April's Ag Advice By April Borders Frost and freeze effects have varied across our county, with some places escaping damage and others places getting hit. Cold temperatures at this time of year are not unusual, generally we have one or two nights of freezing temperatures and then things warm up. But this is not what happened. We have had several nights in a row where our temperatures were below 32 �.
One thing that we need to remember is do not go out right away the next morning and try to assess injury. Under normal conditions of a freeze, we need to wait at least 72 hours to assess crop injury. Because we had several nights in a row of freezing temperatures, we will need to wait until the temperatures warm and see what the crop response will be. One thing to keep in mind is there will be a lot of variation in injury and effect. Conditions will vary according to crop topography and the incidence of how that cold front moved through the area.
When we look at our spring seeded small grains, growers should wait and see what happens. The growing points should be protected enough and freeze-injury plants should come back with warmer temperatures.
As far as our winter wheat is concerned, most of it is in late tillering to early jointing stage, so the growing point is still fairly close to the ground. Because of this, there should not be too much damage. For winter wheat that was at jointing and the crown may not have been as protected, we need to wait and see how the crop comes out of this as the temperatures warm. You will need to open the stem and check to see if the growing point is alive.
Another test you can do is the bag test. This will give you an idea of the survival of the wheat crop after a freeze but the test is not definite. The best way to assess the condition of wheat stand is to wait until the temperature warms up and allow for three to five days of plant growth under warm temperatures and then conduct a stand assessment.
If interested in knowing how to do the bag test contact the Extension Service. I also have a great wheat reference from Kansas State called "Spring Freeze Injury to Kansas Wheat." It has some great pictures of what you need to look for. Stop by if you would like a copy or I can email it to you.
Now let's look at our alfalfa. The regrowth of each alfalfa stem takes place at the tip. Our recent temperatures have caused injury to these growing points causing a stunting of the plant. With severe frost damage the top of the plant will bend over and growth of the tip will cease. A good "rule of thumb" to follow is that if one-third or more of the top growth has been wilted by frost and drying up, immediate mowing will permit earlier development of a new crop.
However, this statement must be qualified by the moisture/precipitation events to permit subsequent regrowth. If the damage is less, the plant should recover adequately to allow harvest at the normal time. Harvest of frosted stands that were clipped should be delayed to about the mid-bloom growth stage for the second harvest to allow recovery of stored food reserves.
New alfalfa seedings need to be carefully scouted to see if there is permanent plant damage. If new seedlings were permanently damaged, you should consider re-seeding as soon as possible. Keep the good area and drill into thin or damaged areas. Moisture will be the key to getting the reseeded crop to germinate.
The toughest management recommendations are those that deal with assessing damage with "light frost." The only thing that you can really do is to wait a week or so to see what the damage is. Be sure to work with your crop insurance agent with any crop injury and any decision as far as tearing up the crop or leaving it.
These cold temperatures affected the weeds too. Remember that weed control can be reduced if the weeds are damaged because there is less active leaf tissue for foliar uptake. Also if herbicides were applied right before a freeze, we could see some damage in our crops. In the case of Bronate or some of the wild oat materials, they are going to be more active and it does react with the wheat plant if treatment is made right before a freeze. The herbicide is taken in prior to the frost but the plant slows down and simply cannot metabolize the material fast enough. The SU (sulfonyl urea) herbicides can cause yellowing of wheat if applied prior to freezing temperatures or after a frost during cool, cloudy conditions.
For more information on frost damage and crop issues, contact the Clay County Extension Office at 677-7111.