Different crops are grown in different seasons as each crop has a time to grow.
Believe it or not, about 6 million, eight hundred crops are grown in Montana every year.
because different plants need to grow at different times of the year.
A crop of wheat will yield once per year. A field may be planted so that two crops per year can be grown.
That is called "crop rotation".
Some spices are harvested at different times of the year. However, often the plant you harvest the spice from grows all year round.
Because of climatic or seasonal variations at different times of the year, the Indus Valley farmers plant different crops in different seasons of the year. For that reason they have classified these crops into rabi (winter) and kharif (summer) seasons.
Corn is one of the major crops grown in the United States. US production is many times that of any other nation. On average, about 80 million acres of corn are raised every year in the US.
plant something different every year
It is when one species of crop is rotated with a different species of crop every year. For instance, a field that was planted with canola one year is planted with wheat another year. That same field may be sown into hay for a few years before being turned back to crop. This is so that the nutrients in the soil are not "mined" out of the soil to the point where crops cannot be grown anymore. Different crops have different nutrient needs than others. For instance, legume/oilseed crops like canola and peas fix nitrogen and put nitrogen back into the soil, whereas cereal crops like wheat or corn use it up.
Example is that much of the corn grown in the US is grown as the only crop grown on a piece of land year after year. There is no crop rotation with other crops, so the land becomes depleted of nutrients that corn uses, and more dependent on fertilization, more dense, and lacking of forms of life.
Beans are grown all year in different parts of the country.
In many parts of the world, where "dry land farming" is practiced, there is only one crop grown per year because there is only water for the plants in winter when it rains. On the other hand, rice growers (rice is a grain like wheat, barley, rye etc.) in the tropics sometimes get three crops per year. It is also a good idea to only grow one crop per year so as not to overwork the land and drain all of the goodness out of the soil. Many farmers grow a crop of legumes (not a grain) to enrich the soil with nitrogen, then grow grain the following year and finally leave the land for a year without crops or simply graze it. It all depends on where you live in the world and what grain is being grown as to how many crops are grown each year.