MICRO-IRRIGATION SYSTEMS FOR POT-IN-POT ORNAMENTAL NURSERY PRODUCTION - Management, Performance, and Applications of Micro Irrigation Systems - page 299

PIP was originally developed as the “Minnesota System” in the 1980s [32] as an
alternative to fi eld and above-ground container production for tap-rooted shade trees
[33]. The system proved to be equally useful for general shade tree production [45].
Although initially costly to establish [27], PIP is arguably the most sustainable produc-
tion system for nursery shade trees. Compared to fi eld produced trees, PIP uses water
and fertilizer more effi ciently and eliminates “soil mining” because it uses a renew-
able bark-based growing substrate rather than digging trees from the nursery fi eld.
For large caliper tree production, about 170 metric tons of soil is removed per hectare
of production [7]. Compared to above-ground container production, PIP results in a
reduced use of plastic where Quonset structures are required for overwintering.
This chapter describes the current features of pot-in-pot nursery production sys-
tems with particular emphasis on micro irrigation.

21.2 POT IN POT (PIP) NURSERY PRODUCTION SYSTEM
Establishing a PIP nursery can involve extensive first year preparation. Installation
procedures are detailed step-by-step in the University of Kentucky video available
on-line at: <http://www.youtube.com/watch?v=wNeBurkznIk>. PIP systems are ei-
ther established in extremely well-drained soils or a drainage line must be installed
just below the bottom of the socket pot. PIP system allows closer spacing and permits
precision application of irrigation and fertilizer compared to typical field production.
Production pots with plants are easily harvested at any time of year providing market-
ing flexibility and potential profits whereas field-grown plants require machines, and
harvesting cannot occur during very dry or wet periods as that could cause root dam-
age [19]. Other advantages of PIP compared to above ground container production
include: no blowing over as plants are anchored in the ground saving labor and money
required to upright plants. Under PIP system, roots experience a moderated tempera-
ture similar to the soil temperature below ground, which reduces evapotranspiration,
and ensures higher root quality and faster plant growth than above ground container
production [24, 39, 58]. The system protects roots from temperature extremes avoid-
ing the need for moving to an overwintering structure or to provide shade during hot
summer. Table 1 presents a comparison of key features of PIP with field and above-
ground containers.

TABLE 1 Comparison of key features of pot-in-pot nursery production compared to above-
ground or in-ground shade tree production.

Pro-
duction
system

Irriga-
tion type

Substrate Staking Over win-

tering

Harvest
time

Plants
per
hect-
are **

Cost
per
plant
($) **

Pot-in-
pot

Micro ir-
rigation

Bark-
based

For plant
structure

No special
require-
ments

Any
time of
year

950 21.50