Paddy AWD & Save Water, Spare Yield
Schedules the re-flood trigger
Alternate Wetting & Drying lets your paddy dry to a safe depth between irrigations instead of staying flooded — enter your soil, season and flood depth to get the re-flood trigger, the water and irrigations saved, the unsafe flowering window to skip, and the methane co-benefit.
Enter your paddy
Next: install a perforated field water tube and re-flood to ~5 cm whenever the water in the tube falls to 15 cm below the surface — about every 18.2 days on your soil. Skip AWD and keep the field flooded through panicle initiation to flowering (56–80 days after transplant), the water-sensitive window, then resume. Expect to save about 3150 m³/ha and cut methane roughly 30%.
Method: IRRI Safe AWD — re-flood at −15 cm tube level; dry-down time = (re-flood + 15 cm) ÷ (ET + percolation); saving 15–38% vs continuous flooding by soil; methane cut 30–70%. Planning-grade — verify the tube level in the field and keep flooded during flowering.
| Growth stage | AWD | Guidance |
|---|---|---|
| Establishment (0–14 DAT) | Keep flooded | Keep shallow flood for seedling establishment & weed control. |
| Early vegetative (15–35 DAT) | Safe | AWD safe — start dry-down cycles once roots establish. |
| Late vegetative / tillering (36–55 DAT) | Safe | AWD safe — maximum water-saving window. |
| Panicle initiation–flowering (56–80 DAT) | Keep flooded | Keep flooded — most water-sensitive; drying causes sterility & yield loss. |
| Grain filling (81–100 DAT) | Safe | AWD safe — resume dry-down; aids even ripening & timely drainage. |
| Ripening / pre-harvest (101+ DAT) | Safe | Final drainage for harvest; AWD safe. |
Paddy AWD — key facts
- Safe re-flood trigger
- 15 cm below surface (IRRI Safe AWD)
- Re-flood depth
- ~5 cm standing water
- Water saving
- 15–35% vs continuous flooding
- Methane reduction
- ~30–70% (≈48% typical)
- Read it with
- a field water tube
- Keep flooded
- panicle initiation → flowering
- Best AWD soil
- medium loam (~25% saving)
- Yield
- unchanged within Safe AWD limits
- Unit
- m³ per hectare
- Privacy
- Runs in your browser; nothing uploaded
Stop flooding what the crop is not using
A continuously flooded paddy spends most of its water on percolation and evaporation just to hold a permanent layer of standing water the rice does not need. AWD breaks that habit: you let the perched water level fall to a safe depth — about 15 cm below the surface — then re-flood. Through each dry-down the roots stay within reach of moisture, so the crop never feels stress and yield holds, while the irrigations you skip are pure saving.
The two guardrails make it work. First, never dry deeper than the safe trigger, which you read directly from a field water tube. Second, keep the field flooded through the most water-sensitive stage — panicle initiation to flowering — where drying causes sterility and real yield loss. Within those rules AWD saves roughly 15–35% of water depending on soil, cuts methane substantially by aerating the soil, and lowers your pumping cost and labour. This tool turns those rules into your field's numbers.
AWD soil percolation & water-saving reference
Dry-down speed and achievable water saving rise with soil percolation — from IRRI AWD guidelines and rice water-productivity studies (Bouman; Lampayan et al.).
| Soil class | Percolation (mm/day) | Water saving | Note |
|---|---|---|---|
| Heavy clay (slow percolation) | 3 | 15% | Slow dry-down; modest saving but very safe — biggest CH₄ cut. |
| Medium loam (moderate percolation) | 6 | 25% | Classic AWD soil — strong saving with safe yield. |
| Light sandy (fast percolation) | 10 | 35% | Dries fast; highest saving but re-flood promptly to protect yield. |
Growth-stage AWD safety windows
AWD is paused (the field kept flooded) through the most water-sensitive stages; applied elsewhere — rice growth-stage drought-sensitivity literature.
| Stage | DAT | AWD | Note |
|---|---|---|---|
| Establishment (0–14 DAT) | 0–14 | Keep flooded | Keep shallow flood for seedling establishment & weed control. |
| Early vegetative (15–35 DAT) | 15–35 | Safe | AWD safe — start dry-down cycles once roots establish. |
| Late vegetative / tillering (36–55 DAT) | 36–55 | Safe | AWD safe — maximum water-saving window. |
| Panicle initiation–flowering (56–80 DAT) | 56–80 | Keep flooded | Keep flooded — most water-sensitive; drying causes sterility & yield loss. |
| Grain filling (81–100 DAT) | 81–100 | Safe | AWD safe — resume dry-down; aids even ripening & timely drainage. |
| Ripening / pre-harvest (101+ DAT) | 101–120 | Safe | Final drainage for harvest; AWD safe. |
DAT = days after transplanting. Sources: IRRI Rice Knowledge Bank, Alternate Wetting and Drying (AWD) technology; rice growth-stage water-sensitivity research.
How to use it — five steps
- 1Pick your soil percolation class
Heavy clay, medium loam or light sandy — it sets the dry-down speed and the saving.
- 2Enter the season and flood depth
Give the flooded-crop length in days and the standing depth you maintain now.
- 3Install a field water tube
Re-flood when the perched level falls about 15 cm below the surface inside the tube.
- 4Keep flooded through the sensitive stage
Pause AWD from panicle initiation to flowering to protect spikelet fertility.
- 5Read the saving and methane cut
See water and irrigations saved per season and the CH₄ co-benefit, then re-check inputs.
Frequently Asked Questions
What is Alternate Wetting & Drying (AWD) in rice?+
AWD is an irrigation practice where the paddy is allowed to dry down between irrigations instead of being kept continuously flooded. You let the perched water level fall to a safe depth below the soil surface, then re-flood. Done within the IRRI 'Safe AWD' guardrails it saves water and cuts methane without penalising yield, because the roots stay within reach of water through each dry-down.
When should I re-flood under Safe AWD?+
Re-flood when the perched water level in a field water tube falls to about 15 cm below the soil surface — the IRRI 'Safe AWD' threshold — and re-flood to roughly 5 cm of standing water. At 15 cm the soil is still moist enough that roots reach water, so yield is protected. If you cannot read a tube, a conservative rule is to re-flood when hairline cracks just begin to appear.
How much water does AWD save versus continuous flooding?+
Typically 15–30% of irrigation water versus keeping the field continuously ponded, and up to about 38% on fast-percolating soils. The saving comes from no longer replacing percolation and evaporation losses to hold a permanent flood — each dry-down replaces several continuous top-ups with one larger re-flood. This tool estimates the saving from your soil's percolation class and reports it in m³ per hectare.
Does AWD reduce rice yield?+
Not when kept within Safe AWD limits. Letting the level fall only to about 15 cm below the surface keeps roots watered, so yield is statistically unchanged in most IRRI and on-farm trials. Yield loss occurs only with 'unsafe' AWD — drying too deep, or drying during the water-sensitive flowering/panicle-initiation stage. The tool flags those stages so you keep the field flooded then.
Which growth stages are unsafe for AWD?+
Keep the field flooded during establishment (the first ~2 weeks after transplanting) and, most importantly, through panicle initiation to flowering (roughly 56–80 days after transplanting), the most water-sensitive stage where drying causes spikelet sterility and direct yield loss. AWD is applied safely in the early and late vegetative stages and again during grain filling and ripening.
How does AWD cut methane emissions?+
Continuous flooding keeps the soil anaerobic, which is exactly the condition methanogens need to produce methane (CH₄). Each AWD dry-down aerates the soil, suppressing methane production. IRRI reports CH₄ reductions of roughly 30–70%, around 48% typically, and more dry-down cycles on faster-draining soils give the bigger cut. This tool scales the methane benefit by your soil's aeration intensity.
What is the field water tube and how do I use it?+
A field water tube is a perforated pipe (about 30 cm long, ~15 cm above and ~15 cm below ground) sunk into the bund-side soil so you can see the water level inside it. After irrigation the level drops with evaporation and percolation; when it reaches about 15 cm below the surface inside the tube, it's time to re-flood. It turns AWD from guesswork into a simple, readable trigger.
Does soil type change how AWD performs?+
Strongly. Heavy clays percolate slowly, so dry-down takes longer and the water saving is modest (around 15%) but very safe, with the biggest methane cut. Medium loams are the classic AWD soil, saving roughly 25% with safe yield. Light sandy soils dry fast, offering the highest saving (~35%) but you must re-flood promptly to protect yield. The tool sets percolation and saving from the soil you pick.
How many irrigations does AWD save per season?+
Because AWD replaces frequent flood top-ups with fewer, larger re-floods after each dry-down, the irrigation count falls in proportion to the water saved. For a medium loam this is often a quarter fewer irrigations across the season; the tool reports the continuous-flooding count, the AWD count and the difference for your inputs, alongside the dry-down length in days.
How long does each dry-down take?+
The dry-down time is how long the tube level takes to fall from the re-flood depth (~5 cm above ground) to the 15 cm safe trigger below ground — about 20 cm of water leaving as evapotranspiration plus percolation. On a heavy clay losing ~8 mm/day that's around two weeks; on a sandy soil losing ~15 mm/day it can be under a fortnight. The tool computes it from your soil's percolation rate.
Is AWD the same as letting the field dry out completely?+
No — that is unsafe AWD and it costs yield. Safe AWD only lets the water level fall to about 15 cm below the surface, where the root zone is still moist; the field is never cracked dry through a sensitive stage. The distinction between 'safe' (15 cm, roots watered) and 'unsafe' (deep drying) drying is exactly what keeps AWD yield-neutral while still saving water.
Will AWD help with my water bill or pump fuel?+
Yes — fewer irrigations and less total water pumped translate directly into lower pump-fuel or canal-water costs. The water saved in m³ per hectare from this tool is the volume you no longer lift or buy each season; multiply it by your pumping cost per m³ to estimate the saving. Many farmers adopt AWD primarily for the pumping-cost and labour reduction, with the methane cut as a bonus.
Can I use AWD with a canal water supply on a fixed rotation?+
It is easiest where you control irrigation timing (tube wells), because AWD needs you to skip a turn when the tube level is still high and re-flood when it falls to 15 cm. On fixed canal rotations (warabandi) you can still practise a milder AWD by not topping up between turns, but match the dry-down to your delivery schedule. Always keep the field flooded through flowering regardless of the rotation.