Challenges of Mesopotamian Agriculture
One of the world’s first civilizations began in the area between the Tigris and Euphrates Rivers known as Mesopotamia(modern Irag) where much of the fertile land was under cultivation by 4500 B.C. Sumer, in southern Mesopotamia, was dominated by eight major cities, including the city of Uruk, which had 50,000 inhabitants by 3000 B.C. But the irrigation that nourished Mesopotamian fields carried a hidden risk. Groundwater in semiarid regions usually contains a lot of dissolved salt. Where the water table is near the ground surface, as it is in river valleys and deltas, groundwater is moved up into the soil where it evaporates, leaving the salt behind in the ground. When evaporation rates are high. sustained irrigation can generate enough salt to eventually poison crops. While irrigation dramatically increases agricultural output, turning sunbaked floodplains into lush fields can sacrifice long-term crop yields for short-term harvests.
Preventing the buildup of salt in semiarid soils requires either irrigating in moderation or periodically leaving fields fallow(unplanted). In Mesopotam, centuries of high productivity from irrigated land led to increased population density. which fueled demand for more intensive irrigation. Eventually, enough salt crystallized in the soil that further increases in agricultural production were not enough to feed the growing population.
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