417density land areas shown on this map have been discussed previously (Baumhardt
and Salines-Garcia 2006 ; Cochran et al. 2006 ; Hansen et al. 2012 ; Schillinger et al.
2006 ). However, previous maps depicting the areas of dryland agriculture in North
America have not illustrated the extent of lower density dryland crop production.
Nearly every state in the western U.S and in northern and central Mexico has signifi-
cant land areas where some dryland farming occurs. In addition to wheat, North
American dryland farming is important for the production of maize (Zea maize L.),
sorghum, pulses, and oilseeds.
The Great Plains region of the United States and Canada is an area of widespread
dryland crop production, with wheat being the dominant crop. This region is char-
acterized by a continental climate, with precipitation in the region ranging from 300
to 500 mm annually. Wide fluctuation in annual precipitation and periods of
extended drought are common. There is a strong, increasing west to east precipita-
tion gradient. Winters become increasing long and cold from south to north. The
majority of the annual precipitation falls during summer months, but winter snow is
important, especially in the central and northern areas. The Great Plains are roughly
divided into the Canadian Prairies and U.S. Northern Great Plains, The Central
Great Plains, and the Southern Great Plains.
Fig. 2 Harvested wheat area within 5 min by 5 min longitude/latitude grid cells was used to show
the dryland farming lands of North America. Only wheat produced in semi-arid zones is show.
Wheat produced under irrigation is shown in blue to separate these from the drylands. Wheat data
from (Monfreda et al. 2008 ) and irrigation data from (Siebert et al. 2013 )
Dryland Agriculture in North America