Swathing and Harvesting Canola
A-1171, May 1999
Duane R. Berglund, Professor and Extension Agronomist,
NDSU - Fargo
Bryan Hanson, Agronomist, NDSU Research Extension Center -
Langdon
Mark Zarnstorff, Agronomist, NDSU North Central Research
Extension Center - Minot
Canola has become a major economic oilseed crop in North
Dakota and northwestern Minnesota in recent years. However, many
growers are relatively inexperienced with canola production and
harvesting. Many new growers have limited experience with the
crop. Proper harvest management in terms of selecting the proper
maturity stage for swathing and combining are very important. As
a canola crop nears maturity, it may ripen very quickly.
Selecting the correct time to swath and combine canola demands
more observations and care than does small grains.
Proper Stage to Swath Canola
Swathing canola at the optimum stage of ripening reduces green
seed problems and seed shatter losses and ensures the quality
required for top grades and prices.
Inspect fields every two to three days when there is some
color change in the first formed pods on the bottom of the main
stem.
To determine when a field of canola is ready to swath (Figure
1), examine plants from different parts of the field. The stage
of maturity in an evenly maturing field will vary from plant to
plant and from area to area within the field. When examining the
plants, take into account varying soil types, low lying areas,
available soil moisture and exposed early ripening areas.
Figure 1. Canola field
ready to swath. (21KB color photo)
Examine only those pods on the main stem (Figure 2). Seeds in
pods on the bottom third of the main stem were formed earlier and
will turn color much sooner than seeds in the pods on the top
third of the plant. When the overall moisture content of seed
from the total plant averages 30 to 35 percent, about 30 to 40
percent of the seeds in pods on the main stem will have changed
color or have started to change color. Seeds with only small
patches of color should be counted as color changed. Remember,
the color of the seed is more important than the overall color of
the field in determining the stage of maturity (Figures 3-6).
Figure 2. Optimum
moisture stage for swathing canola. (12KB
b&w image)
Figure 3. Plants at
various maturity stages. (36KB color
photo)
Figure 4. Change in
pod maturity. (26KB color photo)
Figure 5. Change in
pod and seed maturity. (39KB color photo)
Figure 6. Seed color
and maturity changes. (33KB color photo)
Most of the seeds that have changed color will be from the
bottom third of the stem. When seeds in the bottom pods slightly
turn color, seeds in the top, last-formed pods are filled or
nearly filled. At this time, most of the seeds will be firm and
roll, as opposed to break, when pressed between the forefinger
and thumb.
Seeds in all pods on a plant complete filling (physiological
maturity) at about 40 percent moisture and then slowly turn from
green to light yellow, or reddish brown, brown or black,
depending on the variety. In hot (90 degrees Fahrenheit), dry
weather, canola seed can go from 10 to 50 percent seed color
change in just four to five days or less. Once filled, the seeds
rapidly lose moisture at about 2 to 3 percentage points or more
each day, depending on the weather.
Swathing early can be beneficial if a hard fall frost is
expected. Frost fixes the chlorophyll or green color in immature
seed, making it difficult to remove during processing. Fall
frosts rarely freeze to ground level. A swathed crop will not
only lie below the coldest night temperatures, but much of the
seed will benefit from the insulating properties of the swath and
residual soil heat, preventing or reducing frost-fixed
chlorophyll.
Effect of Swathing Time on Yield, Green Seed and Oil
Studies in North Dakota and Minnesota have been conducted to
show the relationship of seed color change at swathing time to
yield, seed size, green seed and percent oil.
Table 1. Canola Swathing Research Results*.
-------------------------------------------------
Seed Color Green
at Swathing Number Seed Yield Seed Oil
(% change) Seeds/lb (lbs/A) (%) (%)
-------------------------------------------------
0-5 160,800 1603 3.5 39.5
15-20 144,400 1785 1.4 40.0
30-35 138,500 1795 1.1 40.1
LSD .05 8,077 130 1.4 0.4
-------------------------------------------------
* Locations Averaged -1996-97 Langdon, Minot,
Carrington, ND and Roseau, MN
The average green seed at the 0-5 seed color at swathing time
resulted in 3.5 percent green seed content, which is higher than
the 2 percent allowed in the market place before a discount will
occur. Approximately 180 to 200 lbs/A of yield gain was noted
when swathing was delayed to the 15-20 percent or greater seed
color change. There was a problem with seed size shrinking and a
tendency to lower oil percent with the 0-5 color change at
swathing.
The research results suggest that swathing of canola can start
when a minimum of 15-20 percent seed color change has occurred.
This management practice will help ensure maximum yield
potential, acceptable green seed content and percent oil. The
early start is particularly important when large acreage of one
variety of Argentine canola is involved or all the crop was
seeded over a short period of time.
Another sign of canola being very near the swathing stage is
the natural yellowing and senescence of leaves and leaf drop.
When canola plants consist only of stems, stem branches and pods,
the crop is probably very near the optimum time for swathing.
Swathing can begin in Argentine canola at 15 percent seed color
change. Polish canola should be left until 20 to 25 percent seed
color change.
Swathing Canola
Canola is harvested with the same swather and combine
equipment as cereal grains, although the crops are quite
different. Canola is tall and branchy, with thick spongy stems.
However, with a few basic adjustments to most modern swathers, a
good windrow of canola can be formed.
Cutting Height
The swather should be run just low enough to get all the seed
pods, leaving the maximum amount of stubble in which to anchor
the windrow and ensure adequate air circulation through the
windrow. Most stubble height varies from 10 to 12 inches in
canola fields after swathing. This allows good anchoring of the
windrow and drying (Figure 7). To keep the swather moving forward
without bunching, a few low pods may have to be missed. Such
windrows tend to settle into the stubble and escape wind damage.
This also minimizes the amount of material that must be handled
by the swather and the combine. Additional material will only
delay the drying process.
Figure 7. Properly
swathed canola. (25KB color photo)
Swather Table and Throat
The average crop of canola is handled quite readily with most
swathers. However, stands that are exceptionally tall (4-5 feet),
thick, or lodged and tangled make it difficult to lay an
unbunched windrow. The windrow must flow smoothly through the
swather without bunching. Bunching leads to uneven drying and
combine plugging. Therefore, a good swather must have enough
depth of table (40 inches) to handle the crop material. It also
should have a large throat opening - at least as wide (40 to 54
inches) as the distance between the two swather canvasses on
center delivery swathers. It should have a vertical clearance for
the windrow of at least 30 to 40 inches. The throat opening
should be free of projections that may catch and bunch the
windrow as it passes through the machine. A large throat opening
is important, particularly for wider swathers, to ensure the
swath will be of a size and shape which will dry and cure
properly.
The table canvas should be strong enough to carry the heavy
load of material cut and should be run just fast enough to keep
the table clean. If possible, canvas speed should be varied
depending on the maturity of the crop cut. A fast canvas tends to
produce a hollow twisted windrow; a slower canvas produces a more
compact windrow, but it may bunch and sit high on the stubble.
Increase the canvas speed until the windrow is pressed into the
stubble.
Reel and Dividers
The reel should be set as high and as far forward as possible.
Reel speed should be set to correspond with the forward speed of
the swather. This speed will just lay the cut material gently
back on the table to avoid shelling. The ratio of tip speed of
the reel bat in feet per minute divided by the ground speed of
the swather in feet per minute should be a maximum of 1.0 to 1.1.
Finger reels work best in canola to help bring the material back
onto the table and gently handle the ripened canola. For a lodged
or leaning canola crop, finger reels are highly recommended for
ease of swathing.
Ordinary end dividers which are long and gently sloping are
generally less prone to plugging than short, abrupt types. In
lodged or tangled canola, the divider tip must split the crop
down low in the stem area, and then lift and separate the crop as
the swather moves forward. Separation of the crop should be
complete just before the knife cuts the stems. When the crop is
tall, tangled and lodged, or laid across the seeded rows, divider
plugging is almost inevitable unless special vertical cutterbars
or power blades are fitted on the swather (Figure 8). These can
cause minor loss of pods and whole seed tops, but they prevent
stops and bunching. In badly lodged crops it may be advantageous
to swath in a direction parallel to the direction in which the
crop is leaning. For example, if the crop is leaning southeast,
then swath from the southeast to the northwest. Canola crops do
not often flatten so badly that a conventional swather will not
handle them, but in severe conditions, a pickup reel, set well
forward and with a speed ratio of 1.1, will help in swathing.
Also, install lifting guards which lift the crop so it can be
cut.
Figure 8. Swather
equipped with vertical cutter bar. (22KB
color photo)
Swath rollers
In areas where windrows could be lifted and blown by the wind,
a light roller pulled behind the swather will help anchor the
windrow in the stubble (Figure 9). The roller should be set so
that it just anchors the windrow into the stubble without
shelling any ripe pods. Excessive roller pressure will produce a
windrow that is too compact to dry quickly and difficult to pick
up without shelling the canola. The windrow should be left as
high as possible in the stubble so that the combine pickup can
slip under it without tearing the windrow. NDSU research studies
have shown that swath pack density and seeding rates had little
effect on green seed of canola.
Figure 9. Rolling a
canola swath. (22KB color photo)
Swathing Over-ripe Fields
Swathing late, when seed moisture content is much lower
(around 80 percent seed color change), will result in fluffy
windrows susceptible to blowing and increased shattering. To
reduce shattering losses, over-ripe fields should be swathed when
humidity is high, such as after a rain, after a heavy dew, or at
night.
Swathing Unevenly Maturing Crops
It is difficult to determine when to swath unevenly maturing
fields. Uneven maturity is usually the result of uneven spring
germination with two or more flushes of seedling emergence.
When checking uneven stands, its suggested that a producer do
an early count on the ratio of early emerged canola which is
bolting or starting to flower and the late emerged flush of
young, more immature plants.
Knowing the ratio of early to late emerged canola plants
allows making a better decision as to how soon to swath or wait
until the later crop catches up. If the stand is 20 to 25 percent
early and 75 to 80 percent late, then waiting to cut later may be
the best strategy to reduce the amount of green seed.
Time in the Swath
Canola should be allowed to cure and ripen from 10 to14 days
in the swath before combining (Figure 10). If combined too early,
the chance of increased green seed in the harvested crop is much
greater.
Figure 10. Mature
canola in swath. (32KB color photo)
Be in a hurry to swath on time and prevent shattering, but
take your time moving the combine into the field to ensure
maximum drying, maturation and quality of your harvested canola.
While it's better to start on the early side for swathing, the
same doesn't necessarily hold true for combining. Hot or windy
weather at or after swathing can cause canola seed to be at the
appropriate moisture content for combining before it has cured
and cleared the green chlorophyll. This occurs because the plant
dries up before sufficient moisture can move into the seed to
finish curing it. Canola requires at least 20 percent moisture in
the seed for the maturing process to take place and eliminate the
green seed color. It is important to check both moisture content
and green seed count before starting to combine. Delayed
combining can help clear the green color, particularly if the
swath sits through several heavy dews or light rain showers.
Research was conducted at various locations in North Dakota
and Northwest Minnesota to determine canola seed yield and
quality as influenced by the amount of time the crop is cured and
ripened in the swath (Table 2). The results indicated that while
seven days curing in the swath was adequate time for yield, it
was not sufficient time to allow for green seed color change
(reduction in chlorophyll) or drop in moisture content of the
seed.
Table 2. Swathing to Harvest Days.
-------------------------------------------------------
Average
Swathing Harvest Green Number
to Harvest Date Yield Seed Seeds/lb Moisture
Days GDD's* lbs/A (%) (%) (%)
-------------------------------------------------------
7 144-192 1774 2.3 147,400 11.6
14 312-360 1733 2.0 148,100 7.3
21 480-528 1675 1.8 148,200 7.9
-------------------------------------------------------
Locations Averaged: Langdon, Carrington, Minot, ND
and Roseau, MN. 1996-97.
* GDD's - Growing Degree Days - Base 40 F.
Green Seed Problem
There have been problems with green seed in North Dakota.
Cool, wet, and overcast weather during the growing season
promotes green seed. These problems can be made worse in some
instances by sulfur deficiency. Temperatures at maturity are an
important factor in chlorophyll breakdown. Cool temperatures and
light frosts in August and September slow the enzyme activity
that breaks down chlorophyll. Frosts from 32 to 33 F stop the
chlorophyll breakdown and in some cases can reverse it. There
maybe differences between adjacent fields that are only days
apart in maturity, or differ in uniformity of maturity. Canola
swathed four to six days before a frost will retain relatively
high levels of chlorophyll. Two or more germination flushes and
growth stages result in immature seed at swathing and green seed
at harvest. Thin stand counts can result in plants with more
branching and more variability in seed maturity and are more
likely to have immature seed at swathing. Late seeded canola may
be impacted by all these situations.
Practices to Reduce Green Seed
Growers can make management decisions to reduce green seed
problems:
- Choose fields with better surface drainage and fertility.
- Seed as early as possible in the spring to allow for the
maximum ripening time.
- Provide a firm seed bed to achieve correct depth of
planting and good seed to soil contact for rapid and even
emergence. Do not broadcast seed!
- Swath at the recommended color stage for the weather
conditions.
- Maintain adequate fertility levels for canola growth and
ripening. Canola stressed from sulfur nutrient deficiency
will not mature evenly.
- Take soil samples for a general indication of N, P, K,
and sulfur.
- Sample plant tissue early during rosette stage to allow
time for corrective sulfur applications.
- Fields with high fertility levels can be expected to
delay maturity in years with below normal growing degree
day (GDD) accumulation or heat units (cool years).
- Don't swath canola if the weather forecast is for
extremely hot, dry and windy conditions.
- All canola management decisions should be targeted toward
uniform crop maturity.
Combining
All combines work fairly well to harvest canola. (Figure 11).
Canola in the swath is ready to pick up and thresh when the seed
temperature and moisture content have dropped to a safe storage
level and most seeds are mature with no green color. Before
combining or after combining a small sample, use a crush strip
along with a small roller to make sure the seeds are not green
inside (Figures 12,13). A color chart can be used to determine
the green seed content. If there are some green seeds, a few more
days in the swath will probably allow time to clear the
chlorophyll.
Figure 11. Combining
canola. (23KB color photo)
Figure 12. Roller and
crush strip for testing green seed content. (19KB color photo)
Figure 13. Green seed
test guide. (38KB color photo)
Combines should be checked out throughly before starting on
canola. Cover with duct tape or caulking compound any holes or
worn spots in the table/platform or within a combine. Leakage can
easily occur in the stone trap, top feeder housing or through
lower inspection doors.
Travel speed of the combine should be equal to that of the
pickup so a gentle lifting of the swath occurs without tearing or
pushing. Set the pickup to rub just under the swath.
Cylinder speeds will depend on canola crop conditions. Speeds
of one-half to two-thirds of that used for small grains are often
used for canola. The speed should be just fast enough to break
open the pods. Speed reduction is important to prevent
overthreshing of pods and stems and overloading the sieves.
Cracked canola is caused by impact when cylinder speed is too
fast. Examine the threshed seed for cracked canola. Push your arm
into the seeds and observe if cracked canola seed pieces stick to
your skin or hair on your arm. Reduce cylinder speeds if
excessive cracking does occur.
Fan speed should be set low to avoid blowing canola seed out
with the chaff. This will allow large amounts of pods in the
return. Start with low fan speed and increase gradually until
separation of chaff and seed occurs with no canola being blown
over the chaffer sieve.
Direct cutting of Polish canola results in little or no
shatter loss. However, direct cut combining of Argentine type
canola has resulted in yield losses of 8 to 54 percent as
reported by the Canola Production Center in Canada.
These losses were primarily from shattering and gathering
losses when canola was taken into the combine. Some pre-harvest
shattering losses also will occur in Argentine canola.
Storage and Drying
Storage and handling problems of canola are similar to those
of flax. The seed is round, small, heavy and runs freely. Very
tight truck boxes and storage bins are required. The seed can
sweat for up to six weeks after harvest, so heating and spoilage
can occur even at 9 to 10 percent moisture levels. Canola as low
as 8� percent moisture should be examined for heating at regular
intervals. If harvested at high moisture, natural air drying or
artificial drying can be used. To maintain seed quality, a drying
temperature of 110 F or less is maximum for commercial
production. If a significant amount of foreign material (straw)
is included with the seed, it may be advantageous to run it over
a scalper before drying and binning.
Table 3. USDA Grade and Grade Requirements for Canola.
---------------------------------------------------
US Grades 1 2 3
---------------------------------------------------
Grading Factors
maximum percent limits of:
Damaged kernels
Heat damaged 0.1 0.5 2.0
Distinctly green 2.0 6.0 20.0
Total 3.0 10.0 20.0
Conspicuous admixture*
Ergot 0.05 0.05 0.05
Sclerotinia 0.05 0.10 0.15
Stones 0.05 0.05 0.05
Total 1.0 1.5 2.0
Inconspicuous admixture** 5.0 5.0 5.0
---------------------------------------------------
maximum count limits of:
Other Material
Animal filth 3 3 3
Glass 0 0 0
Unknown foreign substance 1 1 1
---------------------------------------------------
US Sample grade - Canola that:
- does not meet the requirements for US Nos. 1, 2 or 3,
or
- has a musty, sour or commercially objectionable
foreign odor, or
- is heating or otherwise of distinctly low quality.
* Conspicuous admixture is all matter other than canola
that is readily distinguishable from canola and which remains
in the sample after the removal of machine-separated dockage.
It is not limited to ergot, sclerotinia and stones.
** Inconspicuous admixture. Any seed which is
difficult to distinguish from canola. This includes, but is
not limited to, common wild mustard (Brassica kaber and
B. juncea), domestic brown mustard (Brassica juncea),
yellow mustard (B. hirta), and seed other than the
mustard group.
A-1171, May 1999
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