Freeze injury update – worse than we thought

Posted on April 5, 2013 by Amanda De Oliveira Silva

On April 4th I toured southwest Oklahoma and surveyed freeze injury to wheat. In my experience, most freeze events are overhyped; however, this one was the real deal Holyfield. I traveled a route from Faxon to Chattanooga to Altus to Blair and ended up at Apache. Damage was similar at all sites, with injury ranging from 50 to 80%.

The best looking wheat was the hardest hit. Particularly troubling are some fields in the Altus area that easily had 80 bushel potential prior to the freeze. In most of these fields we are too far past the tillering stage to have yield compensation from secondary tillers. Late-emerging fields that were jointing or smaller escaped the freeze with little injury. Fields that had been heavily grazed and/or under-fertilized also escaped with relatively minor injury. Conditions improved slightly when I checked wheat in the Chickasha area and injury was more in the 10 – 30% range.

I am frequently asked if the injured wheat head will go ahead and “push through” as the season progresses, and the answer is no. So, if you see heads emerging out of the boot in a few weeks, they are likely not damaged and a head count at this stage will be a reasonable estimate of fertile heads. Since there will not be additional stem elongation in freeze injured wheat, it will not accumulate as much tonnage as in a ‘normal’ year.

I have posted a few pictures below showing freeze injury symptoms. Freeze injury can vary greatly among fields and even within a field. So, it is important to check several sites within a field and split several stems when determining the percent injury. Check early maturing varieties such as Jackpot, Billings, and Everest first, as they are most likely to have injury.

Endurance wheat collected from plots at Chattanooga, OK. The two top heads are freeze damaged and will not recover. Note the shriveled, white appearance of the wheat head. The bottom head was not injured and is healthy green.

A healthy head of Endurance from Apache, OK.

Even though this wheat was just past jointing, it was injured by the freeze and the head was lost.

Freeze injured Billings from the Altus research station

A sign of the drought. Wheat seed still easy to find on a sample from near Altus, OK April 4.

Freeze injury to wheat

Posted on March 26, 2013 by Amanda De Oliveira Silva

Temperatures across Oklahoma dipped into the teens and 20’s March 25 and 26 (see maps below). The rule of thumb is temperatures below 24F will damage wheat at or past the jointing stage, so it was certainly cold enough to injure wheat that was not delayed due to drought stress, grazing, or late emergence.

Freeze injury is not an exact science, and it remains to be seen whether or not we actually have widespread wheat freeze injury in the 2013 wheat crop. My best guess is that we will have some injury and might lose our primary tillers in more advanced fields. Wheat that is at Feekes growth stage 6 – 7 generally has the ability to compensate for primary tiller loss by keeping secondary tillers that would otherwise be sloughed off in April. In this scenario, the effect on final grain yield would be minimal. Wheat that has already aborted secondary tillers does not have this flex ability and will not recover from freeze injury. This is why March freezes are generally yield reducing and April freezes are yield eliminating. I will check fields late next week and post the results on this blog.

Freeze injury is not clearly identifiable until 7 – 10 days after the freeze event. So, the best advice for a wheat farmer after a freeze event is to find something else to do for a week or two and then check your crop. I have provided some pictures below with typical injury symptoms and rules of thumb regarding the extent of the injury. Fields should be checked at several random locations by splitting 10 – 20 stems at each location and looking for injury. Don’t focus solely on the large stems. Split a random sampling and determine the percent damage. A good reference for evaluating freeze injury to wheat is K-State Extension Publication C-646 Spring Freeze Injury to Kansas Wheat (access online by clicking here).

This is a healthy wheat head at approximately growth stage 6 – 7. Note the light green color and healthy, turgid appearance.

Freeze injury just after jointing. Note the pale, milky color of the head. Freeze injury to wheat heads at this growth stage is all or none, so this head is a complete loss.

Leaf tip burn from freeze injury will have no impact on final grain yield

Yellowing is a common reaction to light freeze injury. Wheat will recover quickly from this injury.

Severe freeze injury at or just after jointing can turn the entire plant brown and fields can exude an odor similar to fermenting silage. If conditions are favorable, the plant can produce new tillers (as shown here) and make a partial recovery. It will take a few weeks after a freeze event to determine if the plant will recover from this type of injury

It is common for sub-lethal freeze injury to result in bent or weak lower nodes. These plants might look fine, but will lodge during grain fill.

Time to topdress, but be realistic

Posted on February 1, 2013 by Amanda De Oliveira Silva

Normally, I would be sounding the wheat topdress alarm in early January. When you have 5.5 million acres to cover, it is important to start early. However, this year we have mostly kept the topdress rigs in neutral with a wait and see approach due to the drought. The recent rain brought life to portions of the Oklahoma wheat belt and it is time to make a decision regarding topdress nitrogen. I have posted three slide presentations with audio regarding topdressing wheat at my YouTube channel available by clicking here or by searching YouTube for OSU Small Grains. I have listed some additional facts and items to consider below.

In order to have full benefit, nitrogen must be in the rooting zone by the time wheat is jointing. Jointing occurs around the first of March in southern OK and around the second week of March in northern OK.
On average it takes about 2 lbs/ac of N for every bushel of wheat yield. In addition, dual-purpose wheat requires 30 lbs/ac of N for every 100 lbs/ac of beef removed. You can subtract your soil test NO3-N from these total requirements.
It is okay to adjust topdress N plans based on your current yield potential. When you submitted your soil test, you might have stated a 50 bu/ac yield goal which would require 100 lbs/ac of nitrogen; however, it is important to take a hard look and determine if this yield goal is still realistic based on your current crop status. I am not suggesting to adjust based on what you think the weather might do, but it is okay to take inventory and adjust your topdress N up or down based on current field conditions.
Don’t have an N-rich strip? It would be a lot cooler if you did. An N-rich strip would take the guess work out of adjusting your topdress N up or down based on your current crop conditions. Your county extension educator can provide more information on N-rich strips and you can find more information on the web at www.npk.okstate.edu

2012 versus 2013 greenness maps

Posted on January 30, 2013 by Amanda De Oliveira Silva

I thought I would share a couple of visual greenness maps sent to me by JD Carlson in Biosystems and Ag Engineering. These are from the Oklahoma Mesonet fire danger model site and provide a visual estimate of green vegetation for mid January 2012 (top) and 2013 (bottom). Note the stark contrast in greenness throughout the wheat belt of western Oklahoma. As indicated in the 2013 map, there are some small pockets of wheat with ample stands and average yield potential, but these are not large enough to make up for all of the red.

Check with crop insurance provider prior to drilling mud application

Posted on January 7, 2013 by Amanda De Oliveira Silva

There are more questions than answers when it comes to application of drilling mud to agricultural land. The list of questions expands when the drilling mud is being applied to an established annual crop, such as wheat. We simply do not have enough information to know how a growing crop will respond to drilling mud application from different sources and at different application timings.

If current conditions continue it is highly likely that many Oklahoma wheat farmers will rely on crop insurance to cash flow through 2013. Therefore, wheat farmers should check with their crop insurance provider prior to applying drilling mud to established wheat to see how application of these materials will affect their coverage. Tenants should discuss application of drilling mud with landowners and it is a good idea to address these issue in writing in the lease agreement.

Too little, too late?

Posted on January 1, 2013 by Amanda De Oliveira Silva

It finally rained! Rainfall totals in western Oklahoma (0.1 to 0.3 inches) will not put a dent in the drought, but were probably enough to induce germination of seed resting in dry soil. Oklahoma weather is extremely variable, and who knows when temperatures will warm enough to spur along the germination process. If we retain the recent moisture and have something close to a “normal” year, it is likely that we will see wheat popping through the soil in mid February. I compared February sown winter wheat to spring wheat in a trial at Newkirk, OK a few years ago. The winter wheat made about 15 bu/ac and the spring wheat made about 20 bu/ac. This was in a favorable year that was not plagued by drought. Given current weather trends, a best case scenario for February emerging winter wheat is 50% of normal yield. A worst case scenario is 0 – 10% of normal yield. If I were wagering, I would place my money on 20 – 30% of normal yield potential.

The rainfall might be enough to help emerged wheat west of I-35 survive, but that is about it. Soil moisture is still insufficient to produce a recovery and I would still proceed cautiously regarding inputs on these acres. The rain might have indeed been too little, too late for these acres. IF soil moisture gets recharged by mid February and IF we have a mild spring these acres could have some secondary tillering and make a moderate recovery; however, the odds are against this scenario.

Don’t overgraze no-till

Posted on December 7, 2012 by Amanda De Oliveira Silva

The drought is worsening and forage is getting harder and harder to come by. Crop residue that was once considered of little nutritional value for livestock has become a staple for Oklahoma cattle producers with depleted pasture and hay reserves. John Holman with KSU in Garden City indicated that grazing of sorghum stalks has become commonplace in western KS as well. Some crop residue can be removed without significant damage to long-term gains in soil structure associated with no-till, but overgrazing can lead to some real problems when the wind comes sweeping down the plain.

Wind erosion is commonly thought of as a conventional-till problem, but in an email exchange, Jason Warren recently indicated that there are a few scenarios where wind erosion could actually be worse in no-till than conventional till. No-till results in a relatively smooth, flat soil surface that, in the absence of residue, has few barriers to slow the wind. So, if we have an easily detached soil type (i.e. a sandy soil), a flat surface, and no residue to hold the ground, then we have a recipe for wind erosion. The same would be true for no-till wheat pasture that has been overgrazed. In a wind-erosion-fighting battle royale, I still prefer no-till to conventional till. However, no-till is not immune to wind erosion and it is important to keep some cover on the soil.

Aside from soil protection, it is important to remember that crop residues have value as reservoirs of nutrients. An estimate of nutrient removal of grain, fiber, and forage crops can be found on one of Brian Arnall’s Pete Sheets at http://npk.okstate.edu/petesheets If the cattle are grazing the residue in-field, most of the nutrients will be returned to the soil. If the residue is being baled, the nutrients are leaving with the hay bales. You can estimate the value of these removed nutrients using the linked Pete Sheet and current fertilizer prices.

No-till practices to not make soil immune from wind erosion. Adequate cover must be maintained.

How dry is it?

Posted on November 21, 2012 by Amanda De Oliveira Silva

It was too nice of a day to stay in the office yesterday, so I checked on our wheat variety plots. I started at McLoud, moved west to Kingfisher, and ended up at Marshall. As indicated by the pictures and captions below, neither the wheat nor my mood improved as I traveled west. I am sure if I had traveled farther west, this would have gotten worse. The bottom line is that we are in desperate need of moisture in Oklahoma. Early-sown wheat is backpedaling quickly and cannot hold on too much longer. Much of the later sown wheat has yet to emerge. We are certainly not on our way to a record year, but everything could still turn out okay……..if it rains.

: Wheat at McLoud, OK on 11/20/2012 with three large tillers and three additional tillers initiated. This wheat is on its way to top yield potential.

: This field north of Kingfisher on Hwy. 81 was likely sown around October 20, but never received enough moisture for complete emergence. The seed is still viable, but even if it rains now the effective planting date would be late November

: This is September-sown wheat at the Wheat Pasture Research Unit near Marshall, OK. With adequate moisture this wheat would likely have 8 – 10 healthy tillers by today. Due to the drought, it has three small tillers that are barely hanging on.

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