There is increasing interest in growing strawberries (Fragaria ×ananassa) in indoor environments such as vertical farms, as the continued sustainability of outdoor production is threatened due to reductions in arable land, labor shortages, and an increased frequency of drought. However, the optimal conditions for growing strawberries hydroponically in sole-source lighting conditions have yet to be established. The objectives of this research were to investigate the optimal lighting conditions and nutrient concentrations for strawberry production in vertical farming. In the first study, bare-root plants of two strawberry cultivars, ‘Albion’ and ‘Monterey’, were grown in an indoor vertical farm under a 22 °C air temperature and an 18-h photoperiod with 90 μmol·m−2·s−1 of blue light and 250 μmol·m−2·s−1 of red light with and without 50 μmol·m−2·s−1 of additional far-red light from light-emitting diodes. Adding far-red light increased the fruit number per plant by 36%, total fruit fresh mass by 48%, and total soluble solids content by 12% in ‘Albion’, but not ‘Monterey’. In the second study, bare root plants of strawberries ‘Monterey’ and ‘San Andreas’ were grown under a 23 °C air temperature and an 18-h photoperiod with an extended photosynthetic photon flux density of 350 μmol·m−2·s−1. Plants were subjected to four potassium to nitrogen ratios (K:N) of 1.5:1, 2.5:1, 3.5:1, and 4.5:1 in a deep-water culture hydroponic system. Increasing K:N from 1.5:1 to 4.5:1 increased the root dry mass of ‘Monterey’, but generally had little to no effect on vegetative growth in either cultivar. In addition, in both cultivars, increasing K:N from 1.5:1 to 4.5:1 decreased individual fruit size and increased titratable acidity. These results suggest that for indoor strawberry production, including far-red light in sole-source lighting can improve fruit production in some strawberry cultivars. However, increasing K:N in the hydroponic nutrient solution generally does not benefit plant growth, fruit production, and fruit quality.

Traditional crop production faces a significant challenge due to overapplication, mining, and decreased supply of mineral nutrients. In addition to this, the urgent need to address global food waste has become increasingly apparent, as discarded food scraps in landfills contribute to harmful greenhouse gas emissions. A promising solution that addresses both of these critical challenges includes the innovative utilization of food waste anaerobic digestate as a fertilizer for crop production. This study investigated whether using anaerobically digested food waste as fertilizer can fully replace or reduce the use of chemical fertilizer in vegetable and ornamental crop production. The seeds of lettuce (Lactuca sativa) ‘Nancy’ and petunia (Petunia × hybrida) ‘Easy Wave Velour Berry’ were sown into a soilless medium and grown in the indoor vertical farm at 22℃ under sole-source lighting at a photosynthetic photon flux density of 180 µmol∙m–2∙s–1 with a 20-h photoperiod. Four weeks after sowing, seedlings were transplanted and grown for three weeks in a greenhouse with an average daily temperature of 20 °C under ambient sunlight with an average daily light integral of 22 mol∙m–2∙d–1. The plants were fertilized using tap water mixed with different fertilizers, including a chemical fertilizer (15N-2.2P-16.6K), an organic fertilizer derived from anaerobically digested food waste (0.06N-0.026P-0.1191K), or a blend containing 50% chemical fertilizer and 50% food waste-based fertilizer, at the electrical conductivity of 0.7 mS·cm-1 during the young plant stage and 2.1 mS·cm-1 after transplant. At the young plant stage, lettuce and petunia have similar growth characteristics, including leaf number, SPAD index, and shoot and root fresh mass, when treated with either chemical or chemical + food waste fertilizer. In contrast, in both species, leaf area was 93-152% larger and fresh mass was 82-141% greater in plants treated with chemical or chemical + food waste fertilizer compared to food waste fertilizer. At the finishing stage, lettuce and petunia also showed similar growth and flowering characteristics under chemical or chemical + food waste fertilizer. However, in the lettuce finishing plants, fresh mass was 127-199% larger when supplied with chemical or chemical + food waste fertilizer compared to food waste fertilizer. In petunia, the number of flowers was 123-190% greater in chemical and chemical + food waste fertilizer compared to food waste fertilizer. In both lettuce and petunia at the finishing stage, the SPAD index, leaf number, root fresh mass, and root dry mass were similar among all treatments. These results suggest that food waste fertilizer applied as the sole source of plant nutrition is insufficient in comparison to chemical fertilizer at the same electrical conductivity. However, partially substituting some food waste fertilizer for chemical fertilizer reaps similar plant yield to chemical fertilizer on its own.

Genome-wide, single nucleotide polymorphisms (SNPs) and germination data were analyzed to better understand species delimitation and salt-tolerance within the legume genus Medicago. Molecular phylogenies revealed that the widely-used, genomic model line R108 and two deeply divergent accessions of Medicago truncatula are in fact more closely related to Medicago littoralis than to other accessions representing Medicago truncatula. This result was supported by germination data wherein the two accessions representing deeply divergent Medicago truncatula demonstrated salt-tolerance that was more similar to Medicago littoralis than to other accessions of Medicago truncatula. Molecular phylogenies revealed that two additional accessions representing deeply divergent Medicago truncatula appear to be more closely related to Medicago italica than to other accessions representing Medicago truncatula. The results of the present study elucidate complex evolutionary relationships and contribute to the present understanding of existing salt-tolerance within Medicago.

Chemical fertilizers are commonly used for controlled environment agriculture because they provide essential plant nutrient efficiently. However, rising fertilizer costs, global phosphorous shortage, and the negative impacts of producing and using chemical fertilizer are concerns for sustainable crop production. As sustainable alternatives to chemical fertilizers, there is a growing interest in using organic fertilizers with beneficial plant growth promoting microorganisms. The objectives of this research were to investigate how the application of plant growth promoting bacteria and arbuscular mycorrhizal fungi influences plant growth of lettuce (Lactuca sativa) and tomato (Solanum lycopersicum) seedlings in soilless media under organic fertilization. In the first study, the effects of Azosprillium brasilense and Rhizophagus intraradices inoculation on lettuce and tomato seedling growth were quantified under two different organic fertilizer types compared to under chemical fertilizer. The results showed that A. brasilense and R. intraradices had little to no effect on any growth parameter measured in either species regardless of fertilizer type. In the second study, an investigation of the co-inoculation of A. brasilense and R. intraradices or increasing the application frequency of A. brasilense or/and R. intraradices increased plant growth promoting effects in lettuce ‘Cherokee’ and ‘Rex’ grown under organic fertilization. An application frequency of every 2-days of the R. intraradices without or with A. brasilense increased shoot fresh weight in both lettuce cultivars by 51-58%, compared to un-inoculated control. In contrast, lettuce seedling growth were similar without or with applying R. intraradices weekly or A. brasilense regardless of frequency. Together, the results suggest that applying R. intraradices with a proper application frequency can enhance plant growth of lettuce under organic fertilization.

The partitioning of photosynthates between their sites of production (source) and their sites of utilization (sink) is a major determinant of crop yield and the potential of regulating this translocation promises substantial opportunities for yield increases. Ubiquitous overexpression of the plant type I proton pyrophosphatase (H+-PPase) in crops improves several valuable traits including salt tolerance and drought resistance, nutrient and water use efficiencies, and increased root biomass and yield. Originally, type I H+-PPases were described as pyrophosphate (PPi)-dependent proton pumps localized exclusively in vacuoles of mesophyll and meristematic tissues. It has been proposed that in the meristematic tissues, the role of this enzyme would be hydrolyzing PPi originated in biosynthetic reactions and favoring sink strength. Interestingly, this enzyme has been also localized at the plasma membrane of companion cells in the phloem which load and transport photosynthates from source leaves to sinks. Of note, the plasma membrane-localized H+-PPase could only function as a PPi-synthase in these cells due to the steep proton gradient between the apoplast and cytosol. The generated PPi would favor active sucrose loading through the sucrose/proton symporter in the phloem by promoting sucrose hydrolysis through the Sucrose Synthase pathway and providing the ATP required to maintain the proton gradient. To better understand these two different roles of type I H+-PPases, a series of Arabidopsis thaliana transgenic plants were generated. By expressing soluble pyrophosphatases in companion cells of Col-0 ecotype and H+-PPase mutants, impaired photosynthates partitioning was observed, suggesting phloem-localized H+-PPase could generate the PPi required for sucrose loading. Col-0 plants expressed with either phloem- or meristem-specific AVP1 overexpression cassette and the cross between the two tissue specific lines (Cross) were generated. The results showed that the phloem-specific AVP1-overexpressing plants had increased root hair elongation under limited nutrient conditions and both phloem- and meristem-overexpression of AVP1 contributed to improved rhizosphere acidification and drought resistance. It was concluded that H+-PPases localized in both sink and source tissues regulate plant growth and performance under stress through its versatile enzymatic functions (PPi hydrolase and synthase).

As the global population continues to increase, so does the need for agriculture resulting in increased fertilizer use. Nanofertilizers and biochar have been proposed as alternatives to fertilizers currently in use to reduce negative environmental impacts. In this study, the effects of various nanofertilizers and biochar on the soil microbial community were investigated. Soils treated with graphene nanoplatelet (GNP), graphene oxide (GO), reduced graphene oxide (rGO), graphite nano-additive (GNA) and biochar (BC) at concentrations of 5 mg/kg and 1000 mg/kg were sampled before and after a 28-day incubation period. Quantitative PCR assays were carried out against the following target genes: 16S rRNA, nirK, nirS, nifH, amoA and nosZ. Overall, all treatments experienced a decrease in 16S rRNA abundance after the incubation period with an average decrease of 48% however, all treatments were higher in abundance than the control. The abundances of nitrogen (N) cycling functional genes were evaluated in terms of relative abundance as a percentage of 16S rRNA. There was an increase across all treatments in nirK relative abundance over time and when compared to the control. The most notable differences in abundance were in rGO (high) as well as BC. Both nirS and nosZ exhibited an increase over time but decreased compared to the control. A decrease in relative abundances of nifH in BC as well as GO (low) and rGO (high) was observed. Lastly, there was an increase in amoA relative abundance across all treatments after the incubation period. However, all treatments were significantly lower than the control. The increase of denitrifying genes (nirK, nirS and nosZ) and nitrifying genes (amoA) suggests the potential increase in denitrification which can result in increased N loss into the atmosphere and the potential decrease of nitrification resulting in reduced N loss into waterways, respectively. At the time of writing, this study is one of the first to investigate and provide observations on the effects of nanofertilizers on nifH, which is responsible for N-fixation. The results presented here suggest that rGO and BC impart similar effects on the microbial community, whereas GNP had the most significant impact overall.

Precision agriculture (PA) integrating information technology arouses broad interests and has been extensively studied to increase crop production and quality. Sensor probe technology, as one of the PA technologies, provides people with accurate real-time data, which has become an essential part of precision agriculture. Herein a novel microbial sensor probe (MiProbE) is applied to monitor and study the growth of tomatoes (Solanum lycopersicum L.) in real-time at germination and seedling stages. The result showed the raw Miprobe signals present day/night cycles. Alginate-coated probes effectively avoided signal response failure and were more sensitive to the treatments than uncoated probes. The probe signals from successfully germinated tomato seeds and non-germinated seeds were different, and the signal curve of the probe was closely related to the growth conditions of tomato seedlings. Specifically, the rising period of the probe signals coincided with the normal growth period of tomato seedlings. All probes exhibited sudden increases in signal strength after nutrient treatments; however, subsequent probe signals behaved differently: algae extract-treated probe signals maintained a high strength after the treatments; chemical fertilizer-treated probe signals decreased earlier after the treatments; chemical fertilizers and algae extract-treated probe signals also maintained a higher strength after the treatments. Moreover, the relationship between ash-free dry weight and the signal curve indicated that the signal strength positively correlates with the dry weight, although other biological activities can affect the probe signal at the same time. Further study is still needed to investigate the relationship between plant biomass and Miprobe signal.

As the world’s population exponentially grows, more food production is required. This increasing food production currently has led to the un-sustainable production of chemical fertilizers and resultant overuse. A more sustainable option to enhance food production could be the use of fertilizer derived from food waste. To address this, we investigated the possibility of utilizing a fertilizer derived from food waste to grow hydroponic vegetables. Arugula (Eruca sativa) ‘Slow Bolt’ and lettuce (Lactuca sativa) ‘Cherokee’ and ‘Rex’ were cultivated using indoor deep-flow hydroponic systems at 23 ºC under a photosynthetic photon flux density of 170 µmol∙m−2∙s−1 with an 18-hour photoperiod. Plant nutrient solutions were provided by food waste fertilizer or commercial 15:5:20 NPK fertilizer at the identical electrical conductivity (EC) of 2.3 mS·cm–1. At the EC of 2.3 mS·cm–1, chemical fertilizer contained 150 ppm N, 50 ppm P, and 200 ppm K, while food waste fertilizer had 60 ppm N, 26 ppm P, and 119 ppm K. Four weeks after the nutrient treatments were implemented, compared to plants grown with chemical fertilizer, lettuce ‘Rex’ grown with food waste fertilizer had four less leaves, 27.1% shorter leaves, 68.2% and 23.1% less shoot and root fresh weight, respectively. Lettuce ‘Cherokee’ and arugula grown with food waste fertilizer followed a similar trend with fresh shoot weights that were 80.1% and 95.6% less compared to the chemical fertilizer, respectively. In general, the magnitude of reduction in the plant growth was greatest in arugula. These results suggest that both fertilizers were able to successfully grow lettuce and arugula, although the reduced plant growth with the food waste fertilizer in our study is likely from a lower concentration of nutrients when we considered EC as an indicator of nutrient concentration equivalency of the two fertilizer types.