Long-duration space missions will require the use of bioregenerative life support systems (BLiSS) to ensure renewability of the crews food and oxygen. Sustainable management of these systems will require accurate predictions of biomass accumulation and gas exchanges from crop production. Four energy cascade (EC) models have been developed to predict biomass yield and transpiration rates of BLiSS crop production. Lettuce cultivars Waldmann's Green and BG231-1251 were grown at a daily average temperature of 21 degrees C, ambient CO2, and a daily light integral of 22.03 mol m-2 d-1 to evaluate the ECs predictive abilities. All ECs overestimated lettuce biomass and underestimate transpiration with root mean square errors ranging between 49.58 to 96.99 g m-2 and 0.80 to 2.30 L m-2 d-1, respectively. Global sensitivity analysis indicated that the ECs biomass predictions are insensitive to temperature changes. The ECs are additive with environmental parameters, such as light and CO2, accounting for half of any output's sensitivity. Interactions between parameters accounted for, at most, a third of the ECs sensitivity. The ECs provide a baseline for BLiSS crop management; however, this comprehensive, retrospective analysis reveals systematic biases in predictions of lettuce crops, stemming from erroneous canopy closure methodology and lack of temperature responses. Further work on lettuce, or other crops, can use this analysis as a benchmark to improve the range, accuracy, and reliability of the ECs for sustaining BLiSS and the astronauts they support.

Anthocyanins are non-photosynthetic pigments that absorb photons and thus decrease photosynthesis. Several studies have characterized the reduction in photosynthesis from anthocyanins by comparing high and low anthocyanin genotypes under single light intensity. We hypothesized that high anthocyanin levels would result in a greater reduction in photosynthesis in low than at high PPFD because anthocyanin-induced screening would have a stronger impact under limited conditions. We quantified the reduction of light-saturated gross photosynthesis (Pg) and quantum yield of CO2 (QYCO2) across eight lettuce cultivars ranging from 3.4 to 34 mg m− 2 anthocyanins, and report the photosynthetic effects over a range of wavelengths from 400 to 700 nm. We used spectral reflectance to quantify normalized difference anthocyanin index (NDAI), which ranged from − 0.24 to + 0.12. As expected, photosynthesis decreased as anthocyanin concentration increased, but surprisingly, the photosynthetic reduction was similar over a range of PPFDs from 50 to 1500 µmol m− 2 s− 1. The positive correlation between the absorptance at green wavelengths and NDAI suggest that anthocyanins filtered primarily green photons. Due to the screening effect of the green photons by anthocyanins, Pg and QYCO2 decreased from 45 to 82

Soilless media has long been used to improve fertilizer and water use efficiency of high-value crops in containers, and global demand for these media is predicted to increase 250% to 400% in the next 25 years. The environmental impact of all soilless media products warrants detailed analysis. The unique properties of peat make it the most widely used product. Peatlands are vital carbon stores and the historical degradation of European bogs has prompted regulations restricting peat extraction. Unlike Europe, North American peatlands—particularly in Canada—are largely pristine and have the potential to be sustainably managed. A focus on restoration, coupled with limited human interaction in remote peatlands, means that Canadian peatlands are currently accumulating carbon faster than the rate of extraction for containerized crop production. However, the steadily increasing use of soilless media for high-input agriculture may drive-up international demand for North American peat, requiring careful management to maintain sustainability. Several alternative products have been studied but our review of seven life cycle assessments reveals that their environmental impact is similar to or greater than peat. The expansion of high-input agriculture means that multiple soilless media components will be needed to feed our growing population.

Nighttime evapotranspiration (ETn) has been widely reported across plant species, yet its magnitude and physiological significance in controlled-environment crop production remain poorly understood. This study quantified ETn in lettuce (Lactuca sativa L. cv. Outredgeous) grown under controlled-environment conditions and evaluated nighttime-to-daytime ET dynamics under contrasting surface cover conditions. Plants were grown in peat-based root modules operated as zero-drainage systems, allowing ET to be quantified from continuous mass loss of individual nutrient reservoirs. Two surface treatments were compared: uncovered growth media and growth media covered with flexible silicone-rubber sheets incorporated as part of the evaluated growth-system configuration, which also suppressed evaporation (E). ET was partitioned into modeled E and modeled transpiration (T) components using the fraction of canopy cover derived from digital image analysis. During early development, modeled E was reduced by 87% in covered modules, enabling evaluation of ETn under minimized E conditions. After canopy closure, when T accounted for nearly all measured ET, the hourly nighttime-to-daytime ET ratio (ETn/ETd) averaged 0.46 for the uncovered treatment and 0.42 for the covered treatment (p < 0.001), indicating that substantial nighttime water loss persisted primarily through T in both treatments. However, these ETn/ETd ratios were only approximately half of the estimated apparent nighttime-to-daytime canopy stomatal conductance ratios (g(sn)/g(sd)), which averaged 0.82 and 0.75 in the uncovered and covered treatments, respectively. This difference indicates that nighttime ET was limited mainly by reduced evaporative demand, even though apparent canopy g(s) remained relatively close to daytime levels. Overall, silicone-rubber covers reduced cumulative water use by 32% without affecting biomass production, increasing water-use efficiency (WUE) from 2.5 to 3.8 g dry matter L-1 nutrient solution. These results demonstrate that substantial ETn persisted after canopy closure and was consistent with sustained nocturnal stomatal conductance under controlled-environment conditions, indicating that ETn can represent a major non-productive component of crop water use when E is minimized. Accounting for ETn may therefore improve ET estimates, water-use assessments, and environmental control strategies in controlled-environment agricultural systems.

Cannabis (Cannabis sativa) is a dioecious plant with many flower types. Academia currently uses multiple definitions of cannabis flowering that inadequately capture the diversity that occurs in variable temperatures and photoperiods. This perspective article reviews the imprecise flowering terminology that has created contradictions in research findings and confused the photoperiodic classification of cannabis. We describe new terminology to differentiate between two types of female reproductive structures with subclassifications for specific female flower appearances. "Botanical pistillate flowering" refers to the day-neutral single pistillate flowers that appear at the nodes of female and monoecious plants. "Commercial pistillate flowering" leads to a distinctive compound inflorescence and is marked by the appearance of a domed structure with three stigma pairs on the dominant growing point in female and monoecious plants. Female flowering can be further described as "early- or late-stage incomplete commercial pistillate flowering." Male reproductive structures develop into two forms. "Botanical staminate flowering" produces panicles with bell-shaped pedicellate flowers that have five petals, which open to reveal five anthers attached via anther filaments in male and monoecious plants. "Antheral flowering" is characterized by the appearance of single anthers or clusters of anthers that lack a pedicel and have no petals or filaments at the nodes or within the female inflorescence on monoecious plants. We include descriptive examples and photographs to facilitate the adoption of precise flowering terminology.

The future of agriculture depends on ever more efficient uses of fertilizer inputs. Nutrient management approaches in closed-system hydroponic culture commonly emphasize the need to continuously monitor and control ion concentrations. Here we describe and validate a mass-balance approach that uses the ratio of growth to transpiration (water use efficiency) to calculate nutrient requirements and achieve optimal nutrition without the need for individual ion monitoring. We define optimal nutrition as the minimum fertilizer input to achieve maximum growth. The hydroponic solution volume was maintained by refilling with a nutrient solution in which ion concentrations were calculated based on previously measured leaf nutrient concentrations from healthy plants. Mass-balance recovery of most elements in this closed system was greater than 90%. The yield and nutrient uptake of three diverse lettuce cultivars was consistent over twenty-five consecutive crop cycles (707 days) without replacing any solution. Active absorption of nitrogen (N), phosphorus (P), and potassium (K) led to low and steady solution concentrations of 5 ppm N, 1 ppm P, and 10 ppm K. In the first of three studies, the concentrations of calcium, magnesium, sulfur, boron, and copper increased over time, which indicated that their concentrations were excessive in the refill solution. A high solution concentration did not result in “force feeding” these elements into the plants. Their concentrations were reduced in the second long-term study (seven crop cycles across 196 days) and further reduced in the third long-term study (nine crop cycles across 252 days). These nutrient reductions resulted in constant concentrations and an electrical conductivity of 0.3 mS cm-1, which reduced the potential for gaseous N emissions. The third study included a treatment that replaced the nutrient solution after each harvest to maintain an EC of 1.0 mS cm-1. Despite the higher ion concentrations, solution replacement did not increase nutrient uptake or yield, and the increased calcium in solution did not reduce tipburn severity. We conclude that a mass-balance approach can be used to achieve optimal nutrition, maximum yield, and eliminate discharge across multiple crop cycles without continuous monitoring.

Blue (B; 400–499 nm) light, far-red (FR; 700–750 nm) light, and temperature are key regulators of plant growth and development, with responses varying by species. While the independent effects of these environmental signals are well established, their interactive effects are not clear. We postulated that the effects of FR light and temperature would depend on the photon flux density (PFD) of B light. To test this, we grew cold-tolerant lettuce and cold-sensitive basil at 19 and 24°C under lighting treatments with three FR fractions [FR-PFD divided by the sum of red (600–699 nm) and FR PFD; 0.01, 0.19, or 0.32] and two B-PFDs (40 or 100 µmol m−2 s−1). The total PFD (400–750 nm; 270 µmol m−2 s−1) and photoperiod (24 h d−1) were the same in all treatments. There were significant differences between species. As expected, increasing the FR fraction dramatically increased shoot expansion in lettuce and internode elongation in basil. The shoot expansion in lettuce was amplified by higher temperature but attenuated by higher B-PFD. Unlike lettuce, the FR effect on basil internodes did not interact with either temperature or B-PFD. The increased shoot expansion in lettuce decreased foliage coloration, but coloration was minimally altered in basil. These results reveal fundamentally different species responses to light and temperature that may have implications for shade-avoidant and shade-tolerant species. Overall, these findings demonstrate the complex integration of environmental signals in the regulation of growth.

Following the 2018 Farm Bill, many US states allowed for hundreds of industrial hemp licenses, and the resulting production flooded markets. Floral industrial hemp ( Cannabis sativa L.) offered prospects in essential oils for medicinal, flavoring, and fragrance additives. One major limitation for growers is the expense of Δ9‐tetrahydrocannabinol (Δ9THC) monitoring to meet legal compliance while maximizing cannabidiol (CBD) or cannabigerol (CBG) concentration for financial return. Cannabinoid analysis is not widely available, and shipping samples is legally challenging with state‐by‐state legislation. The study objectives were to evaluate whether near‐infrared spectroscopy (NIRS) could be used to rapidly and inexpensively quantify commonly produced hemp cannabinoid concentrations compared to industry standard high‐performance liquid chromatography (HPLC). A total of 448 tissue samples from 3 years of outdoor hemp cultivar, irrigation, and fertility trials were evaluated. Samples were dried and ground, and Δ8‐tetrahydrocannabinol (Δ8THC), Δ9THCD, tetrahydrocannabinolic acid (THCA), CBD, CBG, cannabichromene (CBC), cannabinol (CBN), cannabidivarin (CBDV), cannabidiol acid (CBDA), and cannabigerol acid (CBGA) were determined by HPLC with a diode array detector as reference measurements, prior to analysis by NIRS. Calibration equations were developed to assess whether NIRS can estimate cannabinoid concentrations. The three cannabinoids of most importance for floral hemp production (THCA, CBDA, and CBD) had the widest range in concentrations and the best correlation ( R 2 = 0.71–0.87) between NIRS and HPLC, while other cannabinoids had limited concentration ranges and poorer correlation. The THC and CBD results are highly encouraging and indicate that NIRS is a robust tool for rapid and inexpensive quantification.

Plant-based bioregenerative life-support systems play an essential role for long-duration space missions, offering a renewable source of fresh, nutritious food and psychological benefits for crew members. As human space missions extend further and last longer, developing efficient technologies for space agriculture becomes increasingly critical. In microgravity, altered fluid dynamics change water, nutrient, and gas distribution within the root-zone, potentially limiting plant growth. The Utah Reusable Root Module (URRM) system housed within NASA's Ohalo III Crop Production System addresses these challenges through five root modules equipped with automated fertigation, redundant moisture sensors, and media containment materials. Designed to support repetitive harvests of pick-and-eat vegetables with minimal crew intervention, the URRM advances water and nutrient management strategies for space-based agriculture. Preliminary ground tests with Mizuna (Brassica rapa var. nipposinica) demonstrated that the URRM maintained optimal root-zone conditions and uniform resource distribution, yielding more than 1 kg of fresh biomass over 17 days. The use of different top cover designs and materials across root modules affected plant establishment and yield, as well as evapotranspiration, whereas water use efficiency (WUE) exceeded 2 g L-1 across the system. These findings highlight the URRM's ability to support crop production using automated state-of-the-art technologies, strengthening the feasibility of long-term human space exploration.

Hemp ( Cannabis sativa L.) cultivar development rapidly progressed with floral hemp production legal in many US states following the 2018 Farm Bill. Desirable floral hemp cultivar traits include high biomass, high cannabidiol (CBD), cannabigerol (CBG), and other cannabinoids, and, most importantly, legally compliant Δ9‐tetrahydrocannabinol (THC) levels that avert crop destruction. As a reemerging crop, limited cultivar trials have been conducted recently in the United States. Further, improved understanding of floral initiation photoperiods and performance of various cultivars under commonly used overhead irrigation is needed. Field performance trials were conducted in 2020–2022 near Logan, UT, to test common regionally available cultivars and to determine floral initiation and subsequent harvest maturities. Available cultivars were different each year in a rapidly evolving market, but many cultivars were tested for multiple seasons. High variation and changes in cannabinoid concentrations near harvest provided evidence that early floral detection and harvest timing are critical for THC compliance. Early cultivars (15 h initiation) produced more floral compared to leaf biomass than those that flowered later. Later flower cultivars often produced statistically similar biomass weight among cultivars, but more leaf material compared to floral, evident with lower amounts of CBD and THC. The greatest CBD‐yielding cultivars at legal THC limits were Berry Blossom, Dutch Delight, and Trump with 10%–17% of all tested cultivars over the limit across the site‐years. However, high variability in performance and ranking of cultivars indicates that longer term testing may be required to select the most ideal cultivars for each region.

Aeration in deep-flow liquid hydroponics provides oxygen for respiration, but even gentle movement from solution agitation can alter the beneficial rhizosphere. Here we report the detrimental effects of bubbling-induced agitation of the rhizosphere on iron uptake and chlorosis of tomato, sunflower, and corn. We grew each species in deep-flow liquid hydroponics with aeration rates from 0 to 2 liters per minute and in a peat-based soilless media, which allowed plants to develop an undisturbed rhizosphere. All three species had ample iron and chlorophyll in soilless media with the same nutrient solution and pH as in liquid hydroponics. Conversely, chlorophyll and iron uptake were dramatically reduced in hydroponic sunflower and corn by gentle agitation of the solution. Tomato, however, was minimally affected by solution agitation. These results indicate that minimizing solution agitation allows the formation of a beneficial rhizosphere. Collectively, these studies demonstrate that controlled agitation might be used to alter root boundary layer thickness and thus quantify rhizosphere effects on nutrient uptake and growth.

An increasing far-red (FR; 700–750 nm) photon fraction typically triggers shade-avoidant responses such as leaf expansion, but previous work in lettuce has indicated that this occurs only at a higher extended photosynthetic photon flux density (ePPFD; 400–750 nm). We report the interaction between the FR photon fraction and ePPFD in spinach. We grew spinach in growth chambers under ePPFDs of 100, 200, and 500 µmol·m–2·s–1, each with an FR photon fraction of 0.03, 0.10, 0.17, or 0.33. Recent studies have demonstrated the photosynthetic value of FR photons, which makes it important to include these in the definition of photosynthetic photons. We thus substituted FR photons for shorter wavelength photons to keep photosynthetic photons (ePPFD) constant among treatments. As expected, leaf area and dry mass increased with increasing ePPFD; but, surprisingly, there was no effect of an increasing FR photon fraction on leaf area, regardless of ePPFD. These results show that FR photons are equivalent to shorter wavelength photons in spinach; but, unlike lettuce, an increasing FR fraction did not increase leaf area.

Elevating nutrient input is thought to increase yield and cannabinoid concentration of medical cannabis, but increased legalization has heightened awareness of the environmental impact of overfertilization. Elevated levels of phosphorus (P) are of particular concern. Here we report the effects of increasing P above levels adequate for other crops (15, 30, 45, 60, or 90 mg per L) and the interactive effects of elevated P with elevated nutrient solution concentration (electrical conductivity; 2 and 4 mS per cm). We used closed-system hydroponics to continuously quantify rootzone nutrient concentrations. The concentration of P in leaf tissue doubled and flower P concentration increased 70% when the P input increased from 15 to 90 mg per L but there was no difference in yield or quality among treatments. Doubling nutrient input from 2 to 4 mS per cm increased nutrient accumulation in solution but did not significantly increase yield or quality. Reducing P in the refill solution from 90 to 15 mg per L reduced P in solution at harvest from 300 to less than 0.1 mg per L. Despite the low steady-state concentration of P in solution in the 15 mg per L treatment, there was no difference in yield or quality among treatments, regardless of the concentration of other elements. Despite the high nutrient concentrations in the rootzone solution there was no leaf necrosis or other visual effects among treatments. These data indicate cannabis tolerates high nutrient concentrations, but neither excessive P nor excessive fertilization improves yield or quality.

Multiple studies have examined the use of chelates to correct pH-induced Fe chlorosis. Here we report the effects of three common chelates on prevention of Fe chlorosis in two sensitive species at high pH. Calibrachoa and soybean were grown in three media pH ranges (6.0 to 6.5, 7.0 to 7.2, and 7.6 to 7.8) and supplied with 1 mg·L−1 Fe as Fe-EDTA, Fe-DTPA, or Fe-EDDHA through fertigation. Chelate effectiveness was quantified by chlorosis rating and dry mass. In Calibrachoa, all three chelates prevented chlorosis at media pH up to 6.5, but above pH 7.2 only Fe-EDDHA was effective. Dry mass decreased as pH increased, but the decrease was less within the Fe-EDDHA treatment. Fe-DTPA was intermediate. There is a wide range in cost: Fe-EDDHA is currently four times, and Fe-DTPA is two times, the cost of Fe-EDTA. Fe-EDDHA binds Fe to pH 9, Fe-DTPA binds to pH 7.5, and Fe-EDTA binds to pH 6.5. Consistent with the stability constants for each chelate, the lower-cost Fe-EDTA chelate was effective in preventing chlorosis in Calibrachoa at media pH below 6.5. We conclude that the additional expense of Fe-DTPA and Fe-EDDHA is only necessary for Calibrachoa when the pH is above 6.5. However, Fe-EDDHA consistently resulted in greater dry mass of soybeans than Fe-EDTA in all pH levels. This suggests that Fe-EDDHA might improve growth of some species, even at a pH below 6.5.

Low concentrations of ammonium in hydroponic solutions typically improve plant growth and better simulate field conditions, but it is challenging to achieve steady-state levels because ammonium uptake is several orders of magnitude faster than nitrate uptake. Millimolar additions of ammonium cause rapid pH decreases because ammonium uptake is coupled with proton release from roots. We used an automated pH control system to add micromolar concentrations of ammonium several times an hour in combination with nitric acid. This stabilized pH and allowed for the addition of 3% to 13% of the nitrogen as ammonium. The type of ammonium salt was important: ammonium sulfate led to sulfur accumulation in solution and ammonium dihydrogen phosphate led to phosphorus (P) accumulation. Both salts caused intermittent pH decreases from pH 6 to 4. When the pH control solution included ammonium nitrate in a 1:2-M ratio with nitric acid there was no anion accumulation and a stable root zone pH. The resulting micromolar equilibrium concentration of ammonium facilitated repeated cropping of lettuce in the same solution at an electrical conductivity (EC) of 0.4 mS/cm without a decrease in yield. This better simulates field environments where ammonium ions are present at a low, steady concentration in the root zone solution.

Few studies have evaluated the fertilizer requirements of floral hemp ( Cannabis sativa L.). When hemp production was first legalized in Utah in 2019, many growers had questions about fertilizer requirements. Some crop consultants were advising growers that hemp required extremely high N and P rates for optimal production. The objective of this study was to evaluate N and P requirements of outdoor irrigated floral hemp production in the Intermountain West. A field study was established in 2020 near Logan, UT, replicated in 2021, and expanded in 2022. In 2020–2021, three treatments included a control (university fertilizer guidelines for corn [ Zea mays L.] given no reference for hemp) and 112 kg N ha −1 or 112 kg P 2 O 5 ha −1 above the control. The 2022 trial was expanded to include five fertilizer N levels, four fertilizer P levels, and a nonfertilized control. Female Trump hemp clones were transplanted in late May and harvested in September and October in all years. The results from 2020–2021 showed no harvest index (leaf and flower biomass: total aboveground biomass), biomass yield, stem yield, and cannabinoid concentration increases due to N or P above the recommended rates for corn. The results from 2022 were similar, and the nonfertilized control had the same oil and floral yield as all fertilized treatments. Collective interpretation indicates that hemp does not require more applied inorganic N or P than recommendations for corn and that fertilizer responsiveness may be limited. Further, excessively high N and P fertilizer rates should not be recommended for outdoor hemp.

An undesired flux of photons during an otherwise dark period is often referred to as light pollution (LP). This pollution is altering the biology of our planet. The effects have been well studied in animals, but are less well characterized in plants. Here were report the threshold sensitivity of three soybean and seven cannabis cultivars to light pollution. The effects of LP are thought to be mediated by phytochrome, and this hypothesis was evaluated by comparing responses from either cool white or red LP with estimated internal phytochrome photoequilbria of 0.57 and 0.87, respectively. Cultivar responses were highly variable, and the most sensitive cultivars of each species responded to a photon flux density of 0.01 mu mol m- 2 s-1 (10 nmol m- 2 s- 1). Plants exhibited delayed flowering, decreased inflorescence development rate, and increased vertical growth. Consistent with phytochrome mediated effects, red light caused greater photoperiodic disruption than white light. We found that soybeans that require longer nights to flower may be more tolerant to LP. Similarly, less-responsive cultivars of cannabis may have a longer critical night length. These findings illuminate the need for unpolluted darkness in photosensitive plants and establish physiological thresholds for LP quantity and quality.

The industrial hemp ( Cannabis sativa L.) industry rapidly emerged in Utah in 2019 with nearly 480 ha of production. Production declined rapidly due to flooded floral hemp markets, but the industry is still viable in the state. Two of the most pressing questions about hemp management among growers in this region include cultivar selection and irrigation management. An outdoor hemp research trial was established in 2020 near Logan, UT (41.66 N, −111.91 W), to investigate fundamental irrigation strategies and cultivar performance. This trial (2020–2021) examined combinations of three hemp cultivars, four irrigation technologies, and three irrigation rates (100%, 75%, 50% of estimated evapotranspiration of corn [ Zea mays L.] given lack of data for hemp) nested within each irrigation technology. Female hemp clones were transplanted in late May and harvested in September and October based on flower maturity. The irrigation technology (mid‐, low‐elevation spray, low‐elevation precision application, and mobile drip) had no significant impacts on hemp yield or cannabinoid concentrations. Hemp biomass yield and cannabidiol concentrations often increased with less applied irrigation in all irrigation technologies. The three hemp cultivars responded similarly to irrigation management, although there was high plant‐to‐plant variability in delta 9 tetrahydrocannabinol (THC) concentrations. This research suggested that floral hemp could be irrigated less than other crops in the region, and irrigation requirements among some hemp cultivars may be similar. Further, robust and representative sampling protocols for THC monitoring are needed to ensure variability is accounted for.

Precision water stress, achieved via osmotic stress, has the potential to control plant size and improve crop quality without reducing yield, but results across species and cultivars have been inconsistent. This study examined the effects of elevated salinity on two diverse Cannabis sativa cultivars, Trump and Cherry. One group (control group) was grown at 4 mS cm⁻¹ (-0.14 MPa), one group at 8 mS cm⁻¹ (-0.28 MPa), and a third (hybrid) group at 8 mS cm⁻¹ (to reduce vegetative growth) until flowering and then reduced to 4 mS cm⁻¹ to minimize effect on flower yield. Plant height was reduced 15

There have been multiple claims regarding detrimental effects of blue light on human health. Protective glasses sold as “blue light blocking” have been recommended for use under electric lights. Here we report the spectral transmission of eight types of lenses, five of which advertise blue light blocking capability. Color rendering index and color fidelity index were calculated to determine effects on color perception. Common light emitting diode (LED) fixtures use a blue LED with a peak output at 450 nm and have little output below 425 nm. Seven of the lenses primarily filtered wavelengths below 425 nm and thus provided minimal protection under LED fixtures. A lens from Bioshield filtered 98% of blue photons up to 500 nm but significantly altered color perception.