KEY WORDS Mulches, biodegradable, high tunnels, tomato, fruit quality, fruit yield

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1 BIOAG PROJECT PROGRESS REPORT TITLE: Effect of High Tunnels and Biodegradable Mulches on Tomato Fruit Quality and Yield PRINCIPAL INVESTIGATOR(S): Carol A. Miles, Vegetable Horticulturist, Dept. Horticulture and Landscape Architecture, WSU- Mount Vernon NWREC, State Route 536, Mount Vernon, WA 98273; Karen Leonas, Textiles Scientist, Apparel, Merchandising, Design & Textiles, PO Box ; Kruegel 55A, Washington State University, Pullman, WA 99164; Preston K. Andrews, Fruit Horticulturist, Dept. Horticulture & Landscape Architecture, Washington State University, Johnson Hall 155E, Pullman, Washington 99164; COOPERATOR(S): Debra Inglis, Vegetable Pathologist, Dept. Plant Pathology, WSU-Mount Vernon NWREC, State Route 536, Mount Vernon, WA 98273; KEY WORDS Mulches, biodegradable, high tunnels, tomato, fruit quality, fruit yield ABSTRACT High tunnels enhance and extend crop production by increasing air temperature and protecting the crop from rainfall. In high tunnel production systems, weeds are often controlled with plastic mulch. There is a desire to reduce non-recyclable waste by using biodegradable mulches (BDMs) that completely biodegrade in situ without detrimentally affecting yield, fruit quality, or the ecosystem. In 2010 and 2011, tomatoes were grown in high tunnels and open field plots at WSU Mount Vernon NWREC utilizing six mulch treatments: 1) BioBag (BB); 2) BioTelo (BT); 3) an experimental spun-bond non-woven composed of 100% polylactic acid (SB-PLA); 4) cellulose paper mulch, completely biodegradable standard; 5) 1.0 mil embossed black polyethylene (PE) plastic; and 6) bare ground as a non-mulch control. In 2010 and 2011, tomato fruit number and weight tended to be higher with the application of plastic mulch films, regardless of biodegradability, though these differences were not consistent in both years. Percent marketability of harvested fruit was significantly lower in mulch plots, especially plastic films, than in bare ground plots. Total number and weight of harvested tomatoes were 4 to 9 times greater, respectively, when grown in high tunnels as compared to open fields. In 2010, juice content was greatest for bare ground and BioTelo plots, and soluble solids ( o Brix) was lowest in bareground plots. The same trends in fruit quality were observed as in 2011, however these differences were not significant. In 2010 there were insufficient fruit to compare between high tunnels and open field, but in 2011 juice content and ph of fresh harvested fruit were greater in high tunnels as compared to open field while soluble solids and titratable acidity (% citric acid) were lower. In stored fruit, juice content was also higher in high tunnels than in the open field.

2 PROJECT DESCRIPTION This study utilizes the SCRI high tunnel and BDM-tomato field plots at WSU Mount Vernon NWREC to measure impact of BDM and high tunnels on tomato fruit quality. In 2009, our research and extension team led by Dr. Debra Inglis at WSU Mount Vernon NWREC was awarded an SCRI SREP grant to investigate the impact of high tunnels and BDMs on the soil ecosystem and on yield of tomatoes, strawberries and lettuce (SCRI Grant No , Biodegradable Mulches for Specialty Crops Produced Under Protective Covers). Expected outcomes from this project include: 1.) Development of effective fruit quality analysis protocols to create standard methodologies for measuring fruit quality in high tunnels and with BDMs 2.) Publication of significant findings regarding tomato fruit quality on our website in WSU Extension newsletters, and through journals (if appropriate given 1 year of data); and 3.) The dissemination of significant findings to stakeholders through site tours. OUTPUTS Work Completed: In 2010 and 2011, a field study was undertaken in the SCRI high tunnel and open field plots at WSU Mount Vernon NWREC. The experiment was developed by SCRI team members as a split-plot design with four replications. The main plots consisted of high tunnel and open field plots and subplots consisted of six mulch treatments: 1) BioBag (BB) (Palm Harbor, Florida); 2) BioTelo (BT) (Dubois Agrinovation, Waterford, Ontario, Canada); 3) an experimental spunbond non-woven (SB PLA) composed of 100% poly(lactic) acid (obtained from NatureWorks, Blair, Nebraska); 4) cellulose mulch (WG), completely biodegradable standard (WeedGuard Plus, SunShine Paper Company, Aurora, Colorado); 5) 1.0 mil embossed black polyethylene (PE) plastic (Pliant Corp, Schaumburg, Illinois); and 6) bare ground as a non-mulch control. Tomato cv. Celebrity was established in all plots and managed organically throughout each growing season. Tomato fruits were harvested one to two times per week upon reaching at least 75% red ripeness. Fruits were sorted and weighed based upon marketability. In 2010, marketable fruits were sorted according to US Standards for Grades of Fresh Tomatoes (1991), and in 2011 the standard for marketability was adjusted to reflect a direct market standard; that is, tomatoes with serious damage and no more than 10% very serious damage were considered as marketable. Marketable fruit were tested for firmness, juice content, soluble solids ( o Brix), ph, and titratable acidity. In 2010, 3-5 fruit were tested for each plot and in g from at least 3 fruit was tested. Both years, samples were collected up to three times, with a minimum of seven days between collections. Additionally, fruit quality was measured for fresh harvested fruit and for fruit that were stored for two weeks at 4 o C. Throughout the 2010 growing season, fruit quality measurement protocols were developed and refined to improve production efficiency, accuracy of measurements, and worker safety. The measurement of total phenolics was dropped from the experimental design as the literature does not support the use of this measurement as a good indicator of tomato fruit quality, and lycopene was added. However, lycopene was not measured in 2010 as there were insufficient marketable fruit from plots to generate replicated data for statistical analysis. Lycopene is currently being measured for 2011 fruit. Field results are presented in Tables 1 and 2, and fruit quality results are

3 presented in Tables 3 and 4. Unmarketable fruits were sorted based upon defects (data not presented). In 2010, tomato fruit number in BB (51.1), BT (49.6), and PE (43.1) plots were significantly greater than bare ground (34.4) plots (p=0.0083; Table 1). Total fruit weight was also significantly greater in BB (12.5 kg) and BT (12.0 kg) plots than bare ground (8.3 kg) plots (p=0.0036). Despite lower yields, bare ground plots produced 21% marketable fruit, significantly greater than all mulch treatments, which ranged from 8 14% (p=0.0011). Mean number of fruit was 5 times greater in high tunnels (p=0.0008) and mean fruit weight was 9 times greater than in the open field (p=0.0005; Table 2). With the strict export marketability standard used in 2010, high tunnel plots produced 21% marketable fruits versus 4% in open field plots (p=0.0011). There were no significant interactions between mulch and tunnel treatments on tomato yield in Uncharacteristically cool summer temperatures and high moisture led to low yields in open field plots resulting in insufficient fruit to compare quality between open field and high tunnel production systems in 2010, and data presented are combined for high tunnel and open field. Due to low yields, we also had insufficient fruit to compare fruit quality between fresh and coldstored tomatoes. In high tunnels in 2010, fresh fruit produced with PE had the lowest juice content while those produced on bare ground had the highest (p=0.0278; Table 3). All mulch treatments had increased soluble solids as compared to bare ground (p=0.0028). No effects on firmness (p=0.6832), ph (p=0.2356), and titratable acidity (p=0.6122) due to mulch treatment were detected in In 2011, tomato fruit number in SB-PLA (47.8) and WG (46.6) were lower than in all other plots (p=0.0036), and there were no differences in total fruit weight (p=0.1927; Table 1). Bare ground and WG produced a greater percentage of marketable fruit number (68.7% and 66.4%, respectively) and weight (71.7% and 68.5%, respectively) than all other treatments (p<0.0001). Mean number of fruit was 5 times greater in high tunnels (p=0.0008) and mean fruit weight was 9 times greater than in the open field (p=0.0005; Table 2). Number of fruit was 4 times greater in the high tunnel (p=0.0007), and fruit weight was 6 times (p=0.0041) than in the open field. The new direct market standard used in 2011 resulted in more fruit being considered marketable, and this increased the number of marketable tomatoes available for fruit quality measurements. There were no significant differences due to mulch treatment in measured qualities of fresh harvested or stored fruit in 2011, however there were differences between high tunnels and open field. In high tunnels, juice content (94.4%) and ph (4.17) of fresh harvested fruit were greater than in the open field (94.1% and 4.09, respectively) (p= and p=0.0016, respectively; Table 3). In contrast, soluble solids (4.72) and titratable acidity (0.364%) were lower than the open field (4.98% and 4.04, respectively; p= and <0.0001, respectively). In stored fruit, both fruit firmness (4.47 N) and juice content (94.7%) were higher in high tunnels than in the open field (4.12N and 94.2%, respectively; p= and <0.0001, respectively; Table 4). Stored fruits had more juice (94.41%) than fresh fruits (94.24%; p=0.0334) and lower soluble solids (4.63% and 4.85%, respectively; p<0.0001).

4 Table 1. Mean yield (number of fruit and weight in kg.) of tomatoes per plot (4.3 m row) produced on six mulch treatments in high tunnels and the open field at WSU Mount Vernon NWREC in 2010 and Total No. (plot -1 ) Total Wt. (kg plot -1 ) Fruit No. (plot -1 ) Fruit Wt. (kg plot -1 ) Mulch BioBag 51.1a 56.5a 12.5a bc 46.6bc 7.8c 50.0b BioTelo 49.6ab 62.3a 12.0a bc 49.0b 8.9bc 50.4b SB PLA 39.3bc 47.8b 9.0b b 52.8b 12.7bc 54.2b Cellulose 42.9abc 46.6b 10.0ab bc 66.4a 14.1ab 68.5a Polyethylene 43.1ab 59.8a 10.1ab c 36.5c 7.1c 38.6c Bare Ground 34.4c 55.3ab 8.3b a 68.7a 19.6a 71.7a P = < < Table 2. Mean yield (number of fruit and weight in kg.) of tomatoes per plot (4.3 m row) produced in high tunnel and open field plots at WSU Mount Vernon NWREC in 2010 and Total No. (plot -1 ) Total Wt. (kg plot-1) Fruit No. (plot -1 ) Fruit Wt. (kg plot -1 ) Location High Tunnel 72.8a 88.5a 18.7a 25.6a 20.8a a 59.4 Open Field 14.0b 20.8b 2.0b 4.1b 4.3b b 51.8 P = Table 3. Mean fruit quality attributes of fresh and stored ( 4 o C) tomatoes produced on six mulch treatments in high tunnels and the open field at WSU Mount Vernon NWREC in 2010 and Firmness (N) z Juice Content (% Water) Soluble Solids ( o Brix) ph Titr. Acidity (% Citric Acid) Mulch Fresh Fruit BioAgri bc a BioTelo ab a SB PLA bc a Cellulose bc a Polyethylene c a Bare Ground a b P= Stored Fruit Biodegradable Biodegradable BioAgri - y BioTelo SB PLA Cellulose Polyethylene Bare Ground P= z N = newtons, unit of force in the international system of measurements. A force of one newton will accelerate a mass of one kilogram at the rate of one meter per second per second, equal to about kilograms of force. y Insufficient fruit were harvested in 2010 to measure both fresh and stored fruit.

5 Table 4. Mean fruit quality attributes of fresh and stored ( 4 o C) tomatoes produced in high tunnel and open field plots at WSU Mount Vernon NWREC in 2010 and Firmness (N) x Juice Content (% Water) Soluble Solids ( o Brix) ph Titr. Acidity (% Citric Acid) Mulch Fresh Fruit High Tunnel a b a b Open Field b a b a P= z < Stored Fruit High Tunnel - y 4.47a a Open Field b b P= < x N = Newtons, unit of force in the international system of measurements. A force of one newton will accelerate a mass of one kilogram at the rate of one meter per second per second, equal to about kilograms of force. y Insufficient fruit were harvested in 2010 to measure both fresh and stored fruit. z Insufficient fruit were harvested in open field plots in 2010 to analyze statistically Publications, Handouts, Other Text & Web Products: Miles, C., M. Taylor, G. Sterrett, P. Kreider, S. Johnson, K. Hasenoehrl and J. Cowan Marketable tomato quality testing protocol. Vegetable Horticulture Program, WSU Mount Vernon NWREC. Cowan, J., Miles, C., Inglis, D., Leonas, K., Moore-Kucera, J., Wszelaki, A., Wallace, R., Hayes, D., and Wadsworth, L Proceedings paper: Evaluating potential biodegradable mulches for high tunnel and field vegetable production. Agricultural Plastics Congress, July 31 August 1, Palm Desert, California. Miles, C., M. Taylor, G. Sterrett, P. Kreider, S. Johnson, and J. Cowan SCRI project tomato harvest protocol. Vegetable Horticulture Program, WSU Mount Vernon NWREC. Plasticulture webpage was updated to include new information on biodegradable mulches, high tunnel suppliers and costs of high tunnel production. Outreach & Education Activities: Washington Tilth Producers Conference, November 11, Poster presented: Cowan, J., Miles, C., and Corbin, A Paper or Plastic? Biodegradable mulches in organic crop production. Attendance: 600. WSU Mount Vernon Graduate Student Symposium, October 27, The high tunnel and BDM project was presented at this event. Attendance: 45. Field tour for students at The Evergreen State College, September 26, The high tunnel and BDM project was featured at this event. Attendance: 20. Field tour for Charlie s Produce buyers, September 14, The high tunnel and BDM project was featured at this event. Attendance: 60. WSU Mount Vernon Field Day, July 14, The high tunnel and BDM project was featured at this event. Attendance: 150 Tilth Producers of Washington Farm Walk, June 13, The high tunnel and BDM project was featured at this event. Attendance: 120

6 WSU Mount Vernon Field Day, July 8, The high tunnel and BDM project was featured at this event. Attendance: 150 IMPACTS Short-Term: We have developed standard protocols for measuring fruit quality in high tunnels and with BDMs. We have measured the impact of BDMs and high tunnels on tomato fruit quality during one field season and are preparing this information for dissemination to colleagues and producers through state and national meetings. Intermediate-Term: Producers will gain knowledge and understanding of the impacts of high tunnels and BDMs on tomato fruit quality. If results are favorable, we expect that 20 producers will transition to the use of high tunnels and BDMs by Long-Term: While it would be presumptuous to assume that polyethylene plastics would be completely replaced by BDMs, positive fruit quality responses will increase the likelihood that both the industry and growers will transition to this more sustainable technology by Likewise, positive crop responses with high tunnels, including enhanced fruit quality, longer seasons and greater crop diversity, will facilitate the adoption of high tunnels in Washington by ADDITIONAL FUNDING APPLIED FOR / SECURED USDA-SCRI - $68,000 secured GRADUATE STUDENTS FUNDED Jeremy Cowan, Ph. D. candidate, WSU Dept. Horticulture and Landscape Architecture RECOMMENDATIONS FOR FUTURE RESEARCH Evaluate mulch degradation and correlate field assessment to laboratory measurements to create a field rating system that is reliable and accurate. Evaluate mulch (bio)degradation in the soil environment to assess long-term impacts on soil quality and health; develop a model to predict degradation and potential residues. Develop an economic model to compare costs of production and yield returns on high tunnel tomato production in western Washington.