How best to test before  new season

• Assess soil acidity in every field

• Measure for nutrient availability

• Remember: test for sulphur too

Growers are being reminded to test soil ahead of next season to ensure crops can meet their full potential.

Testing for acidity and nutrient availability could help offset a potential rise in fertiliser costs by ensuring growers apply what is needed in the right place, believes Phil Burrell, plant health business manager for ProCam.

“As one cropping cycle comes to an end, and growers start to get ready to drill next year’s crops, now is the ideal time to test soils, not just for pH, but also for residual reserves of nitrogen, phosphate, potash and sulphur.”

Optimal level

The fundamental factor to get right at this stage in proceedings is to ensure soil pH is as close to 6.5 as possible – the optimal level for the availability of micro and macro nutrients, says Mr Burrell.

“If soil pH falls below 6.5, meaning soils are too acidic, macronutrients such as phosphate, nitrogen and potassium will be locked up in the soil matrix and therefore be less available for uptake by the next crop in the rotation.”

Phosphate availability falls to 52% at pH 6.0, says Mr Burrell, decreasing to 48% at pH 5.5. Similarly, nitrogen and potassium availability fall to approximately 77% at pH 5.5, he adds.

Fertiliser prices

“According to the latest data, almost two-thirds (62%) of UK arable soils are below the optimum pH of 6.5. Likewise, one-in-three grassland soils are below their optimum pH of 6.0.

“Given the political unrest in the Middle East, and the impact this could have on global fertiliser prices, it makes sense to test and adjust pH now, to ensure those nutrients already in the ground remain available for the next round of crops to utilise.”

There’s no silver bullet when it comes to unlocking crop yield , says Mr Burrell.

But rectifying pH should be on every to-do list, especially as low pH can easily and cost-effectively be resolved with lime.

Closely linked

Mr Burrell also urges growers to test for sulphur. “Sulphur and the efficiency of nitrogen are closely linked, with any deficiency in the former resulting in reduced nitrogen use efficiency,” he explains.

Atmospheric sulphur deposition has fallen steadily since the 1970s when acid rain was at its peak, with 95% of soils now deficient. At the same time, only 55% of arable ground routinely receives a treatment of sulphur.

“Many farmers assume the shortfall will be made up by applications of farmyard manure or slurry. But unless these inputs have been tested to assess their nutrient content, it’s impossible to know if soils are receiving sufficient sulphur.”

Without enough sulphur, oilseed rape yields fall by an average of 0.5 t/ha, while wheat yields fall by about 0.375t/ha.

To counter this, sulphur and nitrogen should be applied at a ratio of between 5:1 and 3:1 depending on soil indices.

Three steps for best crops

Growers should employ a three-pronged approach to get the best from crops, says Phil Burrell, from ProCam.

The first is to test soil for acidity and nutrient content on a field-by-field basis in autumn and spring so appropriate adjustments can be made ahead of cropping, he says.

Secondly, growers should also carry out in-season leaf/plant tissue analysis to assess the crop’s ongoing nutritional needs. Finally, they should carry out post-harvest grain analysis to highlight any enduring nutrient deficiencies.

“Grain analysis from the 2024 harvest indicated that 60% of wheat crops were deficient in sulphur,” says Mr Burrell.

“This points to a significant shortfall in fertiliser programmes and is a clear indication that growers shouldn’t always assume that a ‘standard’ bag of fertiliser will be appropriate.”

Instead, soils should be tested, and the results scrutinised with the help of a FACTS approved agronomist. They will be able to verify the findings and devise a suitable nutrient programme for each field, says Mr Burrell.

“Fertiliser spreaders should also be calibrated to ensure what could become an increasingly expensive commodity is applied accurately and in the right quantity.

“Where the relevant machinery is available, variable rate application maps, such as those produced by ProCam’s FieldSense platform, should be used to maximise the yield benefit and margin over input costs.”