ISSUE 13    July 28, 2005

GUIDELINES FOR HARVEST LOSSES

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.

Species

Seeds/lb*

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

Spring Wheat

14,300

20

Durum Wheat

11,500

16

Barley

13,500

15

Oats

15,500

11

Flax

88,000

113

Rye

18,000

42

Soybeans (small)

3,300

4.5

Soybeans (large)

2,400

3.5

Corn (Med. grade)

1,500

2

Sunflower (oil)

9,000

5

Sunflower (Conf.)

5,000

2.5

Navy Beans

3,000

4

Pinto Beans

1,400

2

Sorghum

15,000

18

Sudangrass

44,000

40

Proso millet

80,000

84

Foxtail millet

220,000

242

Buckwheat

15,000

16

Canola

150,000

172

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

 

SWATHING AND HARVESTING CANOLA

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."

For additional information on harvesting canola, request NDSU Extension Circular - A-1171 entitled "Swathing and Harvesting Canola". It is available on the web at:

http://www.ext.nodak.edu/extpubs/plantsci/crops/a1171w.htm

Duane R. Berglund
Extension Agronomist
duane.berglund@ndsu.edu

 

POLLINATION AND KERNEL DEVELOPMENT IN CORN

Most of the corn crop in North Dakota has tasseled or will soon be tasseling. The appearance of the tassel signals the onset of the pollination process. In corn, unlike most other crops grown for grain, the male portion of the flower (the anthers on the tassel) is located some distance from the female portion (the ear) of the flower. For this reason the pollination process in corn is more sensitive to stress than in most crops and poor pollination can significantly impact the yield of a corn crop. Fortunately, the recent rains throughout most of the state have helped to reduce the potential for water stress during this critical stage of growth.

Pollen shed usually begins two to three days prior to silk emergence and continues for five to eight days with peak shed on the third day. Under severe stress, however, silk emergence may be delayed beyond the period when pollen is available, resulting in barren or partially barren ears. Most pollen is shed in the morning after the dew dries off. Pollen generally is shed from the center of the tassel first and by the lower branches last. Corn pollen can be carried by the wind for considerable distance, though most settles within 20-25 feet of the plant from which it was shed. Because of the large number of pollen grains produced by the tassel over several days, there is little risk that irrigating corn during the period of pollen shed will adversely affect fertilization. Pollen grains can remain viable for up to 24 hours, but are sensitive to very hot and dry conditions. The temperatures of this past week and those forecast for the next week appear to be ideal for the pollination process this year.

For fertilization to occur a viable pollen grain must land on a receptive silk, germinate, develop a pollen tube down the entire length of the silk strand and combine its genetic material with that of the ovule. Often more ovules are fertilized than can develop into mature grains and yield under these conditions is determined more by the photosynthetic capacity of the plant during grain filling than the number of kernels that were fertilized. If demand for photosynthate in the developing ear exceeds that which is available from the plant, some developing kernels will abort. Kernel abortion is most common during the two week period following fertilization. Just as with other growth processes in corn, the development of the kernel is driven by temperature. With normal temperatures (not like those we experienced last year) kernel growth is complete about 55 to 60 calendar days after pollination.

Joel Ransom
Extension Agronomist
Cereal Crops
joel.ransom@ndsu.edu


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