宋元時代の濱海田開發について

Abstract

During the Song and Yuan periods, the drainage and reclamation of wet, low-lying coastal lands were widely undertaken in seaboard regions extending from Hangzhou 杭州 Bay to Guangzhou 廣州. These new coastal fields, named variously in different places either haitutian 海塗田, haitian 海田, or chaotian 潮田, all similarly possessed dikes, ditches equipped with sluices, and water pools. In general, the provisions for irrigation of these new coastal fields, limited to rainfall and the water remaining in the old fields, were unsatisfactory. The situation was particularly bad at the start of their development. In such regions, however, where every kind of improvement in irrigational construction had been put into effect in newly developed lands since early times, as the irrigation system improved in the highland fields, it also improved in the coastal fields. At the same time, new developments continued at the frontier of those coastal fields. In the new coastal fields, where irrigational conditions were thus inferior, Zhancheng占城 varieties of rice were more often cultivated than nonglutinous late-ripening rice. The Zhancheng varieties have the advantages of being able to tolerate drought and alkaline conditions, as well as being early-ripening. Moreover, in regions south of Fuzhou 福州 at that time in addition to cultivation of double-crop, wet rice, planters also used both early- and late-ripening Zhancheng varieties of rice. Frequently, these varieties were used in the new coastal fields. Double-crop cultivation was more effective than single-crop cultivation in transforming the salty soil there. Moreover, the narrow, ten to fifteen mou 畝 areas under cultivation were suitable for double-crop cultivation. It became more advantageous than single-crop cultivation. However, in terms of harvest yield, double-crop cultivation of wet rice in these new coastal fields was inferior to the late-ripening, single-crop rice cultivation in the fields of the interior. It had been chosen in an attempt to avoid the problems of irrigation and poor soil. Consequently, double-crop cultivation of wet rice in the new coastal fields did not attain the height of its productive potential, nor did it attain the standard of Song period techniques of wet rice cultivation.