Agriculture Reference
In-Depth Information
incorporate organic matter from the previous
crop prior to planting.
Depending on the previous crop and the
types of tillage performed, reduced tillage may
be an option for improving the soil (Grant and
Epstein, 1973). Tillage is also used to incorpor-
ate pre-plant fertilizer and other soil amend-
ments. If planting and harvest logistics allow,
one goal of field preparation should be to reduce
compaction from previous field operations. This
can be accomplished by using deep-tillage imple-
ments such as subsoilers, rippers, and para-plows
(Magdoff and van Es, 2000). Soil compaction is
reduced when steel shanks from these imple-
ments are pulled deeply (>30 cm) through the
field. Despite the benefits of deep tillage, there
are production regions where tractors and har-
vesters will sink if the soil is significantly loos-
ened (especially within the furrow) and rain
abundant. Although the fields in these regions
are used for production, yields likely suffer from
soil compaction (Stark and King, 1997).
The top
30-
60 cm of soil in the potato seed-
bed should be loose and moist prior to planting,
and relatively free from rocks, clods, and exces-
sive crop debris. Seedbeds are shaped prior to,
during, and/or after planting. If conditions allow,
seedbeds should be shaped with a minimal amount
of tractor passes. None the less, some growers
must perform multiple operations to disrupt
weeds, incorporate fertilizer and herbicide, re-
locate or reduce stones and clods, and add soil to
the seedbed.
desert areas, it is common to pre-irrigate prior to
planting. Planting into soils that are excessively
cold, hot, wet, or dry may increase the potential
for seed-piece decay and delayed emergence.
Within reasonable limits, the earlier a crop is
established, the more potential there is to maxi-
mize tuber yield and dry matter content. In re-
gions where the growing season does not limit
the plant's ability to mature fully, planting dates
are often selected in an effort to provide the crop
with a growing environment that will produce
the highest economic yield for a desired market.
6.7
Potato Propagation and Seed
Preparation
Vegetative propagation using whole or cut
tubers is the most common method for starting a
potato crop. Depending on the size of the seed
tubers, growers may leave the tubers whole or
cut them into smaller pieces. Tubers left uncut
and planted whole are often referred to as “whole
seed”, “seed”, “seed potatoes/tubers”, or “single
drop”. Cut tubers are also referred to as “seed” or
“seed potatoes/tubers”, but are most often called
“seed pieces”. Most potato plants produce “true”
botanical seed, or true potato seed (TPS); how-
ever, TPS is seldom used because each seed de-
velops into a unique plant with traits unlike
those of the parent plants (Burton, 1989). In
addition, TPS-planted crops require several extra
months of initial growth compared with those
grown from seed tubers; often, the initial growth
takes place in a greenhouse or seedbed and is fol-
lowed by field transplantation. Compared with
TPS, seed tubers allow growers to produce plants
and tubers with traits identical (clone) to the ori-
ginal variety of interest, typically with rapid and
uniform emergence. TPS is occasionally used in
tropical or developing countries because seed
potato storage and transport is often expensive
and unavailable (Golmirzaie
et al
., 1994).
According to Struik and Wiersema (1999),
high potato yields are correlated strongly with
the use of high-quality, certified seed tubers.
Planting high-quality seed is perhaps the most
important step in successful potato production
and cannot be neglected. Seed certification pro-
grams are relied upon to regulate seed quality in
most developed countries and an increasing
number of less-developed countries (UNECE, 2013).
6.6
Planting the Crop
Planting time varies by region, depending on
local climatic conditions, potato variety, and in-
tended markets. Most potatoes grown in the
temperate climates are planted from April to
early June. Winter crops are typically planted
from November to February. Some regions have
weather that is conducive to year-round produc-
tion. Ideally, potatoes should be planted into soils
with temperatures conducive for rapid growth and
wound healing (especially when using cut seed),
which is typically above 7°C (Isleib and Thompson,
1959). However, soils warmer than 19°C may re-
duce tuber number and early-season growth (Van
Dam
et al
., 1996). At the time of planting, soils
should be moist but not excessively wet. In irrigated
