NDSU Extension - Cavalier County

Accessibility


| Share

9/11/2014

Frost (Freeze)
Dry beans are the most susceptible crop we grow to light frost  while soybeans are a bit tougher and can take a couple degrees cooler without significant damage.

Soybeans that had not started to yellow or drop leaves may have some potential for damage but typically a solid seeded field keeps the lower pods of the plant protected from frost by retaining the soil heat so damage if any is confined to the top of the plants.    The most serious frost damage typically occurs on the 2nd frosty morning after the first leaves have been lost!

Canola  -Temperatures  around 30 degree mark will cause little damage to canola but with any reported low temperature  we know there’s pockets in the same field that will have colder temperatures resulting in damage.    The only way to reduce losses in the marketplace is to monitor samples across a field when harvesting the first round and not mixing the damaged seed with the good areas.  The same would apply to fields being combined with other fields in the same bin as damage may vary considerably from field to field.

Frost on pods can stop plant development and lock in green.  Typically the locking in of the green is our biggest concern as no matter how the seed dries down or rewets the green seed count will not go down. It can also cause pods to split but I haven’t seen that as a big problem in the years we had early frosts.  However, a light frost may have no effect at all, and the crop will be better left to mature fully.

The following are comments from several Canadian Agronomists on frost which some of you may have seen on the website.  There are varying opinions out there of what to do after and/or before a frost:

—Check standing canola the morning after a frost.
—Before taking any action, wait at least 4-6 hours after frost to allow the full extent of frost damage to become evident. The crop may look undamaged that morning but by the afternoon wilting, desiccation and pod splitting may begin. This crop may need to be swathed to preserve yield, but keep in mind that high green counts are likely.
—Light to moderate frost damage may take longer to show up. If no damage is evident after the first day and you decide to leave the crop, scout again after 2 to 3 days to reassess.
—If most or all seed is mature and you planned to swath the day after a frost anyway, then don’t bother waiting 4-6 hours. Just start swathing.

Responses for heavy and light frost:
Heavy frost… below 28 F:
Assess the damage in early afternoon. Check pods for a white, wilted appearance. Pod shatter and pod drop could begin within a day, especially with warm sunny afternoons. If pods are desiccating rapidly, swathing right away will preserve as much yield as possible.


For canola with high seed moisture, frost in excess of 23 F is generally lethal, resulting in non-viable seed. At such low temperatures, ice crystals physically disrupt structures such as membranes and enzymes. Pods of immature canola crops frozen at lethal temperatures have been observed to turn black, whereas mild frost turns pods white or white-speckled.

Light frost… above 28 F: Hold off swathing. Check in the afternoon for wilting to make sure frost damage was not heavier than expected. You may see some speckling on the stem and pods, but this is of little concern as long as the plant is still alive. If no wilting, leave the crop standing and check daily.

What to look for during daily monitoring:

—If the majority of the seeds remain watery, delay swathing to allow for further seed maturity.
—If the pods are severely damaged and are beginning to desiccate, swath during periods of dew or high humidity to reduce the amount of pod shelling and pod drop.

Frost and quality. A killing frost will reduce quality, but that can’t be helped — whether you swath today or wait. Immature seeds (moisture content higher than 20%) will be damaged. Seeds with less than 20% moisture will normally escape damage. Green seed is the major downgrade that results from frost.

Here are three specific scenarios:

Scenario 1
If 50% of the field has moderate to severe damage, there’s a risk that hardest hit plants will begin to shell out and any seed that can contribute to yield will be lost. However, the yield and quality of the seed in this part of the field has likely already been significantly reduced. If the remaining 50% of the field has light to minimal damage, swathing too early may further reduce yield and grade. Leaving the field standing and following it to
the proper stage for swathing can allow the remaining intact seed to clear green and continue filling, improving both grade and yield. This part of the field will likely contribute most to yield anyway, and anything severely damaged will likely shell out or be separated with the chaff or dockage.

Scenario 2
When the field is more than 50-60% severely damaged, the crop will shell so it is best to swath to protect any viable seeds. Quality is likely to be poor anyway, so it is more important to protect as much yield as possible. Once swathed, rainfall with warmer temperatures (>15 C) may allow for some enzyme activity to occur in any remaining intact seeds, which can reduce the percentage of green seed. If the decision to swath is made, the
field in question should be one of the last fields to be harvested to allow as much time for green seed clearing as possible. Since yield and grade are likely to be relatively poor, the risk from leaving the crop out will be lower than for other less affected fields.

Scenario 3
The field has light to moderate damage in portions or across the field. It is suggested that this field be left for swathing at the proper stage of maturity, based on remaining healthy seeds in the pods. Any seeds that are damaged will be shriveled and will typically blow out of the combine with the chaff or end up as dockage. In order to maximize economic return, the crop should be left for as long as possible before combining. Areas of moderate damage should be monitored regularly for pods becoming desiccated and prone to shattering. If this occurs, consider swathing either the whole field or just the affected areas, if that is practical.

Canola swath timing - This time of year, mature canola seeds can take a long time to turn brown or black. Growers wondering why seed color change is taking so long may want to check the fields again and look for these other signs of maturity:

All seeds are firm to roll.  If the latest pods have seeds that are firm to roll, the crop can probably be swathed — even if there is no obvious color change. Seed can sit for a long time at firm to roll stages (which are basically mature) without turning color, especially if moisture is adequate and temperatures are cool, slowing the dry-down process. Mature seed may turn color fairly quickly after swathing.

No skin peeling. If the skin peels off when seed is rolled between the thumb and forefinger, then it’s not ready.

If all or most seeds have these characteristics, then the odds of those seeds curing properly in the swath are much better, meaning less risk to yield and quality if the crop is swathed to avoid fall frost risk. However, if there is no heavy frost risk in the forecast, holding off on swathing and letting the plants continue to mature will increase yield and decrease curing time in the swath. As long as the pods are pliable, there is no immediate risk of shattering.

Canola sulfur deficient patches in some fields were quite evident from flowering on with pale flowers along with a distinct purple coloring of the plant and the pods(poorly filled).   Combine yield monitors are finding these patches very easily with yield drops of half or more.    Then the after harvest symptoms are evident until freeze-up with plants still green-purple trying to regrow and produce seed that these plants didn’t do the first time around! 

Mark these area on your field maps and look closely at nearby fields for similar terrains (soil types) and when planting these area to canola (or corn)next time around make sure to get full rates of sulfur applied (20-30 pounds actual sulfate ).  The entire field rarely needs this high sulfur rates so I recommend you apply this high rate on those problem areas then use the average rates that one can put on safely with the seed at planting time on the rest of the field

Cavalier County Soil Health Tour : October 8th  at the Karry Krahn Farm and NDSU Langdon Research Extension Center. Tour begins at 8:30 a.m. at the Krahn farm for doughnuts and coffee followed by a crop cover tour.  We will then travel to the REC for tours and conclude with a lunch.  Mark your calendars!

Farm Bill Meeting:
On October 7th we’ll be holding another farm bill meeting at the Langdon REC so with good weather the harvest should be wrapped up by then.  Please note:   Landowners have received a letter from USDA on the Farm Bill dated July 28th or so and it says to reply back in 60 days!   No deadlines have been set as of yet so for landlords that see this column please ignore the 60 days and for those of you who are asked by the landlord have them relax until actual deadlines have been set and confirmed!  

Safe Harvesting To All!

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.