Amanda de Oliveira Silva, Small Grains Extension Specialist

The wheat growing season up to this point has been extremely tough. The forage situation has been a kick-in-the-knees again this year. Wheat “dusted in” emerged at least one month later than the ideal time to promote fall forage production. It was challenging to get a stand established with a cool November and limited rainfall since planting. As a result, many producers did not have the chance to graze or are grazing at a lower stocking rate.

If the predicted shower events occur, it could help to improve conditions in some areas. Still, most of Oklahoma, especially western OK, is under an extreme drought and needs significant rain. For the producers who have pasture to graze, leaving some leaf tissue after grazing will be important for having any chance of a decent grain crop. Ideally, there should be a minimum of 60% canopy coverage (measured from the Canopeo app) left to allow the crop to recover from grazing (PSS-2170). An additional two weeks of grazing past first hollow stem, when conditions are not ideal for plant regrowth and canopy recovery, could reduce wheat yield by approximately 60% relative to its potential (Figure 1).

The first hollow stem stage (FHS) indicates the beginning of stem elongation or just before the jointing stage. It is a good indicator of when producers should remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8”, or the diameter of a dime) of hollow stem below the developing grain head (Figure 2). This is the optimal period because it gives enough time for the crop to recover from grazing and rebuild the canopy. Also, the added cattle weight gains associated with grazing past the FHS are not enough to offset the value of the potential reduced grain yield (1-5% every day past FHS) (Figure 1). The wheat variety, severity of grazing, time when cattle are removed, and weather conditions after cattle removal determine how much grain yield potential might be reduced.

Mesonet First Hollow Stem Advisor

Researchers at Oklahoma State University developed the Mesonet First Hollow Stem Advisor to help predict when FHS is nearing. This online tool uses soil temperature data to show the current probability of FHS occurrence and 1-week and 2-week projections. With this tool, producers can select their variety from a list of varieties that separates them into three FHS categories: early, middle, and late. Then, maps can be generated to provide the probability of FHS based on current conditions and the 1- and 2-week projections. Charts and tables can also be generated for individual Mesonet sites. Created maps have a color scheme to represent the probability of FHS occurrence. When using this tool, it is recommended to start scouting for FHS from a non-grazed part of the field once the 5% probability is reached (green color). Because stem elongation will begin moving quickly as the air temperature rises, starting your scouting at the 5% level will help give you the time it takes to make the cattle removal preparations by the time FHS occurs. We listed methods for scouting for FHS at the end of this post. For producers who do not want to scout, it is recommended to remove cattle when the 50% probability level is reached. A 50% probability level indicates that over an evaluated period (e.g., 10 years), FHS would have occurred by that date in 50% of those years (e.g., 5 years). The same interpretation is used for other probability levels.

I have generated some statewide maps below to give an example of what the tool provides and show some of the FHS conditions around Oklahoma. For producers along the southern Oklahoma border who planted an “early” wheat variety (e.g., Gallagher), now would be past the time to remove cattle from the field (Figure 3).

Remember that this tool should be used as a proxy to begin scouting for FHS. The best estimate of FHS is still to split stems from plants in each field to determine how developed they are. Another word of caution I want to mention when using the tool for this year is to consider when you finally got stand establishment. If this did not occur until the end of September to the beginning of October (which are most of the cases in Oklahoma this year), this tool might be ahead of where your plants are developmentally. In this case, the tool can still cue you to start scouting. Checking for FHS in each field will let you know if you do have some grazing time left.

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, 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.
• If there is 1.5 cm (~5/8″) of hollow stem present, it is time to remove cattle. 1.5 cm is about the same as the diameter of a dime (see picture below).
• Find detailed information on FHS and grazing by clicking here.

OSU Small Grains Program is monitoring FHS occurrence on a twice-per-week basis

Similar to previous years, we will monitor FHS occurrence in our wheat plots at Stillwater and Chickasha and report the findings on this blog. Remember that we use an accelerated growth system to report the earliest onset of the FHS stage. Trials are seeded early to simulate a grazed system, but the forage is not removed. Varieties reported here with the earliest FHS date should be the first to monitor in commercial fields. In practice, grazed wheat will likely reach FHS stage later than reported here, and differences between varieties will likely moderate.

The latest FHS results for each variety planted in our forage trial at Stillwater and Chickasha are listed below (Tables 1 and 2). Most varieties are not near FHS (values well below 1.5 cm). However, values will likely move quickly with a bit of moisture and warmer conditions in the coming weeks in Oklahoma.

Table 1. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 10/06/22 but not grazed or clipped. 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. Varieties exceeding the threshold are highlighted in red.

Table 2. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 10/07/22 but not grazed or clipped. 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. Varieties exceeding the threshold are highlighted in red.

Contact your local Extension office and us if you have questions. 

Acknowledgments: 

Tyler Lynch, Senior Agriculturalist

Israel Molina Cyrineu, Graduate Research Assistant

Samson Abiola, Graduate Research Assistant

Cassidy Stowers, Undergraduate Student

Lettie Crabtree, Undergraduate Student