Farming, Irrigation and Land Revenue under the Abbasids

The Abbasid caliphate began in 750, and its rulers made Baghdad, founded on the Tigris in 762, their capital. A caliph was the ruler of the caliphate. The Mongol capture of Baghdad in 1258 ended Abbasid rule there; later Abbasid caliphs in Cairo fall outside this account. Its main focus is eighth- to tenth-century Iraq and the connected provinces whose harvests, water systems and tax accounts supported the state. The irrigated alluvial plain between the Tigris and Euphrates, known in Arabic as the Sawad, was a particularly important source of land revenue. The broader Abbasid revenue system began in fields where water access and cultivation shaped what owners, tenants and officials could claim.

On this page5 sections

Canals and the work of maintenance

Canals carried water from the Tigris and Euphrates beyond their banks, but a large channel only worked when smaller branches stayed open and its banks held. Floodwater could breach a bank, while inadequate drainage left fields vulnerable to waterlogging and increasing soil salinity. Clearing silt, repairing embankments and managing water locks were recurring work, not a single act of construction.

Abbasid rulers invested in that infrastructure. Harun al-Rashid, caliph from 786 to 809, built the Qatul Abi al-Jund to irrigate the area between the Nahrawan canal and the Tigris north of Baghdad. This project integrated an existing canal network. Earlier Abbasid works had concentrated around Basra and Wasit, before attention also turned to Baghdad, Samarra and the central Tigris.

The late eighth-century jurist Abu Yusuf, a judge in Baghdad, set out who should pay for upkeep in his Book of Land Tax. He assigned the treasury the cost of maintaining major riverbanks, dams and locks, because failure could damage agriculture across a large area and reduce tax income. Clearing a main canal could be paid for by both the treasury and people who directly benefited. On a jointly owned smaller canal, co-owners shared the cost of digging and dredging in proportion to their interests; if one owner paid for necessary repairs to prevent a breach, the others could be required to contribute. The rules linked a concrete task, such as reinforcing a bank, to shared rights in the watercourse.

Crops, tenants and land claims

Fields in Iraq produced wheat and barley, while southern districts supported date palms and sugar cane. In Khuzestan, in present-day southwestern Iran, sources also record rice and sugar cane; cotton was another crop grown in suitable irrigated areas of Iran. These crops drew on different combinations of land, water and processing.

Landholding and cultivation did not always belong to the same person. A tenant might cultivate a landholder’s field under a sharecropping arrangement, cultivating in return for part of the harvest. Historian Michele Campopiano’s review of early medieval Iraqi evidence finds that grain sharecroppers often held leases for only one or two years. The crop was then divided among several claims: the cultivator kept an agreed portion, the landholder collected rent, and the state assessed kharaj, the land tax. A field’s harvest therefore did not pass directly from the person who planted it to the market or the treasury.

Tax could be calculated by measured area or as a share of produce. The area-based method fixed a sum of money or grain for a measured plot. A crop-share method, called muqasama, took a portion of the harvest instead. The eleventh-century jurist al-Mawardi’s legal formula varied the share with irrigation: one-half for flood-irrigated land, one-third for a waterwheel, and one-quarter for an animal-powered wheel. Campopiano associates a move toward muqasama in Iraq with the caliph al-Mahdi’s reign, 775 to 785, while historian Jürgen Paul’s later review finds the extent of its implementation uncertain even within Iraq.

Under the Buyid dynasty from Iran, which took Baghdad in 945, another collection arrangement expanded: tax farmers promised the state a fixed sum and then collected revenue from the district. In the arrangements Campopiano describes, contractors also had duties to improve land and manage waterworks, but they bore the risk if collections fell short of their contract. That shifted both the burden of collection and the incentive to invest in irrigation as political authority changed.

Measuring and collecting: Qom in 895

Qom, in present-day Iran, supplies a detailed provincial example from the end of the ninth century. Jürgen Paul’s account of the records describes officials measuring cultivated land, signing the measurement with its owner and placing agricultural units in one of seven categories. The owners of those agricultural units owed the assessment, even where another person cultivated the land. The assessment then applied different charges to different products. Grain was charged at three to fifteen dirhams, a monetary unit, per jarib, a local unit of land area; grapes at fifty dirhams per jarib; and cotton at thirty to thirty-eight dirhams per jarib.

Once the assessment was set, a financial official was responsible for collecting it. A collection chief weighed incoming coins and goods and carried them to the fiscal bureau. The district financial official then drew up the final account. The account for 282 AH (895–896 CE) was sent to Baghdad. It recorded shortfalls against the amount assessed, so the central administration could distinguish the planned revenue from what had actually been collected. Currency in the final account did not mean every tax payment arrived as coins: crops and other goods also entered the process.

Qanats and provincial authority in Khorasan

Khorasan was a broad eastern region extending from northeastern Iran far into Central Asia. In parts of this region, cultivators used qanats, gently sloping underground tunnels that tapped groundwater and carried it to the surface for fields by gravity. A qanat required knowledge of the underground water route as well as an agreed way to distribute the resulting flow.

Abdallah ibn Tahir governed Khorasan for the Abbasid caliphs from 828 to 845, with Nishapur as his provincial capital. The later historian Gardizi reports that Abdallah commissioned an authoritative book on qanat law and water rights, which remained in use in Khorasan under the Ghaznavids centuries later. The episode places irrigation knowledge within a provincial administration: local expertise helped define access to water, while the governor represented Abbasid authority. The Tahirid family later established an autonomous hereditary dynasty in the province, one example of how provincial political control changed during the ninth century even while its agricultural systems remained in use.

Basra’s fields and the Zanj revolt

Southern Iraq’s estates included market-oriented sugar-cane production and relied on enslaved laborers among other workers. Before the revolt of 869, large numbers of enslaved people worked in camps throughout the agricultural zone east of historic Basra, on both sides of the Shatt al-Arab. Medieval writers used the term Zanj inconsistently: it could refer to East Africans, enslaved people of different origins and local peasants. Accounts describe harsh working conditions as a major cause of the uprising, which lasted until the Abbasid state regained control of the region in 883. The rebel leadership is thought to have established al-Mukhtara, its headquarters, within the same agricultural zone where many had been forced to work.

A large system of ridges and earthworks on the Shatt al-Arab floodplain has often been tied to the revolt’s labor camps. In 2025, archaeologists Peter J. Brown, Jaafar Jotheri, Louise Rayne, Nawrast S. Abdalwahab and Eric Andrieux reported optically stimulated luminescence dates from four sampled ridge crests. All four accumulated sediment between the late ninth and mid-thirteenth centuries, after the revolt, showing that agricultural activity in the region continued for centuries after 883.