Thünen's“location theory”of agriculture is one of the basic principles in geography and economics. In this theory a visionary uniform space called“The Isolated State (Der isolierte Staat)”has already been established. This isolated state is 50 miles (deutsche meile; about 375km) in diameter, and the agricultural zones are arranged in a concentric circle. In the center only one large city is located, and the concentric circles of agriculture are, from inside, free agriculture (die freie Wirtschaft), forestry (Forstwirtschaft), crop rotation system agriculture (Fruchtwechselwirtschaft), field-grass agriculture (Koppelwirtschaft), three-field system (Dreifelderwirtschaft) and cattle breeding and dairy (Viehzucht). The boundary distances of each type outward from the large city are 4, 7, 24.7, and 31.5 miles respectively.
In this article, I tried to reexamine the structure of Thünen's circles according to Thünen's logical point of view. The basic conditions are as follows: the farm acreage is 100, 000 square Rutes (217ha), the rye crop yield per 100 square Rutes is 8 Sheffels, and the price of 1 Sheffel of rye is 1.5 Taler at the city.
The main problem is the conversion process from the Koppelwirtschaft to the three-field system. Thünen says that a crop of 8 Sheffels in the Koppelwirtschaft is proportional to 6.72 Sheffels in the three-field system. In the case of the Koppelwirtschaft divided into seven, the acreage of one section is about 14, 300 square Rutes, and in the three-field system, the acreage of one field is 12, 000 square Rutes (fields, 36, 000; permanent pasture, 64, 000). According to this, in the conversion process from the Koppelwirtschaft to the three-field system, the total fertilizer given to the rye fields increase 1.17 times. This indicates a larger increase of rye crop in the three-field system than in Koppelwirtschaft. In my calculation, 8 Sheffels in Koppelwirtschaft is proportional to 8.42 Sheffels in the three-field system.
If this is true, the“Landrente”(bid rent) of Koppelwirtschaft is 1, 111 Taler, while the Landrente of the three-field system is 1, 137 Taler; and the dominance of Koppelwirtschaft is overthrown. In Thünen's circles, the Koppelwirtschaft would be replaced by the three-field system, and have to disappear. As a result, in my calculation, the structure of Thünen's circles consists of free agriculture, forestry, three-field system, and cattle breeding and dairy. The distances from the large city should be revised to 4, 7, and 33 miles respectively.

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