Crop Construction Phase
Winter Cereals

We're deep into May and with prolonged  warm sunny weather having finally arrived I thought I'd share the finer points of this critical developmental stage in a winter cereal crop. Most winter cereals will be at booting  (BBCH 40s) with the flag leaf having now fully emerged and will soon be entering the early stages of ear/panicle emergence (BBCH 50s). The weather conditions now can have a dramatic effect on final grain number as water availability, temperature and light levels also serve to influence the ear formation period, though there is also a strong varietal influence too.

Ears are initiated during the foundation phase of crop development that lasts until stem extension in the Spring with spikelet number already set by this point. Floret initiation will then proceed until the start of Flowering (BBCH 61). The total number of florets within a spikelet and the proportion that set grain will determine final grain number per ear/panicle, an important yield component. Again the number of florets will be affected by the variety as well as the weather conditions at the time. The number of potentially fertile florets will depend on the carbohydrate reserves bult up in the stem during the Spring through photosynthesis hence the important of sunny weather during this time. The greater the amount of assimilates available to be supplied to the ear during booting, the more florets that will survive to flowering. This is also were crop density and canopy play a role as too much mutual competition amongst plants will lead to fewer grains in each ear/panicle.

Whilst sunny conditions at this time of year increase grain number, it is cooler temperatures that will prolong ear development and increase grain number.  As mentioned, grains  per ear is also highly influenced by the variety. Quality milling varieties and varieties with smaller leaves tend to have lower grains per ear and those varieties with smaller leaves also tend to have fewer grains/ear.

So, right now, in all this sun with plenty of soil moisture, the crops are happily photosynthesising, building carbohydrate stores and the ear weight is increasingly rapidly as those carbohydrates are translocated from stem to ear. At ear emergence, grain number is set, and the ear/panicle weight is the same pre flowering as the weight of the chaff at harvest. Grain number provides the storage capacity of the ear so the higher the grain numbers the greater the yield potential as the crop moves to grain filling, post flowering. It is here that disease and drought can have a negative impact on the weight of each grain.

Conditions right now are perfect for a good ear formation period of winter cereals which should bode well for final yields, particularly in winter oats where grain number per panicle has a greater effect than grain size.