Analysis carried out by NRM Laboratories has confirmed that a significant proportion of arable soils in the UK are too acidic.
When it comes to soil nutrient analysis, the starting point must be to understand the pH of the soil; incorrect soil pH can have a big impact on nutrient availability, particularly phosphate.
However, analyses carried out by NRM in 2021/2022 showed that soils ranged from pH 4.8 right up to pH 9.
Although the median figure of all the 400,000 individual analyses was close to pH 7.0, approximately 25% of these were below the optimum of 6.5 for arable soils and therefore in need of lime.
Specifically where phosphate (P) is concerned, the median result came in at the top of index 2 (23.2mg/L).
However, the spread ranged from just 4mg/L (low index 0) right up to 56.6mg/L (index 4).
Nearly a quarter of samples came in below an index 2 and therefore below the target for optimal uptake by arable crops and grassland.
Analysis
The NRM work also confirmed that 40% of soils came in at an index 3 value for P. The growing use of sewage sludge soils on UK soils is believed to be accounting for this figure.
As with phosphate, the potash (K) samples showed that the median result was at the target level of index 2 (154.7mg/L).
However, unlike the P samples, a greater proportion was measured at, or below, index 1 (29%) and therefore at risk of K deficiency.
This could reduce crops’ yield potential, especially with the recent history of dry weather patterns throughout spring and summer.
For magnesium (Mg), the median value came in at index 2, which is the target.
Although 27% of samples were measured above the target index, there were still nearly a quarter of the results that were at index 1 or below, which would benefit from Mg applications for most crops.
Soil trends
These soil trends back up and reconfirm the annual position that has been highlighted each year through the Professional Agricultural Analysis Group (PAAG), of which NRM is a member.
This is not surprising, especially last season, considering the large increase in the cost of fertiliser, if not purchased in advance of last spring.
More concerning could be the results of future soil samples, where fertiliser applications may have been reduced or omitted.
There is now the significant prospect that 2022/2023 analysis results will point to a serious reduction in the P and K indices of agricultural soils across the UK.