Agriculture Reference
In-Depth Information
maintenance of crop quality. Proper storage is
essential to maintain the quality and viability of
seed tubers being held until the next production
season.
It is difficult to assess how much of the
world's potato crop goes into storage, because
data are not available for many locations. One
estimate is that approximately 25% of the world-
wide potato crop destined for human consump-
tion is stored for some length of time (van der
Zaag, 1989). A few examples demonstrate the
relative importance of storage in different parts
of the world. In the USA, 59% of the 2010 crop
was in storage for 3 months or more (USDA
National Agricultural Statistics Service, 2011).
Likewise, approximately 58% of the crop in
Great Britain is commercially stored prior to
being utilized, half of which is used for the fresh
market (Cunnington, 2008). In India, 40% of
total production is put into refrigerated storage;
of this, approximately 25% is for consumption
and 15% for seed (CIP, n.d.; Fuglie
et al
., 2000).
In Kenya, harvest occurs regionally every
2-
3
months. Consequently, storage of ware potatoes
in Kenya is not routine (CIP, n.d.). Similarly, in
Ecuador, seasonal climatic variation is minimal
and potato cultivation occurs continually
throughout the year. Few potatoes are put into
storage, since recently harvested potatoes are al-
ways available (CIP, n.d.).
unharvested and kept in the ground for an ex-
tended period of time. Ground storage requires
moderate soil temperatures and even soil mois-
ture following senescence of the potato vines.
Freezing temperatures and waterlogged soils can
be disastrous for the crop, as one increases the risk
of physical breakdown and the other of patho-
genic breakdown. The advantage of ground stor-
age is that infrastructure cost is very low. Ground
storage also eliminates the increased risk of dis-
ease in storage that comes from damage during
harvest, transportation, and handling. Ground
storage is used in Ethiopia for half of the seed
crop (Gildemacher
et al
., 2009).
A potato clamp is another form of simple
storage. It is suitable for locations where winter
temperatures do not fall much below freezing.
Clamps are linear, steep-sided piles of potatoes
that are covered with straw and a layer of soil.
The straw and soil provide insulation. The straw
functions to keep the soil out of the pile, thereby
maximizing the air volume next to the tubers. In
some cases, plastic sheeting is placed over the
straw a few weeks after harvest, and this is
covered with soil. The sheets are arranged to
provide protection from precipitation while al-
lowing for ventilation.
Within the clamp, evaporation from tubers
and the surrounding soil creates an environment
of high relative humidity (RH), which helps to
maintain tuber hydration. Heat produced by res-
piration keeps the tubers warmer than their sur-
roundings, but it can also result in an excessively
high level (0.88%) of carbon dioxide (CO
2
),
which is detrimental to tuber quality (Crook and
Watson, 1950). One benefit of using clamps is
that one can use material readily available on the
farm. As recently as the late 1940s, clamps were
the predominant form of potato storage in England
(Samuel and Wilson, 1949). Due to advances in
technology, only 5% of the potatoes in Great Britain
were stored outdoors
40
years later (Statham,
1989; van der Zaag, 1989).
Excessive heat during storage leads to an in-
crease in disease. Locations with warm climates
like India rely on large-scale refrigerated storag-
es to hold potatoes for an extended period (Fuglie
et al
., 2000); however, these storages are pro-
hibitively expensive to growers in poorer sub-
tropical regions. As an inexpensive alternative,
small landholders may store ware potatoes in
aboveground cribs that allow air movement
15.2 Types of Potato Storage
Potatoes are grown worldwide. The way that po-
tatoes are stored depends on cultural expect-
ations for the quality of tubers coming out of
storage, the desired duration of the storage
period, and local environmental conditions. Po-
tato storage methods are highly diverse, because
each of these parameters varies widely between
production regions. For example, in most of
North America and Europe, harvest occurs in
the fall and is followed by an extended cool or
cold period, whereas harvest in India occurs in
the spring and is followed by an extended warm
period. The methods used to store tubers and the
duration of the storage period reflects these very
different climatic conditions, as well as the in-
tended market.
Ground storage is the simplest type of po-
tato storage. In this case, mature potatoes are left
