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Dr. Marc van Iersel
University of Georgia

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0 Floriculture
0 Horticulture
0 Lighting
0 Photosynthesis
0 Physiology

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Photosynthesis
Lighting
Physiology
Controlled environment agriculture
Horticulture
Vegetables
Floriculture

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Short Biography

Dr. Marc van Iersel received his PhD from the University of Arkansas in 1994. He has been with horticulture department of the University of Georgia since 1995, where he now holds the Dooley professorship. His research focuses on cost-effective supplemental lighting technologies in greenhouses and vertical farms. He is the director of project LAMP (www.hortlamp.org), a $5M, US-based research project that brings together plant scientists, engineers, and economists to develop profitable supplemental lighting strategies. In 2017, he co-founded Candidus, Inc. (www.candidus.us) to help bring novel lighting strategies to the greenhouse industry. Dr. van Iersel has published 130+ scientific papers and has given invited lectures about his research around the world, including in Italy, Spain, Taiwan, Kenya, Canada, Chile, and Brazil.

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Project

Project Goal: Controlled environment agriculture (greenhouses and plant factories) can help meet the challenge of more intensive, profitable, and sustainable specialty crop production. The greenhouse industry is a well-established and important component of US agriculture, with a 2015 farm-gate value of ~$6.5 billion. For efficient year-round production in greenhouses, supplemental light is often beneficial, but the expenses can be high. The electricity required for supplemental lighting in greenhouses can account for up to 20-30% of variable costs. Plant factories, an emerging technology where plants are grown indoors, provide total control over environmental conditions, but production relies entirely on electric lighting. Electric lighting and air-conditioning combined can account for 50-60% of the variable costs in plant factories. A recent Department of Energy report estimated the total annual costs of providing supplemental lighting in controlled environment agriculture to be ~$600,000,000/year in the US. More cost-effective lighting approaches will have a major impact on the sustainability and profitability of controlled environment agriculture (greenhouses and plant factories), reduce energy use and greenhouse gas emissions, and thus provide benefits for the controlled environment agriculture industry, society, and the environment. We will help growers get more value out of their lighting systems by providing horticultural and economical information and tools to manage the lights for optimal crop growth and quality and to maximize the return on investment.

Starting Date:01 August 2018

Current Stage: Ongoing

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Journal article
Published: 16 July 2021 in Computers and Electronics in Agriculture
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Supplemental lighting is an effective means for increasing greenhouse productivity. Recently, the use of light-emitting diodes (LEDs), capable of precise and quick dimmability, has increased in greenhouses. However, electricity cost of lighting can be significant, and hence, it is necessary to find optimal lighting strategies to minimize electrical lighting cost. In this paper, we model supplemental lighting in the greenhouses equipped with LEDs as a constrained optimization problem, and we aim to minimize electricity cost of supplemental lighting. We consider not only plant daily light integral (DLI) need during its photoperiod but also sunlight prediction and variable electricity pricing in our model. We use Markov chains to model sunlight irradiance and predict it during the day. By taking sunlight prediction information into account, we avoid supplying more light than the crop requires. Therefore, our lighting strategy prepares sufficient light for plant growth while minimizing electricity cost during the day. We propose an algorithm to find optimal supplemental lighting and evaluate its performance through exhaustive simulation studies using a whole year of weather data and compare it to a heuristic method, which aims to supply a fixed photosynthetic photon flux density (PPFD) to plants at each time step during the day. In addition to simulation studies, we also implemented the proposed lighting strategy in a research greenhouse in Athens, GA. Our prediction-based lighting approach shows (on average) over 45% electricity cost reduction compared to the heuristic method throughout the entire year.

ACS Style

Sahand Mosharafian; Shirin Afzali; Geoffrey M. Weaver; Marc van Iersel; Javad Mohammadpour Velni. Optimal lighting control in greenhouse by incorporating sunlight prediction. Computers and Electronics in Agriculture 2021, 188, 106300 .

AMA Style

Sahand Mosharafian, Shirin Afzali, Geoffrey M. Weaver, Marc van Iersel, Javad Mohammadpour Velni. Optimal lighting control in greenhouse by incorporating sunlight prediction. Computers and Electronics in Agriculture. 2021; 188 ():106300.

Chicago/Turabian Style

Sahand Mosharafian; Shirin Afzali; Geoffrey M. Weaver; Marc van Iersel; Javad Mohammadpour Velni. 2021. "Optimal lighting control in greenhouse by incorporating sunlight prediction." Computers and Electronics in Agriculture 188, no. : 106300.

Journal article
Published: 06 April 2021 in Plants
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Vertical farming is increasingly popular due to high yields obtained from a small land area. However, the energy cost associated with lighting of vertical farms is high. To reduce this cost, more energy efficient (biomass/energy use) crops are required. To understand how efficiently crops use light energy to produce biomass, we determined the morphological and physiological differences between mizuna (Brassica rapa var. japonica) and lettuce (Lactuca sativa ‘Green Salad Bowl’). To do so, we measured the projected canopy size (PCS, a morphological measure) of the plants throughout the growing cycle to determine the total amount of incident light the plants received. Total incident light was used together with the final dry weight to calculate the light use efficiency (LUE, g of dry weight/mol of incident light), a physiological measure. Plants were grown under six photosynthetic photon flux densities (PPFD), from 50 to 425 µmol m−2 s−1, for 16 h d−1. Mizuna and lettuce were harvested 27 and 28 days after seeding, respectively. Mizuna had greater dry weight than lettuce (p < 0.0001), especially at higher PPFDs (PPFD ≥ 125 µmol m−2 s−1), partly because of differences in the projected canopy size (PCS). Mizuna had greater PCS than lettuce at PPFDs ≥ 125 µmol m−2 s−1 and therefore, the total incident light over the growing period was also greater. Mizuna also had a higher LUE than lettuce at all six PPFDs. This difference in LUE was associated with higher chlorophyll content index and higher quantum yield of photosystem II in mizuna. The combined effects of these two factors resulted in higher photosynthetic rates in mizuna than in lettuce (p = 0.01). In conclusion, the faster growth of mizuna is the result of both a larger PCS and higher LUE compared to lettuce. Understanding the basic determinants of crop growth is important when screening for rapidly growing crops and increasing the efficiency of vertical farms.

ACS Style

Theekshana Jayalath; Marc van Iersel. Canopy Size and Light Use Efficiency Explain Growth Differences between Lettuce and Mizuna in Vertical Farms. Plants 2021, 10, 704 .

AMA Style

Theekshana Jayalath, Marc van Iersel. Canopy Size and Light Use Efficiency Explain Growth Differences between Lettuce and Mizuna in Vertical Farms. Plants. 2021; 10 (4):704.

Chicago/Turabian Style

Theekshana Jayalath; Marc van Iersel. 2021. "Canopy Size and Light Use Efficiency Explain Growth Differences between Lettuce and Mizuna in Vertical Farms." Plants 10, no. 4: 704.

Journal article
Published: 15 March 2021 in Sensors
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Plants naturally contain high levels of the stress-responsive fluorophore chlorophyll. Chlorophyll fluorescence imaging (CFI) is a powerful tool to measure photosynthetic efficiency in plants and provides the ability to detect damage from a range of biotic and abiotic stresses before visible symptoms occur. However, most CFI systems are complex, expensive systems that use pulse amplitude modulation (PAM) fluorometry. Here, we test a simple CFI system, that does not require PAM fluorometry, but instead simply images fluorescence emitted by plants. We used this technique to visualize stress induced by the photosystem II-inhibitory herbicide atrazine. After applying atrazine as a soil drench, CFI and color images were taken at 15-minute intervals, alongside measurements from a PAM fluorometer and a leaf reflectometer. Pixel intensity of the CFI images was negatively correlated with the quantum yield of photosystem II (ΦPSII) (p < 0.0001) and positively correlated with the measured reflectance in the spectral region of chlorophyll fluorescence emissions (p < 0.0001). A fluorescence-based stress index was developed using the reflectometer measurements based on wavelengths with the highest (741.2 nm) and lowest variability (548.9 nm) in response to atrazine damage. This index was correlated with ΦPSII (p < 0.0001). Low-cost CFI imaging can detect herbicide-induced stress (and likely other stressors) before there is visual damage.

ACS Style

Reeve Legendre; Nicholas Basinger; Marc van Iersel. Low-Cost Chlorophyll Fluorescence Imaging for Stress Detection. Sensors 2021, 21, 2055 .

AMA Style

Reeve Legendre, Nicholas Basinger, Marc van Iersel. Low-Cost Chlorophyll Fluorescence Imaging for Stress Detection. Sensors. 2021; 21 (6):2055.

Chicago/Turabian Style

Reeve Legendre; Nicholas Basinger; Marc van Iersel. 2021. "Low-Cost Chlorophyll Fluorescence Imaging for Stress Detection." Sensors 21, no. 6: 2055.

Journal article
Published: 15 February 2021 in Agronomy
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Fertilizer recommendations for peach cultivation in the southeastern United States were developed decades ago and may not reflect the peach trees’ needs under current cultivation practices. Adequate fertilization for young peach trees induces a balanced vegetative/reproductive growth, ensures efficient resource use, and is environmentally sound. Droughts in the region are becoming more common. Supplemental irrigation for peaches from the time of field establishment serves as insurance in case drought conditions occur and can increase/advance the yield of young peach trees. Our objective was to determine the influence of different fertilizer levels (25, 50, 100, and 200% of the recommended rate), irrigation levels (irrigated vs. non-irrigated), and irrigation systems (drip vs. micro-sprinkler) on nitrogen partitioning and concentration in different organs of young peach trees. The cumulative nitrogen (N) removal per tree was not affected by the different fertilizer levels. Most of the N allocation was accounted for by summer pruning and defoliation (68% of the total N removed). Irrigated trees had higher cumulative N removal after three years than non-irrigated trees, with differences between irrigated vs. non-irrigated trees in most vegetative removal events (winter and summer pruning, and defoliation). Drip-irrigated trees had higher cumulative N removal after three years than micro-sprinkler-irrigated tress, with differences in N removal found in vegetative and reproductive removal events. Differences in N removal were mainly driven by differences in dry weight rather than the N concentration of the organs. These results suggest that different fertilizer levels did not alter the N partitioning in young peach trees, indicating that reduction in fertilizer applications can be done without negative effects. Furthermore, irrigation induced greater vegetative growth, especially under drought conditions, which may result in greater canopy volume and fruit yield compared to non-irrigated trees. Differences between irrigation systems are not consistent; however, drip is more efficient than micro-sprinkler irrigation, with ~38% water savings.

ACS Style

Bruno Casamali; Marc van Iersel; Dario Chavez. Nitrogen Partitioning in Young “Julyprince” Peach Trees Grown with Different Irrigation and Fertilization Practices in the Southeastern United States. Agronomy 2021, 11, 350 .

AMA Style

Bruno Casamali, Marc van Iersel, Dario Chavez. Nitrogen Partitioning in Young “Julyprince” Peach Trees Grown with Different Irrigation and Fertilization Practices in the Southeastern United States. Agronomy. 2021; 11 (2):350.

Chicago/Turabian Style

Bruno Casamali; Marc van Iersel; Dario Chavez. 2021. "Nitrogen Partitioning in Young “Julyprince” Peach Trees Grown with Different Irrigation and Fertilization Practices in the Southeastern United States." Agronomy 11, no. 2: 350.

Journal article
Published: 16 January 2021 in Plants
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Light-emitting diodes allow for the application of specific wavelengths of light to induce various morphological and physiological responses. In lettuce (Lactuca sativa), far-red light (700–800 nm) is integral to initiating shade responses which can increase plant growth. In the first of two studies, plants were grown with a similar photosynthetic photon flux density (PPFD) but different intensities of far-red light. The second study used perpendicular gradients of far-red light and PPFD, allowing for examination of interactive effects. The far-red gradient study revealed that increasing supplemental far-red light increased leaf length and width, which was associated with increased projected canopy size (PCS). The higher PCS was associated with increased cumulative incident light received by plants, which increased dry matter accumulation. In the perpendicular gradient study, far-red light was 57% and 183% more effective at increasing the amount of light received by the plant, as well as 92.5% and 162% more effective at increasing plant biomass at the early and late harvests, respectively, as compared to PPFD. Light use efficiency (LUE, biomass/mol incident light) was generally negatively correlated with specific leaf area (SLA). Far-red light provided by LEDs increases the canopy size to capture more light to drive photosynthesis and shows promise for inclusion in the growth light spectrum for lettuce under sole-source lighting.

ACS Style

Reeve Legendre; Marc van Iersel. Supplemental Far-Red Light Stimulates Lettuce Growth: Disentangling Morphological and Physiological Effects. Plants 2021, 10, 166 .

AMA Style

Reeve Legendre, Marc van Iersel. Supplemental Far-Red Light Stimulates Lettuce Growth: Disentangling Morphological and Physiological Effects. Plants. 2021; 10 (1):166.

Chicago/Turabian Style

Reeve Legendre; Marc van Iersel. 2021. "Supplemental Far-Red Light Stimulates Lettuce Growth: Disentangling Morphological and Physiological Effects." Plants 10, no. 1: 166.

Journal article
Published: 28 October 2020 in Agronomy
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Light recommendations for horticultural crops often focus on the optimal daily light integral (DLI) without regard to how that light is delivered throughout each day. Because photosynthesis is more efficient at lower photosynthetic photon flux density (PPFD), we hypothesized that longer photoperiods with lower PPFD results in faster growth than shorter photoperiods with higher PPFD and the same DLI. We quantified the effect of different photoperiods, all providing the same DLI, on photosynthesis and growth of two leafy greens. Mizuna (Brassica rapa var. japonica) and lettuce (Lactuca sativa) “Little Gem” were grown from seed in a controlled environment chamber (20 °C and 819 µmol·mol−1 CO2) under six photoperiods (10, 12, 14, 16, 18, and 20 h). LED fixtures provided white light and PPFD was adjusted so each treatment received a DLI of 16 mol·m−2·d−1. Mizuna and lettuce were harvested 30 and 41 days after planting, respectively. Longer photoperiods with lower PPFD increased light interception, chlorophyll content index, quantum yield of photosystem II, and aboveground biomass, but decreased instantaneous CO2 assimilation of lettuce and mizuna. Aboveground biomass increased 16.0% in lettuce and 18.7% in mizuna in response to increasing the photoperiod from 10 to 20 h. In summary, extending the photoperiod and lowering PPFD increases growth of lettuce and mizuna by increasing light interception and the quantum yield of photosystem II.

ACS Style

Shane Palmer; Marc Van Iersel. Increasing Growth of Lettuce and Mizuna under Sole-Source LED Lighting Using Longer Photoperiods with the Same Daily Light Integral. Agronomy 2020, 10, 1659 .

AMA Style

Shane Palmer, Marc Van Iersel. Increasing Growth of Lettuce and Mizuna under Sole-Source LED Lighting Using Longer Photoperiods with the Same Daily Light Integral. Agronomy. 2020; 10 (11):1659.

Chicago/Turabian Style

Shane Palmer; Marc Van Iersel. 2020. "Increasing Growth of Lettuce and Mizuna under Sole-Source LED Lighting Using Longer Photoperiods with the Same Daily Light Integral." Agronomy 10, no. 11: 1659.

Journal article
Published: 30 September 2020 in Horticulturae
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Blueberry fruit are perishable after harvesting due to fruit softening, water loss and susceptibility to pathogens. Light, especially blue light, increases the accumulation of anthocyanins and reduces postharvest decay in some fruits, but the effect of blue light on postharvest fruit quality attributes in blueberries is unknown. In this study, we evaluated the effect of blue light on fruit quality, anthocyanin accumulation and disease development during postharvest cold storage (2 °C–4 °C) in two experiments with southern highbush blueberry ‘Star’ and rabbiteye blueberry ‘Alapaha’. Overall, diurnal blue light did not affect postharvest fruit quality attributes, such as visual defects, fruit compression, skin puncture, total soluble solid content and titratable acidity, in the two cultivars compared with their respective controls (diurnal white light or continuous darkness). Further, there was no effect of blue light on fruit color and anthocyanin accumulation. Fruit disease incidence in ‘Star’ ranged from 19.0% to 27.3% after 21 days and in ‘Alapaha’ from 44.9% to 56.2% after 24 days in postharvest storage, followed by 4 days at room temperature, but blue light had no consistent effect on postharvest disease incidence for either cultivar. Disease progression following artificial inoculations with Alternaria tenuissima and Colletotrichum acutatum in ‘Star’ was not influenced by light treatment prior to inoculation and during fruit storage. In a separate experiment, we tested the effect of blue light on color development in ‘Farthing’, a southern highbush blueberry cultivar with fruit prone to non-uniform ripening, whereby the stem-end remains green as the rest of the fruit turns blue. Although green stem-end spots turned blue over time, there was no statistically significant effect of the blue light treatment. Overall, these data indicate that blue light does not affect fruit quality attributes or disease development in ripe blueberry fruit during postharvest storage in the conditions investigated here.

ACS Style

Yi-Wen Wang; Helaina Ludwig; Harald Scherm; Marc van Iersel; Savithri Nambeesan. Blue Light Does Not Affect Fruit Quality or Disease Development on Ripe Blueberry Fruit During Postharvest Cold Storage. Horticulturae 2020, 6, 59 .

AMA Style

Yi-Wen Wang, Helaina Ludwig, Harald Scherm, Marc van Iersel, Savithri Nambeesan. Blue Light Does Not Affect Fruit Quality or Disease Development on Ripe Blueberry Fruit During Postharvest Cold Storage. Horticulturae. 2020; 6 (4):59.

Chicago/Turabian Style

Yi-Wen Wang; Helaina Ludwig; Harald Scherm; Marc van Iersel; Savithri Nambeesan. 2020. "Blue Light Does Not Affect Fruit Quality or Disease Development on Ripe Blueberry Fruit During Postharvest Cold Storage." Horticulturae 6, no. 4: 59.

Journal article
Published: 10 September 2020 in Plants
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Controlled environment crop production recommendations often use the daily light integral (DLI) to quantify the light requirements of specific crops. Sole-source electric lighting, used in plant factories, and supplemental electric lighting, used in greenhouses, may be required to attain a specific DLI. Electric lighting is wasteful if not provided in a way that promotes efficient photochemistry. The quantum yield of photosystem II (ΦPSII), the fraction of absorbed light used for photochemistry, decreases with increasing photosynthetic photon flux density (PPFD). Thus, we hypothesized that the daily photochemical integral (DPI), the total electron transport through photosystem II (PSII) integrated over 24 h, would increase if the same DLI was provided at a lower PPFD over a longer photoperiod. To test this, ΦPSII and the electron transport rate (ETR) of lettuce (Lactuca sativa ‘Green Towers’) were measured in a growth chamber at DLIs of 15 and 20 mol m−2 d−1 over photoperiods ranging from 7 to 22 h. This resulted in PPFDs of 189 to 794 μmol m−2 s−1. The ΦPSII decreased from 0.67 to 0.28 and ETR increased from 55 to 99 μmol m−2 s−1 as PPFD increased from 189 to 794 μmol m−2 s−1. The DPI increased linearly as the photoperiod increased, but the magnitude of this response depended on DLI. With a 7-h photoperiod, the DPI was ≈2.7 mol m−2 d−1, regardless of DLI. However, with a 22-h photoperiod, the DPI was 4.54 mol m−2 d−1 with a DLI of 15 mol m−2 d−1 and 5.78 mol m−2 d−1 with a DLI of 20 mol m−2 d−1. Our hypothesis that DPI can be increased by providing the same DLI over longer photoperiods was confirmed.

ACS Style

Claudia Elkins; Marc W. Van Iersel. Longer Photoperiods with the Same Daily Light Integral Increase Daily Electron Transport through Photosystem II in Lettuce. Plants 2020, 9, 1172 .

AMA Style

Claudia Elkins, Marc W. Van Iersel. Longer Photoperiods with the Same Daily Light Integral Increase Daily Electron Transport through Photosystem II in Lettuce. Plants. 2020; 9 (9):1172.

Chicago/Turabian Style

Claudia Elkins; Marc W. Van Iersel. 2020. "Longer Photoperiods with the Same Daily Light Integral Increase Daily Electron Transport through Photosystem II in Lettuce." Plants 9, no. 9: 1172.

Journal article
Published: 01 April 2020 in HortScience
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Supplemental lighting can improve the growth of greenhouse crops, but the electricity required for supplemental lighting can be a significant expense for greenhouse growers. Lighting control strategies that use the dimmability of light-emitting diodes (LEDs) have the potential to decrease this cost. In our experiments, we tested the hypothesis that providing ‘Little Gem’ lettuce (Lactuca sativa) plants with the same daily amount of light, spread out over a longer photoperiod and at lower average photosynthetic photon flux densities (PPFDs), would improve growth because light is used more efficiently to drive photosynthesis at lower PPFDs. We conducted two greenhouse experiments wherein supplemental light was provided to reach a minimum daily light integral (DLI) of 17 mol·m−2·d−1 with a 12, 15, 18, or 21-hour photoperiod using adaptive lighting control of LED lights. As the photoperiod for supplemental lighting was increased and supplemental light was provided at lower average PPFDs, plant dry weight increased. Conversion efficiency, the estimated increase in dry weight per Joule expended on supplemental lighting, increased as the photoperiod was extended from 12 to 21 hours. Leaf size and chlorophyll content index increased with longer photoperiods. The number of plants with symptoms of tipburn, including apical and marginal necrosis, also increased as the photoperiod was extended. These results demonstrate that adaptive lighting control can be used to increase the growth of ‘Little Gem’ lettuce and the energy use efficiency of supplemental lighting by providing supplemental light at relatively low PPFDs.

ACS Style

Geoffrey Weaver; Marc van Iersel. Longer Photoperiods with Adaptive Lighting Control Can Improve Growth of Greenhouse-grown ‘Little Gem’ Lettuce (Lactuca sativa). HortScience 2020, 55, 573 -580.

AMA Style

Geoffrey Weaver, Marc van Iersel. Longer Photoperiods with Adaptive Lighting Control Can Improve Growth of Greenhouse-grown ‘Little Gem’ Lettuce (Lactuca sativa). HortScience. 2020; 55 (4):573-580.

Chicago/Turabian Style

Geoffrey Weaver; Marc van Iersel. 2020. "Longer Photoperiods with Adaptive Lighting Control Can Improve Growth of Greenhouse-grown ‘Little Gem’ Lettuce (Lactuca sativa)." HortScience 55, no. 4: 573-580.

Journal article
Published: 01 March 2020 in Journal of Environmental Horticulture
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A soil moisture sensor-based automated irrigation system was trialed in a commercial ornamental nursery over the 2014-2015 growing seasons. In both years, use of the sensor-based system resulted in an approximate 50% reduction in irrigation application (volume) when compared to grower-managed irrigation. No differences in growth and equivalent or slightly reduced crop losses were noted when comparing the sensor-based irrigation system to grower-managed irrigation in production of Pieris japonica, Hydrangea quercifolia, and Kalmia latifolia. In 2014, Rhododendron catawbiense had equivalent canopy size and reduced mortality when comparing sensor-based irrigation to grower-managed irrigation. However, in 2015 irrigation control with the sensor-based system resulted in significant (>50%) Rhododendron losses. High mortality was thought to have resulted from use of averaged (across crop species) soil moisture readings to establish irrigation set points. Canopy structure of Rhododendron obstructed water capture to a greater degree than the other three species due to canopy architecture. This effect, combined with precision irrigation applications, resulted in persistent drought conditions within the Rhododendron block. Soil moisture sensor-based automated irrigation can be an effective means of automating irrigation. Support from crop consultants is highly desirable to minimize disruption and maximize adoption during implementation. Index words: Pieris Japonica D. Don ex G. Don ‘Prelude', Hydrangea quercifolia W. Bartram ‘Jet Stream', Rhododendron catawbiense Michx. ‘Roseum Elegans', Kalmia latifolia L. ‘Sarah', irrigation groupings, automation, canopy structure, irrigation capture, technology transfer, outreach, education, precision irrigation Species used in this study: Japanese andromeda ‘Prelude' (Pieris Japonica D. Don ex G. Don); Oakleaf hydrangea ‘Jet Stream' (Hydrangea quercifolia W. Bartram); Rhododendron ‘Roseum Elegans' (Rhododendron catawbiense Michx.); Mountain laurel ‘Sarah' (Kalmia latifolia L.)

ACS Style

William D. Wheeler; Matthew Chappell; Marc van Iersel; Paul Thomas. Implementation of Soil Moisture Sensor Based Automated Irrigation in Woody Ornamental Production1. Journal of Environmental Horticulture 2020, 38, 1 -7.

AMA Style

William D. Wheeler, Matthew Chappell, Marc van Iersel, Paul Thomas. Implementation of Soil Moisture Sensor Based Automated Irrigation in Woody Ornamental Production1. Journal of Environmental Horticulture. 2020; 38 (1):1-7.

Chicago/Turabian Style

William D. Wheeler; Matthew Chappell; Marc van Iersel; Paul Thomas. 2020. "Implementation of Soil Moisture Sensor Based Automated Irrigation in Woody Ornamental Production1." Journal of Environmental Horticulture 38, no. 1: 1-7.

Journal article
Published: 01 May 2019 in Journal of the American Society for Horticultural Science
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Bedding plants are at increased risk for exposure to drought stress during production because they are grown in small containers. Physiological mechanisms of bedding plants at leaf and cellular scales that regulate whole-plant photosynthesis under drought conditions are not well understood. This information can be useful for screening bedding plant cultivars with improved drought-tolerance and generate guidelines to mitigate drought stress during production. We subjected drought-sensitive salvia (Salvia splendens ‘Bonfire Red’) and drought-tolerant vinca (Catharanthus roseus ‘Cooler Peppermint’) to gradual drought stress inside whole-plant gas exchange chambers. Substrate water content (Θ), whole-plant net photosynthesis (Pn_avg), whole-plant respiration (Rd_avg), and daily carbon gain (DCG) were measured continuously, whereas stomatal conductance (gS) to water, leaf water (ΨL), osmotic (ΨS), and turgor (ΨP) potentials were measured at the start and end of the drought phase. In addition, ΨS was measured before exposure to stress and after thoroughly rehydrating plants. Dark-adapted quantum efficiency (dark-adapted ΦPSII) was measured after rehydrating plants. The results indicated that, at whole-plant scale, vinca continued to uptake water at lower Θ levels than the Θ level that resulted in wilting of salvia. There were no differences in Rd_avg; however, Pn_avg and DCG of salvia decreased at a higher Θ level than that of vinca. This indicated that salvia experienced drought stress at a higher Θ level than did vinca. At the leaf scale, there were no differences in ΨL; however, a more negative ΨS (P = 0.06) and significantly higher ΨP were observed in vinca (compared to salvia) under drought conditions. In addition, ΨS was not different between species before exposure to drought, whereas ΨS of rehydrated leaves after exposure to drought in vinca was significantly lower than that in salvia. Moreover, ΨS of rehydrated leaves after exposure to drought was significantly lower than that observed before exposure to drought in vinca. This indicated osmotic adjustment (OA) in vinca under drought conditions. Dark-adapted ΦPSII was lower in salvia than in vinca after exposure to drought, indicating damage to photosynthetic mechanisms. Our results suggested that increased OA likely helped to maintain higher ΨP under drought conditions and continuation of water uptake at lower Θ in vinca compared to salvia. In addition, healthier photosynthetic mechanisms of vinca (compared to salvia) under drought conditions likely resulted in its higher Pn_avg and DCG at lower Θ. Screening for OA and dark-adapted ΦPSII may be useful for developing drought-tolerant bedding plant cultivars.

ACS Style

Krishna Nemali; Marc van Iersel. Relating Whole-plant Photosynthesis to Physiological Acclimations at Leaf and Cellular Scales under Drought Stress in Bedding Plants. Journal of the American Society for Horticultural Science 2019, 144, 201 -208.

AMA Style

Krishna Nemali, Marc van Iersel. Relating Whole-plant Photosynthesis to Physiological Acclimations at Leaf and Cellular Scales under Drought Stress in Bedding Plants. Journal of the American Society for Horticultural Science. 2019; 144 (3):201-208.

Chicago/Turabian Style

Krishna Nemali; Marc van Iersel. 2019. "Relating Whole-plant Photosynthesis to Physiological Acclimations at Leaf and Cellular Scales under Drought Stress in Bedding Plants." Journal of the American Society for Horticultural Science 144, no. 3: 201-208.

Journal article
Published: 24 April 2019 in Biosystems Engineering
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Supplemental lighting in greenhouses can increase crop growth, improving rates of greenhouse production. The advent of light-emitting diodes (LEDs) for photosynthetic lighting presents new opportunities for optimising greenhouse supplemental lighting control. Because LED light intensity can be controlled rapidly and precisely in real time, these lights can be controlled such that supplemental light is provided when it will be most efficiently used to drive photosynthesis. This approach to supplemental lighting control has the potential to reduce the electricity cost associated with greenhouse lighting while retaining the beneficial effects on crop growth, thereby decreasing the financial cost and improving the sustainability of greenhouse crop production. In this paper, an optimisation problem is formulated to minimise the total amount of electricity used by supplemental LED lights, subject to achieving a specified daily amount of photochemistry. An algorithm to solve the problem explicitly based on sufficient conditions for a global minimiser is developed. This method represents a computationally simple and broadly applicable means for minimising the amount of electricity required for supplemental lighting in greenhouses.

ACS Style

Geoffrey M. Weaver; Marc van Iersel; Javad Mohammadpour Velni. A photochemistry-based method for optimising greenhouse supplemental light intensity. Biosystems Engineering 2019, 182, 123 -137.

AMA Style

Geoffrey M. Weaver, Marc van Iersel, Javad Mohammadpour Velni. A photochemistry-based method for optimising greenhouse supplemental light intensity. Biosystems Engineering. 2019; 182 ():123-137.

Chicago/Turabian Style

Geoffrey M. Weaver; Marc van Iersel; Javad Mohammadpour Velni. 2019. "A photochemistry-based method for optimising greenhouse supplemental light intensity." Biosystems Engineering 182, no. : 123-137.

Short communication
Published: 01 April 2019 in Scientia Horticulturae
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To acquire accurate volumetric water content (VWC) measurements from horticultural substrates using dielectric sensors, a substrate-specific calibration is critical. Calibrations typically are conducted with a substrate without plants, but water in the root system may affect soil moisture sensor readings. We investigated the effect of root growth on the measured VWC. Lettuce seedlings (Lactuca sativa L. ‘Joek Chi Ma’) were grown in 10 cm round containers (440 mL) filled with soilless substrate. Four EC-5 soil moisture sensors (Decagon Devices Inc., Pullman, WA, USA) were used to determine the effect of root system size on sensor calibration over an eight week period. Both calibration coefficients (slope and intercept) decreased (P < 0.001) with increasing root system size. The actual VWC at 8 weeks after transplanting (WAT) was 9% lower at 65% VWC compared to the estimated VWC from the substrate-only calibration. Multiple regression models indicated that various root size indicators (WAT, root fresh weight, root dry weight, and root water content) all had a negative effect on the estimation of VWC. The effect of root system size on estimated VWC may be tolerable in production, but should be considered in research applications. Careful interpretation is needed when using FDR soil moisture sensors to monitor substrate VWC in the presence of a growing root system.

ACS Style

SeongHwan Kang; Marc van Iersel; Jongyun Kim. Plant root growth affects FDR soil moisture sensor calibration. Scientia Horticulturae 2019, 252, 208 -211.

AMA Style

SeongHwan Kang, Marc van Iersel, Jongyun Kim. Plant root growth affects FDR soil moisture sensor calibration. Scientia Horticulturae. 2019; 252 ():208-211.

Chicago/Turabian Style

SeongHwan Kang; Marc van Iersel; Jongyun Kim. 2019. "Plant root growth affects FDR soil moisture sensor calibration." Scientia Horticulturae 252, no. : 208-211.

Journal article
Published: 01 February 2019 in HortScience
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Plant light use efficiency decreases as light intensity is increased, and a better understanding of crop-specific light responses can contribute to the development of more energy-efficient supplemental lighting control strategies for greenhouses. In this study, diurnal chlorophyll fluorescence monitoring was used to characterize the photochemical responses of ‘Green Towers’ lettuce (Lactuca sativa L.) to photosynthetic photon flux density (PPFD) and daily light integral (DLI) in a greenhouse during a production cycle. Plants were monitored continuously for 35 days, with chlorophyll fluorescence measurements collected once every 15 minutes. Quantum yield of photosystem II (ΦPSII) decreased exponentially with PPFD, whereas electron transport rate (ETR) increased asymptotically to 121 µmol·m–2·s–1. Daily photochemical integral (DPI) is defined as the integral of ETR over a 24-hour period; DPI increased asymptotically to 3.29 mol·m–2·d–1 with increasing DLI. No effects of plant age or prior day’s DLI and a negligible effect of PPFDs 15 or 30 minutes before measurements within days were observed. Simulations were conducted using the regression equation of ETR as a function of PPFD {ETR = 121[1 – exp(–0.00277PPFD)]} to illustrate methods of increasing photochemical light use efficiency for improved supplemental lighting control strategies. For a given DLI, DPI can be increased by providing light at lower PPFDs for a longer period of time, and can be maximized by providing light with a uniform PPFD throughout the entire photoperiod. Similarly, the DLI required to achieve a given DPI is reduced using these same methods.

ACS Style

Geoffrey Weaver; Marc van Iersel. Photochemical Characterization of Greenhouse-grown Lettuce (Lactuca sativa L. ‘Green Towers’) with Applications for Supplemental Lighting Control. HortScience 2019, 54, 317 -322.

AMA Style

Geoffrey Weaver, Marc van Iersel. Photochemical Characterization of Greenhouse-grown Lettuce (Lactuca sativa L. ‘Green Towers’) with Applications for Supplemental Lighting Control. HortScience. 2019; 54 (2):317-322.

Chicago/Turabian Style

Geoffrey Weaver; Marc van Iersel. 2019. "Photochemical Characterization of Greenhouse-grown Lettuce (Lactuca sativa L. ‘Green Towers’) with Applications for Supplemental Lighting Control." HortScience 54, no. 2: 317-322.

Journal article
Published: 01 December 2018 in HortTechnology
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A soil moisture sensor-based automated irrigation system was trialed in a commercial floriculture greenhouse to determine what benefits these types of systems may offer to herbaceous ornamental producers. Water use, crop quality and growth, and grower behavior toward adoption of the new technology were monitored, when all decision making related to system operation was carried out by the grower. Two cultivars of poinsettia (Euphorbia ×pulcherrima) and three cultivars of geranium (Pelargonium ×hortorum) were produced in side-by-side trials over the course of 2 years while comparing grower-controlled, sensor-based automated irrigation with traditional grower-managed (timer-based) irrigation. Plant quality was equivalent between irrigation treatments across all five trials. Differences in plant size were noted in four of the five trials between irrigation treatments, but in all instances these differences were not judged by the commercial grower to impact marketability of the crop. No reductions in irrigation water use were noted with the sensor-based irrigation system, which differed from previous research using this technology in ornamental production. Over the course of 2 years, the number of plants produced using sensor-based irrigation control was scaled up, indicating increasing confidence in, and adoption of, the technology. Managers at the facility found that sensor-based irrigation facilitated reallocation of labor from irrigation management, which was especially valuable during peak production and shipping periods. The payback period calculated from labor savings would be roughly 1.5 years if the sensor-based irrigation system was implemented throughout the facility.

ACS Style

William D. Wheeler; Paul Thomas; Marc van Iersel; Matthew Chappell. Implementation of Sensor-based Automated Irrigation in Commercial Floriculture Production: A Case Study. HortTechnology 2018, 28, 719 -727.

AMA Style

William D. Wheeler, Paul Thomas, Marc van Iersel, Matthew Chappell. Implementation of Sensor-based Automated Irrigation in Commercial Floriculture Production: A Case Study. HortTechnology. 2018; 28 (6):719-727.

Chicago/Turabian Style

William D. Wheeler; Paul Thomas; Marc van Iersel; Matthew Chappell. 2018. "Implementation of Sensor-based Automated Irrigation in Commercial Floriculture Production: A Case Study." HortTechnology 28, no. 6: 719-727.

Photobiology and photosynthesis
Published: 10 September 2018 in Physiologia Plantarum
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Linear electron transport depends on balanced excitation of photosystem I and II. Far‐red light preferentially excites photosystem I (PSI) and can enhance the photosynthetic efficiency when combined with light that over‐excites photosystem II (PSII). The efficiency of different wavelengths of far‐red light at exciting PSI was quantified by measuring the change in quantum yield of PSII (ΦPSII) of lettuce (Lactuca sativa) under red/blue light with narrowband far‐red light added (from 678 to 752 nm, obtained using laser diodes). The ΦPSII of lettuce increased with increasing wavelengths of added light from 678 to 703 nm, indicating longer wavelengths within this region are increasingly used more efficiently by PSI than by PSII. Adding 721 nm light resulted in similar ΦPSII as adding 703 nm light, but ΦPSII tended to decrease as wavelength increased from 721 to 731 nm, likely due to decreasing absorptance and low photon energy. Adding 752 nm light did not affect ΦPSII. Leaf chlorophyll fluorescence light response measurements showed lettuce had higher ΦPSII under halogen light (rich in far‐red) than under red/blue light (which over‐excites PSII). Far‐red light is more photosynthetically active than commonly believed, because of its synergistic interaction with light of shorter wavelengths.

ACS Style

Shuyang Zhen; Mark Haidekker; Marc van Iersel. Far‐red light enhances photochemical efficiency in a wavelength‐dependent manner. Physiologia Plantarum 2018, 167, 21 -33.

AMA Style

Shuyang Zhen, Mark Haidekker, Marc van Iersel. Far‐red light enhances photochemical efficiency in a wavelength‐dependent manner. Physiologia Plantarum. 2018; 167 (1):21-33.

Chicago/Turabian Style

Shuyang Zhen; Mark Haidekker; Marc van Iersel. 2018. "Far‐red light enhances photochemical efficiency in a wavelength‐dependent manner." Physiologia Plantarum 167, no. 1: 21-33.

Research
Published: 02 August 2018 in Energy Informatics
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Greenhouse agriculture is a highly efficient method of food production that can greatly benefit from supplemental electric lighting. The needed electricity associated with greenhouse lighting amounts to about 30% of its operating costs. As the light level of LED lighting can be easily controlled, it offers the potential to reduce energy costs by precisely matching the amount of supplemental light provided to current weather conditions and a crop’s light needs. Three simulations of LED lighting for growing lettuce in the south-east of the US using historical solar radiation data for the area were conducted. Lighting costs can be potentially reduced by approximately 60%.

ACS Style

Richard T. Watson; Marie-Claude Boudreau; Marc van Iersel. Simulation of greenhouse energy use: an application of energy informatics. Energy Informatics 2018, 1, 1 .

AMA Style

Richard T. Watson, Marie-Claude Boudreau, Marc van Iersel. Simulation of greenhouse energy use: an application of energy informatics. Energy Informatics. 2018; 1 (1):1.

Chicago/Turabian Style

Richard T. Watson; Marie-Claude Boudreau; Marc van Iersel. 2018. "Simulation of greenhouse energy use: an application of energy informatics." Energy Informatics 1, no. 1: 1.

Journal article
Published: 01 July 2018 in Journal of the American Society for Horticultural Science
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Water-efficient soilless substrates need to be engineered to address diminishing water resources. Therefore, we investigated soilless substrates with varying hydrologies to determine their influence on crop growth and plant water status. Aged loblolly pine (Pinus taeda) bark was graded into four particle size fractions. The coarsest fraction was also blended with either sphagnum peat or coir at rates that mimic static physical properties of the unfractionated bark or conventional substrate used by specialty crop producers within the eastern United States. Hibiscus rosa-sinensis ‘Fort Myers’ plugs were established in each of the seven substrates and maintained at optimal substrate water potentials (−50 to −100 hPa). After a salable crop was produced 93 days after transplanting, substrate was allowed to dry until plants completely wilted. Crop morphology and water use was affected by substrate hydrology. Increased substrate unsaturated hydraulic conductivity (K) allowed for plants to access higher proportions of water and therefore increased crop growth. Maintaining optimal substrate water potential allowed plants to be produced with Ks). Plants grown in substrates with higher hydraulic conductivities were able to use more water. Soilless substrate hydrology can be modified and used in concert with more efficient irrigation systems to provide more water sustainability in container crop systems.

ACS Style

Jeb S. Fields; James Owen; James E. Altland; Marc van Iersel; Brian E. Jackson. Soilless Substrate Hydrology Can Be Engineered to Influence Plant Water Status for an Ornamental Containerized Crop Grown within Optimal Water Potentials. Journal of the American Society for Horticultural Science 2018, 143, 268 -281.

AMA Style

Jeb S. Fields, James Owen, James E. Altland, Marc van Iersel, Brian E. Jackson. Soilless Substrate Hydrology Can Be Engineered to Influence Plant Water Status for an Ornamental Containerized Crop Grown within Optimal Water Potentials. Journal of the American Society for Horticultural Science. 2018; 143 (4):268-281.

Chicago/Turabian Style

Jeb S. Fields; James Owen; James E. Altland; Marc van Iersel; Brian E. Jackson. 2018. "Soilless Substrate Hydrology Can Be Engineered to Influence Plant Water Status for an Ornamental Containerized Crop Grown within Optimal Water Potentials." Journal of the American Society for Horticultural Science 143, no. 4: 268-281.

Journal article
Published: 01 April 2018 in Agricultural Water Management
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Francesco Fabiano Montesano; Marc van Iersel; Francesca Boari; Vito Cantore; Giulio D’Amato; Angelo Parente. Sensor-based irrigation management of soilless basil using a new smart irrigation system: Effects of set-point on plant physiological responses and crop performance. Agricultural Water Management 2018, 203, 20 -29.

AMA Style

Francesco Fabiano Montesano, Marc van Iersel, Francesca Boari, Vito Cantore, Giulio D’Amato, Angelo Parente. Sensor-based irrigation management of soilless basil using a new smart irrigation system: Effects of set-point on plant physiological responses and crop performance. Agricultural Water Management. 2018; 203 ():20-29.

Chicago/Turabian Style

Francesco Fabiano Montesano; Marc van Iersel; Francesca Boari; Vito Cantore; Giulio D’Amato; Angelo Parente. 2018. "Sensor-based irrigation management of soilless basil using a new smart irrigation system: Effects of set-point on plant physiological responses and crop performance." Agricultural Water Management 203, no. : 20-29.