Plant and soil scientists hope to combine two new technologies – one of which is based on the use of x-rays – to provide a rapid, same-day measurement of soil phosphorus availability, enabling tillage farmers and growers to make more informed decisions about fertiliser application.

The move to develop this technique came about following an unexpected discovery by Dr Shane Rothwell, as part of his PhD studies at Lancaster University in the UK.

Dr Rothwell noticed that, contrary to expectations, pea and bean crop yields were sometimes decreased by up to 30% when they were treated with recommended levels of lime – despite the fact that application of lime is expected to to improve the availability of plant nutrients.

He demonstrated that the reduced crop growth was associated with lower plant phosphorus content but existing ways of measuring the phosphorus in soil available for plant uptake were not picking up on the problem.

Consequently, developing a test to more accurately predict soil phosphorus availability following liming would benefit farmers and the environment, preventing waste and pollution.

The new method will combine two different technologies: the diffusive gradients in thin films (DGT) technique and portable x-ray fluorescence spectrometry (pXRF).

As part of the project, Lancaster researchers will also work with Dr Martin Blackwell, Rothamsted Research to mine an existing data set that has measured phosphorus concentrations within drainage water to determine if regular liming programmes mitigate fertiliser phosphorus losses from the landscape.

“There is still much we don’t understand about phosphorus cycling in soils, its availability to plants and losses via run-off,” said Dr Blackwell.

“Phosphorus is an important plant nutrient. But there is widespread concern that repeated fertiliser applications to agricultural soils are causing phosphorus leakage to the environment due to drainage below the crop rootzone and surface runoff, which can pollute waterways and cause eutrophication of streams and rivers.

The new research aims to create an effective test to plug the gap. The work undertaken should lead to the development of a commercial service that will allow farmers to make better informed fertiliser decisions enabling them to more precisely and sustainably manage phosphorus on their land.