October 2019 - 50

technically speaking
BY ERIK RUNKLE
Greenhouse Environment Checklist
As the days are getting shorter, light levels are decreasing
and it's getting colder outside, now is a great time to
check your greenhouse environmental control systems and
equipment. In particular, ensure systems that regulate the
major environmental parameters that influence plant growth
and development (light, temperature, air flow, humidity and
carbon dioxide) are working well and positioned
properly. A well-functioning environmental control
system can reduce energy consumption as well as
improve crop quality and uniformity, and possibly
reduce production times.
Horizontal air flow (HAF) fans. Check all fans to
ensure they operate when the vents are closed. They
should also be
positioned parallel
to the growing
surface (not pointed
at a downward
angle) so that they
primarily blow air
above the crop, not
toward the crop.
HAF fans mix the
Erik Runkle is
professor and
floriculture
Extension specialist
in the department
of horticulture at
Michigan State
University. He can be
reached at runkleer@
msu.edu.
air, creating a more uniform
thermal environment. In
addition, they can bring
some of the warmer air at
the top of the greenhouse
down to where the plants
are growing.
Photoperiodic lighting. All
bulbs should be functional.
If you have incandescent
or compact fluorescence bulbs, consider replacing them with
more energy-efficient LEDs. Most types of LEDs can be used to
inhibit flowering of short-day plants. However, under low-light
conditions, bulbs that emit both red and far-red light more
effectively promote flowering than conventional white bulbs.
Supplemental lighting. High-intensity lighting is expensive
often begin by turning on and off. If replacing a bulb does not
solve the problem, the fixture needs to be taken down and
repaired. The problem can be a partially or completely failed
capacitor, or less likely, a failed ignitor. For more information
on repairing HPS fixtures, visit https://bit.ly/2zh7aYM. For
information on maximizing the benefits of supplemental
lighting, visit https://bit.ly/30uaewN.
Maximize light transmission. If you applied whitewash,
ensure it has all been removed. Also, remove any unnecessary
overhead obstructions that cast shade on plants below.
Energy curtains. If you have retractable energy (or shade)
Figure 1. High-pressure sodium fixtures need periodic maintenance
to achieve peak performance.
curtains, check their condition and repair or replace as needed.
To maximize their value, the curtains should close tightly so the
warm greenhouse air is trapped
inside the growing area.
Heating system. Clean and
check all of your heaters to
make sure they are operating
efficiently. Clean the heat
exchanger and look for
any cracks that could allow
contaminates (such as ethylene)
into the greenhouse. Also, be
sure the exhaust vents are
unobstructed and release
air sufficiently outside the
greenhouse.
Temperature sensors.
These sensors should be
shielded and aspirated, and
located near the middle of the
greenhouse and as close to
the crop canopy as possible.
Check each temperature sensor to ensure it is connected, clean
and properly positioned.
Greenhouse insulation. Reduce air leaks, which includes
to purchase and operate and thus, it's wise to ensure the
system is performing well. Most greenhouse growers still
use high-pressure sodium (HPS) fixtures, which require more
maintenance than newer, more energy-efficient LEDs (Figure 1).
First, repair or replace inoperable or dim fixtures. Old bulbs
patching or sealing gaps in the glazing material, and ensuring
fan louvers and doors fully close. Growers with double poly
should check all of the small fans that inflate the two layers to
confirm they are working.
Misters. Growers who deliver mist during propagation should
check that the misting/fogging nozzles are not clogged. Repair
or replace as needed so that the mist is uniformly distributed
to plants below.
50 OCTOBER 2019 GPNMAG.COM
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October 2019

Table of Contents for the Digital Edition of October 2019
