Cultivated land
Buck has provided definitions for ‘crop area' and ‘crop mU that are very helpful for the study of changes in cultivated land in Jiangnan. ‘Crop area' represents the land area devoted to crops, while ‘crop mU refers to the number of mu of different crops raised in one year (Buck 1930: 18).
Because multi-cropping is practised, one mu of ‘crop area' may be equivalent to two or even more ‘crop mu'. Total ‘crop area' in Jiangnan did not change much during the period, totalling roughly 45 million mu. But ‘crop mu’ increased remarkably, thanks to the spread of double-cropping. The double-cropping index rose from about 140% to about 170% between the earlyseventeenth and the mid-nineteenth century. This represents an increase of 13.5 million mu of sown area, corresponding to 30% of the total cultivated land of Jiangnan (Bozhong Li 1998: 33).
Another significant change to cultivated land in Jiangnan is the improvement of land quality. These improvements were focused on the transformation of waterlogged land in eastern Jiangnan, the most important agricultural area in the region. This land improvement is called ‘drying the land' (Hamashima 1989). The process took centuries and was completed in the mid-nineteenth century (Kitada 1988: 40—2; Bozhong Li 1998: 28—9). This improvement resulted in a substantial increase in the productivity of land in Jiangnan. For example, in the mid-nineteenth century, one mu of paddy could support a person in the core areas of Jiangnan, but the ratio for the whole country was 4 mu/person (Guo Songyi 1994). In this sense, 1 mu of well improved land may equal several mu of less improved land in terms of productivity. These improvements also facilitated regional specialization of agriculture. Different crops were planted in the respective areas most suited for their cultivation. Consequently, three major crop areas appeared and expanded in Jiangnan in this period; cotton in the east, mulberry in the south, and rice in the remaining areas. In the cotton and mulberry areas, income per mu from these crops was obviously better than incomes from rice. An average year's cotton harvest is equivalent to a very good year's rice harvest in cotton areas, while mulberry produced twice the net income of rice in mulberry areas (Bozhong Li 1995).
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