Agriculture Reference
In-Depth Information
wording and description, tuber number per
plant may change between tuber set and tuber
harvest, especially when the plant is stressed
(MacKerron and Jefferies, 1986). The final
tuber number per plant can be influenced by
temperature (Sale, 1979), soil moisture (Stru-
ik and Van Voorst, 1986; Walworth and Car-
ling, 2002), plant health and disease (Cother
and Cullis, 1985), planting depth and cultivar
(Pavek and Thornton, 2009), plant spacing
(Pavek and Thornton, 2006), seed tuber physio-
logical age (Knowles and Knowles, 2006), soil
fertility (Rosen and Bierman, 2012), and ir-
radiance (Sale, 1976).
source for the potato plant, while the tubers
are the major sink. Conversely, seed tubers be-
come the source of carbohydrates and nutri-
ents during the early stages of plant establish-
ment until plants become autotrophic.
Management of plant growth to maximize
yield and economic return while minimizing water,
fertilizer, pesticides, and other inputs is a primary
goal in commercial crop production. Attention
must be given to the partitioning of assimilates be-
tween canopy and tubers, as too much to one or
the other can lead to an imbalance and a reduction
in tuber yield and/or quality. Maximizing the inter-
ception of solar radiation by the potato canopy
during key growth stages, and in turn the effi-
ciency of conversion of intercepted light to photo-
synthetic assimilates, is essential for maximizing
yield or economic return (Firman and Allen,
1988); provided the plant is healthy and has un-
limited access to nutrients, water, and moderate
temperatures. Often, solar radiation interception is
limited due to seasonal changes associated with a
particular geographical location. Moreover, in an
effort to use land efficiently and to influence tuber
size and yield, commercially grown potato plants
are usually positioned in the field so their canopies
collectively cover 100% of the soil surface (100%
ground cover). As a result, the canopy of one plant
often restricts the maximum solar radiation inter-
ception of its neighbor. The underlying theme is
maximizing economic return on a given piece of
land by producing as much of the right-sized,
high-quality tubers as is biologically possible. Mod-
ern production systems manage plant population,
inter- and intra-row plant spacing, and agronomic
inputs to produce the ideal canopy size and dur-
ation for maximum yield of the highest-valued
tuber sizes.
The ideal canopy architecture maximizes
light interception during key growth stages and
allows for sufficient assimilate translocation during
plant maturity, leading to maximum yield or eco-
nomic return. Because potato fields typically have
100% ground cover for much of the season, keeping
the canopy healthy and alive for as long as pos-
sible becomes the limiting factor for optimizing
output. This is not to say that the canopy should
stay green and vigorous up until harvest; rather,
a healthy canopy should be maintained as long
as possible while still allowing for proper plant
maturity prior to harvest. The ideal canopy size
and duration varies by cultivar and season length.
5.7
Canopy Development
As tuber initiation slows and nears completion,
plants under ideal conditions focus their energy
on maintaining sufficient canopy to feed the
new tubers. The rate at which the tubers and
canopy develop is dependent largely on environ-
ment interacting with genotype. Plants growing
in favorable environments free of pests and dis-
ease, with sufficient water, nutrients, and heat
units are likely to produce a larger canopy and
greater tuber yields than those grown under
stress. Tubers under stressed plants may actually
bulk sooner and faster than those under healthy,
unstressed plants; however, this usually occurs
at the expense of canopy development. To maxi-
mize tuber yield or economic return, a balance
must be struck between canopy size and duration
and the number of growing days in a particular
region. For some cultivars, excessive canopy
growth late in the season may extend tuber
bulking and delay plant maturity, which could
result in reduced tuber yield and quality. On the
other hand, an undersized canopy that senesces
prematurely is likely to result in a loss of potential
yield. Modern cropping systems with state-of-
the-art irrigation/fertigation systems and pest and
disease control allow growers to tailor potato crop
growth for a particular region, cultivar, and intended
market in order to maximize economic return.
Through photosynthesis, potato plants
use light energy to assimilate carbon dioxide
into sucrose, which is translocated from
source to sink. In general, sources are net car-
bon producers, while sinks are net carbon
users. Mature green leaves are the main
