Tipburn is considered a major limiting factor to lettuce production in greenhouses and controlled environment agriculture facilities. Conditions which promote optimal growth also result in high levels of tipburn incidence. It has been reported that air flow directed at inner leaves of rapidly growing lettuce can prevent tipburn without a concurrent reduction of growth, assumedly due to increased transpiration with increased air movement over leaf surfaces.
Lettuce was grown in the greenhouse in nutrient film technique, with additional lighting providing total of 17 to 19 mol m-2 d-1 of PAR. Control plants developed tipburn 20 to 25 days after seeding. Plants with air supplied to inner leaves by a perforated plastic sleeve did not develop tipburn up to 35 days after seeding. Diurnal changes in physiological parameters were measured starting one week prior to harvest. Leaves of control plants had significantly higher stomatal conductance and transpiration than did those of air-supplied plants, although diurnal patterns of control and air-treated plants were similar. Air flow treatment had no significant effect on the rate of photosynthesis. However, air-supplied plants had a slightly lower percentage of dry matter than control plants. The apparent growth reduction resulting from the air flow treatment evidently reduced the demand for calcium.
1 Graduate Student. 2 Professor of Seed Science and Technology. To whom reprint requests should be addressed. E-mail address: email@example.com 3 Emeritus Professor of Controlled Environment Agriculture. This paper is a portion of a thesis
Energy conservation in controlled-environment agriculture is a major concern for both commercial and research facilities as well as extraterrestrial facilities for food production. Supplying optimal irradiance by using electrical lighting for the greatest edible biomass production potentially is the greatest draw on energy during earth-based or extraterrestrial food production in controlled environments. Our objective was to determine the optimal irradiance for greatest edible biomass production of three cultivars of basil (Basilicum ocimum L.) in a controlled-environment production system. Seedlings of the three cultivars were transplanted into soilless medium, one plant per pot, and grew for 17 days in reach-in growth chambers maintained at 25 ± 4 °C with a 16-h photoperiod. Canopy-level irradiances of 300, 400, 500, and 600 μmol·m−2·s−1 were provided by cool-white fluorescent and incandescent lamps. Shoot growth was measured as height, diameter, and number of leaves 0.5 cm long or greater; and edible biomass was measured as leaf fresh weight, shoot fresh weight, and shoot dry weight. There was no irradiance × cultivar interaction, but main effects of irradiance and cultivar were observed. Plant growth and edible biomass production were least at 300 μmol·m−2·s−1 and greatest at 500 or 600 μmol·m−2·s−1. In several cases, 400 μmol·m−2·s−1 yielded intermediate growth or edible biomass. Within the main effect of cultivar, Italian Large Leaf produced greater edible biomass than ‘Genovese’, and ‘Nufar’ yielded an intermediate amount of shoot fresh weight and dry weight. Under our environmental conditions that included ambient CO2 concentration and ambient relative humidity, the rate of growth peaked at 500 μmol·m−2·s−1, and no additional accumulation of edible biomass occurred at 600 μmol·m−2·s−1. Based on our results, canopy-level irradiance of 500 μmol·m−2·s−1 provides maximum edible biomass production of basil in a controlled-environment production system.
Electrical cost, primarily for lighting, is one of the largest factors inhibiting the development of “warehouse-based” controlled environment agriculture (CEA). In a jointly sponsored collaboration, we have developed a reconfigurable LED lighting array aimed at reducing the electrical energy needed to grow crops in controlled environments. The lighting system uses LED “engines” that can operate at variable power and that emit radiation only at wavelengths with high photosynthetic activity. These light engines are mounted on supports that can be arranged either as individual intracanopy “lightsicles” or in an overhead plane of lights. Heat is removed from the light engines using air flow through the hollow LED strip mounts, allowing the strips to be placed in close proximity to leaves. Different lighting configurations depend on the growth habit of the crops of interest, with intracanopy lighting designed for planophile crops that close their canopy, and close overhead lighting intended for erectophile and rosette crops. Tests have been performed with cowpea, a planophile dry bean crop, growing with intracanopy LED lighting compared to overhead LED lighting. When crops are grown using intracanopy lighting, more biomass is produced, and a higher index of biomass per kW-h is obtained than when overhead LEDs are used. In addition, the oldest leaves on intracanopy-grown plants are retained throughout stand development, while plants lit from overhead drop inner-canopy leaves due to mutual shading after the leaf canopy closes. Research is underway to increase the energy efficiency and automation of this lighting system. This work was supported in part by NASA: NAG5-12686.
Sweetpotatoes (Ipomoea batatas) are nutritious, easily stored, and well adapted to a variety of organic farming operations. This widely consumed root crop is propagated through the use of cuttings, known as slips. Slips are commercially grown primarily in the southeastern United States, and growers in the central United States still have limited access to sweetpotato planting material. Production of organic slips in high tunnels (HTs) could be a profitable enterprise for growers in the central United States given the season extension afforded by controlled-environment agriculture, which could allow growers to diversify their operations and facilitate crop rotation. In trials conducted in 2016 and 2017 at two research stations in northeast and south central Kansas, a systems comparison was used to evaluate the yield and performance of organic sweetpotato slips grown in HT as compared with the open field (OF), with four to six replications at each location. Propagation beds planted with ‘Beauregard’ seed roots in 2016 and ‘Orleans’ in 2017 were established in HT and OF under similar cultural methods and planting schedules. Slips were harvested from both treatment groups and transplanted to field plots to investigate the impact of production system on transplant establishment and storage root production. Slip yield from HT was greater than OF at both locations in 2016 (P ≤ 0.001), but this trend was inconsistent in 2017. Slips grown in HT were on average 12% less compact (slip dry weight per centimeter length) with fewer nodes than their OF counterparts in 2016. Nonetheless, mean comparisons for vine length, stem diameter, and total marketable storage root yield were not significant between HT and OF treatments (1.7 and 2.1 lb/plant, respectively). Similarly, the number of marketable storage roots for HT and OF groups was comparable (3.4 and 3.8 storage roots/plant, respectively). Although more research is needed to evaluate the feasibility of slips grown in HT and to determine recommendations for seed root planting densities, results from this study suggest that HT organic sweetpotato slip production could be a viable alternative to OF production as it relates to slip performance. According to this study, HT production could be a useful mechanism for growing sweetpotato slips, which could provide regional growers more control over planting material. Furthermore, HT slip production could promote the adoption of an underused vegetable crop that can be grown throughout many parts of the United States.
regulators. Evans et al. (2006) developed 15 virtual field trips that demonstrate various technologies and management strategies used in greenhouse management and controlled environment agriculture. Although these educational advancements are innovative and
by integrated supplemental light levels in a controlled environment agriculture facility: Experimental results Acta Hort. 418 45 52 Björkman, O. Demmig, B. 1987 Photon yield of O2 evolution and chlorophyll fluorescence at 77k among vascular plants of
.A. 2020 Evaluation of different lighting strategies used to improve efficiencies in plant growth for controlled environment agriculture. Univ. of Georgia, Athens, MS Thesis Evans, J.R. Poorter, H. 2001 Photosynthetic acclimation of plants to growth
In the area of controlled environment agriculture (CEA), one of the most commonly discussed topics is that of lighting. The lighting system is generally the most expensive component of a CEA facility in terms of upfront costs as well as ongoing
. Shad, Z.M. 2018 Advances in greenhouse automation and controlled environment agriculture: A transition to plant factories and urban agriculture Intl. J. Agr. Biol. Eng. 11 1 22 doi: https://doi.org/10.25165/j.ijabe.20181101.3210 Stamps, R