. 1B). In It is important to appreciate not like the aesthetics and/or envi- 2015, 55% of all survey respondents these regional differences in produc- ronmental impacts associated with used PE mulch for other crops, such tion and marketing practices because black plastic (Stevens et al., 2007). as tomato (Solanum lycopersicum), they may influence farmers’ experi- POLYETHYLENE MULCH. In 2015, pepper (Capsicum sp.), melons (Cit- ences with and opinions about PE 49% of survey respondents used PE rullus sp. and Cucumis sp.), squash and biodegradable plastic mulches. mulch on some or all of their straw- (Cucurbita sp.), and cucumber First, farmers with certified organic berry fields. However, Fig. 1A reveals (Cucumis sativus). A higher percent- strawberries cannot use biodegrad- statistically significant regional differ- age of respondents in the Mid-Atlantic able plastic mulch given the current ences. Growers in California were the (71%) and California (52%) used PE National Organic Program standards most likely (88%) to have used PE mulch for crops other than strawberry (Miles et al., 2017). PE mulch, how- mulch in their strawberry fields, fol- compared with respondents in the ever, is allowed in U.S. certified or- lowed by growers in the Mid-Atlantic Pacific Northwest (17%). ganic crop production if the mulch is (51%) and Pacific Northwest (23%). PE mulch disposal methods var- removed from the field after produc- Likely reasons for the popularity of ied by region (Fig. 2). Transporting tion and no fragments remain in the soil. Second, plastic mulch is incom- patible with the matted row system of strawberry production because this perennial system relies on annual ren- ovation and the formation of runners and daughter plants from June-bearing strawberry plants. Plastic mulch would interfere with renovation as well as the rooting and formation of daughter plants. Third, California growers often need to manage sev- eral soilborne diseases and plant- parasitic nematodes to maintain production and profitability, necessi- tating fumigation or other alterna- tive soilborne disease management practices (Bolda et al., 2017; Maz- zola et al., 2018). Soil fumigation often entails the use of plastic tarps to improve fumigation efficacy and re- duce buffer zones around an appli- cation site. For bed fumigation, plastic tarps that are totally or virtu- ally impermeable can be used and retained in a planting to function as Fig. 1. Use of polyethylene (PE) mulch in California, Pacific Northwest (Oregon, a mulch after fumigation is complete. Washington), and Mid-Atlantic (New York, Pennsylvania). Pearson’s chi-square Tarps must be approved by the U.S. (x2) test used to assess regional differences. Data from 2016 survey of U.S. Environmental Protection Agency strawberry growers.
622 • October 2019 29(5) PE mulch after use in strawberry fields to a landfill or other dumpsites was the most common disposal method. Burying was rarely reported in the three regions. A significantly larger percentage of California growers recycled their used PE mulch compared with growers in the Pacific Northwest and Mid-Atlantic. Mid-Atlantic growers were more likely to burn their used PE mulch compared with growers in the other regions. These findings are not sur- prising because of recycling pro- grams and incentives California has undertaken to reduce waste (CalRe- cycle, 2018) and because some states and local ordinances allow burning of plastic waste as a method of dis- posal (EPA, 2018). Survey respondents were asked Fig. 2. Disposal of polyethylene mulch after use in strawberry fields in California, to indicate the extent to which they Pacific Northwest (Oregon, Washington), and Mid-Atlantic (New York, Pennsylvania). Pearson’s chi-square (x2) test used to assess regional differences. disagreed or agreed with five state- Data from 2016 survey of U.S. strawberry growers. ments about PE mulch (Table 3). A small percentage of respondents in
Table 3. Opinions about polyethylene mulch among strawberry growers in California, Pacific Northwest (Oregon, Washington), and Mid-Atlantic (New York, Pennsylvania). Data from 2016 survey of U.S. strawberry growers. California Pacific Northwest Mid-Atlantic Statementz (% respondents)y N x2x df P Polyethylene (PE) mulch is environmentally friendly. Disagree 56.3 ab 62.7 b 35.4 a Neither disagree or agree 21.9 a 33.3 a 43.3 a Agree 21.9 a 3.9 b 21.3 a Total 100.0 100.0 100.0 210 17.37 4 0.002 PE mulch harms the soil. Disagree 62.5 a 34.0 b 69.0 a Neither disagree or agree 21.9 ab 46.0 b 27.0 a Agree 15.6 a 20.0 a 4.0 b Total 100.0 100.0 100.0 208 23.60 4 <0.001 Disposal of used PE mulch is a big environmental problem. Disagree 25.0 a 5.9 b 17.6 ab Neither disagree or agree 18.8 a 23.5 a 25.6 a Agree 56.3 a 70.6 a 56.8 a Total 100.0 100.0 100.0 208 6.87 4 0.143 Recycling is a viable option for used PE mulch. Disagree 31.3 a 39.2 a 37.9 a Neither disagree or agree 18.8 a 43.1 a 29.8 a Agree 50.0 a 17.6 b 32.3 ab Total 100.0 100.0 100.0 207 10.97 4 0.027 Proper disposal of used PE mulch is economically burdensome. Disagree 18.8 a 9.8 a 16.0 a Neither disagree or agree 25.0 a 23.5 a 26.4 a Agree 56.3 a 66.7 a 57.6 a Total 100.0 100.0 100.0 208 2.00 4 0.736 zDisagree includes ‘‘disagree’’ and ‘‘strongly disagree’’ answers. Agree includes ‘‘agree’’ and ‘‘strongly agree’’ answers. yEach subscript letter denotes a subset of region categories whose column proportions do not differ significantly from each other (P £ 0.05, Bonferroni correction). xPearson’s chi-square.
• October 2019 29(5) 623 RESEARCH REPORTS the Pacific Northwest agreed that PE mulch and most (‡90%) expressed some of our survey respondents) mulch is environmentally friendly the desire to learn more and consider may have had negative experiences compared with significantly higher using such mulch in the future. In- with oxo-degradable plastic mulch percentages in California and the terest in biodegradable plastic mulch films erroneously labeled as ‘‘biode- Mid-Atlantic. Respondents in Cali- is likely due to California growers’ gradable.’’ Such films (made with PE, fornia and the Pacific Northwest were current use of PE mulch and the polypropylene, polystyrene, or other more likely than respondents in the annual hill system of strawberry pro- plastics) undergo fragmentation Mid-Atlantic to agree that PE mulch duction. Because adoption is more when exposed to ultraviolet light, harms the soil. One half of California likely when innovations are compati- heat, and/or oxygen but are not respondents agreed that recycling was ble with existing practices (Rogers, necessarily biodegradable, composta- a viable option for used PE mulch 2003), California growers could po- ble, or recyclable (Miles, 2017). At compared with smaller percentages in tentially replace PE mulch with bio- least one plastics manufacturer misled the Mid-Atlantic and Pacific North- degradable plastic mulch with little the public regarding the biodegrada- west. These results suggest U.S. West change to their overall strawberry tion of oxo-degradable plastics (Miles, Coast (California, Oregon, Washing- production system. However, if Cal- 2017); thus, some growers may be ton) strawberry growers may be more ifornia growers bed fumigate using suspicious of agricultural products environmentally minded regarding tarps for soil fumigation and subse- marketed as ‘‘biodegradable.’’ Out- the impacts of farming practices (par- quently maintain the tarps as a mulch, reach may be necessary to reeducate ticularly plastic mulching) on the currently available biodegradable these growers about currently available agroecosystem. However, a majority plastic mulch products will be incom- biodegradable plastic mulch. of respondents (ranging from 56% to patible given the legal requirements Survey respondents were also 71%) in all three regions agreed that for tarps (EPA, 2019). In the other asked about the importance of 18 the disposal of used PE mulch is a big two regions, the majority of survey traits (e.g., different colors, biobased environmental problem and econom- respondents use perennial matted content, equipment compatibility, ically burdensome; however, no rows, which are not necessarily com- compostability, timing of biodegra- statistically significant regional differ- patible with annual plastic mulch use. dation, durability, etc.) for biode- ences were apparent. Survey respondents were asked gradable plastic mulch used in BIODEGRADABLE PLASTIC MULCH. to indicate the extent to which they strawberry production. The top five The survey included several questions disagreed or agreed with five state- traits (based on mean importance on about biodegradable plastic mulch in ments about biodegradable plastic a scale from 1 = ‘‘not at all important’’ strawberry production (Fig. 3). The mulch (Table 4). The high percent- to 4 = ‘‘very important’’) differed percentage of respondents familiar age of ‘‘neither disagree nor agree’’ among the three strawberry produc- with biodegradable plastic mulch did responses in Table 4 suggests that tion regions. Respondents in all three not differ significantly across the three many respondents likely lacked suffi- regions attributed high importance to regions; however, respondents in the cient knowledge of biodegradable compatibility with irrigation equip- Pacific Northwest and California were plastic mulch to disagree or agree ment and remaining intact until the more likely to report a lack of famil- with the statements provided. More end of the growing season. California iarity with biodegradable plastic than 40% of respondents in the three respondents wanted a product avail- mulch (Fig. 3A). Nearly one-fifth of regions agreed that biodegradable able in black that could be laid with California respondents had used bio- plastic mulch is environmentally a plastic mulch layer and would com- degradable plastic mulch in their friendly. Respondents in California pletely biodegrade in soil within 1 strawberry fields, compared with 9% and the Pacific Northwest were more year. The desire for complete biodeg- in the Mid-Atlantic and 0% in the likely than respondents in the Mid- radation in 1 year can be attributed to Pacific Northwest (Fig. 3B) A major- Atlantic to agree that biodegradable the practice of rotating land used for ity of respondents in all three regions plastic mulch harms the soil. A signif- strawberry production to other spe- expressed an interest in learning more icantly higher percentage of Mid- cialty crop producers [e.g., lettuce about biodegradable plastic mulch for Atlantic respondents (38%) agreed that (Lactuca sativa)] within 7 to 14 strawberry production; however, there are no disposal costs associated months after strawberry planting. Sub- higher percentages of respondents in with the use of biodegradable plastic sequent producers do not want plastic the Pacific Northwest (36%) and the mulch compared with respondents in mulch fragments in their soil, regard- Mid-Atlantic (20%) expressed no in- California (10%). Nearly 60% of re- less of whether it is biodegradable. terest compared with California re- spondents in California agreed that Pacific Northwest respondents wanted spondents (7%) (Fig. 3C). Nearly half biodegradable plastic is an unproven a 100% biobased product that could be (48%) of respondents in the Pacific technology compared with signifi- tilled into the soil or composted on- Northwest were not at all likely to cantly smaller percentages in the Pa- farm at the end of the growing season. consider using biodegradable plastic cific Northwest and Mid-Atlantic. Mid-Atlantic respondents wanted mulch in their strawberry fields in the One-third or more respondents across a product that could be laid with next 5 years, compared with signifi- the three regions agreed that biode- a plastic mulch layer, could be tilled cantly smaller percentages in Califor- gradable plastic mulch can replace PE into the soil at the end of the growing nia (10%) and the Mid-Atlantic (26%) mulch; no statistically significant re- season, and would completely biode- (Fig. 3D). In sum, California straw- gional differences were apparent. grade within 2 years. The traits of least berry growers had the most experi- It is worth noting that some U.S. importance to respondents were avail- ence with biodegradable plastic specialty crop growers (including ability in clear (all three regions),
624 • October 2019 29(5) Fig. 3. Biodegradable plastic mulch in California, Pacific Northwest (Oregon, Washington), and Mid-Atlantic (New York, Pennsylvania): familiarity, past experience, interest, and future use. Pearson’s chi-square (x2) test used to assess regional differences. Data from 2016 survey of U.S. strawberry growers. availability in reflective silver (all three (California and Mid-Atlantic). In sum, plastic mulch traits. Manufacturers regions), produced with 50% biobased these results suggest that a one-size- need to be cognizant of these regional materials (California and Pacific North- fits-all approach is not appropriate differences when developing and mar- west), and produced without geneti- given the regional differences in desir- keting their portfolio of biodegradable cally modified organism feedstocks able (and undesirable) biodegradable plastic mulch products.
• October 2019 29(5) 625 RESEARCH REPORTS
Lastly, survey respondents were respondents were moderately or very significant regional differences except presented with seven hypothetical likely to consider using biodegradable for the scenario relating to approval of scenarios and asked about the likeli- plastic mulch if the price dropped, biodegradable plastic mulch for use hood of considering using biodegrad- research indicated no harmful soil in U.S. certified organic produc- able plastic mulch in their strawberry impacts, or products were available tion. One-third (33%) of respondents fields (Table 5). More than 50% of locally. There were no statistically in California were ‘‘very likely’’ to
Table 4. Opinions about biodegradable plastic mulch among strawberry growers in California, Pacific Northwest (Oregon, Washington), and Mid-Atlantic (New York, Pennsylvania). Data from 2016 survey of U.S. strawberry growers. California Pacific Northwest Mid-Atlantic Statementz (% respondents)y N x2x df P Biodegradable plastic mulch is environmentally friendly. Disagree 19.4 a 12.8 a 6.7 a Neither disagree or agree 38.7 a 44.7 a 32.8 a Agree 41.9 a 42.6 a 60.5 a Total 100.0 100.0 100.0 197 8.56 4 0.073 Biodegradable plastic mulch harms the soil. Disagree 20.7 ab 21.3 b 42.6 a Neither disagree or agree 65.5 a 66.0 a 55.7 a Agree 13.8 a 12.8 a 1.7 b Total 100.0 100.0 100.0 191 16.57 4 0.002 There are no disposal costs associated with use of biodegradable plastic mulch. Disagree 40.0 a 23.4 a 25.0 a Neither disagree or agree 50.0 a 55.3 a 37.1 a Agree 10.0 a 21.3 ab 37.9 b Total 100.0 100.0 100.0 193 12.91 4 0.012 Biodegradable plastic mulch is an unproven technology. Disagree 9.7 a 8.7 a 25.2 a Neither disagree or agree 32.3 a 69.6 b 50.4 ab Agree 58.1 a 21.7 b 24.3 b Total 100.0 100.0 100.0 192 22.17 4 <0.001 Biodegradable plastic mulch can replace polyethylene mulch. Disagree 10.0 a 4.3 a 18.1 a Neither disagree or agree 56.7 a 54.3 a 47.4 a Agree 33.3 a 41.3 a 34.5 a Total 100.0 100.0 100.0 192 6.01 4 0.199 zDisagree includes ‘‘disagree’’ and ‘‘strongly disagree’’ answers. Agree includes ‘‘agree’’ and ‘‘strongly agree’’ answers. yEach subscript letter denotes a subset of region categories whose column proportions do not differ significantly from each other (P £ 0.05, Bonferroni correction). xPearson’s chi-square.
Table 5. Likelihood of considering use of biodegradable plastic mulch in strawberry fields: seven hypothetical scenarios. Data from 2016 survey of strawberry growers in five U.S. states: California, New York, Oregon, Pennsylvania, and Washington. Not at all Slightly Moderately Very Hypothetical scenario likely (%) likely (%) likely (%) likely (%) The price of biodegradable plastic mulch drops significantly. 20.5 23.7 26.3 29.5 University research indicates biodegradable plastic mulch does not 22.6 25.8 33.2 18.4 harm the soil. Biodegradable plastic mulch is readily available at local agricultural 27.9 21.6 32.6 17.9 input supply stores. Use of biodegradable plastic mulch improves good agricultural 18.8 32.3 32.8 16.1 practices or sustainability audit score. Consumers are willing to pay a premium for products grown with 38.1 19.1 25.8 17.0 biodegradable plastic mulch. Biodegradable plastic mulch is approved for use in U.S. certified 35.5 26.9 23.7 14.0 organic production. Biodegradable plastic mulch use is required by a processor, wholesale 45.1 20.5 23.6 10.8 buyer, or retailer.
626 • October 2019 29(5) consider using biodegradable mulch if ecosystem functions. Front. Microbiol. Fernandez, G.E., L.M. Butler, and F.J. approved for certified organic produc- 9:819. Louws. 2001. Strawberry growth and development in an annual plasticulture tion compared with 17% in the Pacific Bilck, A.P., M.V.E. Grossmann, and F. system. HortScience 36:1219–1223. Northwest and 8% in the Mid-Atlantic Yamashita. 2010. Biodegradable mulch 2 [c (6,186) = 18.92, P = 0.004]. This films for strawberry production. Polym. Finn, C.E. 2017. Northwest strawberries— finding is not surprising given that Test. 29(4):471–476. Perennially proud of processing quality. certified organic strawberry produc- HortScience 52:S103 (abstr.). Bolda, M.P., O. Daugovich, S.T. Koike, tion was more common in California K.D. Larson, and P.A. Phillips. 2017. Food and Agriculture Organization of the than in the other two regions (Table UC IPM pest management guidelines: United Nations. 2017. FAOSTAT: 2). Strawberries. Univ. California Agr. Nat- Strawberries.23Oct.2018.
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2014. Effects of biodegradable mulch on Rillig, M.C., R. Ingraffia, and A.A.S. Strik, B. 2017. Growing strawberries in soil quality. Appl. Soil Ecol. 79:59–69. Machado. 2017. Microplastic incorpora- your home garden. Oregon State Univ. tion into soil in agroecosystems. Front. Ext. Serv. EC 1307. 7 July 2019. Liu, E.K., W.Q. He, and C.R. Yan. 2014. Plant Sci. 8:1805.
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