For farmers, soil is the foundation of every crop — and understanding its condition is essential to making informed agronomic decisions. One of the most important but often overlooked aspects of soil health is pH. Knowing how to test soil pH helps you optimise inputs, increase yields, and improve long-term soil productivity.

Whether you’re growing cereals, vegetables, grassland, or legumes, testing your soil pH regularly ensures you’re not applying fertilisers or lime blindly. In this guide, we’ll explain what soil pH means, why it matters in agriculture, and how to test it effectively on your farm.

Soil pH is a measure of how acidic or alkaline your soil is, using a scale from 0 to 14:

• pH 7 is neutral

• Below 7 is acidic

• Above 7 is alkaline

Most arable crops in the UK prefer a pH between 6.0 and 7.0, while grassland may benefit from slightly more neutral conditions. If soil pH is too low or too high, it can limit nutrient availability, reduce fertiliser efficiency, and impact crop performance.

Testing your soil pH allows you to:

• Apply lime or fertiliser more effectively

• Tailor crop selection to soil conditions

• Avoid nutrient lock-up in acidic or alkaline soils

• Prevent wasted inputs and unnecessary costs

• Improve yields and soil structure over time

For example, acidic soils can reduce phosphorus availability and impact root development, while alkaline soils can limit micronutrient uptake.

Regular pH testing — ideally every 3–5 years — is a key part of any good soil management plan.

1. Use a Soil Testing Kit for a Quick Field Check

Farm-grade soil pH testing kits are inexpensive and easy to use in the field. These typically include pH tablets or indicator liquids that react with soil-water samples.

Instructions:

• Take samples from different points across the field (15–20 cm deep)

• Mix the soil and remove stones or organic debris

• Add the test solution or tablet according to the kit’s instructions

• Compare the colour result to the provided pH chart

Use for: A rough guide or quick check before applying lime.

2. Use a Digital Soil pH Meter

A digital pH meter provides a more precise reading and is ideal for farmers who want to monitor soil pH regularly across multiple fields.

Instructions:

• Calibrate the meter before use using buffer solutions

• Insert the probe into a moist soil sample or a soil-water slurry

• Wait for the digital reading to stabilise

• Rinse the probe after each use to avoid cross-contamination

Use for: Frequent on-farm monitoring and tracking changes after liming.

3. Send Soil Samples to a Professional Laboratory

For the most accurate and actionable results, farmers should send soil samples to an accredited lab. This is particularly important before making large-scale decisions about lime or fertiliser applications.

Instructions:

• Divide your land into zones based on cropping, soil type, or topography

• Take multiple cores from each zone and mix them into a composite sample

• Label each sample clearly and send it to a soil lab with a request for a full pH and nutrient analysis

Use for: Baseline soil assessments, long-term management, and nutrient planning.

• Before sowing a new crop

• After major land-use changes (e.g., ploughing grassland)

• Before or after liming

• Every 3–5 years as part of a soil health programme

Testing after harvest or during soil sampling for nutrient management is ideal. Avoid testing during very dry or frozen conditions, which can affect accuracy.

Knowing how to test soil pH is essential for farmers who want to maximise yield potential, reduce waste, and manage land more sustainably. Whether you choose to use a quick testing kit, digital meter, or lab analysis, regular monitoring will help you make better decisions for your crops and your soil.

Soil pH might be a small number, but it has a big impact.

1. How often should I test soil pH on my farm?

Ideally every 3–5 years, or more frequently in high-value cropping systems or after major changes to land management.

2. What is the ideal pH for arable crops?

Most cereals, oilseeds, and legumes grow best in soils with a pH between 6.0 and 7.0. Potatoes prefer slightly more acidic soils, around 5.5 to 6.0.

3. Can I correct pH with lime?

Yes. Applying agricultural lime is the most common way to raise soil pH. The rate depends on the current pH, soil texture, and lime quality.

4. Is over-liming a problem?

Yes. Excess lime can push soil pH too high, making certain nutrients like iron and manganese unavailable. Always test before applying.

5. Can soil pH affect herbicide performance?

Absolutely. Some herbicides become more or less effective depending on soil pH, which can impact weed control and crop safety.