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How to read your soil: moisture, pH, EC and NPK explained
What the five numbers on every SoilPulse reading mean, what healthy looks like, and what to do when one of them drifts.
A soil reading is only useful if you know what it is telling you. The numbers in this guide come from the SoilPulse Probe, our in-field soil sensor. This guide walks through the five numbers SoilPulse AI shows for every plot — moisture, pH, electrical conductivity (EC), temperature and NPK — what healthy looks like, and what to do when one of them drifts.
Start with the trend, not the number
One reading is a snapshot. The same plot can read very differently at seven in the morning and three in the afternoon, or on the day after rain. That is why SoilPulse logs readings sector by sector over time. Before acting on any number, look at how it has moved over the past week or two.
Moisture
Moisture is the share of the soil that is water, shown as a percentage. There is no single right figure, because it depends on your soil:
- Sandy soils drain fast and hold little water, so they dry out quickly between rains.
- Clay soils hold much more water but release it slowly, and can stay waterlogged after heavy rain.
- Loams sit in between, which is one reason most crops do well in them.
What matters is whether your reading stays in a comfortable band for your soil and crop. A steady fall over several dry days tells you to water before the plants show stress. A reading that stays high long after rain points to poor drainage, which starves roots of air and invites root rot.
pH
pH measures how acidic or alkaline the soil is, on a scale from 0 to 14, where 7 is neutral. The scale is logarithmic: soil at pH 5 is ten times more acidic than soil at pH 6.
Most vegetables and grains do best between about 6.0 and 7.0. Cocoa tolerates a wider range, but it too suffers in strongly acidic soil.
Many soils in Ghana’s forest zone are naturally acidic, because heavy rainfall washes calcium and magnesium out over time. Below about pH 5.5, aluminium and manganese become more soluble and can damage roots, and phosphorus becomes harder for plants to take up, even when there is plenty of it in the soil.
To raise pH, farmers apply agricultural lime or dolomite, or wood ash in smaller amounts. Liming works slowly — expect change over months, not days — and the right amount depends on your soil, so base it on readings rather than a guess. Too much lime causes problems of its own.
Electrical conductivity (EC)
EC measures how easily electricity passes through the soil, which depends mostly on how much dissolved salt and nutrient is in the soil water. It is a quick way to see whether the soil is fed, starved or overloaded.
- Very low EC usually means few nutrients are dissolved and available to the roots, common in sandy soils and after heavy rain washes nutrients away.
- Very high EC means salts have built up. Roots struggle to take up water from salty soil, so plants can wilt even when the ground is moist. Heavy fertiliser use, poor drainage and salty irrigation water are the usual causes.
EC also rises and falls with moisture, so compare readings taken in similar conditions. A sudden jump after fertilising is a sign to hold back and water well.
Temperature
Soil temperature controls how fast seeds germinate, how active soil life is, and how quickly roots take up water and nutrients. Bare soil in full sun can get much hotter than the air above it. Mulch and cover crops keep it cooler and slow the loss of moisture, so you will often see these two readings move together.
NPK: nitrogen, phosphorus and potassium
These are the three nutrients plants need in the largest amounts. Each one leaves its own signs when it runs short.
| Nutrient | What it does | Signs it is running short |
|---|---|---|
| Nitrogen (N) | Leaf and stem growth | Older, lower leaves turn pale or yellow first |
| Phosphorus (P) | Roots, flowering and early growth | Stunted plants; dark or purplish leaves, especially on young maize |
| Potassium (K) | Water control, disease resistance and fruit quality | Older leaves scorch or turn brown at the edges |
Read sensor NPK values as a guide to direction — rising, falling or steady — and as a prompt to look closer. Before a big decision on fertiliser, a laboratory soil test will give you exact figures.
When a nutrient runs low, match the fix to the gap rather than reaching for a general-purpose fertiliser. Compost and well-rotted manure build all three slowly and improve the structure of the soil at the same time.
Putting it together
Here is how to read a plot on a typical day:
- Moisture 31%. Healthy for many loam soils. Watch whether it holds steady or falls over the next few days before deciding to water.
- pH 6.4. In the ideal range for most vegetables. No lime needed.
- Soil health 84 out of 100. SoilPulse combines the readings into one score. At 84, this plot needs watching, not fixing.
When to ask for help
If a reading surprises you, or you are not sure what to do, send a message or a voice note to a field agent in English, Twi, Ewe, Ga or Hausa. And if you are worried about heavy metals — on land near mining or a busy road, for example — ask about contamination screening. Those results are checked against WHO and FAO safe limits.
