Thirty-eight per cent of arable soils across England and Wales are degraded according to scientists at Rothamsted Research who have developed a new soil health measure.
This is compared with less than 7 per cent of grassland and woodland soils.
Developed from the findings of a number of European studies, the new index classifies soils by the proportion of organic matter versus clay that they contain, as a predictor of how much carbon they can take up and store, as well as a general indicator of how well they are functioning.
The data behind the index is based on more than 3,800 soils collected between 1978 and 1983 as part of a national soil survey, and according to lead author Jonah Prout, changes in soil carbon take time - so the message of these results is likely to still apply today.
The newly developed index is based on two routinely taken soil measurements and could be easily established for any field in England and Wales, which could help farmers or policymakers improve the natural services soils provide, such as food production, flood protection and carbon storage, he says.
Co-author, Prof Steve McGrath says: “Previously no one could tell you what a good level of organic matter for a particular soil was. An index allows farmers and other land managers to determine how best to manage their land – where to grow, where to treat, and where to build - depending on the state of their soil.
“There are various ways to improve a soil, but to do so, we first need to know which ones need what help. This measure is an easy way to do so.”
The index is calculated by measuring the proportion of soil carbon to soil clay, with samples then categorised based on this value as very good, good, moderate or degraded.
Soils where there is at least 13 times more clay than carbon are rated as degraded, whilst those with less than eight times the amount of clay compared to carbon are regarded as very good.
On this scale, soil from 38.2 per cent of arable, 6.6 per cent of grassland, and 5.6per cent of woodland sites were in the poorest conditions.
Having looked at the picture across England and Wales, Mr Prout says the next step is to look at a later survey and long-term experiment data to see how the index values have changed over time.