The number of spikelets is one of three components that ultimately will determine yield, in addition to the number of tillers and conditions during grain fill.
Number of spikelets
As wheat approaches the 5-leaf stage, head initiation begins. Although it’s microscopic at this time, the parts that become the spikelets and kernels are already being formed.
Like tillering, temperature also greatly influences the number of spikelets. The figure below shows what happens as the average maximum temperature increases from 65 to 85: The average spikelet counts decline almost by a third from 17 to 13.
Although cooler daytime temperatures would be desirable to maximize the yield potential, don’t feel completely discouraged or disillusioned.
Wheat has a great ability to compensate among yield components. If the conditions during anthesis and grain fill are favorable for wheat, the crop will put its energy in additional kernels per spikelet (three to four rather than two to three) and larger kernels.
Reviewed in 2018