Search Results

You are looking at 41 - 50 of 3,494 items for :

  • controlled environment x
Clear All
Free access

Kuanglin Chao, Richard S. Gates and Robert G. Anderson

Knowledge engineering offers substantial opportunities for integrating and managing conflicting demands in greenhouse crop production. A fuzzy inference system was developed to balance conflicting requirements of producing a high-quality, single-stem rose crop while simultaneously controlling production costs of heating and ventilation. An adaptive neuro-fuzzy inference system was built to predict the rose status of `Lady Diana' single-stem roses from nondestructive measurements. The fuzzy inference system was capable of making a critical decision based on the principle of economic optimization. Temperature set points for two greenhouses with similar rose status were treated significantly different by the fuzzy inference system due to differences in greenhouse energy consumption. Moderate reduction in heating energy costs could be realized with the fuzzy inference system.

Free access

R.M. Wheeler, C.L. Mackowiak, J.C. Sager, N.C. Yorio, W.M. Knott and W.L. Berry

Two studies were conducted in which `Waldmann's Green' lettuce (Lactuca sativa L.) was grown hydroponically from seed to harvest in a large (20-m2), atmospherically closed growth chamber for the National Aeronautics and Space Administration's controlled ecological life support system (CELSS) program. The first study used metal-halide (MH) lamps [280 μmol·m-2·s-1 photosynthetic photon flux (PPF)], whereas the second used high-pressure sodium (HPS) lamps (293 μmol·m-2·s-1). Both studies used a 16-hour photoperiod, a constant air temperature (22 to 23C), and 1000 μmol·mol-1 CO2 during the light period. In each study, canopy photosynthesis and evapotranspiration (ET) rates were highly correlated to canopy cover, with absolute rates peaking at harvest (28 days after planting) at 17 μmol CO2/m2 per sec and 4 liters·m-2·day-1, respectively. When normalized for actual canopy cover, photosynthesis and ET rates per unit canopy area decreased with age (between 15 and 28 days after planting). Canopy cover increased earlier during the study with HPS lamps, and final shoot yields averaged 183 g fresh mass (FM)/plant and 8.8 g dry mass (DM)/plant. Shoot yields in the first study with MH lamps averaged 129 g FM/plant and 6.8 g DM/plant. Analysis of leaf tissue showed that ash levels from both studies averaged 22% and K levels ranged from 15% to 17% of tissue DM. Results suggest that lettuce should be easily adaptable to a CELSS with moderate lighting and that plant spacing or transplant schemes are needed to maximize canopy light interception and sustain efficient CO2 removal and water production.

Full access

S.R. Drake and T.A. Eisele

Red color of two strains of `Delicious' apples was increased (25%) by a 10-day delay beyond recommended harvest date for long-term controlled atmosphere (CA) storage. Soluble solids content (SSC) and size also increased, but, depending on strain, up to 12% of firmness was lost at harvest with a 10-day delay. In 2 of 3 years, firmness values in all strains were 73 N or greater, and these fruit lost little firmness during 9 months of CA storage. Soft fruit (<63 N) at harvest resulted in unacceptable firmness after storage, regardless of harvest time or strain of `Delicious'. Immediate (<24 h) establishment of CA conditions resulted in good-quality fruit after storage. Quality loss was evident after a 5-day delay in atmosphere establishment, with no further loss after a 10-day delay. `Oregon Spur' apples had the best red color regardless of harvest. Sensory panel profiles were unable to distinguish among strains, harvest dates, or delays in time of atmosphere establishment. Caution should be exercised when initiating new harvest or storage procedures because growing conditions can vary from one location to another.

Full access

Timothy K. Broschat

Five-gram (0.18 oz) samples of two controlled-release fertilizers (CRFs), Osmocote 15N–3.9P–10K (8–9 month) (OSM) and Nutricote 18N–2.6P–6.7K (type 180) (NUTR), were sealed into polypropylene mesh packets that were placed on the surface of a 5 pine bark: 4 sedge peat: 1 sand (by volume) potting substrate (PS), buried 10 cm (3.9 inches) deep below the surface of PS, buried 10 cm below the surface of saturated silica sand (SS), or in a container of deionized water only. Containers with PS received 120 mL (4.1 floz) of deionized water three times per week, but the containers with SS or water only had no drainage and were sealed to prevent evaporation. Samples were removed after 2, 5, or 7 months of incubation at 23 °C (73.4 °F) and fertilizer prills were crushed, extracted with water, and analyzed for ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), phosphorus (P), and potassium (K). Release rates of NO3-N were slightly faster than those of NH4-N and both N ions were released from both products much more rapidly than P or K. After 7 months, OSM prills retained only 8% of their NO3-N, 11% of their NH4-N, 25% of their K, and 46% of their P when averaged across all treatments. Nutricote prills retained 21% of their NO3-N, 28% of their NH4-N, 51% of their K, and 65% of their P. Release of all nutrients from both fertilizers was slowest when applied to the surface of PS, while both products released most rapidly in water only. Release rates in water only exceeded those in SS, presumably due to lower rates of mass flow in SS.

Free access

Mark G. Lefsrud, Dean A. Kopsell, David E. Kopsell and Joanne Curran-Celentano

Crop plants are adversely affected by a variety of environmental factors, with air temperature being one of the most influential. Plants have developed a number of methods in the adaptation to air temperature variations. However, there is limited research to determine what impact air temperature has on the production of secondary plant compounds, such as carotenoid pigments. Kale (Brassica oleracea L.) and spinach (Spinacia oleracea L.) have high concentrations of lutein and β-carotene carotenoids. The objectives of this study were to determine the effects of different growing air temperatures on plant biomass production and the accumulation of elemental nutrients, lutein, β-carotene, and chlorophyll pigments in the leaves of kale and spinach. Plants were grown in nutrient solutions in growth chambers at air temperatures of 15, 20, 25, and 30 °C for `Winterbor' kale and 10, 15, 20, and 25 °C for `Melody' spinach. Maximum tissue lutein and β-carotene concentration occurred at 30 °C for kale and 10 °C for spinach. Highest carotenoid accumulations were 16.1 and 11.2 mg/100 g fresh mass for lutein and 13.0 and 10.9 mg/100 g fresh mass for β-carotene for the kale and spinach, respectively. Lutein and β-carotene concentration increased linearly with increasing air temperatures for kale, but the same pigments showed a linear decrease in concentration for increasing air temperatures for spinach. Quantifying the effects of air temperature on carotenoid accumulation in kale and spinach, expressed on a fresh mass basis, is important for growers producing these crops for fresh markets.

Free access

Craig S. Charron, Daniel J. Cantliffe, Raymond M. Wheeler, Ara Manukian and Robert R. Heath

A system and methodology were developed for the nondestructive qualitative and quantitative analysis of volatile emissions from hydroponically grown `Waldmann's Green' leaf lettuce (Lactuca sativa L.). Photosynthetic photon flux (PPF), photoperiod, and temperature were automatically controlled and monitored in a growth chamber modified for the collection of plant volatiles. The lipoxygenase pathway products (Z)-3-hexenal, (Z)-3-hexenol, and (Z)-3-hexenyl acetate were emitted by lettuce plants after the transition from the light period to the dark period. The volatile collection system developed in this study enabled measurements of volatiles emitted by intact plants, from planting to harvest, under controlled environmental conditions.

Free access

T.W. Tibbitts, J.G. Croxdale, C.S. Brown and R.M. Wheeler

150 ORAL SESSION 34 (Abstr. 243–248) Controlled Environment

Free access

William L. Bauerle* and Joe E. Toler

A multiplicative model of stomatal conductance was developed and tested in two functionally distinct ecotypes of Acer rubrum L. (red maple). The model overcomes the main limitation of the commonly used Ball-Berry model by accounting for stomatal behavior under soil drying conditions. It combined the Ball-Berry model with an integrated expression of abscisic acid-based control mechanisms (gfac). The factor gfac = exp(-β[ABA]L) incorporated the stomatal response to abscisic acid (ABA) concentration in the bulk leaf tissue [ABA]L into the Ball-Berry model by down-regulating the slope and coupled physiological changes at the leaf level with those of the root. The stomatal conductance (gs) down regulation is pertinent in situations where soil drying may modify the delivery of chemical signals to leaf stomates. Model testing results indicated that the multiplicative model was capable of predicting stomatal conductance under wide ranges of soil and atmospheric conditions in a woody perennial. Concordance correlation coefficients (rc) were high (between 0.59 and 0.94) for the tested ecotypes under three different environmental conditions (aerial, distal, and minimal stress). The study supported the use of the gfac factor as a gas exchange function that controlled water stress effects on gs and aided in the prediction of gs responses.