An independent field reference
Cereals feed most of the world, yet the difference between a good crop and a lost one is often decided in the few weeks between ripening and storage. This reference explains when the major grains are harvested in each climate zone, how moisture decides whether grain keeps, and where post-harvest losses come from.
| Crop | Climate zone |
|---|---|
| Winter wheat | Temperate Northern Hemisphere |
| Spring wheat | Continental Northern Hemisphere |
| Grain maize | Temperate and subtropical |
| Rice (paddy) | Monsoon Asia |
| Barley | Temperate and boreal |
| Sorghum | Semi-arid tropics |
| Wheat | Southern Hemisphere temperate |
Grain is ready when the kernel has reached physiological maturity and its moisture has fallen into the crop's harvest range.
Ripening runs through three phases: milky ripe, when the kernel is soft and wet; dough ripe, when it firms and the plant yellows; and full ripeness, when the kernel is hard. Combining starts in the last phase, when kernels separate cleanly from the ear.
Cut too early and the grain is wet, immature and costly to dry. Cut too late and ears shatter, stems lodge and quality falls. Timing is the search for the few days when moisture, weather and machinery line up.
Maturity can be read from the crop itself. In maize a black layer at the kernel base marks it; in wheat and barley the hardening kernel and the yellowing leaves tell the same story.
These are typical windows for major producing regions; each season's weather shifts them by days or weeks.
The same crop can be cut in June in one zone and in November in another, because the window follows temperature, day length and the rainy season.
In the temperate Northern Hemisphere, winter wheat is cut in early summer and spring wheat in late summer. In monsoon Asia, rice follows the retreat of the rains, and irrigation allows a second or even a third crop.
South of the equator the calendar flips: Australian and Argentine wheat comes off from November into January. Near the equator, altitude replaces latitude, and harvest can fall in almost any month.
Within one zone the date still moves from year to year. A cool spring delays everything; a hot, dry finish can pull the window forward by two weeks or more.
Moisture controls every storage risk: mould, insects, sprouting and self-heating all accelerate as grain gets wetter.
Most cereals leave the field at 15–30% moisture but store safely only at about 12–14%. The gap between those two numbers is the entire drying problem.
Wet grain is alive: kernels and the fungi on them respire, releasing heat and water. In a bulk that heat builds into hot spots, and spoilage begins to feed on itself.
Each crop has its own safe level, and the level tightens as storage lengthens. Grain kept for a year or through a warm season must be drier than grain sold within months.
The figures here follow standard public references — FAO post-harvest estimates and university extension guidance on grain drying and storage.