Polyethylene and biodegradable plastic mulches improve growth, yield, and weed management in floricane red raspberry

Scientia Horticulturae 250 (2019) 371–379

Contents lists available at ScienceDirect

Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti

Polyethylene and biodegradable plastic mulches improve growth, yield, and weed management in floricane red raspberry Huan Zhanga, Carol Milesa, Shuresh Ghimireb, Chris Benedictc, Inga Zasadad, Lisa DeVettera,

T

⁎

a

Washington State University, Northwestern Washington Research & Extension Center, Mount Vernon, WA, 98273, USA University of Connecticut, Tolland County Extension Center, Vernon, CT, 06066, USA c Washington State University, Whatcom County Extension, Bellingham, WA, 98225, USA d USDA-ARS, Corvallis, OR, 97331, USA b

A R T I C LE I N FO

A B S T R A C T

Keywords: Rubus Caneberry Summer-bearing raspberry Plasticulture Root lesion nematode

Polyethylene (PE) mulch and biodegradable plastic mulches (BDMs) have been used in annual vegetable and strawberry (Fragaria × ananassa Duch.) production systems for several decades due to their ability to suppress weeds, modify soil temperature and moisture, and promote earlier and greater yields. However, there are only a few studies that have explored mulch use in perennial production systems. The overall objective of this study was to compare PE mulch and BDMs to growers’ standard practice of bare ground (BG) cultivation in a floricane red raspberry (Rubus idaeus L.) production system in northwestern Washington, USA. Cumulative weed growth, root lesion nematode [Pratylenchus penetrans (Cobb) Filipjev and Schuurmans Stekhoven; RLN] population densities, soil temperature and moisture, cumulative plant growth, and fruit yield were evaluated in a ‘Wake™Field’ red raspberry field in 2017 and 2018. Compared to the BG control, PE mulch and BDMs suppressed weeds and generally increased soil temperature. Root lesion nematode population densities were greater in soil covered with PE mulch than Novamont 0.5, and were greater in raspberry roots from plots treated with PE mulch than BASF 0.6 and the BG control. Primocane height and number were higher for plants grown with mulches relative to the BG control in 2017. Average fruit yield of plants from the mulched treatments was 34% greater than the BG control. Overall, this research demonstrated that PE mulch and BDMs improved raspberry plant growth and yield. These findings demonstrate the potential benefits of using PE mulch and BDMs for improving establishment in perennial crops.

1. Introduction The United States (USA) is an important producer of red raspberry (Rubus idaeus L.) with approximately 106,100 tonnes of fruit harvested from 8271 ha in 2017 (United State Department of Agriculture National Agricultural Statistics Service (USDA NASS, 2018). Production of floricane red raspberry for the processing market is concentrated in the Pacific Northwest (PNW), which includes Washington and Oregon in the United States and British Columbia in Canada. Combined, Washington and Oregon produced approximately 37,852 tonnes of fruit from 4168 ha in 2017. Traditional sources of raspberry planting material in the PNW are bare root canes and root cuttings. However, the use of tissue culture (TC) transplants has been increasing, accounting for 26% of total raspberry plant sales in the PNW between 2016 and 2018 (Moore, 2016). Some commercially important cultivars, like ‘Wake™Field’ (Northwest Plant Co., Lynden, WA, USA), are only available as

⁎

TC transplants. Other raspberry cultivars are increasingly being offered as TC transplants as part of a comprehensive strategy to improve management of soilborne diseases because TC techniques generate a clean plant, free of diseases, insects, and viruses (Theiler-Hedtrich and Baumann, 1989). Nurseries can also generate TC plants quickly in small spaces, which is more efficient than producing field-grown nursery plants (Bellincampi et al., 1985). One disadvantage of TC transplants is that they have foliage when planted, which is sensitive to herbicide injury. Current floricane raspberry production systems in the PNW depend on pre- and post-plant herbicides and hand weeding to manage weeds during plant establishment. Plants are also rarely trained during the first year and primocane growth can extend in the rows and alleyways, further limiting the use of herbicides and making hand-weeding difficult. Hand weeding is also costly and labor is increasingly difficult to secure. Moreover, hand weeding new fields during the harvest season is challenging

Corresponding author. E-mail address: [email protected] (L. DeVetter).

https://doi.org/10.1016/j.scienta.2019.02.067 Received 1 December 2018; Received in revised form 21 February 2019; Accepted 21 February 2019 0304-4238/ © 2019 Elsevier B.V. All rights reserved.

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

plant fumigate to manage RLN. However, RLN is not completely eliminated by fumigation (Walters et al., 2017). Knowledge of practices that promote or discourage RLN population densities post-planting is important for enhancing plant establishment and future productivity. Washington State red raspberry growers are concerned that increased soil temperatures under mulches could increase the severity of RLN parasitism in raspberry. In a preliminary study in British Columbia, increased soil RLN population densities were observed under PE mulch relative to bare ground cultivation in floricane red raspberry (Gerbrandt, 2014). However, there are no other complete studies exploring the impacts of plastic mulches, both PE and BDMs, on RLN population densities. If plastic mulches are used to improve red raspberry establishment, their impacts on RLN population dynamics need to be understood given the importance of this plant-parasitic nematode in this production system. The aim of this research was to develop knowledge and practical strategies that can be implemented in commercial floricane raspberry production systems to improve plant establishment and weed management when planted as TC transplants. The specific objectives were to assess the impacts of PE mulch and BDMs on weed management, RLN population dynamics, soil temperature and moisture conditions, raspberry plant growth, physiology, and fruit yield and size. Information from this research will contribute to developing knowledge about mulching with plastics in floricane raspberry and other perennial fruit systems. Successful implementation of plastic mulches may not only enhance TC transplant establishment, but may also promote on-farm efficiencies and profitability through improved weed management, plant growth, and yield.

because farm crews are needed to support harvesting operations. Poor establishment of TC transplants can limit the long-term productivity of a planting and impact on-farm profitability, which are especially important because TC transplants cost more than traditional types of planting materials. Growers need new techniques to manage weeds, improve the establishment of TC transplants, and increase subsequent yields. Accomplishing this would offset or possibly even reduce the costs associated with growing TC transplants. Use of polyethylene (PE) mulch has become a standard practice in many vegetable and strawberry (Fragaria x ananassa Duch.) systems due to the ability of mulches to suppress weeds, modify soil temperature and moisture, and promote earlier and greater yields of highquality vegetables and fruit (Fernandez et al., 2001; Lamont, 2017). However, the removal and disposal of PE mulch are expensive and challenging (Galinato and Walters, 2012; Galinato et al., 2012). This issue results in very limited end-of-life mulch disposal options for farmers, who either dispose mulches in landfills, stockpile, or burn mulch, contributing to plastic waste generation (Goldberger et al., 2015; Kasirajan and Ngouajio, 2012; Levitan and Barros, 2003). Biodegradable plastic mulches (BDMs) are a promising alternative to PE mulch. For a mulch to be considered a BDM, it should achieve at least 90% biodegradation in laboratory-based soil tests within two years or less due to microbial activities and in accordance with ASTM D5988-18 and EN 17033 (American Society for Testing and Materials (ASTM, 2018; EN, 2018). BDMs are designed to biodegrade in soils upon incorporation, thereby reducing the economic and environmental problems associated with PE mulch removal and disposal. Studies in annual vegetable and strawberry production systems indicated that BDMs were comparable to PE mulch and demonstrated their potential suitability in commercial production systems (Anzalone et al., 2010; Costa et al., 2014; DeVetter et al., 2017; Forcella et al., 2003; Ghimire et al., 2018; Miles et al., 2012). For a perennial system like raspberry, where planting longevity may be 6 years or longer, mulch may only be needed for 6 to 12 months during establishment. BDMs are appealing as they may circumvent the need to remove mulch after establishment, which can be labor intensive and costly. Although PE mulch and BDMs represent potential herbicide-free tools that may enhance weed management and establishment of TC transplants, only a few studies have explored plastic mulch use in perennial systems like raspberry. Trinka and Pritts (1992) found PE mulch improved growing conditions for primocane raspberry in New York, USA by reducing weed pressure and increasing soil moisture and temperature. Król-Dyrek and Siwek (2015) compared three mulches [polypropylene (PLP; non-biodegradable), photo-degradable PLP (nonbiodegradable), and polylactic acid (PLA; biodegradable)] to bare soil cultivation in Poland and found primocane raspberry yield was greater for the three mulch treatments compared to bare ground. A case study in northwest Italy reported that BDMs adequately controlled weeds in a primocane raspberry planting and increased yield by 10% (Tecco et al., 2016). In a preliminary study in British Columbia, improved growth and establishment was observed when TC floricane raspberry was planted with PE mulch (Gerbrandt, 2014). In another perennial system, PE mulch and BDMs significantly increased wood production and fruit yield in a newly planted vineyard (Vitis vinifera L.) compared to bare soil cultivation in France (Touchaleaume et al., 2016). These initial studies show the potential benefits of mulching with plastics in perennial systems for improved plant establishment. However, primocane raspberry is very different physiologically and in growth habit compared to floricane raspberry (DeVetter et al., 2019). More information is needed on the impacts of plastic mulches, including PE mulch and BDMs, in floricane raspberry and other perennial fruit systems. Root lesion nematode [Pratylenchus penetrans (Cobb) Filipjev and Schuurmans Stekhoven; RLN] is an important plant-parasitic nematode in the red raspberry production system and is widespread in many production regions, including the PNW (Gigot et al., 2013; Martin et al., 2017; McElroy, 1992; Zasada et al., 2015). Most raspberry growers pre-

2. Materials and methods 2.1. Experimental location and design The study was conducted on a commercial farm in Whatcom County, WA, USA (48°58′N, 122°25′W) from 2017 to 2018. The soil type is a Laxton loam, characterized as a coarse-loamy over sandy or sandy-skeletal, isotic over mixed, mesic Aquic Haplorthods (USDA, 2018). The field was broadcast fumigated [Telone C-35®; 65% 1,3-dichloropropene and 35% chloropicrin (Dow Agrosciences, Indianapolis, IN, USA)] in September 2016 at the rate of 54 l/ha by a commercial fumigation company (Trident Agriculture Products, Woodland, WA, USA). Beds were pre-formed by the grower cooperator one week before mulch application. Bed dimensions were 0.36 m high, 0.91 m wide at the top, and 1 m wide at the bottom. The experimental design was a randomized complete block with six treatments replicated five times. Blocking occurred across rows to minimize within-field variation due to soil texture. The six treatments included one black PE mulch, four black BDMs, and a BG control that represented standard industry practices including pre-plant herbicide application and hand weeding (Table 1). The plots were spaced 3 m center-to-center, each plot was 36 m long, and the entire experimental area was 0.33 ha (18 m by 182 m). 2.2. Mulch laying and field maintenance Mulch treatments were applied over the course of two days in May 2017 due to rain and saturated soil conditions that occurred on the first application date. Mulches were applied with a custom-built flatbed mulch layer (Corvallis, OR, USA) that was modified to allow mulch application over pre-formed raised beds. Mulch was applied over drip tape (emitter spacing 61 cm, BlueLine PC Clipperline, TORO, Bloomington, MN, USA) that was installed by the cooperator down the center of each bed. Mulch treatments in each row were overlapped between plots and soil was placed on top to secure the overlapped mulches. These overlapped areas were approximately 1 m long and no data were collected from these sections. Planting holes were punched by hand immediately after mulch application on 25 May using a 372

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

Table 1 Polyethylene (PE) and biodegradable plastic mulches (BDMs) applied to raspberry in northwestern Washington, USA.2017–2018. Mulch product

z

BASF 0.5 BASF 0.6 Novamont 0.5 Novamont 0.6 Polyethylene z y

Thickness

Converter

Key product ingredient(s)

12.7 μm 15.2 μm 12.7 μm 15.2 μm 22.7 μm

PolyExpert Inc., Laval, Quebec, Canada PolyExpert Inc., Laval, Quebec, Canada Dubois Agrinovation, Saint Remi, Quebec, Canada Dubois Agrinovation, Saint Remi, Quebec, Canada FilmTech, LLC., Stanley, WI, USA

PLA + PBATy PLA + PBAT1 Starch based, PBAT copolyester Starch based, PBAT copolyester Polyethylene

BASF and Novamont are biodegradable products according to ASTM D 5988-18 and EN 17033 standards. PLA = polylactic acid; PBAT = polybutylene adipate-co-terephthalate.

to the drip tape emitters was measured 15 September 2017 when it was observed that soil moisture and temperature fluctuated in the BASF 0.6 treatment. This sensor was then moved to the southern side of the fifth plant in that plot. Data collection stopped on 1 June 2018, as mulches were mostly deteriorated or removed, and the loggers needed to be removed before machine harvesting.

custom-made dibble. Holes were 7.5 cm deep and spaced 66 cm apart along the row center. Tissue culture ‘Wake™Field’ raspberries were hand planted immediately after mulch application, and their initial height was approximately 18 cm. Plants in all treatments were irrigated and fertilized identically, following commercial standards for the region (DeVetter et al., 2019). Fertilizers applied in 2017 were liquid and injected through a single drip line by the grower cooperator. The PE mulch was removed in mid-March of 2018, while the BDMs remained in the field for the duration of the study.

2.6. Cumulative plant growth Plant growth was measured monthly as primocane height and number from 10 permanent plants per plot from 25 May to 27 October 2017. Primocane height was determined by measuring the height of the tallest primocane per plant, starting at the base of the crown and extending to the tallest leaf tip. Primocane number was determined by counting the number of primocanes per plant, with only primocanes emerging from the base of the crown being counted for the first measurement on 28 July 2017. Because ‘Wake™Field’ tends to produce primocanes above the crown, primocane number was then determined by counting the number of primocanes that were over 30 cm in length starting August 2017. Primocane emergence was enumerated on 5 July 2018 from a 10 m length in the center of each plot, and primocane height and number were measured on 26 September 2018 from the same 10 permanent plants per plot. Primocane emergence in July was determined by counting all primocanes emerging from beyond the crown, including those injured by cane burning (DeVetter et al., 2019). Plant height measurement in 2018 was done using the same procedures as in 2017, whereas primocane number was measured by counting the number of primocanes emerging from the crown area and soil near the crown area and no above-crown primocanes were counted in September 2018 because they were tangled with floricanes and could not be separated.

2.3. Cumulative weed growth Total weed number as well as fresh and dry shoot biomass within a permanent 1 m2 area located in the middle of each plot were recorded monthly starting 30 June and continued until 27 October 2017. Total weed number and biomass for each date was cumulative. Weeds were clipped at the soil surface and weighed to determine fresh weight. Weeds were then dried at 38 °C for 5 days (or until constant weight) and re-weighed to determine dry shoot biomass. 2.4. RLN population densities Baseline pre-plant RLN population densities were determined in each plot from soil samples collected in May 2017. Post-plant RLN population densities were determined in each plot from soil and root samples collected in October 2017, and in May and September 2018 using established protocols (Walters et al., 2017). Eight soil cores within 15 cm of the plant crown were collected and combined per plot using a soil probe (2.5 cm diameter and 30 cm deep). For the collection of roots, two 15 × 15 × 15 cm samples were collected within 15 cm of the plant crown in each plot using a shovel. Soil and root samples were then placed in the same bag and kept at 4 °C until nematode extraction and enumeration. Mixed stages of RLN were extracted from soil by placing 50 g of soil on a Baermann funnel with nematodes being collected after 5 days (Walters et al., 2017). For extraction of RLN from roots, roots < 2 mm in diameter were preferentially collected and placed under intermittent mist with nematodes being collected after 5 days (Walters et al., 2017). Identification and enumeration of RLN occurred using a stereomicroscope at 40x magnification with identification based on morphological features and the presence of males (Castillo and Vovlas, 2007). Roots were dried for 1 week at 70 °C to determine dry weight biomass. Values were expressed as number of RLN per g dry root or number of RLN per 100 g soil.

2.7. Fruit yield and average fruit weight Yield was measured from a 10 m length in the center of each plot. Fruit were harvested from 29 June to 10 August 2018. Harvest occurred 14 times by the grower and total machine harvestable yield was determined from 13 harvests. Harvests were categorized as early (1st–3rd harvests; 20 June to 7 July), middle (4th to 8th harvests; 11 to 23 July), and late (9th to 13th harvests; 26 July to 10 August) based on the production cycle. Average fruit weight was calculated from 30 randomly selected berries per plot and was measured on 4 July, 17 July, and 10 August 2018. 2.8. Stem water potential and photosynthesis

2.5. Soil temperature and moisture Stem water potential was measured on 27 and 28 July 2017 and 16 July 2018 using a pressure chamber instrument (Model #600, PMS Instrument Co., Albany, OR, USA). Photosynthesis measured as net CO2 assimilation (A) was determined on 15 August 2017 and 16 July 2018 using a portable photosynthesis system (Model #CIRAS-3, PP Systems, Amesbury, MA, USA). Photosynthetically active radiation was set at 1500 μmol/m2s1. Stem water potential and photosynthesis were both measured during the peak growth time of the year for raspberry, when

Starting 25 May 2017, data loggers with sensors (EM50 Digital Data Logger and 5 TM sensors, Decagon Device, Pullman, WA, USA) monitored soil temperature and moisture every 15 min in all treatments in the third replicate block. The third block was selected for these measurements because of its interior location that minimized potential border effects. Sensors were installed 5 cm from the southern side of the fourth plant in each plot at a depth of 10 cm. The distance of the sensors 373

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

air temperature was highest in general, as this provided the greatest opportunity to see differences between treatments. Both measurements were collected from three recently expanded primocane leaves (fourth or fifth leaf from the shoot apex) per plot between 1000 h and 1400 h. Leaves were covered and allowed to equilibrate with the plant stem for at least 15 min. prior to measuring water potential (Meron et al., 1987). 2.9. Soil and leaf nutrient analysis Soil samples were collected 1 June 2017 and 31 May 2018 and sent to a commercial laboratory (Brookside Laboratories, Inc., New Bremmen, OH, USA) for soil macronutrient determination. Samples were collected by combining eight cores (2.5 cm diameter and 30 cm deep) from the raised bed of each plot. Leaf macronutrient content were determined from leaf tissues collected 28 July 2017 and 26 July 2018. Five recently expanded and representative primocane leaves, 30 cm from the apex, were randomly collected and combined per plot. Leaf samples were subsequently dried at 38 °C for 5 days or until constant weight and then sent to a commercial laboratory (Brookside Laboratories, Inc.) for macronutrient determination.

Fig. 1. Cumulative weed number per m2 for establishing raspberry grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG) in 2017. * Indicates significant difference at P ≤ 0.05 using a non-parametric multiple comparisons Wilcoxon test.

2.10. Statistical analysis Data that met the assumptions of analysis of variance (ANOVA) were analyzed using ANOVA with JMP®12.2.0 (SAS Institute, Cary, NC, USA). Data were analyzed as a randomized complete block design for leaf water potential, net CO2 assimilation rates, and soil and leaf tissue nutrient contents. A repeated measures procedure was used for cumulative plant growth, fruit yield, and berry weight. A Tukey’s honest significant difference test was used for post hoc comparisons at the 5% level of significance except for total fruit yield. Fisher’s least significant difference test was used to compare treatment means for total fruit yield at the 5% level of significance. Data are presented by year when there was a year effect or year by treatment interaction. Cumulative weed growth and RLN population densities determined in October 2017 and May and September 2018 were analyzed with a Wilcoxon non-parametric multiple comparison method because these data did not meet the normality assumptions for ANOVA; nontransformed means are presented.

the BG control, both of which were similar to the remaining treatments (P = 0.04). Root population densities of RLN did not differ across treatments at this sampling time (P = 0.20). In September 2018, soil treated with PE mulch had greater RLN population densities, which were 202% higher than densities found in soil treated with Novamont 0.5 (P = 0.01). Root population densities of RLN were higher for plants treated with PE mulch relative to BASF 0.6 and the BG control (P = 0.01). 3.3. Soil temperature and volumetric water content Soil temperatures under the mulch treatments were always higher than the BG control until December 2017 (Table 3; data excludes Novamont 0.6 from 11 December 2017 to 28 April 2018 due to a malfunctioned sensor). PE mulch tended to result in higher soil temperature and volumetric water content than the other treatments (Tables 3 and 4). From June to September 2017, the average soil temperature across all mulch treatments was 20.7 °C (range was 19.5 to 21.5 °C), which was 1.5 °C higher than the BG control (Table 3). Soil temperature under PE mulch was 0.7, 0.6, 0.6, and 2.2 °C higher than BASF 0.5, Novamont 0.5, Novamont 0.6, and the BG control, respectively. From June 2017 to May 2018, the average soil temperature across mulched treatments was 12.1 °C (range was 11.6 to 12.6 °C), which was 0.6 °C higher than the BG control. The average soil volumetric water content at 10 cm depth across mulched treatments from June to September 2017 and June 2017 to May 2018 was the same at 0.24 m³/m³, which was 0.04 m³/m³ and 0.02 m³/m³ lower than the BG control, respectively (Table 4). However, PE mulch had a higher soil volumetric water content than the remaining treatments during these two periods, at 0.31 and 0.30 m³/m³, respectively.

3. Results 3.1. Weed density and biomass Cumulative weed number was greatest in the BG control, while there were minimal weeds across BDMs, and no weeds in the PE mulch throughout the 2017 growing season (Fig. 1). On 27 October 2017, which was the last weed measurement, cumulative weed number was greatest in the BG control than all mulched treatments (P = 0.02). Treatments differed in cumulative weed biomass on all dates except 30 June 2017 (data not presented). On 27 October 2017, the BG control had 0.278 g/m2 of total cumulative weed biomass, which was 0.178 g/ m2 higher than BDMs (P = 0.01). 3.2. RLN population densities

3.4. Primocane height and number

Pre-plant RLN soil population densities did not differ among treatments (Table 2). Root lesion nematode population densities in soil ˜5 months after planting (10 October 2017) were highest in Novamont 0.6 and PE mulch, lowest in the BG control, but similar for other treatments (P = 0.03). At this sampling date, plants treated with Novamont 0.5 had the highest RLN population densities in roots, which were 260% higher than plants treated with the BG control and PE mulch (P = 0.02), but were similar to other treatments. These trends did not carry over to next spring, ˜12 months after planting. In May 2018, RLN soil population densities in the BASF 0.5 treatment were 420% higher than

Baseline primocane height measured on 25 May 2017 was not different across treatments (P = 0.25; Fig. 2A). However, one month after mulch application, the average primocane height was 36% higher for plants treated with BASF 0.5, Novamont 0.5, and PE mulch than the BG control (P = 0.001; Fig. 2A). Plants treated with BASF 0.6 and Novamont 0.6 had primocane heights that were similar to the BG control and the remaining treatments. Differences in primocane height persisted after this sampling time and height was greater among plants grown in 374

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

Table 2 Population densities of root lesion nematodes (Pratylenchus penetrans; RLN) in raspberry soil and roots grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG) in 2017 and 2018. May 2017z

October 2017

RLN/100 g soil

RLN/100 g soil

RLN/g root

RLN/100 g soil

RLN/g root

RLN/ 100 g soil

RLN/ g root

BASF 0.5 BASF 0.6 Novamont 0.5 Novamont 0.6 PE BG

0 1 0 0 1 0

51 aby 50 ab 66 ab 100 a 72 a 5b

105 ab 134 ab 165 a 164 ab 45 b 44 b

52 50 40 38 40 10

1538 937 1471 1109 995 997

258 225 116 209 350 212

1352 ab 430 b 1620 ab 1445 ab 2605 a 692 b

P-value

0.40

0.03

0.02

0.04

0.20

0.01

Treatment

May 2018

a ab ab ab ab b

September 2018

ab ab b ab a ab

0.01

z

Pre-plant densities. Means followed by the same letter within a column are not significantly different at P < 0.05 using a means comparison with a Tukey’s honestly significant difference test for the May 2017 data and a non-parametric multiple comparisons Wilcoxon test for the October 2017 and May and September 2018 data. y

Table 3 Average monthly soil temperature (°C) from June 2017 to May 2018 in raspberry grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG). Sensors were installed at a depth of 10 cm and data are averaged by month. Monthly soil temperature (°C)

June July August September October November December January February March April May

BASF 0.5

BASF 0.6

Novamont 0.5

Novamont 0.6

PE

BG

20.3 22.8 21.5 18.3 11.5 7.1 3.9 3.5 4.4 5.9 10.7 15.6

18.0 20.9 21.0 18.2 11.34 7.0 3.7 3.3 4.4 5.7 10.4 15.2

20.6 23.5 21.4 18.1 11.5 7.4 3.9 3.5 4.6 5.9 10.8 15.8

20.5 23.2 21.6 18.2 11.9 7.5 -z – – – – 15.4

20.9 23.6 22.3 19.0 11.9 7.7 3.9 3.4 4.9 6.9 11.0 15.5

18.2 21.0 20.3 17.6 11.1 6.8 3.7 3.3 4.5 5.7 10.5 15.5

z Soil temperature data for the Novamont 0.6 treatment from December 2017 to April 2018 are not presented due to a logger malfunction.

Table 4 Average monthly volumetric water content (m3/m3) from June 2017 to May 2018 in raspberry grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG). Sensors were installed at a depth of 10 cm and data are averaged by month. Monthly volumetric water content (m3/m3)

June July August September October November December January February March April May

BASF 0.5

BASF 0.6

Novamont 0.5

Novamont 0.6

PE

BG

0.18 0.17 0.17 0.15 0.17 0.20 0.22 0.25 0.22 0.21 0.19 0.15

0.33 0.26 0.20 0.18 0.21 0.23 0.24 0.26 0.25 0.24 0.20 0.15

0.27 0.24 0.23 0.19 0.23 0.27 0.27 0.26 0.25 0.23 0.21 0.15

0.26 0.26 0.25 0.22 0.24 0.28 -z – – – – 0.12

0.32 0.31 0.31 0.27 0.27 0.32 0.33 0.34 0.35 0.34 0.32 0.26

0.27 0.26 0.27 0.24 0.28 0.31 0.32 0.33 0.32 0.30 0.29 0.22

Fig. 2. Primocane height (A) and primocane number (B) of ‘Wake™Field’ raspberry in 2017 grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG) during establishment. NS, **, *** indicate nonsignificant or significant differences at P ≤ 0.001 or 0.0001, respectively, using a means comparison with a Tukey’s honestly significant difference test.

There were no differences in primocane number until 30 August 2017, which was also when our method of counting primocanes changed to enumerate primocanes that were produced above the crown (Fig. 2B). At this time, plants treated with mulches had a similar primocane number ranging from 14 to 17 primocanes/plant, which were greater than the BG control (P < 0.0001). By 27 October 2017, plants treated with PE mulch had the greatest number of primocanes/plant, which was similar to BASF 0.6 and Novamont 0.5. The lowest primocane number occurred in the BG control, which on average had 4 fewer primocanes per plant than plants grown with mulches (P < 0.0001). Primocane emergence on 5 July 2018 was greatest in the BG control and lowest in Novamont 0.5 and PE, while all remaining treatments were similar (Table 5; P = 0.05). There were no differences in primocane height and number in September 2018 across all treatments,

z Soil volumetric water content data for the Novamont 0.6 treatment from December 2017 to April 2018 are not presented due to a logger malfunction.

all mulched treatments relative to the BG control from July to October 2017 (P < 0.0001). By October 2017, average primocane height was similar across all mulched treatments, but was 36 cm greater than the BG control (P < 0.0001).

375

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

Table 5 Average raspberry primocane emergence, height, and number when grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG) in 2018. Treatment

Primocane emergence/10 m (5 July 2018)

Table 7 Nitrogen (N), phosphorus (P), and potassium (K) levels in raspberry soil and primocane leaf tissue grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG) in 2017 and 2018.

Primocane number/ plant (26 September 2018)

Primocane height (cm) (26 September 2018)

Treatment

Soilz y

abz ab b ab b a

BASF 0.5 BASF 0.6 Novamont 0.5 Novamont 0.6 PE BG

35 37 30 41 23 45

P-value

0.05

317 319 325 317 329 316

5 6 6 6 5 6

0.71

0.28

N (kg/ ha)

z Means followed by the same letter within a column are not significantly different at P < 0.05 using a means comparison with a Tukey’s honestly significant difference test.

Leaf P (mg/kg)

K (mg/kg)

N (%)x 2017

2018

P (%)

K (%)

BASF 0.5 BASF 0.6 Novamont 0.5 Novamont 0.6 PE BG

107.0 107.5 107.4 107.1 169.9 107.2

113.4 108.4 114.7 115.6 109.0 112.9

211.1 229.2 225.1 219.5 214.3 216.9

3.9 3.9 3.8 3.8 3.7 3.8

3.5 3.3 3.4 3.3 3.5 3.3

0.2 0.3 0.2 0.3 0.3 0.2

1.5 1.5 1.3 1.5 1.5 1.4

P-value

0.2

0.08

0.1

0.93

0.95

0.1

0.7

z Means followed by the same letter within a column are not significantly different at P < 0.05 using a means comparison with a Tukey’s honestly significant difference test. y Nitrogen release was estimated based on the percentage of organic matter in the soil. x Data are presented by year when there is a year effect.

and the average primocane height and number for all treatments was 320 cm and 6 primocanes/plant, respectively.

3.5. Fruit yield and average fruit size 3.6. Leaf water potential and leaf gas exchange rates

Total fruit yield was greater across mulched treatments than the BG control (Table 6; P = 0.04). The average total yield of 13 harvests for mulched treatments was 28.4 kg/10 m (range was 26.0–29.8 kg/10 m), which was 7.3 kg/10 m greater than the BG control. The middle harvest produced the greatest yield among the three harvest periods, followed by late then early harvests (P < 0.0001). Although there were no treatment differences for the early harvest period, average yield was 3.4 kg/10 m for all mulch treatments and 2.5 kg/10 m for the BG control, which was a 0.9 kg/10 m difference. For the middle harvest period, all mulched treatments except BASF 0.5 had greater yields than the BG control (P = 0.004). Average yield across the mulched treatments, excluding BASF 0.5, during the middle harvest period were similar and 54% higher than the BG control. For the late harvest period, fruit yield was 40% higher across the BDM treatments compared to the BG control, but yields between BDMs and PE mulch were similar (P = 0.002). Although there was an effect on berry weight due to harvest time, there were no differences among treatments (data not presented). Average berry weight was greatest early in the season (3.9 g/berry), decreased by mid-season to 2.8 g/berry, and was lowest at the end of the harvest season at 2.3 g/berry (P < 0.0001).

There were no differences in leaf water potential across treatments in 2017 and 2018, although there was an effect due to year (P = 0.01). The average stem water potential was -463 and -743 kpa for 2017 and 2018, respectively (data not presented). CO2 assimilation was the same across all treatments in both years but there was a year effect (P = 0.01). The average net CO2 assimilation was 3.1 and 14.8 μmol/m2s1 in 2017 and 2018, respectively (data not presented). 3.7. Soil and leaf tissue macro- and micro-nutrients There were no treatment differences for soil and leaf tissue nitrogen, potassium, and phosphorus content in 2017 and 2018 (Table 7). However, leaf tissue nitrogen concentrations were 13% higher overall in 2017 than in 2018 (P < 0.001). 4. Discussion To our knowledge, this is the first study to evaluate the effects of using PE mulch and BDMs in floricane-fruiting raspberry established as TC transplants. Overall, raspberry plant growth, fruit yield, and soil temperature were increased by PE mulch and BDMs compared to the industry standard of bare ground management. Population densities of RLN in soil and raspberry roots were also increased under PE mulch. PE mulch and BDMs suppressed weed growth during the 2017 growing season (Fig. 1). Although the grower cooperator in this study hand weeded the BG plots three time during the growing season in 2017, weed number and biomass were still greater in the BG control than PE mulch and BDMs. TC transplants are sensitive during the establishment year and competition from weeds could negatively impact raspberry plant establishment (Lawson and Wiseman, 1974, 1976; Pritts et al., 1989). Traditionally, both pre- and post-plant herbicides are used in raspberry production for weed management (DeVetter et al., 2019). However, post-plant herbicides would not be suitable for TC transplants during the establishment year as foliage is present and herbicide application could damage the plants (Mudge et al., 1987; Neal et al., 1990). Mulch application impacted RLN soil and root population densities (Table 3). Understanding the impacts of elevated soil temperatures on RLN population dynamics is extremely important because RLN is a significant plant-parasitic nematode in the PNW red raspberry system

Table 6 Average fruit yield (kg/10 m) of raspberry grown with polyethylene (PE) and biodegradable plastic mulches (BASF and Novamont treatments) compared to bare ground (BG) during establishment in 2017. Treatment

Harvest time

Total yield

Earlyz (6/29-7/ 10)

Middle (7/11-7/ 25)

BASF 0.5 BASF 0.6 Novamont 0.5 Novamont 0.6 PE BG

3.2 3.1 3.2 3.5 4.1 2.5

15.2 18.1 17.3 16.6 18.2 11.4

P-value

0.08

0.004

aby a a a a b

Late (7/26-8/ 10) 7.6 9.1 8.1 7.9 6.8 5.8

a a a a ab b

26.0 29.3 28.6 28.1 29.8 21.1

0.002

0.04

a a a a a bz

z

Yield was determined in 2018 from a 10-m region in each plot. Averages followed by the same letter within a column are not significantly different at P < 0.05 using a means comparison with a Tukey’s honestly significant difference test except total yield, which was analyzed with Fisher’s least significant difference test. y

376

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

and is the primary reason that growers fumigate their fields (Rudolph and DeVetter, 2015). Pudasaini et al. (2008) found that a soil temperature of 20 °C increased RLN egg hatch compared to 10, 15, or 25 °C in some vegetable crops. In the current study, soil temperature from June to September 2017 under PE mulch and BDMs was 1.3 and 0.4 °C higher, respectively, and 0.9 °C lower in the BG control compared to 20 °C (Table 3). Although there was a chance that mulched treatments and subsequent elevated soil temperatures increased RLN egg hatch and therefore RLN densities tended to be greater in mulched relative to the BG treatments, RLN activity in this study did not appear to reduce plant productivity as indicated by plant growth and yield (Fig. 2 and Tables 5 and 6). Population densities of 140 to 550 P. penetrans/100 g soil (1000–4000 P. penetrans/500 cm3 soil) were measured, and these densities have been observed to decrease raspberry growth in established fields (McElroy, 1992). Although this range of soil RLN population densities occurred in September 2018 across all treatments except Novamont 0.5, it is believed RLN population densities in the soil are not the best indicator to predict potential damage in raspberry. Han et al. (2014) reported that RLN population densities of approximately 2300 P. penetrans/g of dry roots did not decrease floricane raspberry yield compared to plants treated with nematicide with only 31 P. penetrans/g of dry root after 18 months of protection. This indicated that raspberry plants were able to remain productive despite some level of RLN parasitism. In the current study, although plants treated with PE mulch had higher RLN population densities in roots compared to plants treated with BASF 0.6 and the BG control in September 2018, there were no reductions in the yield and plant growth measured in 2017 and 2018 (Tables 5 and 6). This suggests the horticultural benefits of plastic mulches outweigh the potential impact they have on increasing RLN population densities. PE mulch and BDMs generally increased soil temperature compared to the BG control, with soil temperature under PE mulch being greater than the BDMs (Table 3). Volumetric water content was also greatest under PE mulch, but BDMs were similar or slightly lower than the BG control (Table 4). Mulch thickness may have contributed to the observed differences in soil temperature and volumetric water content. The thickness of the PE mulch used in this study was 22.7 μm, which was greater than the BDMs (thickness ranged from 12.7 to 15.2 μm). The difference in mulch thickness for this experiment was because 22.7 μm PE mulch was available locally in the market and recommended by the distributor for our application. Thinner BDMs reduce the costs associated for this more expensive mulch alternative (Zhang et al., 2017). Furthermore, thinner BDMs should biodegrade faster in soil and preliminary trials suggested that these thicknesses should be appropriate for raspberry (DeVetter, unpublished). Previous studies have also shown mulch effects on soil temperature and moisture. Trinka and Pritts (1992) reported raspberry plants grown with black PE mulch had the highest soil temperature compared to straw and bare ground. Black plastic mulch absorbs solar energy and reradiates thermal radiation and long-wavelength infrared radiation to the soil, thereby increasing soil temperature (Lamont, 2017). Bilck et al. (2010) showed that BDMs [polylactic acid (PLA) +polybutylene adipate terephthalate (PBAT)] have 100–250 times greater water vapor permeability than PE mulch and higher permeability could accelerate soil-water evaporation. In another study, water vapor permeability in a BDM (PLA + PBAT) was 3.3 times greater than PE mulch and soil moisture levels in a vineyard were lower under the BDM than PE mulch (Touchaleaume et al., 2016). These studies suggest that the higher soil temperatures and lower volumetric water content observed across the BDM treatments may be due to mulch color and their high water vapor permeability. Furthermore, increased soil temperature may have also accelerated water evaporation from the soil. Soil temperature and volumetric water content followed a different trend in the BASF 0.6 treatment relative to the other BDMs (Tables 3 and 4). The lower soil temperature and higher volumetric water content in BASF 0.6 in June and July 2017 were likely due to soil compaction

around the sensor. Once moved to a new location, the data from this treatment became more similar to BASF 0.5. Soil covered by BASF 0.5 still had lower volumetric water content and higher soil temperature from June to November 2017 compared to BASF 0.6, which were attributed to the water vapor permeability of BASF mulch (PLA + PBAT) and the thinner thickness of BASF 0.5 (personal communication with Ruth Watts, BASF). Soil under Novamont 0.5 and Novamont 0.6, in general, had higher volumetric water contents than BASF 0.5 and BASF 0.6, which could be due to differences in the materials’ chemistry and manufacturing processes. Plant growth increased through the use of PE mulch and BDMs relative to the BG control (Fig. 2). This has been observed in other studies with primocane-fruiting raspberry grown with PE mulch or BDMs (KrólDyrek and Siwek, 2015; Tecco et al., 2016; Trinka and Pritts, 1992). Trinka and Pritts (1992) also noted that ‘Heritage’ raspberry in mulched plots had better primocane growth in the first and second years relative to treatments with herbicide or hand weeding. In October 2017 (the last date primocanes were measured during the establishment year), average primocane height and number were greater in mulched treatments than the BG control. Raspberry plants grown with PE mulch and BDMs had the same primocane height, but primocane numbers among plants treated with PE mulch were 22% and 23% higher, respectively, than BASF 0.5 and Novamont 0.6. These differences were likely due to higher soil temperature and volumetric water content in soil covered with PE mulch, as there were no differences in weed incidence among the mulched treatments (Fig. 1 and Tables 3 and 4). Despite the higher temperatures and volumetric water content of soils covered by PE mulch relative to BDMs, Gastaldi et al. (2013) predicted that using BDMs was better for grapevine growth compared to PE mulch because mulch degradation allowed plants to acclimate to changes in soil temperature and moisture compared to one-time removal of PE mulch. However, we did not observe this benefit in our study. In the second growing season, plants grown in the BG control had almost 100% and 36% greater primocane emergence than plants grown with PE mulch and BDMs, respectively (Table 5). Primocane emergence and regrowth is important for floricane raspberry, as they provide renewal tissue that supports fruit production in subsequent years. Primocane emergence measured in July 2018 was greater in the BG control because no mulch obstructed their growth from the soil, while emergence in the BDM treatments was greater than PE mulch because the BDMs degraded leading to exposed soil over time (data not presented). Although growers practice “caneburning”, which is the physical or chemical removal of the first flush of emerging primocanes early in the spring (DeVetter et al., 2019), restricted primocane emergence could be a potential problem for future implementation of plastic mulches. However, no differences in primocane height and number were detected among treatments when they were re-measured in September 2018, suggesting that mulch application did not negatively impact primocane growth in the second growing season after caneburning practices had been implemented (Table 5). Primocane height of plants treated with PE mulch and BDMs was numerically higher by 4% and 1%, respectively, compared to plants in the BG control. This increase in primocane height suggests plants mulched with PE may have a higher yield potential during the second harvest season. Plants grown with PE mulch or BDMs produced greater yields during their first harvest year compared to plants in the BG control (Table 6). Fruit production in floricane raspberry has a non-linear pattern where there will be a peak fruiting time during the middle of the harvest season. This pattern of fruit production is observable in our data, with the mid-harvest point having the greatest yield, followed by late and early harvests. There were no differences in fruit yield between mulched treatments across the three harvest periods. However, yield was slightly lower in BASF 0.5 at mid-harvest and PE mulch at late harvest. In Italy, primocane-fruiting raspberry grown with BDMs had 10% higher yield than the BG control (Tecco et al., 2016). In our study, the yield of plants from the mulched treatments were overall 34% 377

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

Declaration of interest

higher than the BG control, which is attributed to greater primocane growth (Table 6; Fig. 2). It was observed that PE mulch may advance the raspberry fruiting season because yields were numerically greater than the other treatments during the early and middle harvests but relatively lower than the other treatments at late harvest (Table 6). Increased fruit yield from plastic mulch application was also reported in a grape study in France, where PE mulch and BDMs had the same impact on grape yield but were higher than the BG control (Touchaleaume et al., 2016). In a separate study, grape yield was found to be greater in the first four seasons when plants were grown with PE mulch compared to the BG control (van der Westhuizen, 1980). Mulching did not lead to differences in leaf water potential or CO2 assimilation rates among treatments in both years. However, leaf water potential was lower in 2018 while CO2 assimilation was higher in 2018. Bryla and Strik (2005) reported water potential of ‘Marion’ blackberry (R. ursinus Cham. and Schldl.) primocanes was approximately -710 kpa when the primocane and floricane were on the same plant between June and August, which is comparable to what was observed in our study. The lower leaf water potential measured in 2018 indicated that the plants were under a greater water stress, which may be due to fruit production and competition for water among floricanes and primocanes that share a single root system. The higher CO2 assimilation rates observed in 2018 indicated that the plants had higher photosynthetic rates as more CO2 was converted to organic forms that may be used for plant growth and metabolism (Farquhar and Sharkey, 1982). Although previous studies found that the presence of fruit did not increase primocane leaf CO2 assimilation rates, chlorophyll has been found to increase in floricane leaves and may impact photosynthetic rates of floricanes relative to primocanes (Cameron et al., 1991; Fernandez and Pritts, 1994; Privé et al., 1997). Farquhar and Sharkey (1982) also reported that the presence of fruit stimulated CO2 assimilation, suggesting that our observed increase in assimilation may be partially attributed to the presence of fruit. Mulches did not impact soil or leaf tissue nitrogen, phosphorus, and potassium levels. Although leaf tissue nitrogen was lower in 2018, all tissue nutrients were above or within the recommended range (DeVetter et al., 2019; Hart et al., 2006). These data suggest that mulching impacts on nutrient management in floricane raspberry are minimal to negligible.

None. Acknowledgements We gratefully acknowledge the financial support for this work by the Washington Red Raspberry Commission, Washington Commission on Pesticide Registration, Novamont S.p.A, and Washington State Department of Agriculture Specialty Crop Block Grant program. This project was also supported by USDA National Institute of Food and Agriculture Hatch projects 0011 and 10/7286. We are thankful for the on-farm cooperation and assistance of Juan Garcia and Riley Spears at Radar Farms. We thank Sara Guerrini and Dan Martens of Novamont and Ruth Watts of BASF for donating the biodegradable mulches tested in this study and for technical advice. We also thank Sean Watkinson, Edward Scheenstra, Weixin Gan, Clara Tevelde, and Nadia Bostan from Washington State University Northwestern Washington Research and Extension Research Center for technical support. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.scienta.2019.02.067. References American Society for Testing and Materials (ASTM), 2018. Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil. ASTM D 5988-18. ASTM International, West Conshohocken, PA. Anzalone, A., Cirujeda, A., Aibar, J., Pardo, G., Zaragoza, C., 2010. Effect of biodegradable mulch materials on weed control in processing tomatoes. Weed Technol. 24, 369–377. Bellincampi, D., Baduri, N., Morpurgo, G., 1985. High plating efficiency with plant cell cultures. Plant Cell Rep. 4, 155–157. Bilck, A.P., Grossmann, M.V., Yamashita, F., 2010. Biodegradable mulch films for strawberry production. Polym. Test. 29, 471–476. Bryla, D.R., Strik, B.C., 2005. Do primocanes and floricanes compete for soil water in blackberry? IX Int. Rubus and Ribes Sym. 777, 477–482. Cameron, J.S., Klauer, S.F., Chen, C., Foote, P.W., 1991. The influence of cane fruiting status, leaf type, and leaf position on red raspberry photosynthesis. HortScience 26, 754. Castillo, P., Vovlas, N., 2007. Pratylenchus, Nematoda, Pratylenchidae: diagnosis, biology, pathogenicity and management. Nematol. Monogr. Perspect. 6, 1–530. Costa, R., Saraiva, A., Carvalho, L., Duarte, E., 2014. The use of biodegradable mulch films on strawberry crop in Portugal. Sci. Hortic. 173, 65–70. DeVetter, L.W., Zhang, H., Ghimire, S., Watkinson, S., Miles, C.A., 2017. Plastic biodegradable mulches reduce weeds and promote crop growth in day-neutral strawberry in western Washington. HortScience 52, 1700–1706. DeVetter, L.W., Strik, B.C., Moore, P., Finn, C., Dossett, M., Sagili, R., Miller, T., Benedict, C., Bryla, D.R., Zasada, I., Martin, B., Pscheidt, J., Weiland, J.E., Peever, T., Tanigoshi, L., Gerdeman, B., DeFrancesco, J., Lee, J., Korthuis, S., Zhao, Y., 2019. Commercial Red Raspberry Production in the Pacific Northwest. Washington State University Extension Publication PNW598. European Norms (EN) 17033, 2018. Plastics – Biodegradable Mulch Films for Use in Agriculture and Horticulture – Requirements and Test Methods. European Standard, European Committee for Standardization, Brussels, Belgium. Farquhar, G.D., Sharkey, T.D., 1982. Stomatal conductance and photosynthesis. Annu. Rev. Plant Physiol. 33, 317–345. Fernandez, G.E., Pritts, M.P., 1994. Growth, carbon acquisition, and source-sink relationships in ‘Titan’ red raspberry. J. Am. Soc. Hortic. Sci. 119, 1163–1168. Fernandez, G.E., Butler, L.M., Louws, F.J., 2001. Strawberry growth and development in an annual plasticulture system. HortScience 36, 1219–1223. Forcella, F., Poppe, S.R., Hansen, N.C., Head, W.A., Hoover, E., Propsom, F., Mckensie, J., 2003. Biological mulches for managing weeds in transplanted strawberry (Fragaria x ananassa). Weed Technol. 17, 782–787. Galinato, S.P., Walters, T.W., 2012. Cost Estimates of Producing Strawberries in a High Tunnel in Western Washington. Washington State Univ. Ext. Publ. FS093E. Galinato, S.P., Miles, C., Ponnaluru, S., 2012. Cost Estimates of Producing Fresh Market Field-Grown Tomato in Western Washington. Washington State Univ. Ext. Publ. FS080E, Washington State Univ., Pullman, WA. Gastaldi, E., Touchaleaume, F., Chevillard, A., Berger, F., Jourdan, C., Coll, P., Toussaint, M., Rodriguez, C., 2013. 18th International Symposium GIESCO Proceedings 28, 406–411 Cienc. Tec. Vitivinic. (J. Vitic. Enol.). Gerbrandt, E., 2014. Working Toward Better Raspberry and Strawberry Establishment. 2014 Lower Mainland Horticulture Improvement Association Horticulture Growers’ Short Course. Available from (http://www.agricultureshow.net/horticulture-

5. Conclusion Overall, PE mulch and BDMs provided adequate weed suppression, increased soil temperature, and promoted plant growth and fruit yield compared to BG cultivation. Plastic mulches may contribute to improving production efficiencies and profitability by reducing labor needs for weed management while promoting growth and yield of floricane raspberry planted as TC transplants. Additional cost-benefit studies should be conducted to further elucidate the economic impacts of plastic mulch application in floricane raspberry. Although PE mulch increased RLN soil and root population densities ˜18 months after mulch application, there were no reductions in yield and plant growth. Future research monitoring long-term RLN population dynamics and their potential impacts on plant growth, yield, and longevity is needed. The benefits of plastic mulch application in a floricane raspberry production system indicate that other perennial production systems may benefit from using plastic mulches during establishment. Use of BDMs in perennial systems is a new application for these materials and they show promise as a sustainable alternative to PE mulch. The rate of mulch biodegradation in soil is influenced by moisture, temperature, oxygen, microbial activity, mulch chemical structure and formulation, and farming practices. These conditions can differ between locations and annual and perennial systems, underscoring that soil biodegradation of BDMs should be characterized in these systems before they are recommended to growers. 378

Scientia Horticulturae 250 (2019) 371–379

H. Zhang, et al.

phytotoxicity to tissue culture-propagated ‘Heritage’ red raspberry. J. Am. Soc. HortSci. 115, 416–422. Pritts, M.P., Handley, D., Eames-Sheavly, M., Ohira, A., 1989. Bramble Production Guide. Northeast Reg. Agr. Eng. Serv. Publ. 35, Ithaca, N.Y. Privé, J.P., Sullivan, J.A., Proctor, J.T.A., 1997. Seasonal changes in net carbon dioxide exchange rates of Autumn Bliss, a primocane-fruiting red raspberry (Rubus idaeus L.). Can. J. Plant Sci. 77, 427–431. Pudasaini, M., Viaene, N., Moens, M., 2008. Hatching of the root-lesion nematode, Pratylenchus penetrans, under the influence of temperature and host. Nematology 10, 47–54. Rudolph, R., DeVetter, L.W., 2015. Management strategies for Phytophthora rubi and Pratylenchus penetrans in floricane red raspberry (Rubus idaeus L.). J. Am. Pom. Soc. 69, 118–136. Tecco, N., Baudino, C., Girgenti, V., Peano, C., 2016. Innovation strategies in a fruit growers association impacts assessment by using combined LCA and s-LCA methodologies. Sci. Total Environ. 568, 253–262. Theiler-Hedtrich, R., Baumann, G., 1989. Elimination of apple mosaic virus and raspberry bushy dwarf virus from infected red raspberry (Rubus ideaus L.) by tissue culture. J. Phytopathol. 127, 193–199. Touchaleaume, F., Martin-Closas, L., Angellier-Coussy, H., Chevillard, A., Cesar, G., Gontard, N., Gastaldi, E., 2016. Performance and environmental impact of biodegradable polymers as agricultural mulching films. Chemosphere 144, 433–439. Trinka, D.L., Pritts, M.P., 1992. Micropropagated raspberry plant establishment responds to weed control practice, row cover use, and fertilizer placement. J. Am. Soc. Hortic. Sci. 117, 874–880. United State Department of Agriculture National Agricultural Statistics Service (USDA NASS), 2018. USDA Noncitrus Fruits and Nuts 2017 Summary. Available from (http://usda.mannlib.cornell.edu/usda/current/NoncFruiNu/NoncFruiNu-06-262018.pdf) (accessed in August 2018). . USDA, 2018. Web Soil Survey. Available from (https://websoilsurvey.sc.egov.usda.gov) (accessed in June 2018). . Van der Westhuizen, J.H., 1980. The effect of black plastic mulch on growth, production and root development of Chenin blanc vines under dryland conditions. S. Afr. J. Enol. Vitic. 1, 1–6. Walters, T.W., Bolda, M., Zasada, I.A., 2017. Alternatives to current fumigation practices in western states raspberry. Plant Health Prog. 8, 104–111. Zasada, I.A., Weiland, J.E., Han, Z., Walters, T.W., Moore, P., 2015. Impact of Pratylenchus penetrans on establishment of red raspberry. Plant Dis. 99, 939–946. Zhang, H., DeVetter, L.W., Miles, C., Ghimire, S., 2017. Dimensions and Costs of Biodegradable Plastic Mulches and Polyethylene for Raspberry Production. Washignton State University Small Fruit Horticulture Program. Available from (http://smallfruits.wsu.edu/biodegradable-mulches-in-small-fruit-productionsystems/) (accessed in July 2018).

growers-short-course) (accessed in October 2018). . Ghimire, S., Wszelaki, A.L., Moore, J.C., Inglis, D.A., Miles, C., 2018. The use of biodegradable mulches in pie pumpkin crop production in two diverse climates. HortScience 53, 288–294. Gigot, J., Walters, T.W., Zasada, I.A., 2013. Impact and occurrence of Phytophthora rubi and Pratylenchus penetrans in commercial red raspberry (Rubus ideaus) fields in northwestern Washington. Int. J. Fruit Sci. 13, 357–372. Goldberger, J.R., Jones, R.E., Miles, C.A., Wallace, R.W., Inglis, D.A., 2015. Barriers and bridges to the adoption of biodegradable plastic mulches for US specialty crop production. Renew. Agric. Food Syst. 30, 143–153. Han, Z., Walters, T.W., Zasada, I.A., 2014. Impact of Pratylenchus penetrans on established red raspberry productivity. Plant Dis. 98, 514–1520. Hart, J., Strik, B., Rempel, H., 2006. Caneberries Nutrient Management Guide. Ore. State Univ. Ext. Serv., EM. Available from (https://catalog.extension.oregonstate.edu/ sites/catalog/files/project/pdf/em8903.pdf) (accessed in Sept 2018). Kasirajan, S., Ngouajio, M., 2012. Polyethylene and biodegradable mulches for agricultural applications: a review. Agron. Sustain. Dev. 32, 501–529. Król-Dyrek, K., Siwek, P., 2015. The influence of biodegradable mulches on the yielding of autumn raspberry (Rubus idaeus L.). Folia Hortic. 27, 15–20. Lamont, W.J., 2017. Plastic mulches for the production of vegetable crops. A Guide to the Manufacture, Performance, and Potential of Plastics in Agriculture. Elsevier. Lawson, H.M., Wiseman, J.S., 1974. Effect of weeds and herbicides in young raspberry plantations. Proc. Br. Weed Cont. Conf. 12, 683–690. Lawson, H.W., Wiseman, J.S., 1976. Weed competition in spring planted raspberries. Weed Res. 16, 155–162. Levitan, L., Barros, A., 2003. Recycling Agricultural Plastics in New York State. Environmental Risk Analysis Program. Cornell Univ., Ithaca, NY. Available from (http://cwmi.css.cornell.edu/recyclingagplastics.pdf) (accessed in May 2018). Martin, R.R., Ellis, M.A., Williamson, B., Williams, R.N., 2017. Compendium of Raspberry and Blackberry Diseases and Pests (No. Ed. 2). APS Press, St. Paul, MN. McElroy, F.D., 1992. A plant health care program for brambles in the Pacific Northwest. J. Nematol. 24, 457–462. Meron, M., Grimes, D.W., Phene, C.J., Davis, K.R., 1987. Pressure chamber procedures for leaf water potential measurements of cotton. Irrig. Sci. 8, 215–222. Miles, C., Wallace, R., Cowan, J., Inglish, D.A., 2012. Deterioration of potentially biodegradable alternatives to black plastic mulch in three tomato production Regions. HortScience 47, 1270–1277. Moore, P., 2016. 2015–16 Raspberry Plant Sales. Available from (http:// nwberryfoundation.org/SFU/2016/sufdocs16/Raspberry%20sales%202016.pdf) (accessed in September 2017). . Mudge, K.W., Borgman, C.A., Neal, J.C., Weller, H.A., 1987. Present limitations and future prospects for commercial micropropagation of small fruits. Proc. Intl. Plant Prop. Soc. 36, 538–543. Neal, J.C., Pritts, M.P., Senesac, A.F., 1990. Evaluation of pre- emergent herbicide

379