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ISSUE 15  August 9, 2001

 

SPECIALTY CROPS-WHEN TO SWATH AND COMBINE

Hot weather in recent days has tended to push many crops to mature at an increased rate. Questions on when to swath and harvest certain alternative crops are being asked. Below are some comments and suggestions:

Crop

Other Information

Lentil

Swath when lowermost pods are tan colored and rattle when shaken. Thresh when seeds test 18% moisture content or lower. Overdry lentils (8-10%) are hard and difficult to process or consume. Plants may still be green when pods are ripe. Crop typically matures in patches. Some shatter loss usually occurs.

Yellow Field Pea

Swath when peas and pea vines are yellow colored. Thresh when seeds are firm and can no longer be penetrated with thumbnail. 20% moisture content or lower. Some shatter loss usually occurs. Mixing wet soil with peas can cause staining - a discount grading factor.

Green Pea

Swath when peas are mature and have a good green color. Pea vines are yellow colored. If desiccating, apply when vein pattern of uppermost pods is easily recognized and 75% to 90% of the pods have turned to yellow tan. Seeds are firm but no longer penetrable with a thumbnail. Pea vines may or may not be prostrate depending on variety and conditions. 2% bleached peas is maximum. Bleached seeds are caused by high humidity, bright sunshine and warm temperatures.

Feed Pea

Swath when pea vines are yellow colored. Vines are often prostrate. Seeds are firm, but no longer penetrable with a thumbnail. Combine settings and operation are not as critical for feed peas as to human food peas. Admixture of various pea kinds are allowed. Some bleached peas, split, cracked or split peas, and earth tagged peas are accepted for feed peas.

Millet, Proso

Swath when seeds in the upper one-half of the panicle have matured. Seeds in lower portion will be in dough stage but will have less color. Harvest millet when its below 13% moisture. Shatters easily if not cut on time.

Mustard Swath when seed moisture content is 25%. Seeds are firm when pressed between fingers. Oriental-75% yellow seeds. Brown-60% reddish brown seeds. Yellow (White)-100% yellow seeds. Straight combine yellow mustard whenever possible. Watch for cracked seeds. Moisture content of seed should be 13% or lower. Swaths are fluffy and subject to wind damage. Lay swaths in direction of prevailing winds. Immature green seed will not change in color in the swath. Use swath roller.
Safflower Crop has finished blooming. Seeds heads are tan to brown in color. Leaves and heads are spiny with little green evident. Crop should be straight combined if evenly matured. Mature seed is striped or white and rubs freely from the heads.
Buckwheat 75% of the seed coats have turned brown. Flowering is nearly complete. Difficult to penetrate seed with thumbnail. Seeds continue to fill in the windrow or after light frost for about 3 days. Bottom seeds will likely be lost due to shattering.
Canaryseed Straw is bleached, hulls are shiny and golden colored. Seeds are reddish-brown. Delay cutting canaryseed until it is fully mature. Canary seed will not thresh cleanly until the heads are dry. Canaryseed is resistant to shattering and weathering. Dehulled seed is severely discounted.

 

SWATHING AND HARVESTING 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. Field inspections should be made every "2 to 3 days" when there is some color change in the first formed pods on the bottom of main stem. Canola seeds within the pod will change color an average of 10 percent every 2 to 3 days. Under hot conditions, seed color changes can be very rapid.

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

Green Seed Problems

Cutting too early with high temperatures and rapid drying can lead to excessive green seed count. Two percent or less green seed is currently the allowable limit. Any higher than the 2 percent and market discounts can occur. The key to curing the crop is moisture. The enzyme responsible for clearing the chlorophyll requires moisture. Therefore, seed moisture is critical. If the stems and seeds dry too rapidly after swathing, then chlorophyll can be fixed.

Leaving canola in the swath longer can help eliminate some green seed problems or potential. A rain will also help reduce green count in canola. Once the moisture content of seed is 20 percent, chlorophyll will begin to be moved out. In some cases however, when swathed too green in hot weather the chlorophyll will not be reduced to any great extent. 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. Thin stand counts can result in plant 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.

Two years of NDSU research has shown that at 0-5 seed color at swathing time resulted in 3.5 percent 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 if 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 in the field to ensure maximum drying, maturation and quality of your harvested canola."

Duane R. Berglund
Extension Agronomist

dberglun@ndsuext.nodak.edu


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