Dry down 30 to 40 days

Whole grain photographs


The whole grain at Dry Down. Water has been lost by the physical action of the sun and the grain has started to shrink. As the seed dries down the ability to germinate straight away is reduced. But in damp seasons residual moisture would allow internal pre-germination and germination programs to start during the winter storage. Go to the text link in the introduction to Dry Down for more information on pre-harvest sprouting.
Assessment of the crop in the field, before combining, will help determine what the grain will be used for.
The endosperm is packed with starch and protein reserves ready to nurture the embryo when favourable conditions allow the seed to germinate and growth to start again. Biologically the grain has achieved the first level of dormancy or 'resting state'. This includes the expression of genes encoding proteins that allow tolerance of the desiccation process.
An individual spikelet 40 days after pollination. floret 2 has been cut away and its component parts are separated. The grain has started to shrink and the colour has changed to a light brown. The glumes, lemmas and palea, which have protected the grain, are now dry and brittle.
Embryo dormancy is induced at this stage. Deeply dormant grain is produced under cool growing conditions whereas high temperatures during the later stages of grain growth can cause the embryo to break dormancy early.
Ears are held vertically within the canopy during dry-down. Individual spikelets dry at different rates; the last to dry down will be at the base of the ear. When the crop is completely ripe the will ears bend over to allow the ripe seed to fall away.
The grain moisture content at harvest is typically about 20%. Grain must be further dried down, mechanically, to a moisture content of 14.5% or less for safe storage.