Agriculture Reference
In-Depth Information
TABLE 1
(Continued)
Pro-
duction
system
Irriga-
tion type
Substrate
Staking
Over win-
tering
Harvest
time
Plants
per
hect-
are
**
Cost
per
plant
($)
**
Field
Prin-
cipally
overhead
irrigation
Soil
For plant
structure
No special
require-
ments
Primari-
ly Spring
and Fall
770
23.71
Above-
ground
con-
tainer
Overhead
irrigation
Bark-
based
For plant
structure
and blow
over sup-
port
Quonset
structures
in Northern
production
areas
Any
time
870
23.73
**
Plants per hectare and costs were from a 1996study for three-year crape myrtle (Lagerstroemia)
production on a typical 15 acre (6 hectare) USA nursery with plants grown on a spacing of 5.6, 6.3, and
6.2 plants per m
2
for pot-in-pot, field and above-ground containers, respectively [27].
21.3 IRRIGATION OVERVIEW OF SHADE TREE NURSERIES
Many container nurseries irrigated with overhead sprinklers [4] even those growing
larger trees. Overhead irrigation has great disparity in water output across an indi-
vidual zone [55]. Yeager et al. [54] reported that irrigation zones can have as much as
300% variability in water output within a single zone. Container nurseries using over-
head irrigation could use more than 40,000 gallons of water per acre per day during
the peak-growing season with 40% to 90% losses through evaporation and runoff [52].
Also, efficiency and nonuniform wetting decrease with increasing container volume
[4] along with nonuniform wetting pattern. Beeson and Knox [4] reported overhead-
irrigation application efficiency of 37% when plants were adjacent to each other and
25% at a spacing of 3.0 inches (7.6 cm) between containers. It is estimated that 50%
to 75% of the water applied through overhead irrigation systems misses the containers
completely [59].
Nurseries have two main strategies for alleviating competition for water: improved
irrigation effi ciency and use of alternative, possibly lower-quality water from non-
traditional sources. Many practices infl uence effi ciency, including irrigation schedul-
ing, irrigation system selection and delivery, substrate composition, plant spacing, and
plant grouping based on water requirements within irrigation zones [15]. Increasing
irrigation effi ciency can reduce both over and under irrigation, which cause issues dur-
ing nursery production. Over irrigation can cause problems related to wasted water and
environmental pollution due to nutrient and pesticide contaminated runoff (removing
nutrients and pesticides from the foliage, root zone and production surfaces), energy
costs for pumping water, vulnerability to biotic and abiotic stresses; reduced plant
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