Progress report for GNE18-169

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

Cultivars: Albion, San Andreas, Seascape 

Substrates:

BC5-Peat+Coir   

Mix BC5+Fr2+Perlite  

Composition: 

• Whitepeat
• Cocopeat RHP export 
• Perlite 0-6mm 
• Dolokal
• PG mix

BC3-Peat

Mix BC3  

Composition: 

• Whitepeatfraction 2  
• Whitepeat0-20  
• Blackpeatfibre  
• Perlite 0-6mm 
• Dolokal
• PG mix

Experimental Design:

This experiment consisted of a split-plot+ randomized complete block (RCB) design with 3 strawberry cultivars (subplots) and 2 substrates (whole plots) for a total of 6 treatments. Plants were grown in Bato WAVE meter buckets (A.M.A Horticulture, Ontario), with six plants in each bucket, staggered so that  plants were approximately 8 inches apart. There were six blocks in the experiment, each block consisting of two buckets, one filled with each substrate (BC5 and BC3). Of the six plants within each bucket, two plants of each cultivar were planted side-by-side, to avoid any competition between cultivars. In this design, substrate was assigned to whole plots using RCB design and cultivar was assigned to subplots using RCB design (blocked by substrate).

Methods

72 Strawberry fragariacv. Albion, Seascape, and San Andreas runners were propagated from mother plants on June 11^th, 2018. Mother plants, primarily used for propagation, were planted on 4/1/2018. Runners were placed into Terra Plug Oasis Cubes (Smithers-Oasis, OH) and rooted in the propagation house at Macfarlane Greenhouses Research Facility for 14 days. The runner tips were irrigated through misters in a greenhouse. After two weeks, strawberry plugs were transported to Kingman Research Facility and transplanted into the Bato WAVE meter buckets. Buckets were placed in 10 ft long troughs that sat on a table that was on a 1-inch slant to allow leachate to drain out of buckets and collected at the end of the table. Leachate was not captured for reuse, and was drained into a large holding tank behind the greenhouse. Two lines of string were tightly tied to each end of the table and along both sides of each trough. String was used to separate fruit and runners to improve aeration and minimize the plant material that comes in direct contact with the soil.

The BC3 and BC5 substrates were highly non-uniform with large aggregates of coir and peat throughout the media, and therefore unsuitable for the purpose of this study. Substrate was further mixed prior to potting to provide a more evenly uniform media.  For the mixing process, substrates were poured into 44 gallon trash cans. A mortar mixer attached to a drill was used to break up all aggregates larger than 3cm in diameter. Water was then added to the substrate and further mixed to provide the media and plants with moisture upon planting.

Irrigation 

To determine a standardized irrigation protocol, two Meter buckets were filled and lightly compacted with each substrate and weighed, for a total of four buckets. The buckets were then placed into a drying oven at 65°C for 48 hours. After 48 hours, the plants were removed from the oven and weighed for a dry weight. The buckets were then watered until saturated (when the buckets were dripping water from underneath). Substrate was mixed within buckets until there were no dry spots. Buckets were then weighed for a wet weight. The wet weight was subtracted from the dry weight, and the difference was multiplied by .55 and added to the initial dry weight, to best predict the weight of the buckets at 55% saturation.  The final weights were averaged between the two buckets. When all buckets were filled and wet to 55% saturation, soil moisture sensors were placed in four of the buckets (two in each substrate). Within the Wadsworth Environmental Seed Controller (Colorado, US), the soil moisture was manually entered at 55%. The strawberries were then watered once the saturation level was at 55% for 4 minutes. 6-3/8” Netafim Drip emitters with 5/3’’ irrigation tubing (Griffin Greenhouse Supply, Tewksbury, MA) were used to supply nutrient solution to the plants. The plants were fed Peters Professional 5-11-26 Hydroponic Solution (Dublin, OH) 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 .5-16 gallon/minute DosatronÒ(Dosatron USA, Fl). To ensure nutrient solution concentrations were accurate upon each mixing date, solution was collected from the sample port prior to irrigation. 500mL was of solution was samples and pH & EC were collected. The same thing was repeated two more times. If the samples were within the target range, nothing was changed. If not, Dosatron flows were adjusted until the target pH/EC were achieved.

Environmental Parameters

            Strawberries were grown in a 10’x10’ space within a 30’x96’ triple polycarbonate greenhouse. The plot was located in the back right corner of the greenhouse, with at least 60cm between the wall and the table at any point. There was a vent (dimensions of vent) located at the end wall of the greenhouse, within the 10×10 area the plants were located. Roof and side vents were automatically opened and closed to maintain target temperature ranges throughout the study. The target temperatures had to be compromised at some points throughout the summer, with high daytime temperatures reaching well above the 30°C set cooling temperature. The greenhouse was heated when temperatures dropped below 18°C. Redusolâ(Redusystems, Chilliwack, B.C.) was painted on the entire surface of the greenhouse walls and roof to maintain cooler temperatures and less light intensity through the summer months.

Pollination

Once flower initiation has occurred, plants will be manually pollinated daily using a leaf blower. A leaf blower can be used as a substitute for bees and other natural pollinators by pollinating strawberry flowers through artificial wind that vibrates the flower to shed pollen from anthers to pistils (CEA Basics, University of Arizona). Each plant was exposed to wind produced by the leaf blower until the plant was visibly shook to ensure maximum efficacy. To avoid sticky pollen that is difficult to disperse, we did not artificially pollinate in early mornings (associated with high humidity and condensations). Rather, plants were pollinated daily between early and late afternoon.

Pest and disease management

Yellow sticky cards were placed throughout the crop for the purpose of scouting, as well as pest removal. Fungus gnats (Bradysiaspp.) and thrips were managed by applying beneficial nematode Steinernema feltiae (Biobest Inc.) weekly to the pots at approximately 225 nematdoes per plant.Nematodes were distributed and mixed in water and applied to each pot (300 mL of solution per pot). Precautionary measures were taken to prevent thrips and whitefly establishment using Swirskii predatory mite sachets (Amblyseius swirskii, Biobest Inc.) and Encarsia cards. Slow-release Swirskii sachets were placed on every strawberry plant every 6-8 weeks, while Encarsia cards were placed on 2 plants per greenhouse every other week. Crysopa carnea(green lacewing) were used to control aphids, spider mites, whiteflies, and thrips. Crysopabran was sprinkled on strawberry leaves monthly. Phytoseiulus persimilis are predatory mites (bran formulation) that was sprinkled biweekly to plant leaves to control spider mites.

Runner Removal

All runners were removed every three weeks from all plants. Old leaves on the bottom of plants were removed from plants every three weeks.

Nutrient Solution

Tank A

1842 g Peter’s Professional 5-11-26 Hydroponic Special mixed in 5 gallons of tap water

Tank B

610 g Jack’s Professional Calcium Nitrate mixed in 5 gallons of tap water

Data Collection

The following data was collected and used as metrics to compare the effect of cultivar and substrate on greenhouse strawberry yields.

1. Agronomic Data- number of days to runner production, number of days to flower production, number of days to ripened fruit on all cultivars. Three days a week (Monday, Wednesday and Friday) through the duration of the study, data was collected on number of runners, flowers, and unripened fruit per plant.
2. Fruit Yield- Ripened fruit was picked from all plants 3 days a week (Monday, Wednesday and Friday) from July 23^rdto September 5^th, 2018. Marketable fruit was defined as fruit with 80% red color development, weighed equal to or greater than 10g, and had no deformed fruit (Cantliffe et al., 2007). Data was collected on the number of ripened fruit per plant and the number of marketable fruit per plant. All ripened fruit harvested was weighed for a total ripe fruit weight per plant at each date.

Data Analysis

            All data was analyzed using ANOVA one-way analysis. Statistical analyses where used for significance in the effects of substrate and cultivar on fruit yield, size, marketability, runner production, and flower production. When p-values between treatments were equal to or less than 0.05, additional Tukey HSD tests were run in JMP PRO 14.1.

Objective 2: Quantify nutrient requirements for greenhouse strawberry production using hydroponic and aquaponic nutrient solutions

1. Experiment 2= Nutrient uptake of strawberry cultivar Albion using inorganic and organic nutrient solutions. Strawberry plants were grown from runners under three treatments: a hydroponic strawberry nutrient solution, an aquaponic nutrient solution and aquaponic nutrient solution with the addition of phosphoric acid. Nitrogen concentrations in all nutrient solutions were held around 70-85 ppm-N. The pH of the hydroponic and aquaponic with phosphoric acid were maintained around 5.5-6.0, but the untreated aquaponic nutrient solution held a much higher pH, around 6.5-7.2. The EC of all three solutions were maintained between 1.0-1.20mS.

Data was collected on runner production, flower production, fruit yields, and overall marketability of fruit between all treatments. Additionally, fresh and dry weights were collected to evaluate overall plant vigor and biomass. Vegetative growth and fruit was dried and analyzed for a full macro and micronutrient analysis. We were interested in comparing the ability of solutions to uptake nutrients overtime.

Crop: Strawberry cultivar Albion  

Nutrient Solutions:

(1) Inorganic – YamazakiHydroponic Nutrient solution

(2) Organic – Aquaponic nutrient solution 

(3) Organic – Aquaponic nutrient solution with addition of phosphoric acid  

Experimental Design:  

3 nutrient solutionswith24 replicateplants grown in each nutrient solution. Each treatment was assigned to a table, 3 tables total (each with a different nutrient solution). This design was used due to space restrictions. Randomized samples were taken for a nutrient mass balance.

Methods:

Plant material

72 strawberry cv. Albion runners were propagated from mother plants (maintained at the Kingman Farm Research Greenhouse) on 9/17/18. Propagated runner tipswereharvestedfrom mother plants and rooted in Oasis root-cubes provided by Smithers-Oasis(Kent, OH), and rootedin the propagation house in Macfarlane for 14 days. The strawberry runner tips wereirrigated throughmisters in a greenhouse with no supplemental lighting. The greenhouse benchtop was set at 72°F and was heated when temperatures dropped below 68°F and cooled when temperatures rose above 78°F.

Production area set-upand plant growth

Runners werethen transplanted into Classic 3008-inch potsfilled with HPCC mycorrhizae substrate (Pro-Mix) (Pots and substrate were purchased from Griffin Greenhouse Supply based in Tewksbury, MA). Plants were grown on 3, 3-foot tall tables at the Kingman Farm Greenhouses Research Facility under drip irrigation. Each table was irrigated with one of the three nutrient solution treatments. For the Yamazaki solution, an A/B irrigation systems was installed using two 19 L tanks each with a .5-16gallon/min dosatron®. For the aquaponic treatments, pvc pipes were installed to connect the aquaponic effluent to a pump. Tubing ran from the pump to the drip lines extended to each table. A third dosatronÒwas installed to the AQ+PA table to supply phosphoric acid to the aquaponic effluent to reach a target pH of 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 approximately 1-100. The rate of injection was slightly adjusted at every irrigation event to achieve a pH of 6.0, to account for the variation in pH of the aquaculture effluent.

The aquaponic drip lines were checked every two weeks to ensure the emitters were not clogged with solids by removing emitters from each pot and running clear water. Irrigation was turned on and run until pots were saturated and dripping leachate through the bottom of the pot. Plants were irrigated at 55% saturation based on weight (when pots weigh 815g or less). To determine the average weight of all 72 pots, 3 pots from each tablewererandomly weighed and averagedevery other day. Tables/treatments were irrigated once the moisture content of the sample pots drop below 55%.

The pour-thru method was used to monitor the pH and EC of the leachate of 5 pots per treatment. Saucers wereplaced under pots and approximately 300mL of DI water was supplied to each pot. Leachate wascollected in saucers underneath pots and then transferred to a beaker where pH and electrical conductivitywastested. PH wastested using a HannaHI98128 pHep®5 probe. The electrical conductivity wastested using Hach: Pocket Pro Low Range Conductivity Sensor. If pH and EC werenot within acceptable range,*set parameters* clear water wasrun through emitters until saturation occurred.

High pressure sodium lights wereplaced above each table to ensure sufficient light throughout the fall and winter months. Lights werecontrolledto ensure a minimum of 15-20moles of photons per meter square perday wasachieved at amaximumof 16hour lighting cycle.Light accumulation was monitored using a PAR sensor and controlled using a Wadsworth Environmental Seed Controller (Colorado, US). 

Nutrient Solutions  

Nutrient solutions wereapplied through the drip irrigationas described above.

Table 1: Nutrient solutions used in this experiment

(3)*** 3^rd Nutrient solution= ‘aquaponic nutrient solution’ with the addition of phosphoric acid (through acid injector) to maintain a pH of 6.0 and increase phosphorous in system  

Data Collection 

The following data wascollected and used as metrics to compare the effect of nutrient source on plant production.

1. Nutrient Mass Balancewas established by monitoring nutrient input and output to quantify uptake by the plants.
   • Plant/tissue samplesof 3 plants grown in each nutrient solution (total of 9 plants) were collected at three-timepoints; (1) at time of vegetative growth(2) during fruit productionand (3) at harvest, for a total of 27 full plant samples throughout the experiment . Additionally, 3 plant tissue samples were collected on the day of transplanting. Tissue samples wereseparated into vegetative plant and fruit, andweighed for a fresh weight. Samples were thendried in an oven for 48 hours at 65°Cand weighed to obtain adry weight. Dry samples wereground into a powder using a mortar and pestle, and transferred into a test tube for analysis. Samples weresent out weekly to JR Peters Inc. (Allentown, PA).
   • Nutrient solution samples was taken at the time of each irrigation to observe macro and micronutrient levels of the nutrient solution input.200mL ofeach nutrient solutionwere collected and combined from four extra drip emitters using a 250 mL test tube and sent every week to JR Peters Inc. (Allentown, PA). Sampleswerestored at 4°C until shipment. Nutrients collected from the four extra drip emitters at each irrigation event were measured and averaged for an average input volume of solution to each pot.
   • The mass balance calculations are based on the input (irrigation solution), output (leachate) and tissue samples (captured) at four time points (transplant, runner production, peak fruiting, harvest).
   • Leachate was collected from each plant that was harvested for tissue analysis using clear 10-inch saucers. After 10 minutes, leachate from each pot was measured for a volume lost per pot. The volume lost was then subtracted from the input volume for a captured volume (or volume retained in the pot) for each plant sample. Leachate from each sample plant was collected in individual 5-gallon buckets. Leachate from every irrigation event was combined in their respective sample plant buckets. To prevent denitrification during storage, HCL wasadded to all nutrient solution samples containing Nitrogen to reduce the pH to 2.0. At a pH of 2.0, nitrogen in the form of ammonia, nitrite,and nitrate will be preserved.
2. Agronomic Data- Number of days to runner production, # of days to flower production, # of days till ripened fruit(80% red coloration of an individual fruit) in all 3 nutrient treatmentswas observed and recorded.

• Fruit yield collectedtwice a week for 6 weeks from every plant. The number of fruit per plant, weight of fruit per plantand marketablefruit per plant wasrecorded at each harvest.Marketable fruit will be defined as fruit with 80% red color development, weighsequal to or greater than 10g, and has no deformed fruit(Cantliffe et al., 2007). Number of living plants was updated every two weeks for accuracy of data.

Data analysis

1. Nutrient Mass Balance

Nutrient solution

To quantify the nutrient uptake of each strawberry plant, simple calculations were carried out. The leachate composition (nutrients collected in sample leachate*volume) was subtracted from the original input (nutrient solution*volume) irrigated to each pot to calculate the volume and composition of nutrient solution that remained in the pot. We will consider nutrient solution captured in the pot as solution that was taken up by the plant.

 Tissue/Fruit Analysis

Based on what was supplied to the plant, the composition of nutrients within the plant tissue and fruit was then analyzed to evaluate the nutrient uptake efficiency in the plants between the nutrient solutions. Comparisons were made on nutrient content in fruit based on size of fruit (g).

 Statistics

Analyses were conducted using JMP pro 13.1 (SAS institute, Cary, NC). Effects of specific nutrient content (N, P, K) on growth yields will be tested in ANOVA.  ANOVA test was used to determine if there was any significant variation in data due to environmental parameters, such as temperature.

2. Yield, marketability, flowering and ripening

Effects of nutrient solution and specific nutrient concentrations on total runner production, fruit yield (marketable and unmarketable), fruit weight (g) was determined using Analysis of Variance in ANOVA. If significance amongst data was found (p value= 0.05 or less), Tukey HSD test will be run in JMP for specific details.

Objective 3: Evaluate the effects of daily light integral on plant growth and fruit quality in greenhouse strawberries

2. Experiment 3= Evaluate the effects of Daily Light Integral (DLI) on day-neutral strawberry cultivars based on growth rates, yields, and marketability.

Cultivar: Strawberry cv Albion

Treatments- Daily Light Integral (DLI):

14 mol·m^-2·d^-1

20 mol·m^-2·d^-1

26 mol·m^-2·d^-1

Experimental Design

            The experiment consisted of a randomized complete block design with three lighting regimes and three replicate blocks of each lighting regime, for a total of 9 blocks. 9 strawberry plants were grown under each light fixture, for a total of 81 plants in the experiment. Plants were grown under 100% supplemental lighting. Ground cover (VMInnovations, Lincoln, NE) was used to block natural sunlight during the day. Plants were enclosed under ground cover 24 hours a day. Plants were grown in Classic300 8-inch pots (Griffins Greenhouse Supply, Tewksbury, MA) filled with HPCC mycorrhizae substrate (Pro-Mix, Quakertown, PA). Pots were spaced evenly 6 inches apart and 6 inches from the edges of the chamber walls.

Methods

            81 Strawberry cv. Albion runners were propagated from mother plants on December 21st, 2018. Runners were placed into Terra Plug Oasis Cubes (Smithers-Oasis, OH) and rooted in the propagation house at Macfarlane Greenhouse Facility for 14 days. The runner tips were overhead irrigated using misters. From day 14 to day 21, plug plants were removed from the mist and overhead watered using a 5-11-26 standard Jacks Professional nutrient solution (JR Peters, PA) twice a day to ensure complete rooting of oasis cubes and provide an acclimation period to prevent shock. Plugs were then transplanted into media filled pots. Media was dampened with clear water prior to transplanting to provide saturation to the plants at the time of planting.

Lighting Control

            ARC 600 LED full spectrum lights with integrated dimmers (HortLED, Ithaca, NY) were used for the study. All plants were exposed to a 16 hour photoperiod. Lights were set to one of three target DLI’s; 14, 20, or 26 mol·m^-2·d^-1with a light intensity of 260, 347, or 434 umol·m^-2·s^-1respectively.  Ground cover was draped above each bench and light fixture to eliminate any outdoor 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 

To determine a standardized irrigation protocol, three pots were filled and lightly compacted with media and weighed. The pots were then placed into a drying oven at 65°C for 48 hours. After 48 hours, the pots were removed from the oven and weighed for a dry weight. The pots were then watered until saturated (when the pots were dripping water from underneath) and weighed. The wet weight was subtracted from the dry weight, and the difference was multiplied by .55 and added to the initial dry weight, to best predict the weight of the buckets at 55% saturation. The final weights were averaged between the three pots. Three randomly chosen pots within the experiment were weighed every other day, and watered when the average weight of the three pots was 55% saturation or below. A 3/8” Netafim Drip emitter with 5/3’’ irrigation tubing (Griffin Greenhouse Supply, Tewksbury, MA) was placed in every pot and used to supply nutrient solution to the plants. Zones for each lighting regime were created so that pots could be irrigated based on treatment. The plants were fed the Yamazaki nutrient solution. An A/B irrigation system was installed using two 19L tanks each with a 0.5-14 gallon/min dosatron^Ò(Dosatron USA, Fl). To ensure nutrient solution concentrations were accurate upon each mixing date, solution was collected from the sample port prior to irrigation and pH & EC were recorded. 

Nutrient Solution

Table 1: Nutrient solution used in this experiment

Measuring Brix

Brix (total soluble solids) was measured in strawberry fruit for sugar content using the Hanna digital refractometer (model HI96801) (Hanna^ÒInstruments, Woonsocket, RI). 9 fruit from each treatment were randomly sampled and cut into 4 pieces for replication. Quartered fruit were directly pressed onto the digital refractometer and data was recorded. Refractometer was cleaned using Kimpwipes^Ò(FisherScientific) after every sample.

Data Collection

The following data was collected and used as metrics to compare the effect of light exposure on plant productivity and fruit quality.

1. Fruit yield- Ripened fruit was collected twice a week from every plant for the duration of the study. Ripened fruit was characterized by 80% red color development. The number of fruit per plant, weight of fruit per plant and marketable fruit per plant was recorded at each harvest. Marketable fruit was defined as fruit that equals or is greater than 10g, and fruit that is not deformed or soft (Catliffe et al., 2007). The number of living plants was updated every two weeks for accuracy of data.
2. Fruit Quality- Samples of fruit from each treatment was evaluated every two weeks based on sugar content (total soluble solids), measured in units of brix. Total soluble solids for each treatment was averaged between plants at each sampling date.
3. Agronomic Data- Number of days to runner production, # of days to flower production, # of days till fruit emergence was observed and recorded under all treatments. Number of runners per plant was collected every two weeks.