Few published studies provide foliar tissue nutrient concentrations for strawberry (Fragaria × ananassa) mother and daughter plants. Recommendations primarily focus on tissue concentrations for field-grown plants during fruit production. As controlled environment production of strawberry increases, a need exists to define tissue nutrient concentration ranges for healthy foliar tissue, for both vegetative and fruit production. Defining deficient, sufficient, and toxicity ranges will assist growers in selecting nutrient solution recipes and correcting nutritional issues that arise. The objective of this study was to identify nutrient concentration ranges for healthy strawberry mother and daughter plants grown in controlled environments. Foliar tissue samples were collected from two separate experiments: 1) ‘Albion’, ‘Fronteras’, and ‘Monterey’ grown in a peat-based substrate, and 2) ‘Monterey’ grown indoors in deep water culture. Plants received a modified strawberry nutrient solution (Yamazaki) that provided 100 mg·L-1 nitrogen (N). The percent total N provided as ammonium (NH4 ) ranged from 0% to 40% in both experiments. Plants did not exhibit any visual symptoms of foliar nutrient deficiencies or toxicities. Foliar tissue from mother (n=72) and daughter plants (n=144) were collected and analyzed individually. Nutrient concentration ranges comprised the middle 75% of plant samples (12.5% – 87.5% quantiles). Mother plant macronutrient concentrations ranged from 2.12%–2.64% nitrogen (N), 0.53%–1.23% phosphorus (P), 2.05%–3.88% potassium (K), 2.01%–3.36% calcium (Ca), 0.33%–0.56% magnesium (Mg), and 0.14%–0.28% sulfur (S). Daughter plant foliar macronutrient concentrations ranged from 2.18%–3.38% N, 0.49%–0.92% P, 2.20%–4.19% K, 1.01%–3.03% Ca, 0.31%–0.53% Mg, and 0.15%–0.30% S. Mother plant foliar micronutrient concentrations ranged from 158–233 mg·kg-1 boron (B), 1.5–5.6 mg·kg-1 copper (Cu), 57–587 mg·kg-1 iron (Fe), 131–384 mg·kg-1 manganese (Mn), and 11–29 mg·kg-1 zinc (Zn). Daughter plant foliar micronutrient concentrations ranged from 69–212 mg·kg-1 B, 1.2–4.5 mg·kg-1 Cu, 56–347 mg·kg-1 Fe, 78–315 mg·kg-1 Mn, and 18–36 mg·kg-1 Zn. In general, these macro- and micronutrient ranges overlap between mother and daughter plants. These values represent a first step in developing and refining foliar nutrient ranges for strawberry mother and daughter plants in controlled environments.
Established guidelines for electrical conductivity (EC) for strawberry (Fragaria ×ananassa) fruit production exist for plants grown in soilless substrates. However, EC recommendations for strawberry mother plants may differ when the goal is prolific runnering instead of flowering and fruiting. Our objective was to evaluate the impact of EC concentration strawberry runner and daughter number. Strawberry ‘Monterey’ were grown in a greenhouse in 19.1-cm diameter pots filled with a soilless substrate (50 perlite : 25 coco coir : 25 peat). To formulate the EC treatments, all components of a strawberry nutrient solution (Yamazaki) increased equally, which corresponded to nitrogen (N) concentrations of 50, 100, 150, 200, 300, and 400 mg·L-1 N. After adding 0.8 mM potassium bicarbonate as a buffer and adjusting pH to 5.7, the final nutrient solution EC values were 0.9, 1.6, 2.3, 2.8, 3.9, and 4.9 mS·cm-1. After 12 weeks of treatment, runner and daughter plant number, morphological assessments, and mother plant leaf burn index were evaluated. The qualitative assessment of leaf burn utilized a 1 to 5 scale (1 = no tip burn; 2 = mild, margins of ≥ 3 leaves; 3 = moderate, necrosis on at least half of ≥ 3 leaves; 4 = moderate to severe, complete necrosis on ≥ 3 leaves; and 5 = severe, complete necrosis on ≥ 4 leaves and necrosis of daughter plants). Leaf burn values ranged from 1.6 ± 0.2 (± SE) in the 50 mg·L-1 N treatment to 5.0 ± 0.0 in the 400 mg·L-1 N treatment. Runner number exhibited a quadratic response and ranged from 2 ± 0 at 50 mg·L-1 N to 7 ± 1 at 300 mg·L-1 N. Daughter plant number also exhibited a quadratic response. It increased from 14 ± 3 at 50 mg·L-1 N to 44 ± 4 at 200 mg·L-1 N, then declined to 30 ± 13 at 400 mg·L-1 N. Total plant biomass (mother plant, stolons, and daughter plants) exhibited a quadratic relationship. It increased from 23.5 ± 4.0 g at 50 mg·L-1 N to 65.9 ± 7.9 g at 200 mg·L-1 N, then declined to 40.0 ± 5.2 g at 400 mg·L-1 N. Overall, the optimal nutrient solution EC range for strawberry mother plants was 100 to 200 mg·L-1 N (or 1.6 to 2.8 mS·cm-1). In this range, mother plants produced a high number of runners and daughter plants, with minimal leaf burn due to high substrate EC values.
Unavailability of pathogen-free strawberry propagules in commercial quantities necessitates the development of a novel completely indoor precision propagation technology for the crop, which also seeks to reduce dependence on soil fumigants including methyl bromide. Artificial chilling of plug plants could also enhance transplant vigor, flowering, and yield of strawberry. Under this novel technology, strawberry tips which consisted of five short day (SD) cultivars (Fronteras, Camarosa, Chandler, Sensation and Brilliance) and one long day (LD) cultivar (Monterey) were collected from tissue cultured mother plants. Plants were propagated under completely controlled environment (CE) conditions in a plant factory. Strawberry daughter plants were rooted in 50 cc trays filled with a commercial substrate and were arranged in the controlled environment under 90 – 100 % humidity, 27 °C temperature, 80 – 100 µmol m-2 s-1 light (LED), 18 hours photoperiod, and fertigated using the ebb and flow technique for 28 days. Our hypothesis was that artificial chilling will improve plant vigor and yield of CE-propagated strawberry transplants. We therefore assessed the impact of 350 – 450 hours of artificial chilling on the plant performance and yield of the transplants in four different locations in the US. Monterey, Brilliance, and Sensation cultivars received 350 hours of chilling while Fronteras, Chandler, and Camarosa cultivars were chilled for 450 hours. Strawberry plug plants (chilled and no-chill) were planted in replicated field trials in California, Florida, and North Carolina. Camarosa and Chandler cultivars were transplanted in North Carolina, Fronteras in Southern California, Monterey in Central California, while Brilliance and Sensation were transplanted in Florida. Preliminary results show improved vigor and yield from chilled plants in Florida and North Carolina field trials, while no differences were observed in California. Final results of the study will be shared during the conference.
The use of controlled environments to produce disease-free vegetative clones of strawberry (Fragaria ×ananassa) is increasing. However, protocols for mother plant management that optimize runner and daughter plant number need to be developed. Studies have shown that decreasing the fraction of nitrogen (N) supplied as nitrate (NO3-) can encourage vegetative growth in other crops. Our objective was to identify the %NO3--N that maximized runner and daughter plant number. Strawberry ‘Albion’, ‘Fronteras’, and ‘Monterey’ were grown in 19.1-cm pots filled with a peat-based substrate. Plants were irrigated with a modified strawberry nutrient solution (Yamazaki) that provided a total of 100 mg·L-1 N. The percent of total N supplied as NO3- ranged from 0% to 100%, with the remainder supplied as ammonium (NH4 ). Runners and daughter plants were harvested after eight and 16 weeks of treatment. The impact of %NO3- on cumulative runner number was cultivar specific. ‘Albion’ was not impacted, and the overall mean was 9 ± 1 (± SE).‘Fronteras’ exhibited a quadratic response. It increased from 10 ± 2 at 0% NO3- to 17 ± 2 at 60% NO3-; the calculated maximum runner number was with 64% NO3-. ‘Monterey’ exhibited a linear increase, from 14 ± 1 at 0% NO3- to 22 ± 1 at 100% NO3-. The impact of %NO3- on cumulative daughter plant number was also cultivar specific. ‘Abion’ exhibited a linear increase, from 28 ± 2 at 0% NO3- to 37 ± 10 at 100% NO3- . ‘Fronteras’ exhibited a quadratic response and increased from 19 ± 2 at 0% NO3- to 45 ± 7 at 60% NO3-. ‘Monterey’ also exhibited a quadratic response and increased from 49 ± 4 at 0% NO3- to 90 ± 7 at 80% NO3-. Calculated maximum daughter plant number occurred at 66% and 81% NO3- in ‘Fronteras’ and ‘Monterey’, respectively. Overall, at least 60% NO3- provided robust runner and daughter plant number, but the response depended on cultivar evaluated. ‘Monterey’ and ‘Albion’ appear to prefer a higher %NO3- than ‘Fronteras’ for maximum runner and daughter plant number.
Due to the high operation costs of indoor crop production, improving resource use efficiency to reduce costs has gained importance for sustainability in recent years. Silicon (Si) is not an essential plant nutrient since it is not a component of any structural or metabolic molecule, and plants do not suffer from Si deficiency. However, Si applications have shown beneficial effects on various crops, including improved growth, quality, stress tolerance, and water use efficiency (WUE). This study evaluated the effects of Si on indoor lettuce production to enhance lettuce growth and WUE. Two-week-old lettuce seedlings (Lactuca sativa cv. ‘Green Forest’ and ‘Rouxai’) were transplanted into 5-L deep water culture systems and grown for four weeks in a custom growth chamber with an average temperature/relative humidity of 22.4°C/58.8% and light intensity of 230 µmol/m²/s PPFD. The nutrient solution was weighed and replenished weekly. Si (DUNE™ stabilized monosilicic acid) was applied weekly to plants following two application methods (RA=root application and FS=foliar spray) and three concentrations (Control=0 ppm, C1=264 ppm, and C2=528 ppm). RA C1 significantly improved the shoot fresh weights (FW) and dry weights (DW) of both lettuce cultivars, while FS C1 was less effective than RA. Root growth showed the opposite trend, with FS C1 having the highest root FW and DW of both cultivars. However, root morphology showed cultivar-specific responses, with RA C1 producing the highest root length and surface area in ‘Green Forest’ and FS C1 the highest root surface area and volume in ‘Rouxai.’ WUE was significantly improved by RA C1, RA C2, and FS C2 in ‘Green Forest’ and RA C1 in ‘Rouxai’ compared to the control. Taken together, root application of Si at C1-264 ppm concentration most effectively improved the indoor lettuce growth and WUE.
Zinc (Zn) is a micronutrient crucial for human health, impacting gene expression, cell division, and immune system development. Zinc deficiency affects about 17% of the global population, particularly children, pregnant women, and elderly people, and can lead to disorders and even death. Agronomic biofortification implemented by applying Zn-enriched solutions via fertigation to increase crops Zn content may be a valuable strategy to combat Zn deficiencies. Microgreens, known for their nutrient density, rapid growth cycle, and low phytic acid content, are emerging as promising candidates for Zn agronomic biofortification. However, research is needed to evaluate the effect of factors like light intensity and genotype which can affect Zn accumulation in microgreens. To this purpose, a study was conducted to examine the effect of Zn application rate (0, 5, 10, and 15 mg/L) and light intensity (100, 200, 300, and 400 µmol/m2/s) on yield components, mineral content, and phytochemical profile of pea and radish microgreens. The study revealed that Zn concentration increased with increasing concentration of Zn applied in both species. In peas, a 4-fold increase was observed when applying 15 mg/L of Zn without affecting fresh and dry biomass, while an almost 13-fold increase of Zn content was observed in radish, associated with a 7.8% reduction of fresh biomass and no effects on radish microgreens dry biomass. However, with the increase of Zn content, there was a reduction in Fe concentration in both peas and radish microgreens. The light intensity did not affect Zn content in both species; however, it affected the concentration of macro and other microelements and influenced yield, but the result varied by species. In pea microgreens, low light intensity determined higher fresh biomass but did not affect dry biomass. Instead, the opposite result was observed in radish microgreens; light intensity did not affect fresh yield but increased dry biomass with increasing the level of light intensity applied. Regarding the nutritional profile, total phenols, total antioxidants, and flavonoids increased with increasing Zn concentration and light intensity in both pea and radish microgreens. In conclusion, Zn fertigation effectively enhanced Zn in pea and radish microgreens, and although light intensity had no effect on Zn content, contributed to improve their nutritional profile. These findings provide valuable insights into the production technique of Zn biofortified microgreens and the potential enhancement of their overall nutritional profile using agronomic biofortification techniques.
Organic farming practices, such as the use of organic substrates, fertilizers, pesticides, and biological control, are gaining popularity in controlled environment agriculture (CEA) since soilless production was approved for organic certification in the US. Our past study showed that liquid organic fertilizers are more effective than substrate-incorporated compost fertilizers. Although many liquid organic fertilizers are commercially available, they vary widely in their nutritional composition. Therefore, selection of a suitable fertilizer can be complicated and confusing for CEA growers. The current study aimed to evaluate the effectiveness of different liquid organic fertilizers and compare their performance with that of a synthetic fertilizer for growing lettuce in two different containerized hydroponic systems. Two greenhouse experiments were conducted in a randomized block design with five replicates. In Experiment 1, two types of container (regular container and Dutch bucket) and three fertilizers (earthworm castings and kelp (ECK), molasses with other natural plant extracts (MPE), and hydrolyzed fish protein (HFP)) were considered. The fertilizers were selected from the Organic Materials Review Institute (OMRI) list based on their nutrient profile and reports from other studies. In Experiment 2, selected liquid organic fertilizers (ECK, MPE) were compared with a commercial synthetic fertilizer (CSF). In Experiment 1, ECK performed better, resulting in 28% greater fresh weight, 20% greater dry weight, 48% greater leaf area, 26% greater shoot width, 126% greater average root fresh weight, and 47% greater root length in containerized production compared to the Dutch bucket system. No significant growth difference was observed between MPE and HFP. In Experiment 2, there was no significant growth difference between ECK and CSF; however, the shoot width, leaf area, and dry weight of lettuce were significantly lower with MPE treatments compared to ECK. Results show that ECK performed similarly or better than synthetic fertilizer for growing lettuce in these container hydroponic systems. The findings of this study indicate that a single organic fertilizer could be used instead of several for organic leafy green production in soilless substrate.
