Expanding Northeast Strawberry Production in Controlled Environment Agriculture with Naturally-Derived Nutrient Source

Final report for GNE18-169

Project Type: Graduate Student
Funds awarded in 2018: $14,758.00
Projected End Date: 08/31/2020
Grant Recipient: University of New Hampshire
Region: Northeast
State: New Hampshire
Graduate Student:
Faculty Advisor:
Anissa Poleatewich
University of New Hampshire
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Project Information


In the Northeastern US, availability of locally produced strawberries is limited to the summer months and the majority of fresh market strawberries come from field-production in California, Florida, and Mexico. Controlled environment agricultural (CEA) systems have the potential to provide year-round strawberry production in the Northeast. There is a need however, to determine production parameters for day-neutral cultivars in order to optimize production and evaluate the economic feasibility of CEA strawberry production. The overall goal of this research was to quantify nutrient and light requirements for hydroponic greenhouse production of day-neutral strawberries. Specific objectives were to (1) determine how cultivar and substrate affect growth and yield of greenhouse grown day-neutral strawberry (2) compare growth and yield of day-neutral strawberries fertilized with a synthetically derived and a naturally-derived nutrient solution (3) evaluate daily light integrals that optimize plant growth and yield of greenhouse grown strawberry and (4) disseminate research findings by hosting a hands-on, technology transfer workshop for organic Northeast fruit and vegetable growers.

To achieve our research objectives, experiments were conducted at UNH research greenhouse facilities (MacFarlane greenhouse complex and the Kingman greenhouse complex). For objective 1, three strawberry cultivars Albion, San Andreas, and Seascape were grown in a peat-based and a coconut coir-peat blend, and yield was measured over eight weeks. There was no significant effect of the interaction between cultivar and substrate on yield, however Seascape produced the highest yield regardless of substrate at week three. Additionally, there was no significant difference in yield of plants grown in a peat-based substrate compared to a peat-coir-based substrate. For objective 2, we compared yield of strawberries fertilized with a synthetic hydroponic nutrient solution to strawberries fertilized with a naturally derived aquaponic solution with and without supplementation of phosphorous. The naturally derived solution was sourced from a recirculating aquaponics system at the UNH Kingman Farm Greenhouses. Plants grown under the aquaponic effluent and the aquaponic effluent supplemented with phosphoric acid produced higher total yield compared to plants grown in the synthetic hydroponic treatment. A trend was observed in which plants fertilized with an aquaponic solution produced higher marketable yield compared to plants in in the hydroponic treatment. In our initial project proposal, we planned to repeat this study at the farm scale. Since additional funds were needed for this work than originally budgeted for, this replication was not completed but will be included in follow-up projects. For the third objective, we studied supplemental lighting needs, based on daily light integral (DLI), to optimize production during the ‘off season’ when light is a limiting factor. Day-neutral strawberry plants were grown under 14, 20, and 26 mol·m2-2·day-1 of light with an 18-hour photoperiod. Plants grown under a DLI of 26 produced significantly higher yields, a greater number of fruit, and fruit had higher sugar content compared to plants grown under a DLI of 14.

This research provides important data for the longer-term goal of determining the feasibility of year-round production of day neutral strawberries in the Northeastern US. Furthermore, this research provides insight into the potential of decoupled aquaponics for greenhouse production of greenhouse strawberries that could be organic. While conducting this research, results were disseminated to stakeholders through one-on-one discussions, presentations and workshops. An Aquaponic Workshop was held at the University of New Hampshire Kingman Research Greenhouses in 2019 in which growers were provided recommendations based on our preliminary project results. Growers were also provided advice on plant nutrition, climate control, irrigation techniques and system design.  

Project Objectives:

The overarching goal for this research was to develop and disseminate recommendations to Northeast farmers to facilitate the supply of locally grown strawberries year-round to the regional berry market. Utilizing the newly constructed research facilities at the UNH Kingman Farm, this results from this research provides the necessary preliminary data to develop an understanding of integrated hydroponic strawberry production with a naturally derived nutrient source. 

Specific objectives were to:

1. Compare performance of three day-neutral cultivars grown under conventional hydroponic conditions using soilless substrates.

2. Investigate nutrient requirements of hydroponically grown day-neutral strawberry, test a naturally-derived nutrient source, and use a nutrient mass balance to determine the temporal nutrient uptake requirements during the vegetative, flowering, and fruiting stages of strawberry growth. 

3. Evaluate the effect of daily light integral (DLI) on yield of day-neutral strawberry grown in a CEA hydroponic system. 

4. Host a hands-on, technology transfer workshop for organic Northeast fruit and vegetable growers. Workshops will provide hands-on training on propagation, substrates, drip irrigation, fertilization, runner production and general maintenance with regards to hydroponic/aquaponic production systems.


There is a growing desire for produce in the United States to be grown sustainably and locally (Darby et al., 2008), and yet an uncertainty about access to food due to environmental conditions and farming practices (Conner et al., 2009). The majority of strawberry production in the US is located in California and Florida (Samtani et al., 2019), where flood and drought conditions are on the rise (Rowley et al., 2011). Research has suggested that consumers prefer locally grown produce over imports and are willing to pay premium prices for these products (Darby et al, 2008). In the northeast, locally grown strawberries are generally not available during November through May due to climactic restrictions. As a result, there is an opportunity to expand the strawberry industry to include greenhouse production. The use of greenhouse production or controlled environment agriculture (CEA) could allow northeast growers to produce strawberry fruit year-round. More specifically, growing day-neutral cultivars under CEA where light and temperature are controlled, a continuous harvest model is possible in which fruit are harvested every month of the year (Lieten, 2013). This production strategy could allow local growers to access the specialty market for off-season sales.

Hydroponically grown greenhouse strawberries are just beginning to reach the US wholesale markets (Samtani et al., 2019), but there is little research-based information on optimal environmental parameters such as plant nutrition, lighting, and cultivar and substrate selection. Recent studies have provided some information on day-neutral strawberry varieties grown in soilless substrates, but more research is needed to determine how growth and yield of each cultivar will perform under CEA conditions (Cantliffe et al., 2007; Cecatto et al., 2013; Garcia, 2016; Kubota, 2015). In terms of plant nutrition, research has been conducted to provide conventional growers with recommendations for hydroponic nutrient solutions however, there are limited options available for organic growers. Naturally derived nutrient solutions obtained from aquaculture effluent has the potential for use in organic CEA strawberry production since the use of fertilizers from natural sources is required for organic certification. Finally, limited information is available on the lighting requirements for day-neutral strawberry cultivars grown under CEA. Lighting is particularly important for year-round production of strawberry in the northeast due to the low solar radiation characteristic of northern regions in the winter months. As a result, artificial light is needed to supplement natural sunlight (Gottdenker et al., 2001; Hao et al, 2018).  The overall goal of this research was to quantify nutrient and light requirements for hydroponic greenhouse production of day-neutral strawberries.


Click linked name(s) to expand/collapse or show everyone's info
  • Peter Konjoian (Educator and Researcher)
  • Ross Williams
  • Alex Bodell (Researcher)
  • Kaitlyn Orde (Researcher)
  • Steve Haendler
  • Shelby Anderson
  • Dr. Todd Guerdat (Educator and Researcher)


Materials and methods:

Objective 1: Evaluate the effect of substrate and cultivar on plant growth and fruit production of greenhouse grown strawberries.

This experiment evaluated 3 strawberry cultivars and 2 substrates for a total of 6 treatments. Plants were grown in 16 Liter Bato WAVE meter buckets (A.M.A Horticulture, Ontario), with six plants in each bucket, staggered so that plants were approximately 8 inches apart.

Cultivars and substrates: Strawberry fragaria cv. Albion, Seascape, and San Andreas runners were propagated from mother plants, placed into 25 mm Terra Plug Oasis Cubes (Smithers-Oasis, OH) and rooted in a propagation house at the UNH Macfarlane Greenhouse for 14 days. After two weeks, strawberry plugs were transported to the Kingman Research Facility and transplanted into Bato WAVE meter buckets. Buckets were placed in 3.05-meter-long troughs placed on a table with a 25.4 mm slope to allow leachate to drain out of buckets and collect at the end of the table. Leachate was not captured for reuse and was drained into a large holding tank behind the greenhouse.

The two substrates tested in this experiment (Table 1) were chosen based on their composition and commercial use in strawberry CEA production in Ontario and Quebec. To improve uniformity, each substrate was further mixed prior to potting using a mortar mixer attached to a drill was used to break up all aggregates larger than 3 cm in diameter. Water was then added to the substrate and further prior to filling the pots.

Table 1. Composition of the Peat (P) and Peat amended with coconut coir (PC) substrates used in this study. BVB substrates were supplied by A.M.A plastics (Ontario, CA)

Media Media components Percent make-up
BVB BC5 (Peat + Coir =PC) Whitepeat 10% fraction 1, 30% fraction 2
  Cocopeat RHP export 40%
  Perlite 0-6mm 20%
  Dolokal 0.3Kg
  PG Mix 0.5Kg
BVB BC3 (Peat=P) Whitepeat fraction 2 50%
  Whitepeat 0-20 25%
  Blackpeat fibre 15%
  Perlite 0-6mm 15%
  Dolokal 0.3Kg
  PG mix 0.3Kg

Plant production: Plants were irrigated via drip irrigation based on weight. The weight of each of each bucket at 55% saturation was calculated based on wet and dry weights. Soil moisture sensors (Decagon 10hs, Pullman, WA) were placed in four of the Bato Buckets and calibrated to irrigate for 4 minutes when soil moisture in the buckets fell to 55%. Netafim Drip emitters with 3 mm irrigation tubing (Griffin Greenhouse Supply, Tewksbury, MA) were used to supply nutrient solution to the plants at a rate of 2 Liters per hour. Plants were fertilized with Peters Professional 5-11-26 NPK Hydroponic Solution in Tank A, and Jack’s Professional Calcium Nitrate (JR Peters Inc., PA) in Tank B. The nutrients were mixed in stock solutions that were injected at a 1:100 rate using a D14MZ2 Dosatron (Dosatron USA, FL). At each mixing date, 500 ml of solution was collected from the sample port prior to measure pH and electrical conductivity (EC). If the samples were within an EC of 0.2 µS/cm of the ideal range (1.0-1.20), nothing was changed. If not, Dosatron flows were adjusted until the target pH/EC was achieved. Strawberries were grown in a triple polycarbonate greenhouse. The greenhouse control system was set to vent when temperatures reached 30ºC and heat when temperatures fell below 18ºC during the daytime.

Plants were manually pollinated daily using a leaf blower which is a substitute for bees and other natural pollinators (Kubota, 2015). Yellow sticky cards were placed throughout the crop for the purpose of scouting and pest removal. Fungus gnats and thrips were managed by applying the beneficial nematode Steinernema feltiae biweekly to the pots at approximately 33,000 nematodes per plant. Precautionary measures were taken to prevent thrips and whitefly using Swirskii predatory mite sachets (Amblyseius swirskii) and Encarsia cards. Slow-release Swirskii sachets were placed on each strawberry plant every 6-8 weeks, while Encarsia cards were placed on 2 plants per greenhouse every other week. A bran formulation of Crysopa carnea (green lacewing) was used to control aphids, spider mites, whiteflies, and thrips. Phytoseiulus persimilis (predatory mites) were sprinkled in a bran formulation biweekly to plant leaves to control spider mites.

Runners were removed every three weeks from all plants at the base of the plant using pruners. Dead and dying leaves on the bottom of plants were also removed every three weeks.

Data collection: The following data was collected to compare the effect of cultivar and substrate on greenhouse strawberry performance.

  1. Agronomic data - Data was recorded on number of days until runner and flower production per treatment when 50% of the plants in each treatment had at least one or more runners or flowers. Flowers were counted when fully opened and petals were still present.
  2. Fruit yield - Ripened fruit was harvested 3 days a week from July 23rd to September 5th, 2018 to determine yield in grams. Ripened fruit was defined as fruit with 80% or more red color development. Fruit were considered Marketable if they exhibited 80% red color development, weighed equal to or greater than 10g, and had no deformities. Percent of marketable fruit was calculated by dividing the number of marketable fruit by the total number of fruit from each treatment at the end of the experiment.

Data analysis: Data were analyzed using a split-plot analysis in JMP Pro (JMP Pro. 14.1 Statistical Software, Cary, NC) to evaluate differences in effects of the substrate, cultivar and the interaction between substrate and cultivar on total fruit yield and fruit yield each week. A Tukey’s HSD test was used to separate treatment means. Statistical significance was determined at α=0.05.


Objective 2: Compare growth and yield of day-neutral strawberries fertilized with a synthetically derived hydroponic solution and a naturally-derived aquaponic solution.

The goal of this study was to evaluate the effect of nutrient source on plant nutrition, plant growth, and yield of greenhouse grown strawberries. The experiment was designed to (1) to understand the relationship between nutrient availability and nutrient uptake of strawberry plants grown under a naturally-derived aquaponic nutrient source and a synthetically-derived nutrient source, (2) evaluate the effect of nutrient source on yield of greenhouse grown strawberry plants, and (3) evaluate the effect of phosphoric acid supplementation of a naturally-derived nutrient source on strawberry yield.

This study evaluated three nutrient sources (Table 2); two naturally derived and one synthetically derived. Each of the solutions were assigned to 24 replicate plants. For the synthetically derived treatment, a Japanese hydroponic strawberry recipe known as the Yamazaki solution (Yamazaki, 1982) was used (H). For the naturally derived treatments, aquaponic solutions were collected from the Aquaponic facility at the UNH Kingman farm facility (described below). This aquaponic solution was used alone (AQ) or amended with phosphoric acid (AQ+PA).

Table 2. Concentration of macronutrients of the three nutrient solutions used in this study (concentrations are reported in mg/L). The Aquaponic solutions were obtained from the UNH Kingman Farm Aquaponic facility.









(1) Yamazaki-strawberry








(2) Aquaponic Nutrient Solution








(3) Aquaponic Nutrient Solution w/ Phosphoric Acid








Plant production: Strawberry plants were propagated as described in objective 1 on September 17, 2018. Runners were transplanted into Classic 300 20.3 cm pots filled with Pro-Mix HPCC substrate. Plants were grown on three 91 cm tall tables at the Kingman Farm Greenhouses and irrigated as described in objective 1. The greenhouse was set to 30ºC for cooling, 18ºC for daytime heating, and 15ºC for nighttime heating. For the Yamazaki solution, an A/B irrigation system was installed using two 19 L tanks each with a D14MZ2 Dosatron nutrient distribution system (Dosatron USA, Fl). The EC of the Yamazaki solution was maintained at 1.0 mS/cm and pH 5.5. The EC of the aquaponic effluent was maintained at 1.1 mS/cm and pH 7.0. A third Dosatron was installed to the AQ+PA table to supply phosphoric acid to the aquaponic effluent to reach a target pH of 5.5-6.0. A tank was filled with 20mL of phosphoric acid and 19L of RO water and injected into the Dosatron at a rate of 1-50. The EC of the supplemented aquaponic effluent was maintained at 1.1 mS/cm and the pH at 5.9. A pour-thru method was used to monitor the pH and EC of the leachate of 3 pots per treatment. If the pH and EC were not within 0.2 µS/cm of the target range (1.0-1.5), clear water was run through emitters until saturation occurred.

Four-hundred-Watt high pressure sodium lights were placed above each table for supplemental lighting (PL Light Systems, Beamsville, ON). Lights were programmed to ensure 24 mol·m-2·d-1 was achieved at a maximum of a 16-hour photoperiod. Plants were pollinated, and pests managed as described in objective 1.

Data collection: The following data was collected to compare the effect of nutrient source on plant production.

  1. A nutrient mass balance was established by quantifying nutrient input and output masses, and assimilated plant nutrient mass. The mass balance calculations were based on the mass of nutrients in the input (irrigation solution), output (leachate) and tissue samples (captured) at four time points throughout the study: at the time of transplant, at runner production, at fruiting, and at harvest.
    1. To determine nutrients in plant tissues, root, shoot, and fruit tissues of three plants from each nutrient solution treatment were collected. Fresh and dry weights of samples were recorded. Dry samples were ground into a powder and sent to JR Peters Inc. for nutrient analysis.
    2. To characterize nutrient inputs, irrigation solution was collected from four drip emitters per treatment at each irrigation event to quantify macro and micronutrient concentrations in the source water. Samples were sent to JR Peters Inc. for nutrient analysis.
    3. To characterize nutrient output, leachate was collected from the same 3 pre-selected plants per treatment. Ten minutes after am irrigation event ended, leachate volumes from each replicate pot were measured to determine the volume lost per pot. The volume lost was then subtracted from the input volume to estimate the captured volume (or volume retained in the pot). Leachate from each irrigation event was combined into one bucket per treatment as a composite sample.
  1. Agronomic data - The number of days until runner production, number of days until flower production, and number of days until ripened fruit was collected for all treatments. Symptoms and signs of nutrient deficiencies were recorded weekly. Percentage of plants that showed signs of nutrient deficiency per treatment was also recorded.
  2. Fruiting data- Ripened fruit was collected three times a week for 8 weeks. Marketable fruit was defined as fruit with 80% red color development, weighed equal to or greater than 10 g, and has no deformations (Cantliffe et al., 2007). Brix content, a measurement of soluble sugars, was collected on all harvested fruit using a Hanna H196801 Digital Refractometer (Hanna Instruments, Smithfield, RI).


Data analysis: Analysis of nutrient mass balance, agronomic and fruiting data were conducted as described below.

  1. Nutrient mass balance
    1. To quantify nutrient uptake of each strawberry plant, a series of calculations were carried out. The leachate nutrient composition subtracted from the nutrient irrigated to each pot to calculate the volume and composition of nutrient solution that remained in the pot. We considered nutrient solution captured in the pot as solution that was taken up by the plant.
    2. Based on nutrients supplied to the plant, the composition of nutrients within the plant tissue and fruit was then analyzed to determine the nutrient uptake efficiency of each plant.
    3. An ANOVA was used to compare mean percent assimilation of Nitrogen, Phosphorous, and Potassium in sample plants grown in each nutrient source at two stages of growth: 1st at the fruiting stage and then at final harvest. In all analyses, statistical significance was assessed at α=0.05.
  2. The effect of nutrient source on plant fresh weight, number of fruit, and brix was analyzed using an ANOVA. Tukeys HSD post hoc tests were conducted to separate treatment means.
  3. A mixed model ANOVA with a repeated measure was conducted using SAS 9.4 (SAS Institute, Cary, NC) to evaluate the cumulative yield and cumulative marketable yield over the 8 harvest dates per plant (g) in each treatment. Orthogonal contrasts were then used to compare treatment means across the three nutrient sources. A mixed model ANOVA was also conducted to compare total yield and total marketable yield per plant of aquaponically grown plants compared to hydroponically grown plants.

In our initial project proposal, we planned to repeat this study at the farm scale. Since additional funds were needed for this work than originally budgeted for, this replication was not completed but will be included in follow-up projects. 


Objective 3: Evaluate daily light integrals that optimize plant growth and yield of greenhouse production of strawberry

This experiment evaluated three daily light integral (DLI) regimes (14, 20, and 26 mol/m2/day) with three replicate blocks of each lighting regime. Each block consisted of three chambers (one for each lighting treatment) with 9 plants for a total of 27 plants per treatment. Treatments were randomly assigned to a chamber on each bench.

Plant material and plant production: Strawberry cv. Albion was propagated from mother plants as described in objective 1 on December 31, 2018. Plugs were then transplanted into Classic300 20 cm pots filled with ProMix HPCC substrate 27 days post rooting. The greenhouse temperature was set to a 16°C daytime temperatures and 13°C nighttime temperature. Pests and diseases were managed, and plants were pollinated as described in objective 1.

Lighting control: ARC 600 full spectrum LED lights with integrated dimmers (HortLED, Ithaca, NY) were used for the study. All plants were exposed to an 18-hour photoperiod. Lights were set to one of three target DLI treatments: 14, 20, or 26 mol•m-2•d-1 with a light intensity of 216, 308, or 401 umol•m-2•s-1 respectively. Plants were grown inside chambers covered with UV stabilized black ground cover (VMInnovations, Lincoln, Nebraska) to block natural sunlight and ensure plants were exposed to 100% supplemental light. Photosynthetically active radiation (PAR) was measured underneath the ground cover using a line quantum meter with ten integrated PAR sensors (MQ-301, Apogee, UT) to ensure equal light intensity was provided to each plant.

Irrigation: Plants were irrigated with the Yamazaki solution as described in objective 1.

Data collection: The following data was collected to compare the effect of light exposure on plant productivity and fruit quality.

  1. Fruit yield. Ripened fruit was harvested two times a week. The number of fruit, fruit weight, and marketability of fruit was recorded for each plant. These data were also averaged to determine yield per replicate chamber.
  2. Sugar, measured as total soluble solids, was analyzed in fruit using the Hanna digital refractometer (model HI96801) (Hanna Instruments, Smithfield, RI).
  3. Chlorophyll index. A Soil-Plant Analyses Development (SPAD) meter (Minolta Camera Co., Japan) was used to analyze leaf chlorophyll index for each treatment. SPAD measurements were taken on the youngest fully expanded leaflets of 3 plants within each chamber. Chlorophyll index was measured at 4, 6 and 11 weeks from transplant.
  4. Plant biomass. To determine the effect of lighting treatment on plant growth, above ground plant biomass was measured. Shoots from each plant were cut at the crown, flush with the substrate. All ripened and unripened fruit on the plant on harvest day were removed before weighing. Plants were dried for 48 hours at 65°C, removed from the drying oven, and weighed for a dry weight.


Data analysis: Effects of DLI treatment on total yield and marketable yield per plant (g) over the 10-week harvest period were analyzed using an ANOVA in SAS 9.4 (SAS Institute, Cary, NC). Differences between treatment means were evaluated using a Tukey’s honestly significant difference (HSD) test at the α=0.05. Analyses were also conducted to evaluate the effect of DLI on fruit production per chamber, fruit sugar content (brix), plant biomass, and chlorophyll index using a one-way ANOVA in JMP Pro version 14.1 Statistical Software (SAS Institute, Cary, NC). A Tukey-Kramer HSD test was used to compare differences between treatments.

Research results and discussion:

Objective 1: evaluate the effect of cultivar and growing substrate on plant growth and fruit production of greenhouse grown strawberries.

Overall performance of cultivars and substrates as characterized by fruit and runner production was similar. There was no significant effect of the interaction between cultivar and substrate on yield (p=0.766). Cultivar had a stronger effect on yield than substrate. Seascape tended to have the highest total yield (p=0.200).

Results from this study indicate that cultivars Seascape, Albion, and San Andreas performed similarly in a hydroponic greenhouse with respect to yield. In terms of year-round production, it is important to consider how each cultivar will perform under all temperatures (Garcia, 2016; Marcelis et al, 2018). In this study, all cultivars displayed signs of heat stress including a substantial decline in fruit production across all treatments. It is hypothesized that this decline in fruit production was caused by prolonged periods of temperatures above 35°C in the greenhouse. This reduction in fruiting has been observed by other researchers who report that temperatures above 30°C for prolonged periods will lead to a reduction in fruit quality (Hancock, 1999; Kuack, 2017; Lantz et al., 2010; Peterson, 2018; Rubinstein, 2015) with optimal daytime temperatures for strawberries ranging between 18°C-24°C and nighttime temperatures between 10°C-12°C. Reducing temperatures within a greenhouse in the summer and early fall to a range suitable for strawberries can be difficult, so active greenhouse cooling systems would be required to achieve year-round production.

The cultivar Albion was chosen for all further research experiments, due to its desirable traits (high yields, large fruit, excellent flavor) (Samtani et al., 2019; Orde, 2018; Weber, 2012) and overall success in our system.


Objective 2: Compare growth and yield of day-neutral strawberries fertilized with a synthetically derived hydroponic solution and a naturally-derived aquaponic solution.

Nutrient solution had an effect on plant production: Differences in fresh weight were observed across the three nutrient solutions tested. Mean shoot biomass was greater for plants grown in the AQ+PA treatment and H treatment compared to the AQ treatment (p≤0.0153). There were also significant differences in brix readings between the treatments (Table 4). Plants grown in the AQ nutrient solution produced fruit with significantly higher brix content than fruit grown in the AQ+PA nutrient solution (p=0.0295). There was no significant difference in brix content between fruit grown with the AQ+PA and H nutrient solutions or the AQ and H treatment (p≤0.8701) (Table 3).

Table 3. Mean Brix content of strawberry fruit harvested from all replicate plants within each treatment over eight weeks of fruit production.

Treatment Mean Brix Content
Aquaponic +PA 8.72 b*
Aquaponic 9.52 a
Hyrodoponic 9.31 ab

*Values that share the same letter are not significantly different from one another as determined by the Tukey-Kramer test at α = 0.05.

Nutrient solution had an impact on yield: Cumulative yield per plant after eight weeks was higher in plants grown in the AQ+PA treatment compared to plants grown in the H treatment (p=0.0083) (Figure 1). Plants grown in an aquaponic solution (regardless of PA supplementation) produced significantly higher total yield (p=0.045) compared to plants grown in the hydroponic solution. Plants grown in the H treatment had a greater average berry weight than the AQ and AQ+PA treatment (p≤0.0473).

Figure 1. Cumulative yield (g) per plant during each week of fruit production throughout the experiment. Treatments connected by the same letter are not statistically different (p=0.05). Results include plants that did not produce fruit throughout the duration of the experiment.


Overall, plants fertilized with the hydroponic solution had the greatest percentage of marketable fruit relative to total fruit produced in the treatment. Of the total fruit collected, 93% of fruit in the H treatment was marketable, 77% of fruit in the AQ+PA treatment was marketable, and 73% of fruit in the AQ treatment was marketable. There was a trend in which total marketable yield was higher in plants grown in an aquaponic solution (AQ & AQ+PA) compared to plants grown in a hydroponic treatment (p=0.085). Mean cumulative marketable yield per plant was highest in plants grown in the AQ+PA treatment and was significantly greater compared to plants grown in the H treatment (p=0.024).

Nutrient mass balance: Macronutrients captured by the plants in each treatment were calculated by subtracting the leachate concentrations in each sample pot from the mass of nutrients applied from all irrigation events. Nitrogen captured among plants were not significantly different across nutrient solutions (p≤0.9888). Potassium captured was significantly higher in the aquaponic treatments (AQ and AQ+PA) when compared to H (p≤0.0128). Average phosphorous captured in plants grown in the AQ solution was lower than in plants grown in the AQ+PA and H solutions (p<0.0001). Average phosphorous captured was significantly higher in plants grown in the H treatment compared to plants grown in the AQ+PA solution (p=0.0064) (Table 4).

Table 4. Results of the nutrient mass balance at the time of harvest, reported as an average of the three sample plants. Only samples that produced fruit were included in the average fruit analyses.


Mean dry weight (g)

Captured (mg)A

Tissue (% DM)(plant/fruit)B

% nutrient dosed that was assimilated: (plant/fruit)C












































*only samples that produced fruit were included in the average fruit analyses

A Captured refers to the concentration of nutrients delivered to the plant that was captured in each pot

B Tissue (%) is the composition of nutrients in plant and fruit dry matter (DM), respectively.

C Percent nutrient dosed that was assimilated in plant and fruit tissues is the concentration of nutrients found in the plant and fruit tissue analysis relative to the amount of solution captured in each pot. 

Nutrient concentrations in plant tissues: No significant differences were found in concentrations of potassium or nitrogen in plant tissue (roots, shoots, and runners) and fruit between the three treatments. However, phosphorous concentrations were significantly lower in plants grown in the AQ solution compared to plants grown in the H and AQ+PA solutions (p<0.0001).

Percent uptake of nutrient in plants and fruit: Phosphorous assimilation in sample plants and fruit was not significantly different across the three treatments (p≤0.999). Values greater than 100% assimilation of phosphorous were calculated in the AQ treatment and may be reflective of the very low content of phosphorous present in the fertilizer solution and some unaccounted for phosphorous in the substrate.

Plants grown in the H treatment exhibited significantly higher percent assimilation of potassium compared to the AQ treatment at the fruiting stage (p=0.0325). Percent assimilation of potassium was similar in the AQ and AQ+PA, and AQ+PA and H treatments (p≤0.4283). No differences were observed in percent assimilation of potassium in plants sampled at the final harvest stage across the three treatments (p≤0.4738).

Significantly higher percent assimilation of nitrogen was observed in the H treatment compared to the AQ treatment during the fruiting stage (p=0.0179). Percent assimilation of nitrogen was similar in the AQ and AQ+PA, and the AQ+PA and H treatments (p≤0.3543). No differences were observed in percent assimilation of nitrogen in plants sampled at the final harvest stage across the three treatments (p≤0.9146).

Visual assessment of plant nutrition: Nutrient deficiencies were present in all treatments (Table 5). Phosphorous deficiency was seen on approximately 74% of plants in AQ+PA treatment, characterized by reddening of leaves (Figure 2). A purple-brown color developed on the edges of many leaves (94% of plants), indicative of potassium deficiency (Figure 2). Tissue results indicated that plants in the hydroponic treatment had the lowest levels of potassium, at 2.32, with aquaponic treatments averaging around 2.53 which is on the low end of the target range (2.0-8.8). Lab results showed that Manganese was limited in both aquaponic treatments (19-46 ppm) but within the target range (75-300 ppm) in the hydroponic samples. Boron deficiency was observed on both aquaponic treatments as misshapen, deformed fruit (Pritts, Cornell) (Figure 2).

Table 5. Nutrient deficiencies observed and confirmed through assessment of visual symptoms and laboratory tissue analysis of plant leaves.



Nutrient concentration

Target range*

Plants effected








19-46 mg/kg

75-300 mg/kg


Aquaponic + Phosphoric Acid


19-46 mg/kg

75-300 mg/kg









23-29 mg/kg

50-175 mg/kg


Aquaponic + Phosphoric Acid


23-29 mg/kg

50-176 mg/kg


* Target ranges for each nutrient were provided by JR Peters Laboratory

Figure 2. Symptoms of Phosphorous deficiency (A), symptoms of Manganese deficiency (B), symptoms of Potassium deficiency (C), and symptoms of Boron deficiency on the fruit (D) observed over the course of the greenhouse experiment.

In summary, plants grown in the naturally-derived solutions produced greater fruit yields than plants grown in the synthetic solution. The highest sugar content was found in berries fertilized with the aquaponic solution. Interestingly, the addition of phosphoric acid to the aquaponic effluent did not significantly increase fruit yield when compared to the non-augmented effluent.

The non-augmented aquaponics solution resulted in significantly smaller plants. This lower plant biomass is most likely due to the unavailability of nutrients at a high pH, and low phosphorous content (Tyson et al., 2011). Additionally, the aquaponic solutions contained less than 1ppm-NH4+, while growers suggest that no less than 8-10% of nitrogen in a solution should be in the form of NH4+ for optimal vegetative growth (Jacques Painchaud, Personal Communication). Decoupling recirculating aquaculture systems allows the grower to supplement specific nutrients lacking in the aquaponic effluent (Goddek et al., 2016). In this case, Phosphorous and Boron were the most limiting nutrients. Furthermore, the ability to add acid to reduce pH without impacting effluent traveling to the fish tanks allows for the reduction of high pH, a common issue in recirculating aquaponic systems (Cerozi & Fitzsimmons, 2016).

Overall, the amount of nutrient uptake by plants relative to the mass of nutrients dosed (percent assimilation) was similar across the synthetic and naturally-derived treatments. Percentage of phosphorous uptake values were extremely high in the AQ treatment despite the low levels of phosphorous dosed throughout the duration of the study. Interestingly, some sample plants resulted in a large negative value for percent uptake, suggesting there was a source of phosphorus provided to the plant that was not accounted for in our calculations (i.e nutrients not provided via the nutrient solution). Analysis of the nutrients in the source substrate revealed higher levels of N, P & K in the substrate than expected. The uptake of the charged nutrients from the substrate most likely led to some of the unaccounted-for phosphorus values in the AQ treatments.

Another possible explanation for the high percent uptake of phosphorous in the AQ treatments could be related to low P in the nutrient solution. Luxury consumption is a concept which refers to the plant’s ability to absorb and store nutrients in excess of their immediate needs (Marschner, 1995). It is hypothesized that the initial supply of phosphorous provided by the charged fertilizer was stored by the plant early on in plant production and utilized when plants allocated their energy into fruit production.   

Conclusion: There is large variability in each aquaponics system as it is a biological system (Palm et al., 2018). Some of these factors include but are not limited to microbial populations and diversity, fish species, feed type, nutrient profile, organic carbon, pH, and filtration processes (Lennard and Leonard, 2006). This study provides insight, but it cannot be assumed that our results would be replicable in another aquaponics system. For this reason, it is important to establish standardization in the aquaponic industry to optimize production (Chow et al., 1992). Additionally, more research is needed to support the transition from traditional hydroponic inorganic solutions to alternative naturally-derived, organic nutrient solutions.

Objective 3: Evaluate daily light integrals that optimize plant growth and yield of greenhouse production of strawberry

DLI had an effect on fruit yield: Plants grown in the highest light treatment (DLI 26) produced significantly greater yield per chamber (grams of fruit and number of fruit) than the plants in the lowest light treatment (DLI 14) (p≤0.0437). Total mean fruit per plant produced over the 10-week harvest period was significantly higher in plants grown under the high light treatment compared to the low light treatment (p=0.0080). Similarly, total marketable fruit per plant was higher in plants grown under the medium and high treatments compared to plants grown in the low treatment (p≤0.0247).

DLI had an effect on fruit sugar content: Mean sugar content was significantly higher in fruit in the DLI 26 treatment compared to the DLI 20 (p=0.0288) and DLI 14 (p<0.0001) treatments. No differences were found in mean sugar content between the DLI 20 and 14 treatments (p=0.0735).

DLI had an effect on plant biomass: Plants grown in the high and medium light level treatments had significantly higher mean biomass weights compared to plants in the low light treatment (p≤0.0178).

In our system, strawberry cv. Albion performed optimally under a DLI of 26 mol•m-2•day-1. Plants grown under the highest light treatment also produced berries with the highest soluble solids content, suggesting that a higher DLI may results in a sweeter, more flavorful fruit in cv. Albion. Finally, plants grown under a DLI of 26 mol•m-2•day-1 were largest in size amongst the three treatments. A replication of this experiment with higher lighting treatments would better illustrate the relationship between plant performance of Albion and DLI. The plants grown under a DLI of 20 produced similar yields to the DLI 26. A medium light treatment (DLI 20) may be a more economically feasible even with the tradeoff of a slight reduction in fruit production. An economic model is needed to compare these two lighting regimes under a typical greenhouse operation in the Northeast before concluding to a more suitable option.

Throughout the experiment there were distinct fluctuations in fruit production from week to week in all treatments (Figure 3), although it was most prominent in the medium and high DLI treatment. Research to date has been inconclusive on the fruiting tendencies of day-neutral cultivars, as well as the photoperiodic responses (Bradford et al., 2010; Garcia, 2016). Some research and industry information suggest that day-neutral cultivars will flower and fruit continuously for several months regardless of the photoperiod (Pritts, 2015), and upwards of six months outdoors if the weather conditions allow (Nourse Farms, 2018). A cyclical fruiting pattern has been observed in day-neutral strawberry fruit production but not well documented. Kubota (2014) found that Albion exhibited a significant decline in fruit production after four weeks of consistent fruiting, and again at approximately 19 weeks. Results from this research revealed a similar cyclical fruiting pattern in cv. Albion where a decline in yield at week six and seven was observed. This cyclical fruit production phenomenon will be important to consider for year-round strawberry growers as it may be necessary to stagger strawberries plantings that correlate with the cyclical fruit production pattern of each cultivar. This will ensure consistent fruit production, with different crop cohorts producing fruit at peak production on a rotating basis. 

Figure 3. Weekly total fruit yields (sum of all replicate plants under each lighting treatment). Fruit was collected throughout the ten weeks of fruit production in the experiment, from February 7th, 2019 until April 17th, 2019.

Research conclusions:

     Currently, alternative production methods for strawberry are beginning to emerge. With the adoption of CEA strawberry production, fruit can be produced in virtually any region of the US. There is insufficient data to determine if there is a yield per acre difference between field grown and greenhouse grown strawberries. Greenhouses, however, offer a unique opportunity for 12 month production. The goal of this project was to evaluate growing techniques to develop grower recommendations for day-neutral strawberry production in the Northeast.

     From the preliminary research evaluating cultivar and substrate, we concluded that the addition of coconut coir to a peat-perlite blend had no negative effects on plant productivity. More recently, coconut coir has been used to completely replace peat in production operations as it is a cheaper, more sustainable alternative. Due to its lower CEC (depending on source and particle size), a 100% coconut coir may pose issues in terms of nutrient availability. Further research is needed to quantify the effects of different peat-coconut coir blends. Similar yields were produced from cultivars Albion, San Andreas, and Seascape. Albion, however, possesses desirable traits such as its flavor, large fruit, and dark color, and was therefore used for follow-up studies (Samtani et al., 2019; Orde, 2018; Weber, 2012). While Albion performed well in our studies, there is a need for breeding programs to develop new cultivars bred specifically for greenhouse production to optimize yields and promote the economic viability of the strawberry industry (Choi et al., 2017; Yue et al., 2014).

     Day-neutral strawberry cultivars have specific nutrient requirements to achieve continuous fruiting production for several months at a time. Little information is known about the impact of the use of naturally-derived, specifically aquaculture based solutions for strawberry production. The results from our experiment showed that when compared to a synthetically derived nutrient source, strawberries grown in a naturally-derived nutrient source produced significantly greater yields. Supplementing the aquaculture effluent to reduce the pH and increase phosphorous levels further increased fruit yields as well as plant biomass. Decoupled aquaponics systems allow for supplementation of nutrients to optimize a solution that may have otherwise been limiting.

A nutrient mass balance was conducted to evaluate nutrient uptake under naturally-derived and synthetic nutrient solutions. Overall, nutrient uptake by plants relative to the mass of nutrients dosed (percent uptake) was similar across the inorganic and organic nutrient solution treatments. Mean percent uptake of potassium was highest in the inorganic (hydroponic) treatment at the fruiting stage. Mean percent nitrogen was highest in the inorganic treatment at the fruiting stage also. Percentage of phosphorous uptake values were extremely high in the AQ treatment despite the low levels of phosphorous dosed throughout the duration of the study. Interestingly, some sample plants resulted in a large negative value for percent uptake, suggesting there was a source of phosphorus provided to the plant other than that of the nutrient solution. We hypothesized that nutrients available at the early stages of production from the charged substrates were stored and utilized by plants in the non-augmented aquaponic solution slowly throughout the production cycle. More in-depth research is needed to understand the effects that microbial communities within aquaponics systems have on nutrient availability and uptake.

       Lighting intensity and duration plays a large role in plant productivity. Supplemental lighting is key to optimize production during the ‘off season’ but understanding the impact daily light integral and photoperiod play on day-neutral cultivars is key to optimizing production and minimized excess electrical costs associated with lighting. Our results showed that when grown at a DLI of 26 mol·m-2·d-1 under a 18-hour photoperiod, strawberry plants were larger in size, produced greater yields and greater number of fruit, and also produced the highest sugar content compared to strawberries grown at a DLI of 14. Fruit yields of plants grown under a DLI of 20 were slightly less than plants grown under a DLI of 26. By conducting an economic analysis, we can better understand which lighting regime will result in the highest profit for the producer. The cyclical fruiting model resulting from this experiment is key for achieving year-round production of Albion, with the adoption of a cyclical planting model. The interaction between photoperiod and DLI is cultivar dependent; future research should evaluate production of Albion grown with a DLI of 26 under various photoperiods, to optimize production.

        To optimize the full potential of year-round production of day-neutral strawberries, a grower could incorporate all of these growing techniques. Adopting a production system where cv. Albion are grown using an aquaculture effluent in a decoupled aquaponic system under a DLI of 26 has potential to improve the yield and quality of strawberries grown under CEA. Future research should focus on (1) the breeding of day-neutral cultivars specific for greenhouse production, (2) the impact of microbial communities in an aquaponic substrate system, and (3) the interaction between photoperiod and DLI for various day-neutral cultivars.

      Ultimately, an economic analysis is needed to understand the feasibility of CEA production of strawberries. The future of indoor food production as an alternative to field production in the Northeast is exciting and has the potential to significantly increase availability of local food. We are already seeing development and distribution of such systems with leafy greens and tomatoes; strawberries could be the future of year-round local fruit production.

Participation Summary
2 Farmers participating in research

Education & Outreach Activities and Participation Summary

5 Consultations
7 On-farm demonstrations
10 Tours
3 Webinars / talks / presentations

Participation Summary:

3 Farmers participated
10 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:


         I have participated in many on-farm consultations with farmers located in New Hampshire. During these visits, I was able to provide information/tools to growers, and gain knowledge through discussions about cultivation practices and plant productivity. Connecting with larger hydroponic operations such as Lef Farms (hydroponic lettuce production, Loudon, NH) and La Frissonante (strawberry greenhouse production, Quebec, Canada), we were able to discuss how precision of growing techniques in terms of nutrient application and growing media can have significant effects on yields and overall economic growth.

            I have also been consulting with smaller farms that are newer to the business and traditionally have limited access to the newest up-to-date research findings in the field. During these visits, I was able to provide information on broader system designs, such as what crops and cultivars are suitable to be grown in high tunnels during the winter months. Other information provided to aquaponic farms included how to keep clean systems (prevent algae growth, reduce pest pressure, reduce buildup of organic carbon through filtration, etc.). Additionally, we talked about how to check/monitor water quality/pH/electrical conductivity/dissolved oxygen in systems on a regular basis to maintain healthy plants and fish.

            I attended the Aquaponics Association annual conference this past fall, and gave an oral presentation on growing strawberries aquaponically. My advisor and I presented primarily on the environmental and economic benefits of Northeast greenhouse strawberry production, as well as system designs and nutrient requirements. Many growers from all over the world responded quite positively to the talk, and have reached out for more information since. I also gave a presentation to a panel of health care practitioners at hospitals in New Hampshire, who were interested in incorporating more local foods in hospitals, and specifically interested in integrating hydroponics into their facilities.  

            I attended the North America Strawberry Growers Association Conference in Orlando, Florida, where I gave a poster presentation of my ongoing research. My presentation focused on ways to optimize aquaponic strawberry production through nutrient supplementation. During this time, I connected with other growers and researchers to work towards future collaboration endeavors. Through communication with growers all over the world, I gained a better understanding of what research is needed for industry and what some of the shortcomings in current production are.

NASGA poster

            Over the past two years I have given countless tours of our hydroponic facility and the University Of New Hampshire to several groups, both small and big. Some of these groups include elementary school students in the area, and 4H camps for youth interested in growing plants. Additionally, I’ve given tours to farmers in the area that either have an existing hydroponic or aquaponic farm, or are interested in expanding/transitioning to the field.

            Dr. Todd Guerdat and I connected with collaborators (in the field of research and commercial growing), to coordinate a 3-day hands-on workshop for current and future hydroponic and aquaponic growers. The workshop was held in early June 2019 and was open to any and all growers or researchers interested in learning more. The workshop consisted of an in-depth tour of our aquaponic/hydroponic facility, where we gave a detailed description of how the facility was built and why we chose the system designs that we did. We then talked specifically about lettuce production and strawberry production, and how each system was designed differently based on crop needs. I gave a more focused talk on hydroponic and aquaponic strawberry production, with topics including, but not limited to: irrigation, substrates, nutrient requirement/uptake, supplemental lighting, temperature/humidity, harvesting, yields, pest control, pollination, etc. My goal was for new growers to leave feeling confident that they have the knowledge to establish their own greenhouse strawberry operation. AquaponicsAnnualWorkshop-June2019-Agenda-PresentationAssignments. WORKSHOP pp


Project Outcomes

4 Farmers reporting change in knowledge, attitudes, skills and/or awareness
3 Farmers changed or adopted a practice
5 New working collaborations
Project outcomes:

This project has provided much needed preliminary data on optimal conditions for CEA strawberry production. In this project we have evaluated cultivars, substrate selections, nutrient solutions, and lighting for their effect on strawberry production in a hydroponic system. These data a essential to accurately evaluate the environmental and economic sustainability of this production system.

Economic sustainability.

    While an economic analysis was not a part of this study, we have collected data that could be used in future economic studies. For example, this research has characterized growth and yield of three commercially available strawberry cultivars under CEA conditions. These data are important as, growth patterns and yield may vary significantly between outdoor production and CEA. Our data suggest that cultivars Albion, Seascape, San Andreas perform similarly in terms of yield. Under higher temperatures, marketability of cultivar Seascape fruit was greatly due to abnormal fruit shape, texture, and ripening. The cultivar Albion was chosen for two additional studies, due to its success in our systems and other research systems with regard to fruit size, quality, and flavor.

    Costs associated with supplemental lighting in the winter months in the northeast can be some of the highest in production, along with heating. The findings from this research will help growers make lighting decisions so that light is provided to plants to maximize production without excess, which would lead to unnecessary costs. Since graduating with a masters degree, I have began working at a commercial hydroponic operation. I have been able to use the knowledge I gained from this research to help set parameters for production on a large scale. Researchers at the university have implemented the results from this research to continue strawberry production in the winter months. 

Environmental sustainability.

    Through the evaluation of substrates and nutrient source, this project generated infromation to help growers make decisions that will maximize inputs for production. In this project we focused on coconut coir peat blends for CEA strawberry production. While a substrate-less production system such as a deep water raft hydroponic system may reduce farm inputs, there are not the more productive. Research has shown that strawberries perform best in a drier root zone compared to system in which the roots are suspended in water. Commonly used substrate components in greenhouse production include peat moss, coconut coir, perlite, wood fiber, wood chips, rockwool, and compost. Finding a substrate, or combination thereof, that are environmentally sustainable and optimize production for specific crops is critical to environmentally sustainable production. Our experiment tested two commercially available substrates used for strawberry production. One susbtrate was peat based and the other consisted of a coconut coir-peat blend. Coir tends to be less expensive and more sustaiable compared to peat (due to shipping and methods used to harvest peat bogs). We concluded that a peat-coir mix could be used in greenhouse strawberry production. By partially replacing peat with coir, this has the potential to improve environmental and economic sustainability by reducing the amount of peat required.

    This research provided insights into quantities of macro and micronutrients needed for day-neutral strawberry cultivars grown in CEA hydroponic conditions. Growers can choose to integrate both fish farming and plant production as a sustainable alternative to hydroponics to improve crop quality. The results of this research suggest that an aquaponic nutrient solution is a suitable nutrient source for strawberries. Growers that attended our workshop held at UNH reported adding strawberries to their production since our meeting. Since presenting this work through the university platform, one researcher has continued working with CEA strawberry production- focusing on how nutrient solution source influences Pythium root rot in a hydroponic strawberry production system. 

Farmer outreach. Information gained in this project was disseminated to stakeholders during a hands-on workshop. Specifically, we reached farmers and researchers in the field of hydroponic, aquaponic, or greenhouse strawberry production. The workshop was held in June of 2019, which included 40 farmers and researchers. Research results and knowledge of sustainable systems was shared with attendees. Equally exciting, the workshop stimulated networking between strawberry/greenhouse researchers and farmers. This workshop created a community for greenhouse strawberry producers where we shared experiences and knowledge to establish a market in the Northeast. Since the workshop, we have collaborated on ways to develop a platform in which such conversations will be promoted moving forward.  

Knowledge Gained:

      Since beginning this project, my knowledge of sustainable agriculture has expanded through countless discussions with farmers and researchers in the area of strawberry, aquaponic, hydroponic, and greenhouse production. The topic of sustainable agriculture in relation to controlled environment agriculture (CEA) is considered controversial to some. Where some aspects of CEA can be more sustainable than traditional farming (such as increased production of local foods), others may be less sustainable (increased energy requirements). Above all, what we do know is that with a changing climate, the implementation of CEA provides us with systems that can better withstand environmental changes that will undoubtedly affect what we can grow in the northeast.

      I have adopted certain practices within my research discipline that I feel are improving the sustainability of greenhouse strawberry production. These practices are reflections of the work of colleagues that has been shared with me throughout my graduate school experience, as well as my own discoveries through trial and error. For example, the concept of strawberries requiring less nitrogen than what had previously been thought has directly impacted the way we operate our aquaponics facility. Reduction of nitrogen in the fish waste means that we are now feeding the fish less, and therefore reducing inputs onto the farm. In addition, using a crop like strawberries in a greenhouse has reduced the heating costs throughout the winter season.

     Knowledge gained in this project has served as a baseline for two other graduate student projects in the lab at UNH. For example, a plant pathology student has used the data generated in this project to design a new project evaluating the effect of nutrient solution type on strawberry susceptibility to root rot pathogens. 

     Currently, I am in the process of partnering with an agricultural engineer to establish a consulting business that incorporates our knowledge of horticulture and system designs. By doing so, we will not only help growers improve efficiency and increase productivity, but also work on R&D alongside farmers to eventually share with others. Additionally, after completing my master's degree, I hope to work with or on a commercial operation to gain knowledge and experience with advanced greenhouse systems. I will be able to share my knowledge and skills gained working in greenhouse production and operating hydroponic and aquaponic systems to help improve commercial farms.


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    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.