The short answer. In England, the Farming Rules for Water require nutrient plans for cultivated land to use soil test results, no more than five years old, for pH, phosphorus, potassium and magnesium, and for nitrogen or an assessment of soil nitrogen supply. Those results guide lime and fertiliser. They do not tell you whether the soil itself is getting better or worse. Soil health covers structure, water, biology and organic matter as well as nutrients. Soil organic carbon represents soil health, and stock change tracks the effectiveness of your practices in each climatic year. Annual soil carbon measurement sits alongside the standard test rather than replacing it: the standard test tells you what to apply this season, and the carbon measurement tells you which way the soil is heading. Across our UK monitoring, projects with declining soil organic carbon averaged yield losses of 20 to 50% in the 2025 and 2026 droughts, while projects with stable or increasing carbon typically stayed within 5 to 15% of average.
What UK soil testing covers today
Under the Farming Rules for Water in England, if you apply organic manure or manufactured fertiliser to cultivated land, your plans must take account of soil test results for pH, phosphorus, potassium and magnesium that are no more than five years old when you apply. Nitrogen can be assessed from the soil nitrogen supply rather than sampled. Cultivated land means land that has been ploughed, sown or harvested in the last year, or that has received organic manure or manufactured fertiliser in the last three years. The Environment Agency enforces the rules.
Many standard analysis packages also report organic matter, usually by loss on ignition. That figure converts to carbon with an assumed factor.
What a standard soil test does not tell you
- Which way the soil is heading. A nutrient index every few years shows what is available to the crop, not whether the soil is improving or declining.
- The carbon stock. Stock needs the concentration, the bulk density of the soil and the depth sampled. A standard test measures none of that as a stock.
- The variation within a field. A composite sample gives one average for the field. The headland, the old field boundary and the wet corner can be doing very different things.
- How the soil will hold up in a hard season. Soil organic carbon governs structure, infiltration, water holding and nutrient availability, and when it declines it declines invisibly.
What soil health means on a farm
A healthy soil holds its structure, lets water in and holds it, cycles nutrients and supports the life that does much of that work. Soil organic carbon governs structure, infiltration, water holding and nutrient availability. Rising soil carbon reflects better structure, more water infiltrating and held, and more organic nutrients available to the crop.
Where soil carbon measurement fits
Annual soil carbon measurement adds the part a nutrient test cannot see. We take real soil samples on every farm we monitor, analyse them by dry combustion in an ISO-accredited laboratory, and tie them to satellite imagery at 100 readings a hectare, so every field has a map and a total rather than one average. The error is measured against samples the AI never saw and deducted in full, and the change is reported against your own baseline with the accuracy stated. What five years of monitoring show explains the link to yield.
Simple field checks, such as counting earthworms and assessing soil structure in a spade pit, add useful context between measurements.
Putting it together
- At least every five years: pH, phosphorus, potassium and magnesium, and nitrogen or an assessment of soil nitrogen supply, to meet the Farming Rules for Water and plan lime and fertiliser.
- Every year, in the same window: soil organic carbon stock, field by field, to see whether the soil is improving and which practices are working.
- Whenever you walk the fields: earthworms, structure and how water behaves after rain.
Questions we are asked about soil health testing
How often should soil be tested in the UK?
In England, if you apply manure or fertiliser to cultivated land, the Farming Rules for Water require soil test results for pH, phosphorus, potassium and magnesium, and for nitrogen or an assessment of soil nitrogen supply, that are no more than five years old. We measure soil organic carbon every year, at the same point in the year, so that the change is real and a bad year shows up in that year, while the fix is still cheap.
Does a standard soil test include organic matter?
Many do, usually by loss on ignition. It gives a figure for the sample tested, not a soil organic carbon stock or its change over time.
Is soil carbon measurement a legal requirement?
Not in England. Measuring the change in soil carbon stock every year shows which of your practices are working and catches decline while you can still act. More in farm carbon audit or soil carbon measurement.
Does soil carbon measurement replace my nutrient testing?
No. They answer different questions. The nutrient test tells you what to apply this season. The soil carbon measurement tells you whether the soil is getting better or worse.
How do I get started?
Send us your SBI number and your hectares and we will send a written quote within two working days. Minimum project area 150 hectares, and it does not have to be your whole farm. Get a quote.
Part of soil carbon measurement for farms: the complete guide. Related: soil carbon testing for your farm · soil carbon testing in the UK: the methods compared · what soil organic carbon is · soil organic carbon and yield · farm carbon audit or soil carbon measurement.
