ASGSB 2003 Annual Meeting Abstracts


OPTIMIZING LED LIGHTING STRATEGIES FOR ALS-RELATED CROPS.  G.D. Massa1, J.A. Montgomery1, J.M. Badger2, G.T. Chiu2 and C.A. Mitchell1     1Dept. of Horticulture & Landscape Architecture, and 2 Mechanical Engineering, Purdue Univ., West Lafayette, IN.

   Providing adequate illumination is one of the challenges facing crop growth in a closed environment on a planetary surface or in a space station.  Intracanopy (IC) and close-canopy (CC) crop-lighting systems are being developed using narrow-spectrum light-emitting diodes (LEDs).  Operation at low power permits LEDs to be arrayed close to and/or within foliar canopies without overheating or scorching plant tissues.  Vertical LED strips will switch on in sectors from the bottom up, keeping pace with increases in stand height of upright-growing crops without lighting empty headspace.  Horizontal LED panels will be designed to switch on in concentric circles above each seedling of compact rosette crops such as lettuce. These panels will be maintained at constant, close distance from leaf surfaces during crop development.  For vertical arrays, parallel rows of alternating red and blue LEDs will be mounted closely along thin, printed-circuit plastic strips, allowing a uniform blend of photon output from each array. Hue control will be achieved by establishing a given ratio of photon flux from red and blue LEDs, and intensity will be controlled by varying the input voltage applied to each LED type.  For vertical IC LED strips, control signals for on-off switching and hue and intensity control will be multiplexed to any number of “lightcicles” hanging in a given growth compartment for upright-growing crops such as soybean, basil, or tomato.  For horizontal CC LED panels, hue and intensity controls will be applied in expanding, concentric circles as seedlings expand laterally. Both types of LED arrays will be designed for ease of removal prior to crop harvest and replanting, a procedure that could be readily automated.  Measured crop responses to LED IC and/or CC lighting include edible yield, cropping time, harvest index, edible yield rate, crop quantum yield, electrical energy conversion efficiency, and real-time photosynthetic gas-exchange rate for small crop stands expressed on a growth area and/or growth-volume basis. 

(Supported by NASA: NAG5-12686.)


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