Making More of Slurry: Can Better Decisions Unlock Its Value?

Slurry and anaerobic digestate are some of the most valuable nutrient resources availalbe. They contain nitrogen, phosphorus, potassium and sulphur, can reduce the need for manufactured fertiliser and offer a genuine opportunity to recycle nutrients within the farming system.

But using those nutrients effectively isn't always straightforward.

The nutrient content of slurry and digestate can vary considerably, while the amount available to the crop depends on factors such as timing, weather, application method and soil conditions. At the same time, farmers are working within increasingly stringent environmental and regulatory requirements around nutrient losses, water quality and ammonia emissions.

In practice, slurry applications are often dictated as much by logistics as agronomy. Storage capacity, weather windows, machinery availability and workload can all determine when and where material is applied. That can make it difficult to match nutrient supply with what the crop actually needs.

So how can we make better use of this valuable resource?

A new project will investigate two complementary approaches: Improved Decisions and Improved Slurry Practices.

Working with commercial farms, farmers, agronomists, researchers and technology providers will come together through a Smart Slurry Hub to identify and test practical approaches to smarter slurry management.

The first year will establish a detailed picture of current practice. Farmers will continue managing slurry as they normally would, while measurements will be taken of slurry nutrient content, soil nutrient status, crop response, yield and grain protein. Technologies including John Deere HarvestLab, Plant Root Simulator probes and leaf tissue analysis will help build a better understanding of what nutrients are being supplied and taken up by the crop.

Importantly, the project will also record how farmers make slurry decisions — including the timing, application rate, triggers and reasoning behind them. This will help identify where uncertainty exists and where opportunities to improve nutrient use may be being missed.

In Year 2, the project will test what happens when better information is available at the point of decision. Real-time slurry nutrient analysis will be used to help determine application rates and timing, with the aim of matching nutrient supply more closely to crop demand.

Using the same fields, measurements and decision records across both years should provide a valuable comparison between current practice and a more information-led approach.

The overall aim is to establish whether better information can deliver measurable improvements in nutrient efficiency, crop performance, costs and environmental risk.