Depth of water in the furrows also had a large effect on rice irrigation amount on both fresh and permanent beds. Irrigation amount with a full furrow depth of water at each irrigation was much higher than with a half-furrow; however, there was a yield penalty in reducing furrow water depth from full to half. The amount of irrigation water applied to TRB-2d with a full furrow exceeded that applied to PTR-2d, probably because of higher permeability of the soil in the unpuddled furrows and greater macropore development on the permanent beds. Consistent with this, the irrigation amount on permanent beds irrigated with a full-furrow depth of water was about 600 mm (20%) higher than on fresh beds with the same irrigation scheduling. Total irrigation amounts for wheat (212-383 mm) were about one-tenth of those for rice. The amount of water applied at each irrigation was usually less on the beds than on the flats because of the volumetric limitation of the furrows. However, there was no effect of layout on total irrigation application to wheat in either the small plots or large blocks because irrigation management was based on the same ratio of irrigation amount to CPE-rain for both beds and flats, meaning that the beds were irrigated more frequently after CRI. Deep drainage during the wheat season was very small (negligible to less than 100 mm) in comparison with that from rice (up to ～2,000 mm) in both flat and bed layouts. Our studies demonstrate the importance of providing sufficient contextual detail in reporting the results of comparisons of soil and water management for RW systems to enable sound interpretation and extrapolation of the results. In particular, they highlight the importance of appropriate controls in understanding the potential irrigation water savings in switching from puddled transplanted rice to beds. They also show the need for caution in interpreting the results of water balance studies in small rice plots unless adequate measures have been undertaken to prevent disproportionately high seepage losses, especially from continuously flooded rice. To understand the effects of raised beds on components of the water balance for RW systems and to develop irrigation management guidelines for rice and wheat on permanent raised beds, further detailed investigations are needed in farmer-field-sized blocks for a range of soil types, watertable conditions and irrigation management.
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