Agriculture Reference
In-Depth Information
potato cultivars in the ability to tolerate weed
competition and retain tuber yield when grown
in similar conditions, yet growers seldom con-
sider variety for its competitive ability. Instead,
market demand and regional influences such as
season length determine which varieties are
planted. There may be an opportunity to in-
crease potato competitiveness by incorporating
population and variety decisions into integrated
weed management plans.
The first and most important tillage prac-
tice is primary tillage. Tillage in late fall is often
necessary to reduce surface residue where pota-
toes are produced, and provides an opportunity
for producers to conduct subsequent tillage
operations in the spring before early planting.
Primary tillage is accomplished by using a mold-
board plow, disc, field cultivator, or field finisher
to control early flushes of weeds while preparing
the seedbed (Bohl and Johnson, 2010).
Secondary tillage is often used to control
weeds that have emerged after planting and before
hilling. As with other production practices, timing
of hill formation varies by region and producer.
Many producers plant their seed pieces under a
small row hill, returning with cultivation and hill-
ing once the shoots have emerged approximately
3
weeks after planting. A regional variation on
this practice involves using a larger row hill at
planting. Producers then wait to cultivate until
the potatoes have emerged and grown for approxi-
mately
3
weeks. Soil is then added to the row as a
consequence of hilling operations (Bohl and John-
son, 2010). As previously mentioned, late tillage
may be undesirable due to the potential for root
damage and subsequent yield loss.
A third option, popular in the Pacific North-
west USA, is used to minimize equipment passes
through the field seedbed, loosen compacted
soil, prevent erosion and water runoff, and dis-
rupt weeds within the furrow. Following planting,
producers use a Dammer Diker
®
(AG Engineer-
ing and Development Co, Kennewick, Washing-
ton, USA), which rips furrows between potato
rows with a deep shank (Bohl and Johnson,
2010). Wings on the sides of each shank move
and disrupt soil on the side of the potato hill,
while paddle-type wheels implant small tillage
reservoirs used to collect water and prevent ero-
sion. The Dammer Diker
®
tillage operation typically
occurs between planting and early post-emergence,
and relies heavily on pre-emergence herbicides
as the main weed control mechanism; post-
emergence applications are used only where
necessary.
Mechanical weed management
Hand pulling, chopping, and hoeing weeds are
simple forms of weed control used on smaller
farms where weed control options are limited,
particularly those in less developed countries or
those growing potatoes organically. Most com-
mercial farms, however, use tractor tillage for
mechanical weed control. Tillage is an import-
ant component of weed control in potatoes, re-
gardless of region or production system. Before
the development of herbicides, weeds in potatoes
were controlled through cultivation (Wallace
and Bellinder, 1989). Pre-emergence herbicides
are used to supplement tillage, but many grow-
ers continue to cultivate from one to six times to
control late-germinating weeds (Dallyn and
Fricke, 1974). Multiple tillage operations are
often employed by producers prior to and
throughout the season; however, cultivation
after emergence can injure potato roots and re-
duce yields (Nelson and Giles, 1986; Pierce and
Burpee, 1995; Bailey
et al
., 2001). Excessive till-
age and improperly timed cultivations can affect
potato yields adversely (Bailey
et al
., 2001).
Tillage operations generally begin with pri-
mary tillage for seedbed preparation the fall be-
fore sowing if a crop with high residue has been
produced. This is later followed by multiple till-
age operations in the spring, prior to hilling and
planting. Tillage practices vary by region, with
tillage type, frequency, and timing determined
by cropping system and producer preferences.
Cultivation and hilling are very useful for weed
control in season, but the operations can break
the prophylactic layer of pre-emergence herbi-
cides applied at planting. Consequently, some
growers apply additional pre-emergence herbi-
cides after hilling (Rioux
et al
., 1979).
Vine desiccation
Vine desiccation of potato is performed pri-
marily to improve harvest efficiency and stora-
bility, with the added benefits of improved fresh
