Mulch Water Saving & Cover the Soil, Save the Water
Saves evaporation
Enter crop ET, the soil-evaporation share and the evaporation cut from your mulch to see the water saved in mm/day and m³, the percentage of ET saved, and the depth saved over the season.
Enter your crop & field
Next: mulch to save ~1.08 mm/day (~131 m³ over the period); use straw/residue or plastic film, keeping it off the stems.
Savings depend on climate, crop cover and mulch quality; benefit is largest on young/open crops in hot, dry weather.
Mulch water saving — key facts
- Saved mm/day
- ET × evap share × evap cut
- Total saved
- saved depth × area × days
- 1 mm over 1 ha
- = 10 m³ (10,000 L)
- Evaporation cut
- ≈ 50–80% with good mulch
- Biggest on
- young / open crops, hot & dry
- What it cuts
- evaporation, not transpiration
- Mulch types
- straw / residue or plastic film
- Privacy
- Runs in your browser; nothing uploaded
A blanket on the soil keeps the water in
Bare soil bleeds water. Between rows and around young plants, the sun and wind pull moisture straight off the surface — water the crop never used. Mulch shades the soil and traps that loss, so you irrigate less to deliver the same water to the roots. The saving is largest exactly when you need it most: on open canopies in hot, dry weather, when evaporation is at its worst. As a bonus, the same cover suppresses weeds and steadies soil temperature.
This tool computes the water saved in mm/day and m³, the percentage of ET saved, and the depth saved over the season from your ET, the soil-evaporation share and the evaporation cut for your mulch. Use it to decide whether mulching pays and which mulch to use, then pair it with the Water Use Efficiency, Drip Water Saving and Pan Evaporation ET tools to fine-tune the whole system.
Cut wasted evaporation
Stop water leaving the bare soil between plants.
Compare mulch types
See straw, residue or film side by side.
Best when it counts
Biggest saving on open crops in hot, dry weather.
Size the saving
Daily and seasonal water saved in m³.
Frequently Asked Questions
How does mulch save irrigation water?+
Crop water use has two parts: transpiration through the plant and evaporation straight off the soil surface. Mulch shades and covers the soil, so it mainly cuts the evaporation part. On young or widely spaced crops a lot of bare soil is exposed, so the evaporation share is large and the saving from mulching is biggest. The plant's transpiration carries on as normal.
How is the water saved calculated?+
Saved depth per day = ET × the soil-evaporation share × the fraction of evaporation the mulch cuts. For example 5 mm/day × 0.30 evaporation share × 0.70 cut ≈ 1.05 mm/day saved. Multiply the saved depth by the area over the period to get the total volume — 1 mm of water over 1 m² is 1 litre, so 1 mm over a hectare is 10 m³.
What is the soil-evaporation share of ET?+
It's the proportion of total crop water use that leaves as evaporation from the soil rather than transpiration through the plant. It is high (often 0.3–0.5 or more) when the canopy is open — early growth, wide rows, orchards — and low under a full closed canopy that already shades its own soil. The bigger the bare-soil exposure, the more mulch can save.
How much evaporation does mulch actually cut?+
A good organic mulch (straw, crop residue) or plastic film can reduce soil evaporation by roughly 50–80% while it stays intact and covers the surface. Thicker, lighter-coloured and well-laid mulch cuts more; thin, patchy or decomposed mulch cuts less. The tool lets you set the cut so you can compare mulch types and depths.
When is mulching most worthwhile for water?+
The benefit is largest on young or open crops in hot, dry, windy weather, when bare soil loses the most water and the canopy gives little shade. As the canopy closes the soil is already shaded and the extra saving falls. Mulch also suppresses weeds and moderates soil temperature, which add value beyond the water saving alone.
Does mulch reduce a crop's total water need?+
Mostly it reduces the wasted evaporation, not the productive transpiration the crop needs to grow. So you irrigate less to deliver the same water to the roots, raising water-use efficiency. In very hot conditions mulch can also slightly cool the root zone and reduce stress, but the headline benefit is cutting evaporation losses.
Straw mulch or plastic film — which saves more water?+
Plastic film, especially when it seals the bed, can cut evaporation more and warms the soil, which suits early or high-value crops; but it costs more and needs disposal. Straw and crop residue are cheaper, add organic matter and keep the soil cooler, with a slightly lower but still large evaporation cut. Both should be kept off the stems to avoid rot.
How do I apply mulch correctly?+
Spread organic mulch evenly to a good depth over moist soil, keeping it a little away from stems and trunks so they don't stay wet and rot. For plastic film, lay it tight over a well-prepared bed with the edges anchored, and plant through holes. Top up organic mulch as it breaks down so the cover — and the saving — is maintained.
Can I use this with drip irrigation?+
Yes, and the two work well together. Drip already wets only a small area and limits evaporation; adding mulch over the wetted strip cuts the remaining surface loss further and holds moisture between pulses. Combine the saving here with the Drip Water Saving and Water Use Efficiency tools to plan a very water-efficient system.
Are these figures exact?+
They're a planning estimate. The real saving depends on crop, canopy, climate, mulch type, depth and condition, and how much of the soil is actually covered. Use realistic values for the evaporation share and the cut, treat the result as a guide for the season, and adjust as the canopy closes and the mulch ages.