Propagation/Greenhouse ManagementUnit 1.3 | Part 1 – 117D. Supplemental Lighting
Lighting systems that supplement available sunlight can increase crop productivity and
quality
- Can improve plant growth in low light and short day length conditions, e.g., during winter
in northern climates - Can manipulate photoperiod, and bring day length-sensitive crops to bloom out of their
normal cycle and thus have crops such as sunflowers blooming year round - Benefits must be weighed against the cost of purchasing and installing supplemental
lighting, as well as ongoing energy costs. Careful Return on Investment (ROI) calculations
should be made prior to purchasing any supplemental lighting to see if the initial expense
and ongoing costs can by justified by yields. - Incandescent and fluorescent lighting are the least expensive options but are only effective
in impacting day length sensitivity, and will not improve quality of growth - High Intensity Discharge (HID) and High Pressure Sodium (HPS) lighting units are required
if growers need to increase available light to improve plant growth. These are more
expensive to purchase and operate. If you are growing photoperiod-sensitive crops in low
light and short day length regions, then HID and HPS lighting can be used both to impact
day length and the quality of crop growth.
E. Irrigation Systems
- Manual irrigation
Hand delivery requires the lowest amount of capital investment. One only needs a water
source, faucets, hoses, and tools such as a Fogg-It nozzle, the “rose on a hose,” or a wand
and water breaker combination to deliver water across the seedling life cycle. However,
relying exclusively on hand watering is very labor intensive and can lead to uneven plant
performance unless water is being delivered by a highly skilled irrigator.
- Overhead delivery via semi-automated and automated sprinkler systems
A well designed sprinkler system can uniformly deliver water to an entire crop with very
little time/labor required
a) In semi-automated systems, typically the grower must assess plant/soil needs and then
determine when and how much water to apply. However, using mechanical timers
to semi-automate the system, delivery and shut off are provided by the timer and
overhead sprinkler system.
b) In fully automated systems, environmental sensors and computer-driven programming
are synchronized to respond to current environmental conditions and the needs of
developing seedlings. While much more costly to set up, well-designed automated
systems typically have a rapid return on investment, due to improved crop quality and
huge savings in labor.
c) Because of the “edge effects” of increased sun exposure and air circulation, plants at
the edges of benches and blocks will normally dry out faster that those in the interior,
so even automated and semi-automated systems usually require some hand watering
follow up. Even with this limitation, the labor savings such systems offer is immense and
can pay for the cost of investment in a single season.
Lecture 3: Greenhouse Climate Control Systems