*2.6. Data Collection and Calculation*

Field water tubes were used to guide the implementation of AWD [6], and to estimate the amount of irrigation input in the field experiment. Field water depths in the main plots of the experiment were regularly monitored using field water tubes that were installed at a depth of 15 cm below the ground surface. Monitoring of field water depths was done every other day, between 8:00 and 9:00 AM for all treatments from transplanting until 15 d before harvesting. Water level inside the tube was measured from the top to the level of the water inside the tube. To get the actual depth of water inside the tube, the reading will be subtracted from the height of the AWD tube that protruded above the soil surface.

Irrigation dates were all noted and during irrigation events, field water tubes were read before and after each irrigation. The irrigation water input under AWD conditions was then computed using a procedure outlined by [15] as follows:

$$\mathbf{I} = \mathbf{d}\_{\mathbf{f}} - ( (\boldsymbol{\Theta}\_{\mathbf{s}} - \boldsymbol{\Theta}\_{\mathbf{i}}) \times \mathbf{D} ), \tag{1}$$

where I = irrigation (mm); df = final water depth above soil surface (mm); θ<sup>s</sup> = soil water content at saturation (cc/cc); θ<sup>i</sup> = soil water content when field water falls below the ground surface (cc cc−1), which was assumed as the field capacity, especially when the perched water table is 15 cm or more from the soil surface; and D = depth of the perched water table.

Since flooded conditions were essential during flowering stage, irrigation water input was computed as:

$$\mathbf{I} = \mathbf{d}\_{\mathbf{f}} - \mathbf{d}\_{\mathbf{s}\star} \tag{2}$$

where ds = initial field water depth (mm) above the soil surface.

Total water input was the sum of total irrigation and rainfall from transplanting to 15 d before harvesting. Rainfall was taken from the automatic weather station (Vantage Pro2 Weather Station, Davis Instruments Corp, USA) installed adjacent to the experimental area. Groundwater depths were also monitored using three observation wells (2-inch diameter PVC pipe, 2 m long, driven down to 1.5 m) installed along the bunds in the upper, middle, and lower portions of the experiment field. Reading of the water levels in the observation wells was also done every 2 d, from transplanting to 15 d before harvest between 8:00 AM and 9:00 AM. The water level in the observation wells was measured from the top to the level of the water inside the tube. To get the actual depth of the groundwater, the reading was subtracted from the height of the tube that protruded above the soil surface.

Plant height and number of tillers per hill were monitored every 2 wk from transplanting to flowering. Phenology dates (mid-tillering, panicle initiation, flowering, grain filling, and physiological maturity) were monitored for each sub-subplot. At harvest, crop cut samples were taken from 110 h at the center of each plot to determine grain yield. Moisture content of the grains was measured with a digital grain moisture meter (OGA Electric Co., Ltd, Japan), and grain yield was calculated at 14% moisture content. Grain yield components, number of panicles m<sup>−</sup>2, % spikelet sterility, number of spikelet per panicle, 1000-grain weight, and total biomass of grains and vegetative matter were determined in five-hill samples near the harvest area. Harvest index (in percent) was also determined by dividing grain yield by total biomass and then multiplying it by 100. Irrigation water productivity (WPI) and total water productivity (WPI+R) were calculated as kg grain m−<sup>3</sup> water input. For WPI, water input was from the sum of all irrigations, while for WPI+R, water input was from total rainfall and the sum of all irrigations received by the plants from transplanting up to 15 d after harvesting.

Selected weather data (rainfall, minimum, and maximum temperatures) were taken from the agrometeorological station in the ARC. Seasonal means and sums were reported based on the actual growth duration per treatment.
