Agriculture Reference
In-Depth Information
predict stem number is difficult, growers typic-
ally opt for spatial configurations determined via
research, or those that historically have provided
the best returns across years and seed lots.
Generally, the average harvested tuber
weight per plant or unit area decreases as
plants are crowded together and increases
when plants have less competition from their
neighbor (Pavek and Thornton, 2006). With-
out proper uniform spatial arrangement, plant
population by itself is of marginal importance
in optimizing economic return. Pavek and
Thornton (2006) demonstrated this principle
by altering the in-row spacing of identical
plant populations within the same unit of
area. In this case, the uniform, properly spaced
treatment produced a higher-valued tuber size
profile than the irregular spacing treatment,
which contained the same number of potato
plants. Once the optimum inter- and intra-row
spacing is determined, the accompanying
plant population can be calculated.
In-row spacing values in the range of
15-
30 cm are common. Variety characteristics like
average stem and tuber number per plant, aver-
age tuber size, and days to reach maturity need
to be defined prior to selecting the appropriate
seed piece spacing. To minimize oversized tubers,
varieties with low tuber numbers per plant
should be spaced closer together than those with
higher tuber sets, and vice versa. Wider in-row
spacing may be used to increase average tuber
size when growing late-maturing varieties in re-
gions with short seasons. Closer in-row spacing
may be more desirable where season length is
long and moisture and nutrients are not ex-
pected to be limiting. Rapidly growing and exces-
sively large tubers are more prone to internal
defects such as hollow heart and brown center;
therefore, a simple in-row spacing reduction
could lead to higher-quality tubers, simply by
regulating tuber growth and preventing the pro-
duction of oversized tubers (Rex and Mazza,
1989).
Because growing conditions, varieties, and
market needs vary from region to region, seed
piece spacing requirements for particular var-
ieties are not consistent across regions. The
proper inter- and intra-row spacing for each var-
iety and region must be determined through
local research.
6.9
Conventional Rows
versus Beds
Potatoes are typically planted into some type of
row configuration. Furrows between convention-
ally-ridged potato rows help prevent tuber dam-
age from tractor tires and allow for inter-row
post-planting weed disruption, incorporation of
fertilizer and herbicides, water drainage, furrow ir-
rigation, potato hill enlargement, increased seed
piece depth, erosion prevention, and soil compac-
tion mitigation. Conventional rows are essentially
raised mounds of soil (ridges/hills), commonly
76-
91 cm wide, that run parallel to each other the
length of the field; each ridge contains one row of
linearly spaced potatoes. Some growers forego con-
ventional row systems and plant their potatoes
into wide beds. Beds are essentially wide ridges that
contain multiple closely spaced rows. In this sys-
tem, furrows are only located at intervals consist-
ent with the tractor, planter, and harvester track
width. Furthermore, furrows are absent between
all rows contained within the bed. Beds are more
conducive to high planting densities intended to
minimize average tuber size (Mundy
et al
., 1999).
In addition, bed systems are occasionally more
efficient at capturing irrigation water or rainfall
than conventional ridge systems (Robinson,
1999). In areas with excessive rainfall, however,
capturing and holding rainfall during certain
times in the season may prove undesirable. On
average, soil temperatures throughout the bed
fluctuate less than those in ridges (Mundy
et al
.,
1999), presumably due to the insulating factor as-
sociated with the extra soil found between each
bed-planted row, which is normally removed when
conventional ridges are formed. Prior to emer-
gence, the insulating factor in beds may actually
inhibit the accumulation of early-season soil heat
units and delay emergence.
Bed systems do present some disadvantages
when compared with conventional rows. Inter-
row post-planting operations commonly con-
bed systems due to the lack of furrows between
every row. The conventional row system also al-
lows for furrow irrigation. In addition, tractor
horsepower requirements might increase when
harvesting from beds, as harvesters must sift
through more soil than with conventional rows.
