Crop seasons around the world
How rain and temperature create crop seasons in monsoon, two-rain, Mediterranean and temperate climates, cool- and warm-season crops, and degree-days.
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A crop can only grow when it has enough warmth and enough water at the same time. Where that happens, and for how long, defines a region's crop seasons: the windows in the year when particular crops are sown and harvested. They differ completely between a monsoon plain, an equatorial highland, a Mediterranean coast and a temperate continent, and they have different local names.
Crop seasons are basic to agronomy everywhere, and exams expect students to classify crops by season and to explain what limits each one.
What sets the season
Two factors set the growing season:
- Water: in the tropics and subtropics, temperature is usually warm enough all year, so the rainy season sets the main crop season, and irrigation or stored soil water makes a second one possible.
- Temperature: in temperate and high-altitude regions, frost and cold set the limits, and the season runs from the last spring frost to the first autumn frost (for warm-season crops), or across the winter for hardy autumn-sown crops.
Day length also matters, through the photoperiod responses that make many varieties flower in a particular season.
Crop seasons in different climates
Monsoon climates (one long rainy season)
Large parts of South and South-East Asia, West Africa's savanna, northern Australia and parts of Central America have a single rainy season with a long dry season.
- Wet-season crops, sown with the onset of rains and harvested as the rains end: rice, maize, sorghum, millets, cotton, groundnut, soybean, pigeonpea. In South Asia this is the kharif season.
- Dry, cool-season crops, sown after the rains on stored soil moisture or with irrigation: wheat, barley, chickpea, lentil, mustard, potato. In South Asia this is the rabi season.
- A short hot pre-monsoon or summer season, with irrigation, for short crops such as mungbean, vegetables and fodder (zaid in South Asia).
Equatorial and bimodal climates (two rainy seasons)
Much of East Africa, parts of the Andes and of maritime South-East Asia have two rainy seasons a year.
- In East Africa these are the long rains (roughly March to May) and the short rains (roughly October to December), each with its own maize, beans, sorghum and vegetable crops.
- In the Ethiopian highlands the main meher season (June to September rains) and the shorter belg season are distinguished.
- Two crops a year are possible without irrigation, but each season is shorter and less reliable.
Mediterranean climates (winter rain)
The Mediterranean basin, California, central Chile, south-western and southern Australia and the Western Cape of South Africa have mild, wet winters and hot, dry summers.
- Winter crops are sown in autumn with the first rains and harvested in late spring: wheat, barley, oats, canola, chickpea, lentil, faba bean.
- Summer crops need irrigation: vegetables, maize, cotton, rice, fruit.
Temperate continental climates
North America, Europe, northern and eastern Asia and the southern parts of South America and Australia have cold winters and warm summers.
- Spring- and summer-sown crops fill the frost-free period: maize, soybean, sunflower, potato, sugar beet, spring wheat and barley.
- Autumn-sown (winter) crops such as winter wheat, winter barley, rye and winter canola establish in autumn, survive winter (and are vernalised by it) and are harvested in early summer.
Multiple seasons with irrigation
Where water is reliable, as in irrigated deltas and plains, two or three crops a year are grown regardless of rainfall, such as the two or three rice crops a year of parts of South-East Asia, or Brazil's safra (main summer crop) followed by safrinha (second-season maize after soybean in the same rainy season).
Cool-season and warm-season crops
| Group | Typical needs | Examples |
|---|---|---|
| Cool-season crops | grow best at about 15–25 °C; tolerate cold, many tolerate frost; often C3; many are long-day plants | wheat, barley, oats, rye, peas, chickpea, lentil, faba bean, mustard and canola, potato, cabbage, carrot, lettuce, onion |
| Warm-season crops | need warmth, often above about 20–30 °C; damaged by frost and chilling; many C4; many short-day or day-neutral | rice, maize, sorghum, millets, cotton, sugarcane, soybean, groundnut, cowpea, pigeonpea, tomato, pepper, cucurbits |
Each crop has a base temperature below which development practically stops: often taken as about 0 to 5 °C for wheat and other cool-season crops and about 8 to 10 °C for maize, sorghum and many warm-season crops.
Measuring warmth: degree-days
Crop development depends more on accumulated warmth than on calendar days. Growing degree-days (GDD) add up, day by day, how far the mean temperature exceeds the base temperature:
How long will a maize crop take?
A maize hybrid needs about 1,400 growing degree-days (base 10 °C) from sowing to physiological maturity.
- In a warm season with mean daily temperature of 25 °C: each day adds 25 − 10 = 15 GDD, so maturity takes 1,400 ÷ 15 ≈ 93 days.
- In a cooler season with a mean of 20 °C: each day adds 10 GDD, so it takes about 140 days.
The same hybrid can be a "short-season" variety in a hot lowland and a "long-season" one in a cool highland. Degree-day ratings, rather than days to maturity, let farmers match varieties to their season, and help time operations such as fertiliser, irrigation and harvest. (Many methods also cap maximum temperatures, for example at 30 °C for maize, because development does not keep speeding up in extreme heat.)
Planning around seasons
- Choose varieties whose duration fits the season, so that flowering avoids the hottest, driest or coldest weeks.
- Sow on time: late sowing shortens the season and often costs yield.
- Use contingency plans when rains start late or fail.
- Irrigation, protected cultivation and stored soil moisture extend or add seasons.
- Climate change is shifting seasons: earlier springs, longer frost-free periods at high latitudes, and less reliable rainy seasons in many tropical and subtropical regions, which makes flexible sowing dates and adapted varieties more important.
Key points
- Water (in the tropics) and temperature (in temperate and highland areas) set the growing season; day length affects flowering.
- Monsoon climates have wet-season and dry or cool-season crops; bimodal climates have two rainy-season crops (long and short rains); Mediterranean climates grow winter crops on winter rain; temperate climates grow spring–summer crops and autumn-sown winter crops.
- Cool-season crops (wheat, barley, pulses, brassicas, potato) and warm-season crops (rice, maize, sorghum, cotton, soybean) differ in temperature needs and often in photosynthetic pathway.
- Growing degree-days = mean daily temperature − base temperature, summed over the season.
- Variety duration, sowing date and contingency planning fit crops to the season.
What the exams ask
- School-leaving and entrance papers: classification of crops by season with examples, and the conditions each season provides.
- Degree and research-fellowship entrances: cool- and warm-season crops, base temperatures, degree-days and phenology, crop seasons in different climates, and sowing-date effects.
- Professional examinations: choosing varieties and sowing dates, contingency crop planning, and adapting to shifting seasons.
Described in general terms: the kind of examination, not a past paper. Laisha never reproduces exam questions.
Questions people ask
Why are wheat and chickpea grown in the dry season in monsoon regions?
They are cool-season crops that grow best in mild temperatures and are damaged by heat and waterlogging. In monsoon climates the cool, dry months after the rains suit them, using moisture stored in the soil or irrigation.
What is the difference between winter wheat and spring wheat?
Winter wheat is sown in autumn, needs a period of cold (vernalisation) to flower, and is harvested in early summer; spring wheat has little or no cold requirement and is sown in spring where winters are too severe, or in autumn in mild climates.
Can I grow two crops a year without irrigation?
Where there are two rainy seasons, or a long rainy season followed by enough stored soil moisture, yes. Otherwise a second crop needs irrigation or is very risky.
Sources
- FAO. Crop calendar and GIEWS Country Briefs. Food and Agriculture Organization of the United Nations, online.
- McMaster, G. S. and Wilhelm, W. W. "Growing degree-days: one equation, two interpretations." Agricultural and Forest Meteorology 87, 291–300 (1997).
- Sacks, W. J., Deryng, D., Foley, J. A. and Ramankutty, N. "Crop planting dates: an analysis of global patterns." Global Ecology and Biogeography 19, 607–620 (2010).
- Reddy, S. R. Principles of Agronomy. Kalyani Publishers, latest edition.
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