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ISSUE 12  July 18, 2002



What’s a good guide to determine the amount of any given crop loss in a field prior to or following harvest? There can be pre-harvest losses due to shattering, gathering losses at the combine header and also separation losses due to the threshing operation itself. In the chart below is an approximate loss guide to determine how much if any is being left in any given field. Usually crop harvest losses in the 2 to 3 percent loss range are tolerated.

Kernels or seeds per pound and number per square foot to equal one unit loss per acre at harvest.



Seeds/sq. ft. to equal 1 bu/Acre

Spring Wheat



Durum Wheat















Soybeans (small)



Soybeans (large)



Corn (Med. grade)



Sunflower (oil)



Sunflower (Conf.)



Navy beans



Pinto beans









Proso millet



Foxtail millet









*These are average numbers from past seasons, and individual varieties or hybrids will vary among themselves as well as be influenced by environmental factors.

Duane R. Berglund
NDSU Extension Agronomist



One very important management aspect of growing canola is estimating the correct time to swath and harvest. A canola grower must attempt to maximize yield and yet maintain quality with as little green seed content as possible in the threshed oilseed.

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.

Field inspections should be every "one to two days" when there is some color change in the first formed pods on the bottom of the mains stem.

To determine when a field of canola is ready to swath, plants from different parts of the field must be examined. 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.

Examine only those pods on the main stem. 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 only 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.

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 to brown, depending on the variety. Once filled, the seeds rapidly lose moisture at about 2 to 3 percent or more per day, depending on the weather.

Green Seed Problem: Temperatures at maturity is 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 degrees F disrupts that system, more specifically it can reverse it and restart the synthesis process. This is very sensitive in the seed development stage, and the window is very narrow. This can cause differences between adjacent fields that are only days apart in maturity, or differ in uniformity of maturity. Even 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. When looking at uneven stands, its suggested that one do a count early on the ratio of early emerged canola which is bolting or starting to flower and the late emerged flush of young more immature plants.

If one knows the ratio of early to late emerged canola plants, a better decision can be made as to how soon to swath or wait until the later crop catches up. If the stand is on 20-25% early and 75-80% late, then waiting to cut later may be the best strategy to reduce the amount of green seed.

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.

The average green seed at the 0-5 seed color at swathing time resulted in 3.5% green seed content which is higher than the 2% allowed in the market place before a discount will occur. Approximately 180 lbs/A of yield gain was noted when swathing was delayed to the 15-20 percent seed color change.

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, it is probably very near the optimum time for swathing.

Canola should be allowed to cure and ripen from ten to 14 days in the swath before combining. If combined too early, the chance of increased green seed in the harvested crop is much greater.

"Be in a hurry to swath on time and prevent shattering, but take your time in moving the combine into the field to ensure maximum drying, maturation and quality of your harvested canola."

Duane R. Berglund
Extension Agronomist



Pea growers need to carefully monitor the crop as it nears maturity in order to harvest on a timely basis. Harvest timing is especially important if the crop is to be marketed as seed, or to meet contract specifications for human food or specialty feed markets.

Field pea generally reaches physiological maturity in 85 to 105 days depending on the variety. Field pea may be swathed before combining or straight (direct) combined. Peas are normally swathed if a variety with prostrate type of growth is grown, there is uneven crop maturity, or heavy weed pressure is present. When swathing peas, vines and pods should be a yellow to tan color. The crop matures from the bottom pods upward. Yellow-cotyledon peas should have seed that has turned yellow in color.

Swathing will normally result in increased harvest losses. Modifications on the swather makes the procedure easier and reduces harvest loss. Modifications like vine-lifters enable producers to get under the pea vines and lift them over the cutting knife. Many growers use a pickup reel as well. Peas should be swathed in the early morning or late afternoon when the pods are tough to reduce shattering losses. A roller is recommended to push the swathe into the stubble for protection from wind. It is best to swath just before combining.

Field peas should be combined when the seed contains 16 to 20% moisture, to reduce splitting and cracking of the seed coat. At this moisture level, the seeds are firm and longer penetrable with a thumbnail. Also, pea vines must have turned yellow (no green color present) otherwise harvest will be extremely difficult.

Straight combining is possible depending on variety grown and harvest equipment available. Short-vine and semi-leafless pea grain varieties have characteristics that are adaptable to straight harvesting compared to varieties with indeterminate and prostrate-vine growth. For example, semi-leafless peas have a more open canopy, remain erect longer, and dry down more rapidly after a rain or heavy dew compared to conventional vining varieties.

Direct harvesting can be accomplished using an aggressive pickup attachment on a standard combine. Another option is use of a combine header with a floating cutterbar. Also, attachments such as lifter guards and pickup reels reduce losses and improve harvest efficiency.

Correct combine settings and operation are important to maintain seed quality. Also, adjust combine settings as weather and harvest conditions change.

Duane R. Berglund
NDSU Extension Agronomist

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