Agriculture Reference
In-Depth Information
(Mikitzel and Knowles, 1990; Blauer
et al
., 2013a).
For each variety, growing region, and market,
the proper combination of cultural management,
plant population, and spatial positioning is needed
to produce the highest-valued tuber size profile.
Because tuber bulking is dependent on canopy
health and duration, preventing foliage damage
from pests is essential.
milestones and measurable indices of develop-
ment for late-season cultivars that relate to yield
2013). Regardless of production area, these
milestones can be used to gauge the effects of
agronomic inputs on season-long crop develop-
ment to facilitate formulating best management
practices for a particular cultivar and end use.
5.10 Milestones of
Crop Development
5.9 Stages of Crop Growth and
Development: A Long-Season
Cultivar Case Study
•
Harvest index (HI) at maximum foliar
growth.
The principal stages of crop growth and develop-
ment include: (i) sprouting; (ii) plant emergence
and establishment; (iii) vine growth and foliar
canopy development; (iv) flowering and tuberi-
zation; (v) tuber bulking; (vi) foliar senescence;
and (vii) tuber maturation. The timing and overlap
among these stages can vary considerably and
depend on cultivar, management, climatic, and
edaphic variables, and stresses experienced by the
crop throughout the season. Managing a crop to
coordinate and synchronize the onset and dur-
ation of these stages within the environmental
constraints of a particular growing area is the
key to optimizing yield and quality for maximum
economic return.
Potato inherently has an indeterminate
growth habit, and thus vegetative growth con-
tinues during flowering and throughout the sea-
son. However, cultivars vary in their expression
of indeterminism, which affects how the crop uses
and partitions water and nutrients to foliage and
tubers. Tuber yield and quality can be affected
negatively if the seven stages of development are
not synchronized correctly for a particular culti-
var and area of production.
The relative and optimal timing of each de-
velopmental stage depends on many factors, in-
cluding cultivar, length of the growing season,
management inputs, growing environment (e.g.
light intensity, photoperiod, day/night tempera-
ture), and market expectations for yield and tuber
size distribution. Achieving optimum tuber yield
and quality involves managing source-sink (foliar/
tuber growth) relationships at critical periods
during the growing season. In the highly pro-
ductive areas of the Pacific Northwest USA (e.g.
Columbia Basin of Washington and Oregon),
crop growth profiling studies have revealed key
•
DAP and/or cumulative degree days to 50%
HI and yield at 50% HI (foliar biomass =
tuber biomass at 50% HI).
•
DAP and/or cumulative degree days to:
- maximum foliar fresh weight;
- maximum tuber yield;
- maximum tuber
specific gravity;
- minimum tuber sucrose
concentration;
- minimum tuber reducing
sugar concentration; and
- tuber physiological
maturity.
}
These
milestones
define tuber
physiological
maturity
(PM)
•
Maximum foliar biomass.
•
Maximum tuber yield.
•
Specific gravity at harvest.
Source-sink relationships are indicated by the HI.
The HI is dynamic, increasing rapidly at the
beginning of the season during early to mid-
bulking, and coincident with the period of rapid
canopy (foliar) and tuber development. At max-
the HI should fall within the range of
40-
50%,
favoring foliar growth over tuber growth, for
most (but not all) indeterminate late-maturing
cultivars in long-season growing areas like the
Columbia Basin. The HI at point (A) in
Fig. 5.4
is
44% (e.g. tubers account for 44% of plant fresh
weight at this point in the growing season). This
index can inform management; for maximum
yield potential, early-season fertility and irriga-
tion should be managed to promote rapid foliar
development during plant establishment, tuberi-
zation, and early bulking to produce sufficient
leaf area to support continued bulking over the
prolonged growing season (150+ days). If foliar
