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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.

The key problem for Sumerian agriculture was that the timing of river runoff did not coincide with the growing season for crops. Flow in the Tigris and Euphrates peaked in the spring, when the rivers filled with snowmelt from the mountains to the north. Discharge was lowest in the late summer and early fall, when new crops needed water the most Intensive agriculture required storing water through soaring summer temperatures. A lot of the water applied to the fields simply evaporated, pushing that much more salt into the soil.

Salinization was not the only hazard facing early agricultural societies. Keeping the irrigation ditches from becoming blocked by silt(mud) chief concern as extensive erosion from upland farming in the Armenian hills poured dirt into the Tigris and Euphrates Rivers. Conquered peoples were put to work pulling mud from the all-important ditches. Sacked and rebuilt repeatedly, Babylon was finally abandoned only when its fields became too difficult to water. Thousands of years later, piles of silt more than thirty feet high still line ancient irrigation ditches. On average, silt pouring out of the rivers into the Persian Gulf has created over a hundred feet of new land a year since Sumerian time. The ruins of the city of Ur. a once thriving seaport. now stand hundred and fifty miles inland.

As Sumer prospered, fields lay fallow for shorter periods because of the growing demand for food. By one estimate almost two-thirds of the thirty five thousand square miles of arable land (land suitable for farming) in Mesopotamia were irrigated when the population peaked at around twenty million. The combination of a high load of dissolved salt in irrigation water, high temperatures during the irrigation season, and increasingly intensive cultivation pumped ever more salt into the soil.

Temple records from the Sumerian city-states inadvertently recorded agricultural deterioration as salt gradually poisoned the ground. Wheat, one of the major Sumerian crops is quite sensitive to the concentration of salt in the soil. The earliest harvest records, dating from about 3000 B.C., report equal amounts of wheat and barley in the region Overtime, the proportion of wheat recorded in Sumerian harvests fell and the proportion of barley rose. Around 2500 B.C., wheat accounted for less than a fifth of the harvest. After another five hundred years, wheat no longer grew in southern Mesopotamia.

Wheat production ended not long after all the region’s arable land came under production. Previously, Sumerians irrigated new land to offset shrinking harvests from salty fields Once there was no new land to cultivate, Sumerian crop yields fell precipitously because increasing salinization meant that each year fewer crops could be grown on the shrinking amount of land that remained in production By 2000 B.C., crop yields were down by half. Clay tablets tell of the earth turning white in places as the rising layer of salt reached the surface. 

1.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.