Abstract
Hanging basket (HB) production alters the light environment in the lower canopy of ornamental greenhouses by intercepting and altering the spectral quality of incoming light. If shading is sufficiently high, the quality of the lower crops can be reduced. This work investigated changes in light quantity and quality at the lower crop level caused by HB production in Ontario, Canada. Light sampling occurred at three commercial greenhouse facilities throughout the Spring 2012 HB season. The greenhouses represented a range of HB densities (1.8, 2.4, and 3.0 baskets/m 2 ) and different HB canopy architectures (one, two, and three tiers of HBs). Light samples were taken at three fixed locations within each greenhouse facility: outside, HB level, and lower crop level. Photosynthetically active radiation ( PAR ) was logged continuously at each location within each greenhouse environment. Spectral scans were made at each sampling location, within each greenhouse facility, at various times throughout the season to assess how HB production altered the red to far red ratio (R:FR) at lower crop level. As the season progressed, outdoor daily light integrals (DLIs) more than doubled from <20 to >40 mol·m −2 ·d −1 . Light reduction caused by polyethylene films and structural components varied among locations, but remained steady throughout the season, averaging 48.3% for the three locations. As the HB crops matured, the rate of decrease in PAR at lower crop level varied according to facility and HB density with mean reductions of 42.5%, 32.6%, and 37.7% for the one-, two-, and three-tiered facilities, respectively. Mean lower crop level DLIs were all very similar, between 9.4 and 9.9 mol·m −2 ·d −1 . Accordingly, there may be insufficient light below HB canopies to produce high-quality crops of many varieties of bedding plants that are commonly grown in Ontario. The one- and two-tiered systems reduced the R:FR at lower crop level by 14% and 10%, respectively, whereas the three-tiered system caused no reduction. More work is required to determine if the observed far red shift is sufficient to alter crop quality. These case studies provide a backdrop against which to help determine and interpret horticultural management strategies for a variety of greenhouse crops.
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Claims 9
Claim · model-written summary
With one-tiered hanging baskets, PAR at lower crop level was reduced by a mean of 42.5% as crops matured.
Verbatim
e6“bedding plants”
e1“the rate of decrease in PAR at lower crop level varied according to facility and HB density with mean reductions of 42.5%, 32.6%, and 37.7% for the one-, two-, and three-tiered facilities, respectively”
Claim · model-written summary
With two-tiered hanging baskets, PAR at lower crop level was reduced by a mean of 32.6% as crops matured.
Verbatim
e6“bedding plants”
e1“the rate of decrease in PAR at lower crop level varied according to facility and HB density with mean reductions of 42.5%, 32.6%, and 37.7% for the one-, two-, and three-tiered facilities, respectively”
Claim · model-written summary
With three-tiered hanging baskets, PAR at lower crop level was reduced by a mean of 37.7% as crops matured.
Verbatim
e6“bedding plants”
e1“the rate of decrease in PAR at lower crop level varied according to facility and HB density with mean reductions of 42.5%, 32.6%, and 37.7% for the one-, two-, and three-tiered facilities, respectively”
Claim · model-written summary
Mean lower crop level daily light integrals were similar, 9.4 to 9.9 mol m-2 d-1, across facilities.
Verbatim
e6“bedding plants”
e2“Mean lower crop level DLIs were all very similar, between 9.4 and 9.9 mol·m −2 ·d −1”
Claim · model-written summary
Light reduction caused by polyethylene films and structural components averaged 48.3% across the three greenhouse locations.
Verbatim
e6“bedding plants”
e3“Light reduction caused by polyethylene films and structural components varied among locations, but remained steady throughout the season, averaging 48.3% for the three locations”
Claim · model-written summary
Insufficient light below hanging basket canopies may limit production of high-quality crops of bedding plants.
Verbatim
e6“bedding plants”
e4“there may be insufficient light below HB canopies to produce high-quality crops of many varieties of bedding plants”
Claim · model-written summary
The one-tiered system reduced the red to far red ratio at lower crop level by 14%.
Verbatim
e6“bedding plants”
e5“The one- and two-tiered systems reduced the R:FR at lower crop level by 14% and 10%, respectively, whereas the three-tiered system caused no reduction”
Claim · model-written summary
The two-tiered system reduced the red to far red ratio at lower crop level by 10%.
Verbatim
e6“bedding plants”
e5“The one- and two-tiered systems reduced the R:FR at lower crop level by 14% and 10%, respectively, whereas the three-tiered system caused no reduction”
Claim · model-written summary
The three-tiered system caused no reduction in the red to far red ratio at lower crop level.
Verbatim
e6“bedding plants”
e5“whereas the three-tiered system caused no reduction”