Irrigation
for Container Nursery Stock
The two most widely used irrigation systems used in nursery production
are overhead and drip (or trickle). Overhead irrigation is designed
to cover a large area, and these systems are the least expensive
to install. However, this method produces uneven water distribution,
which can slow plant growth, encourage disease, and contribute to
runoff. Also, a container nursery using overhead irrigation can
use from 15,000 to 40,000 gallons of water per acre per day in the
summer (1), a reminder that sufficient water is a prerequisite to
nursery production.
Large containers are usually watered with a drip or trickle system,
which uses 60%-70% less water than overhead systems. Drip irrigation
systems cost more to install than overhead systems, but have superior
application uniformity and efficiency. They are also less affected
by wind and crop canopies, and they produce less runoff. Another
advantage is that workers can continue working while the plants
are being irrigated. The biggest disadvantage to trickle irrigation,
besides the initial cost, is keeping the pipes and emitters clean.
A third, less-used type of irrigation system, is subirrigation,
using capillary sandbeds. In this system, water rises into containerized
plants through capillary action. Usually, the sandbed is covered
with at least one inch of fine sand, and slopes very slightly from
one end to the other. Water is released at the high end and slowly
percolates to the low end. These systems cost the most to install,
but they have no runoff or leaching.
Sandbeds are normally constructed using wood sidewalls, a plastic
bed liner, sand, a small tank, a drainpipe, and a float valve. They
do not require any electrical parts, and provide a uniform and consistent
supply of water without forming a saturated water table at the base
of the soil column in the container. In short, you get efficient
and uniform crop growth while providing less water, less fertilizer,
and less pesticide. It also requires less labor, as sprinkler heads,
timers, pumps, valves, and water-treatment systems don't need to
be monitored (1).
The biggest disadvantage of sandbeds is that weeds and containerized
plants grow into them. There is a product designed to alleviate
this problem: the Agroliner™, a mat that has been treated with
Spin Out™, a product that prevents root growth. The mat is
placed over the sand and under the containers.
Regardless of the system used, it is vital that the plants be watered
often, especially on hot, sunny days. A typical nursery plant in
a one-gallon container may consume a pint of water a day, while
the growing medium capacity may be only 1 1/2 pints. One important
aspect of irrigation management is to group plants according to
water requirements.
The most important issue in sustainable nursery production, as
it relates to irrigation, is the runoff of water, fertilizers, and
pesticides. Many states now have regulations limiting runoff and
groundwater nitrate levels.
Subirrigation systems are designed for zero runoff, but overhead
and drip systems may require special attention. Runoff water can
be collected using ditches (planted with grass to slow down water
flow) or tile systems, which direct water to a pond or other holding
area.
The water (and some fertilizers present) can then be recycled by
pumping it back out of the holding tank or pond, after some of the
impurities (sand and silt) have settled out. Recycled water has
actually been shown to improve plant growth. "In experiments
with more than one hundred species of ornamentals grown in 2.8 liter
containers, the mean relative growth of plants irrigated with continuously
recycled water was over 103% over that of the control" (2).
Another way to reduce runoff is to use pulse irrigation. In this
system, instead of applying one heavy watering daily, a small amount
of water is applied five or six times during the day. Very little
water escapes from the container or runs off from the field. The
production advantage to this is that less fertilizer has to be applied,
because there is less leaching. Most nurseries that use this system
use a computer to control water flow, since watering plants repeatedly
by hand would cause a huge increase in labor expenses.
There are several cultural practices that can reduce runoff:
- Avoid irrigating bare soil
- Have rough soil surfaces to provide surface storage of water
- Use less-porous media that retain moisture and nutrients
- Use slow-release fertilizers instead of liquid fertilizers
Researchers at Ohio State University have been conducting experiments
to reduce the amount of pesticides and growth regulators leached
from nursery pots and trays. They have had excellent success in
mixing chemicals in ordinary latex paint and then painting the interior
of the pots. Not only was there less leaching from the pots, but
the growth regulator and pesticide they used (Bonzi™ and Marathon™
) provided more consistent control. This method also reduced worker
re-entry intervals into the nursery area, since the chemicals were
applied only once, at the beginning of the growth process (3).
This article is from: "Sustainable Small-scale Nursery
Production", May 2000 (Revised Nov. 2001) by Steve Diver and
Lane Greer, National Center for Appropriate Technology, University
of Arkansas, Fayetteville. Submitted by Ron Kujawski, UMass Extension.
References:
Svenson, Sven E., Dave G. Adams, and Robert L. Ticknor. 1997. Slow
and steady. American Nurseryman. January 15. pp 50-59.
Skimina, Conrad A. 1992. Recycling water, nutrients, and waste in
the nursery industry. HortScience. September. pp 68-971.
Metzger, Jim. 1998. OSU research update: New production methods
to reduce pesticide leaching and run-off. Ohio Florists' Association
Bulletin. January. P. 13.
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