1st hollow stem signals end to wheat grazing
The unique climate characteristics of the Southern Great Plains allow producers to use wheat as a forage and grain crop. Date of grazing termination is an important factor in determining wheat’s recovery potential and ability to produce grain. First hollow stem (FHS) is the optimal time to remove cattle from wheat pastures to protect yield potential.
FHS is the point at which a 1.5 cm length of hollow stem can first be identified below the developing head. This length is roughly equivalent to the diameter of a dime. FHS occurs when the developing head is still below the soil surface. This means that producers have to dig plants out of the ground to measure it.
To look for FHS, start by digging up some plants from fields or areas that have not been grazed, such as field corners or just outside the fence. Date of FHS is variety- and field-specific, so it is important to sample each field. Select the largest tillers to examine, and slice the stem open from the crown area up. Look for the developing head, which will be very small. Next, see if you can find any hollow stem between the developing head and the crown area. If there is any separation, the hollow stem is elongating. If that separation is 1.5 cm, the wheat plant is at FHS. FHS occurs between a few days to a week or more prior to jointing, depending on temperatures.
If the wheat has reached FHS, cattle should be removed to prevent yield loss. If cattle removal is followed by cool, moist weather, yield losses will often average about 1% per day grazed after FHS; if weather is hot, dry, and harsh, yield losses of 5% per day or more can be expected. It is easy for producers to be late by a few days in removing livestock as they wait for obvious nodes and hollow stems to appear, and even the first few days can be significant.
Two things can occur when wheat is grazed too long: 1) fewer heads per acre because the primary tiller has been removed, and 2) smaller and lighter heads than expected because leaf area has been removed. As cattle continue grazing, the wheat plant is stressed and begins to lose some of the tillers that would produce grain. A little later, if there are not enough photosynthates, the plant begins aborting the lower spikelets in the head or some of the florets on each head. Finally, if there is not enough photosynthate during grain filling, the seed size will be reduced and if the stress is severe enough, some seed will abort.
For more information on managing wheat in dual-purpose systems, check the K-State Research and Extension publication MF3375, “Dual-purpose wheat: Management for forage and grain production”
Alicia Boor is an Agriculture and Natural Resources agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact her by e-mail at firstname.lastname@example.org or calling 620-793-1910