Soil Infiltration Rate & How Fast Does It Soak?
Sets sprinkler rate
Enter the water-level drop and time from a ring test to get the basic infiltration rate, your soil class, the maximum safe sprinkler rate and the time to soak in an irrigation.
Enter your ring test
Very fast — water drains quickly, irrigate little and often.
Next: set your sprinkler precipitation rate at or below 40 mm/hr; on clay, irrigate in shorter cycles with soak time between.
Measured by the double-ring infiltrometer field method; texture ranges follow USDA soil-texture infiltration guides. The basic rate is the steady value reached once the soil is wetted.
Soil infiltration — key facts
- Rate
- drop (mm) ÷ time (min) × 60
- Sand
- > 30 mm/hr
- Loam
- 10–20 mm/hr
- Clay
- < 5 mm/hr
- Safe sprinkler rate
- ≈ 80% of basic rate
- Too fast
- water ponds & runs off
- Improve it
- organic matter, no compaction
- Privacy
- Runs in your browser; nothing uploaded
Match your irrigation to the soil, not the other way round
Every soil drinks at its own pace. Pour water on faster than it can soak in and the rest ponds, runs off, erodes the surface and never reaches the roots. The infiltration rate is the number that tells you that pace — and it's the single most useful figure for designing a sprinkler system or setting irrigation runs that don't waste water.
From a simple ring test, this tool gives the basic infiltration rate in mm/hr, your soil class, the maximum safe sprinkler application rate, and the time to soak in a target depth. Use it to pick nozzle rates, set cycle times, and decide whether to irrigate in one set or several short ones. Pair it with the Drip, Sprinkler and Irrigation Scheduling tools to run a tight, efficient system.
Stop the runoff
Keep application at or below what the soil can take.
Size your sprinklers
Pick a precipitation rate the soil can absorb.
Set soak times
Know how long to apply a given depth of water.
Read your soil
Classify the soil straight from the field test.
Frequently Asked Questions
What is the soil infiltration rate?+
It is how fast water soaks into the soil, measured in mm per hour. The 'basic' infiltration rate is the steady rate reached after the soil has wetted up. It governs how fast you can irrigate before water ponds and runs off — and so how you should design and run a sprinkler or surface irrigation system.
How do I measure infiltration in the field?+
Pond water in a ring (a single or double-ring infiltrometer, or any open-bottomed cylinder pushed into the soil), then time how far the water level drops. Enter the drop in mm and the time in minutes here. Repeat until the rate steadies — that steady value is the basic infiltration rate.
How is the rate calculated?+
Rate (mm/hr) = water-level drop (mm) ÷ time (minutes) × 60. For example, a 25 mm drop in 30 minutes is 25 ÷ 30 × 60 = 50 mm/hr. The tool also converts to cm/hr and classifies the soil from the rate.
What infiltration rate is normal for my soil?+
Typical basic infiltration rates: sand over 30 mm/hr, sandy loam 20–30, loam 10–20, clay loam 5–10, and clay under 5 mm/hr. Sands take water fast but hold little; clays take it slowly and pond easily. Compaction, crusting and organic matter all shift the rate.
Why must sprinkler rate stay below infiltration rate?+
If your sprinkler applies water faster than the soil can absorb it, the excess ponds and runs off — wasting water, causing erosion and leaving the crop short. Keeping the application (precipitation) rate at or below the basic infiltration rate ensures the water actually enters the root zone.
What is the maximum safe sprinkler rate shown?+
The tool suggests about 80% of the basic infiltration rate as a safe maximum application rate. The margin allows for slope, surface sealing and uneven distribution. On sloping ground reduce it further, or irrigate in shorter cycles with rest periods so water can soak in.
How long should I irrigate to apply a set depth?+
Enter your target application depth and the tool gives the time to soak it in at the current rate (depth ÷ rate). On slow soils, split that time into several short sets with soak periods between, rather than one long set that causes runoff.
How can I improve a low infiltration rate?+
Build organic matter (compost, mulch, cover crops), avoid working or grazing wet soil, break up compaction and surface crusts, and keep the soil covered to stop raindrop sealing. Gypsum can help sodic clays. Higher infiltration means more rain and irrigation reaches the roots.
Does infiltration change as I irrigate?+
Yes — it starts high on dry soil and falls to the basic rate as the soil wets up and pores fill. Always design irrigation around the basic (steady) rate, not the high initial rate, or you'll get runoff later in the set. Measure until the rate stops dropping.
Is the ring test method standard?+
Yes — the ring/double-ring infiltrometer is the standard field method (USDA, FAO) for measuring infiltration. The soil-class ranges here follow USDA texture guidelines; your field value may differ with structure, compaction and moisture, so measure your own soil.