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First Hollow Stem Update – 2/26/2021

Amanda de Oliveira Silva, Small Grains Extension Specialist

First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8” or the diameter of dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

The latest FHS results from our forage trials in Chickasha (Table 1) and Stillwater (Table 2) are listed below. A few more wheat varieties in Stillwater have reached or passed the 1.5 cm threshold.

The Mesonet First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, it is extremely important to check for FHS on a field-by-field basis

Table 1. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/29/2020. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Table 2. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/21/2020. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Similar to previous years, we will monitor occurrence of FHS in our wheat plots at Stillwater and Chickasha and report the findings on this blog.

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First hollow stem update – 02/25/2021

Amanda de Oliveira Silva, Small Grains Extension Specialist

First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8” or the diameter of dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

The photo shows the first hollow stem in wheat
Figure 1. First hollow stem occurs when hollow stem equivalent to the diameter of a dime (1.5 cm) is present below the developing grain head.

The latest FHS results from our forage trials in Chickasha (Table 1) and Stillwater (Table 2) are listed below. Few wheat varieties in Stillwater have reached or passed the 1.5 cm threshold.

The Mesonet First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, it is extremely important to check for FHS on a field-by-field basis

Table 1. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/29/2020. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Table 2. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/21/2020. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Similar to previous years, we will monitor occurrence of FHS in our wheat plots at Stillwater and Chickasha and report the findings on this blog.

What will these cold temperatures do to the wheat crop?

Amanda de Oliveira Silva, Small Grains Extension Specialist

Weather forecasts indicate that temperatures will continue to drop in the next few days. The extent of possible damage from these below-normal temperatures on wheat will depend on several factors such as wheat developmental stage, soil moisture, snow cover, field conditions, and how cold and for how long these cold weather stays.

Most of the wheat in Oklahoma was dormant or just starting to come out of dormancy before this extreme cold front came in. The more advanced in growth the wheat is, the more exposed the growing point is and susceptible to injury. On the other hand, wheat fields planted late in December are also vulnerable as the wheat may not have had the time to develop its crown roots and tiller to sustain these cold temperatures. The most important part of the plant is the crown at this moment. We may see leaf damage, but if the crown remains alive, the plant can survive. Figure 1 provides a general guide to the minimum temperature threshold and its impact on yield. Keep in mind these temperature thresholds are not exact but provide a decent rule of thumb. Temperatures closer to the soil surface might be higher than those reported by weather stations one meter above the soil surface, especially if moisture is present. 

Figure 1. Temperatures that can cause injury to winter wheat at different growth stages. Source: Kansas State University publication C646: Spring Freeze Injury to Kansas Wheat.

Except for the western OK and Panhandle regions, most areas of the state were with adequate soil moisture, which helps to insulate the crop and improves survival chances. Also, if we receive the snow cover that is forecasted, the wheat will be more protected from the harsh conditions.

Regarding my last post that some varieties may have reached first hollow stem (FHS). Growers should keep in mind that FHS is based on the largest tiller on the plant. Even if we lose the largest tillers, we are fine as long as other tillers are viable and we have favorable growing conditions.

Figure 2. Leaf tips which have turned necrotic due to freezing temperatures. Photo taken in March 2017 courtesy of Josh Bushong, OSU Northwest area Extension agronomist.
Figure 3. More severe freeze damage causing the leaves to turn yellow-white with plants losing their overall turgidity. Source: Kansas State University publication C646: Spring Freeze Injury to Kansas Wheat.

Each freeze event is unique. It will take some time (1-2 weeks after the cold weather passes) to assess the actual impact of the below-normal temperatures on wheat. We will have to keep watching it as it will vary on a field-by-field basis.  

Resources

Contact your local county Extension office.

For additional read refer to:

Assessing Freeze Damage on Wheat

 C646 – Spring Freeze injury to Kansas Wheat

First hollow stem update

Amanda de Oliveira Silva, Small Grains Extension Specialist

First hollow stem (FHS) occurs just prior to jointing and is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8” or the diameter of dime) of hollow stem below the developing grain head (Fig.1). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

The photo shows the first hollow stem in wheat
Figure 1. First hollow stem occurs when hollow stem equivalent to the diameter of a dime (1.5 cm) is present below the developing grain head.

Several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). Varieties can differ by as much as three weeks in onset of first hollow stem, and later maturity varieties generally reach first hollow stem later. Dual-purpose producers are encouraged to select varieties that are characterized as medium, late or very late in occurrence of FHS.

The latest FHS results for each variety planted in our forage trial at Stillwater are listed below (Table 1). A few varieties are at FHS (values at or above 1.5 cm), but values are likely to move slowly with current cold conditions in Oklahoma.

The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, it is extremely important to check for FHS on a field-by-field basis.

Methods for scouting for FHS:

  • Check for FHS in a non-grazed area of the same variety and planting date. Variety can affect FHS date by as much as three weeks and planting date can affect it even more.
  • Dig or pull up a few plants and split the largest tiller longitudinally (lengthways) and measure the amount of hollow stem present below the developing grain head. You must dig plants because the developing grain head may still be below the soil surface at this stage.
  • If there is 1.5 cm (~5/8″) of hollow stem present, it is time to remove cattle.

Table 1. First hollow stem results for each variety collected at Stillwater on 02/06/21. Plots were planted on 09/21/21. The threshold target for FHS is 1.5 cm. The value of hollow stem for each variety represents the average of ten measurements.

Similar to previous years, we will monitor occurrence of FHS in our wheat plots at Stillwater and Chickasha and report the findings on this blog.