Comparison of Irrigation Requirements between Transplant Cultivation and Direct-Seeding Cultivation in Large-sized Paddy Fields

Abstract

In large-sized paddy fields with groundwater level control systems in the town of Moseushi, Hokkaido, ponding depth levels and groundwater levels were observed. In the same paddy field, irrigation requirements were compared among the three types of paddy rice cultivation: direct-seeding cultivation without puddling in flooded paddy fields, transplant cultivation, and direct-seeding cultivation in well-drained paddy fields.
The observation results are as follows. 1) In transplant cultivation and direct-seeding cultivation, changes in the groundwater level depend on soil puddling. However, differences of percolation in those cultivation styles are small. 2) The difference of the total volume of water as a sum of irrigation water and effective rainfall is 10%-30% in all cultivation methods because the groundwater level around the paddy fields is high and the amount of percolation is small. 3) The quantity of water intake during the period of shallow water management in direct-seeding cultivation is comparable to the puddling water requirement in transplant cultivation. 4) On the assumption that direct-seeding cultivation will increase in the future, the timing of water intake after mid-summer drainage of paddy fields is likely to vary depending on the cultivation method when the drainage starts at the same time in transplant cultivation and direct-seeding cultivation.