Soil Sampling Insights: Improving Farming Practices Across Wales
- Sam Alexander James
- Jul 14
- 5 min read
Updated: 2 days ago
Last year, we soil sampled 3,238 fields for Welsh farmers. From Anglesey to Gower, Fishguard to Newport, upland sheep to lowland intensive dairy. Fodder beet, maize, and root crop mixtures, 5-cut silage, and arable cropping. If a field was in Wales and it was soil tested last year, there’s a high chance it was us! For us at Brynmair, this means two things:
We have a ‘bulk discount’ with the labs. Because we sample such a large proportion of Wales each year, we have a bulk discount with the labs which we pass straight back to our farmers. This allows us to take £5.50 off the RRP of each analysis, including Soil Organic Matter (SOM). With Sustainable Farming Scheme universal actions introducing extra admin and advisory costs, we don’t want soil analysis to cost more than it needs to. It provides vital, actionable data to drive both short and long-term business decisions, and it shouldn't cost the earth.
We have a huge amount of data on Welsh soils. Now we could go very in-depth on this, but if it’s not your own farm data then that’s not much use. So, we’ll just keep it to the main take-home points and what we found most interesting. You’ll most likely encounter these on your land if you haven’t undertaken soil analysis recently. In the coming weeks, you’ll find more detail on pH, Phosphate, Potash, and Magnesium in the News section.
What the 3,238 Soil Analyses Tell Us
The overwhelming majority of the fields tested are too acidic, with 79% below pH 6.2. This highlights a significant challenge in maintaining optimal nutrient availability within soils, manures, and applied fertilisers. When pH drops this low, the biological activity of the soil slows down. The efficiency of both your organic manures and expensive applied fertilisers drops off a cliff due to chemical reactions in the soil.
This suggests that across Welsh agriculture, regularly applying lime has slipped down the priority list. Perhaps the importance of it has been forgotten. Addressing this is the single most cost-effective way to unlock hidden performance on your farm. When soils are acidic, always spend on lime before on fertiliser.
pH | Number of Fields | % of Fields Tested | |
|---|---|---|---|
High | Above pH 6.5 | 215 | 7% |
Target | pH 6.2 to pH 6.5 | 456 | 14% |
Low | Under pH 6.2 | 2535 | 79% |
More than half of the fields analysed (61%) had an optimal P index (P2 or P3). This means grazed fields require no P, and silage crops have small maintenance applications. Optimal P reserves in the soil support root development and tiller formation, which is key for forage-based farms. However, a third of fields (32%) came back at P0 or P1. Without a strategic, long-term phosphate building plan, quality and yield will decline. For these fields, our advice has focused on targeting organic manures or slow-release options like soft rock phosphate to steadily build soil reserves over several years. We also recommend using targeted, crop-available P within fertilisers to feed the immediate season's crop.
Considering environmental enrichment and poor water quality can often be linked to phosphate over-application, it is reassuring that only 7% had soil indexes P4 or greater. However, we did see some very high P indexes (P8) in this category. These extreme indices were almost exclusively found on sacrificial blocks or fields located closest to the yard, receiving disproportionate volumes of slurry. Our advice here was immediate: Stop all P applications entirely and redistribute that valuable slurry to the hungry P0 and P1 fields. Where a whole holding sat above target, a rarity, we advised increasing P removal by maximising crop offtake via high P demand crops (like multi-cut silage or maize), exporting slurry, and entirely cutting out P-containing starter fertilisers.
Phosphate Index | Number of Fields | % of Fields Tested | |
|---|---|---|---|
High | P4 or Greater | 238 | 7% |
Target | P2 & P3 | 1,967 | 61% |
Low | P1 | 1,033 | 32% |
Potash, the nutrient in highest demand by our forage crops, was for most at or near target (K2-, K2+). At K1, grazing fields require only small amounts of K to maintain soil reserves, usually from a light dusting of muck or application of slurry. Silage fields, however, have much larger demands and require heavier muck and/or slurry applications to meet K demand and prevent soil reserves from falling too low.
However, over 700 fields had low K reserves (K0-K1). At these low soil reserves, potash will be limiting grass growth and hay/haylage/silage and crop yields. A long-term plan is needed to build soil K reserves through muck and slurry application as well as fertilisers, and manage potash offtakes in crops.
113 fields have high Potash reserves (K4+). This is fine as long as the remainder of the farm has good reserves also. Unlike phosphate, there are no known adverse environmental links with potash over-application.
Potash (Potassium) Index | Number of Fields | % of Fields Tested | |
|---|---|---|---|
High | K4 or Greater | 113 | 3% |
Target | K2-, K2+ & K3 | 2,399 | 74% |
Low | K0 & K1 | 726 | 22% |
Soil Analysis Data Helps Make Strategic Decisions on Farm
Correcting acidity enables more efficient fertiliser and manure utilisation. Applying the right amount of lime, keeping your grassland fields around pH 6.2 and arable pH 6.5 (on clay loams), keeps soil and plant biology happy. It enables fertilisers and manures to be utilised most efficiently. Last year, 2,535 of the soils we sampled were below pH 6.2. When soils are below pH 5.5-6.0, approximately 15% of the applied nitrogen and 48% of applied phosphate is lost.
Informed fertiliser purchasing. Yes, it's convenient and easy to buy one load of 27-5-5 or 20-10-10 for all fields, but we don’t often see a farm where every field has the same nutrient requirements, even when cropped the same. Soil analysis shows which fields, or areas of the field, need more PK or less PK. With ongoing high fertiliser prices, soil analysis is a useful tool in cost saving. It tells us whether the field or farm can take ‘PK holidays’, applying nitrogen and small amounts of sulphur only. There’s nothing more expensive than PK, or excessive N, when the field doesn’t need it.
Strategic manure application. While you’ll rarely buy muck or slurry, how and where you apply it, and at what rate, determines just how much of a business asset it is or isn’t on the farm.
Asset: Applying 5t/ha (2t/acre) of cattle muck onto silage ground with P2K1 soil. Potash-rich asset, potash-hungry soil, potash-hungry crop.
Wasted asset: Applying 5t/ha onto a grazing field at P2K4 near the yard, which always gets a 1t/acre dusting as it is close to the muck heap. Potash-rich asset, potash high soil, not hungry potash crop.
Soil indices have a direct impact on yield and quality. Yes, nitrogen and sulphur drive yield and quality, but if your field is one of our 1,033 fields where P is low, or 726 fields where potash is low, nitrogen and sulphur aren’t your limiting nutrients - P and K are. In these fields, increasing PK supplied and often reducing N would give you a better outcome.
Soil analysis also plays a part in understanding and preventing metabolic issues such as staggers. Knowing how your soils and applied nutrients will interact is useful!
Treating soil analysis as a core business tool, rather than a compliance tick box exercise, allows for targeted management and direct cost savings. If you want to arrange soil sampling and soil nutrient advice, please get in touch or order online through the website. Otherwise, look out for our upcoming posts in the News section, where we will break down practical management steps for pH, phosphate, potash, and magnesium.
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