From data to decisions: getting phosphorus management right

Author: Lauren Skinner

9th October 2025

NRM

Agriculture

Insights from the “Making the most of soil phosphorus” webinar

As a nutrient, phosphorus underpins crop growth, yield, and quality. Yet, when applied in excess or misaligned with crop needs, it accumulates in soils and risks being lost to water, reducing its quality and causing  pollution.

During our latest webinar, “From data to decisions: making the most of soil phosphorus for sustainable agriculture”, experts at NRM and Natural England explored the contrasting consequences of phosphorus in modern farming: an essential driver of crop growth; and a potential source of environmental harm if mismanaged.

For those who missed the live session, you can watch the full webinar recording here. Read on if you want:

• An even deeper dive into phosphorus nutrition
• Valuable scientific insights
• Analysis of data from over 170,000 samples gathered over 5 years
• Practical strategies for managing phosphorus effectively in UK soils to support optimal crop yield whilst minimising environmental impact.

Why does effective phosphorus management matter?

Phosphorus is a cornerstone of plant biology. Dr Sajjad Awan, Soil & Crop Nutrition Agronomist at NRM, explained that phosphorus powers cell division, DNA and RNA synthesis, and energy transfer through ATP. Without it, roots cannot develop, leaves cannot form, and yields collapse. Essentially, no phosphorus means no growth.

However, phosphorus rarely acts alone. Crops require a balanced diet, and phosphorus interacts closely with nitrogen, potassium, sulphur, and other nutrients. Imbalances reduce efficiency and hold back yield potential.

NRM’s soil data confirms widespread phosphorus imbalances across the UK

One of the major findings shared in the webinar is that phosphorus imbalances are widespread across the UK. Dr Awan drew on NRM’s extensive soil test data, drawing on 170,000 fields analysed over five years, to discuss just how widespread they are.

Nearly 30% of soils were deficient in phosphorus (at or below Index 1). Only one third hit the national target of Index 2, while the rest (over 40%) were above Index 2, containing more phosphorus than multiple crops over a rotation realistically need.

Regional differences were significant. Northeastern arable regions, where livestock numbers are lower, tended to show deficiencies. Meanwhile, the livestock-intense northwest region often tested above target. This is likely a result of intensive livestock farming and a legacy of repeated manure applications, where the nutrient supply hasn’t fully been accounted for.

Why?

Soil pH was highlighted as a crucial factor. Dr Awan explained that, when correcting the pH of soils, the target is 6.7 for arable land and 6.2 for grassland. This ensures that the optimal pH of 6.5 for arable soils and 6.0 for grassland soils can be met. When pH drifts above or below the optimal range, phosphorus can bind with iron, aluminium, or calcium, reducing availability and preventing crops from achieving optimal yield.

Additionally, as highlighted in the webinar’s Q&A, it seems that many farmers may not realise that different tillage methods and required sampling depths may have an effect on P levels. For example:

• If the fields are ploughed, it is advised to sample to the traditional 15cm
• If fields are min-tilled, it is advised to sample to 23cm to avoid overestimating the soil P content as it tends to accumulate nearer the soil surface
• Permanent grassland should be sampled to 7.5cm
• Grassland being reseeded should be sampled to 15cm

Sampling to the correct depth prevents inaccuracies in the assumed content of P in the soil, giving farmers a clearer indication if they need to supplement with fertiliser or not.

From data to decisions: insights from plant tissue & grain analysis data

The webinar highlighted that it’s not enough to perform soil analysis every few years. Analysing different parameters throughout the season is important to help you monitor crop progress and, if necessary, adjust nutrient management plans to protect productivity.

With this in mind, Dr Awan shared the analysis of thousands of crop samples collected between 2021 and 2023. The first data review summarised winter wheat tissue results gathered from NRM’s CropCheck service. The second data review summarised the findings from 4,000 winter wheat grain samples submitted to NRM between 2021 and 2024 as part of its GrainCheck service.

Analysis of the data revealed that:

• There were strong correlations between phosphorus and other macronutrients. For example, phosphorus uptake in plant tissue was closely tied to nitrogen, sulphur, and potassium. Deficiencies in soil phosphorus levels can impact uptake and utilisation of these nutrients.
• Nearly 60% of GrainCheck samples fell below the RB209 recommendation of 0.32% phosphorus levels, and none of the years analysed reached this critical value.

The data highlighted the effect of yield on grain nutrient concentration: as yields increased, grain phosphorus concentration reduced in 2022 and 2023. In 2024, grain yields were lower, but the grain phosphorus concentration was also lower. This could be due to poor crop establishment during the exceptionally wet autumn and winter of 2023-24.

This shows the value of grain testing for individual farms. While grain analysis can’t help the season past, it does provide a “post-mortem” review that can help guide future nutrient strategies.

The conclusion was clear: farmers should not treat nutrients in isolation. While it’s important to focus on nitrogen and phosphorus, their efficiency relies on the supply and availability of the other major and minor nutrients. Ultimately, the data shows that crop performance relies on a well-balanced nutrient plan.

Phosphorus management in the wider landscape

Nigel Simpson, Catchment Sensitive Farming (CSF) Agricultural Lead at Natural England, placed phosphorus within a broader environmental and practical context. He explained that only around 0.2% of soil phosphorus is immediately available to crops, and that availability depends heavily on soil pH.

Phosphorus losses to water are a major environmental issue. Excess phosphate fuels algal blooms, which strip oxygen from lakes and rivers, threatening biodiversity, fish stocks, and rural livelihoods. In England and Wales, an estimated two million tonnes of soil and organic matter are lost to water each year, much of it carrying phosphorus with it. Losses can be especially severe on sloping clay soils, where runoff and erosion risk can be high.

So, what can we do to avoid these issues?

Practical recommendations: managing phosphorus nutrition for optimal crop yield and sustainable agriculture

The key management message was that one size does not fit all. Farmers with low phosphorus soils must rebuild reserves carefully, while those with excess must hold back and allow levels to decline. The sweet spot, Index 2, requires a maintenance approach: replacing crop offtakes to hold a steady balance.

Knowing that phosphorus imbalances are widespread throughout the UK, what do our experts suggest farmers do to improve their soils, optimise crop production, and limit losses into the environment?

1. Field management: buffer strips, beetle banks, grassed tramlines, cover crops, and sediment ponds will help limit phosphorus loss to the environment.
2. Soil care: maintaining soil structure and organic matter to improve water infiltration rates and reduce the risk of compaction.
3. Careful nutrient planning and timing: avoiding applications on high-index soils, applying manure and fertiliser when the crop is going to use the nutrients they supply, and regularly analysing organic manures for accurate nutrient values before applying.
4. Analyse all year round with soil, plant tissue (CropCheck), and grain (GrainCheck) analysis to help provide a complete picture of nutrient status.

In reference to point 3, with fertiliser nutrients valued at over £1 per kilogram, failing to measure the nutrient content of manure is both a financial and environmental gamble. Livestock farms in particular often import phosphorus-rich feed, creating surpluses. Calculating a nutrient balance means you can better align inputs and offtakes, which is essential to help avoid waste and pollution.

As seen in point 4, holistic view of soil health is also very important. It is not just about chemistry, but also soil structure, organic matter, and biological life. Earthworms, fungi, and microorganisms drive nutrient cycles, linking directly to phosphorus availability. By supporting soil biology, farmers also support nutrient efficiency.

From data to decisions: how NRM can help

Good decisions depend on good data. For Dr Awan, this meant making full use of soil, tissue, and grain tests: not filing them away, but acting on them. For Simpson, it meant linking those insights to wider catchment goals, balancing crop productivity with environmental stewardship.

Phosphorus is indispensable, but it is also finite and vulnerable to misuse. The challenge for farmers is to manage it with precision, aligning agronomic need with environmental responsibility. The opportunity lies in using data not just as evidence, but as a guide to smarter, more sustainable farming.

By prioritising routine testing, growers can optimise management plans and support sustainable farming practices. Contact NRM for more information on all our analytical services.

Missed the webinar? Watch the full recording here.