Example Data Table
| Sample | Bulk Density | Particle Density | Gravimetric Water | Porosity | Saturation |
|---|---|---|---|---|---|
| Raised vegetable bed | 1.20 g/cm³ | 2.65 g/cm³ | 18% | 54.72% | 39.47% |
| Loam border | 1.35 g/cm³ | 2.65 g/cm³ | 22% | 49.06% | 60.55% |
| Container mix | 0.80 g/cm³ | 2.40 g/cm³ | 35% | 66.67% | 42.00% |
Formula Used
Soil percent saturation = (volumetric water content ÷ porosity) × 100.
Volumetric water content from gravimetric water = gravimetric water content × bulk density ÷ water density.
Porosity from densities = 1 − (bulk density ÷ particle density).
Porosity from void ratio = void ratio ÷ (1 + void ratio).
Air-filled porosity = porosity − volumetric water content.
Water needed = max(target water content − current water content, 0) × soil depth ÷ efficiency.
How to Use This Calculator
- Select the calculation method that matches your available soil data.
- Enter water content, density, porosity, sample, or void ratio values.
- Add bed depth, bed area, target saturation, and efficiency for watering estimates.
- Press the calculate button to view the result above the form.
- Use the CSV or PDF button to download the same calculated result.
Understanding Soil Percent Saturation
Soil percent saturation shows how much of the pore space is filled with water. It compares the current water volume with the total pore volume. A value near zero means the pores are mostly air. A value near one hundred means the pores are almost full of water.
Why Gardeners Measure Saturation
Garden soil needs both water and air. Roots take water from thin films around soil particles. They also need oxygen in open pores. When saturation stays high for too long, roots may slow down. Friendly microbes may also change activity. When saturation is too low, plants wilt and nutrient movement becomes limited.
Useful Inputs
This calculator accepts several practical input paths. You can enter volumetric water content when a moisture probe gives that value. You can enter gravimetric water content with bulk density when you have a weighed soil sample. You can also use wet mass, dry mass, and sample volume. These values help estimate the water volume and pore volume.
Reading the Result
The saturation percentage should be read with soil texture and crop needs in mind. Sandy soil drains quickly. Clay soil may hold water longer. A vegetable bed may perform well below full saturation. A seed tray may need a different range. The air filled pore result is useful because it shows the remaining breathing space for roots.
Better Water Planning
Use the target saturation field to estimate extra water. The calculator converts the water deficit into depth. It can also estimate gallons for a bed area. This is helpful for irrigation planning. It is still a guide, not a substitute for field checks. Mulch, slope, compaction, and drainage can change real results.
Good Sampling Practice
Take samples from the active root zone. Avoid only testing the surface after rain. Mix small subsamples when the bed is uneven. Record the date, weather, and recent irrigation. Repeating the same method gives better trends. Over time, the numbers can show when a bed dries too fast or stays wet too long.
Common Texture Notes
Coarse mixes often need more frequent checks. Fine soils need drainage attention. Compost can raise water holding capacity. Raised beds can change results after heavy rain or deep watering.
FAQs
What is soil percent saturation?
It is the share of soil pore space filled with water. It uses volumetric water content and porosity. A higher value means less air remains in the pore space.
Is one hundred percent saturation always bad?
Not always. It can happen after rain or irrigation. Long periods near full saturation can reduce oxygen around roots. Sensitive crops may suffer if drainage is poor.
What is a good saturation level for gardens?
There is no single best level. Texture, crop type, and growth stage matter. Many beds perform well when water is available and air-filled pore space remains adequate.
Can I use a moisture meter reading?
Yes, if your meter gives volumetric water content. Select the volumetric method. Then enter the reading and supply porosity or density values for the soil.
Why does the calculator ask for bulk density?
Bulk density helps convert gravimetric water content into volumetric water content. It also helps estimate porosity when particle density is known.
What particle density should I use?
Many mineral soils use about 2.65 g/cm³. Organic mixes may differ. Use a measured value when available for better accuracy.
Why is my saturation above one hundred percent?
This usually means an input mismatch. Check sample volume, density, water content, and units. Swelling soil or measurement error can also affect the result.
Can this replace field observation?
No. It supports decisions, but garden conditions vary. Confirm results with soil feel, plant response, drainage patterns, and repeated measurements.