the area where crops are grown is called the "cropping area", as in this example:

***Cropping Area***
The region represents 24 percent of the cropped area of Queensland.
Cotton is the most valuable crop in the region. 89.5 percent of the area where cotton is grown is irrigated. In 1999 production was 116 107 tonnes, which represented 16.09 percent of the Queensland total (Agstats 1999). Processing gins are located at Emerald, Yamala, Biloela and Moura.
Grain crops are predominant in the Central Western areas and include grain sorghum, barley, peanuts, wheat, ***sunflower*** and cotton. The region produces 20 percent of the State’s wheat and 30 percent of cotton. Minor crops produced are mung beans, soybeans, navy beans, oats, cow peas, fodder crops and safflower.
http://www.cqris.com.au/opencms/export/sites/default/resourc...