The equal-field system (juntianzhi 均田制, also called juntianfa 均田法) was in theory a system in which fields were equally and fairly distributed to the peasantry for lifelong use. The size of fields depended on the number of household members. Created by the Northern Wei 北魏 (386-534), the system spread over all China, or at least to all regions in northern China, during the Tang period 唐 (618-907).
The generous distribution of land in northern China had been possible because large tracts and of land were devastated as a consequence of decades-long warfare, famine and pestilence, and could therefore be allotted freely to new settlers. As all land was declared property of the state, the allotment of fields was more or less a kind of lifetime lending. This measure allowed the government not only to allow all peasant families a sufficient base for their livelihood, but also to establish reliable household registers, on which the tax registers were based. The tax handed over to the government can thus be seen as a kind of rent paid to the landowner, the government.
Li Anshi 李安世 (443-493) developed the blueprint for this system and in 485 submitted the concept to the throne. It was inspired by an earlier model, the "field occupation system" (zhantian zhi 占田制) of the Jin dynasty 晉 (265-420), and the field allotment system of the Xianbei 鮮卑, a pastoral tribe invading northern China and deciding to settle down in the Central Plain. They were the founders of the Northern Wei dynasty. The land allotment was first carried out around the capital of the Wei empire, Pingcheng 平城 (present-day Datong 大同, Shanxi), and then expanded to other regions.
The regulations said that each male above 15 sui of age was given 40 mu 畝 (an area measure) of arable land (lutian 露田), and each female above 20 sui of age 20 mu. Even persons of the status of serf or slave were included in this regulation. For each serf 20 mu of land were given. The government also lend out buffaloes (4 at the most), with 30 mu of pasture per animal. Each male person was furthermore given 20 mu of land (women half of this amount), defined for the rearing of 50 mulberry trees (sangtian 桑田), 5 dates, and 3 elms (yu 榆). In order to allow the soil some repose in a "fallow cultivation system" (xiugengfa 休耕法), owners of land were given double the amount (peitian 倍田) with the condition to have half the land lie fallow each second year, and thrice the amount of land, if one third was lying fallow for two years. Additional land for trees was not granted under such conditions. Instead of land for mulberry trees, peasants might be given land for hemp (matian 麻田) in regions where this type of plant was more common. The according size was 10 mu per male person, and 5 per women.
The Northern Wei and Northern Zhou 北周 (557-581) abolished the double allotment method and instead permitted for male persons 80 mu of arable land and 20 mu of mulberry land, and half of this for females. Wherever settlers moved to new land, they were additionally granted 1 mu of land for a cottage (zhaidi 宅地, zhaitian 宅田) for each three free persons, or for five serfs.
Arable land and land for hemp cultivation was to be given back to the state when an elderly peasant "retired" or died. The same was valid for buffaloes, and serfs, in case they were "state-owned". In contrast to this, the land with mulberry trees planted upon was inheritable (shiyetian 世業田). It was not allowed to sell or to buy the state-owned real estate, barring the mulberry land. In case a family could not live of the land it was given, the purchase of additional land was allowed, respectively the sale of this property.
The government of the Northern Wei did everything to enlarge the amount of cultivable land, and therefore did not allow peasants, once they had been given land, to move to another place. State officials of all ranks were likewise allotted land, so-called "public land" (gongtian 公田), which served as part of their salary.
In 486 the tax for the newly distributed land was fixed. Each couple had to deliver annually 2 shi 石 "bushels" (see measures and weights) of millet, and one bolt of silk (bo 帛). The same amount was to be delivered by four unmarried persons over 15 sui of age, for eight serfs, or by owners of a herd of twenty buffaloes, which means in turn that one lone woman or man delivered only half the amount of tax of what a married person paid.
The system was adopted by the later dynasties, yet the regulations were not exactly the same under the Sui 隋 (581-618) and Tang. Males, for examples, were only given land above 21 sui of age under the Sui, and 18 sui under the Tang, and for women, serfs and buffaloes no land was given at all. Under the Northern Zhou, a couple was given 140 mu of land, a single person 100. The "age of retirement" was raised to 64 sui, and the difference between arable and mulberry land was blurred. The Tang discerned between "allotted land" (koufen tian 口分田), of which 80 mu were given that fell back to the state after the dissolution of the household, and "inheritable land" (yongye tian 永業田), of which each male persons was accountable for 20 mu. Elderly and ill persons were only given 40 mu of farming land, widows and secondary wives 30.
In case that a household head was younger than 18 or order than 64 sui, he was only given 30 mu of arable and 20 mu of inheritable mulberry land. State officials could be given three types of land, namely "office land" (zhifen tian 職分田), inheritable land, and "public land" (gongjie tian 公廨田). The amount of land given to officials corresponded with the official rank (pinji 品級), and the concrete size changed over time. Land was also given to Buddhist and Daoist monks and nuns (30 mu for male, and 20 for female persons), as well as to some non-farming households (half of the farming population). A great problem was the allotment of fields in areas with a small size of arable land (xiaxiang 狹鄉). People were often just given half of the normal size of land, and had to buy additional land at own cost.
The reasons for the eventual failure of the system were a population increase during the first half of the Tang period, ways of the gentry or Buddhist monasteries to bypass the land allotment and to accumulate more and more land, a relaxation of the prohibition of the sale of allotted land, and the poverty of many peasants haunted by famine and natural disasters. More and more public land was thus converted to private land (sitian 私田), often in the form of large estates (zhuangyuan 莊園, zhuangtian 莊田, zhuangye 莊墅), and an increasing number of free farmers became land tenants (diannong 佃農). The Tang finally gave up the equal field system and in 780 introduced a different method with the twice-taxation system (liangshuifa 兩稅法), in which the size of the land played only a secondary role. Scholars still dispute whether the equal-field system was only applied to northern China during the Tang period, or to the whole empire. The economic effect of the equal-field system is quite clear: The government had a tighter control over the ownership of land, and accordingly over the tax revenues. At the same time, more land was made arable than without such a control, and this increased the total agricultural output of the country.