7 tips to make fertiliser go further this spring

While many farmers have already purchased fertiliser for this season, there will be some who haven’t been able to do that, whether it’s because of storage restrictions, cashflow or other reasons.

Agrovista head of soil health Chris Martin says these growers will have difficult decisions about whether to stump up the extra cost, assuming supplies are available to be delivered in time.

“Careful calculations will be needed about the value of the last kilogramme of nitrogen applied, and the risk of whether specifications for crops like milling wheat can be hit.”

See also: How 6 farmers are managing fertiliser use in tight season

The old story of making sure nitrogen use efficiency is as high as possible will remain crucial, he adds, while noting there are potential alternative sources of nitrogen to consider.

Chris outlines his seven tips to improve nitrogen use efficiency

1. Nitrogen efficiency doesn’t just depend on nitrogen

A wide range of other nutrients are required along the pathway from nitrogen uptake to the formation of amino acids and proteins, Chris says.

“If any of these are missing it can cause a bottleneck along the protein pathway, reducing the efficiency of a fertiliser programme.

“Sulphur is particularly important for nitrogen efficiency, so foliar applications might be required where insufficient sulphate has been secured to use with nitrogen fertilisers and elemental sulphur was not applied in the autumn.” 

Regular growth stage related tissue or sap tests will help identify micronutrient deficiencies, allowing them to be treated.

2. Monitor nitrogen through the season

Monitoring nitrogen levels in the crop during the season through leaf testing and satellite imagery can help ensure nitrogen is timed and applied as efficiently as possible.

“Variable rate application maps can be created to ensure nitrogen is applied where it is needed.”

3. Use nitrification and urease inhibitors

Nitrification inhibitors slow down the natural nitrification process in the soil, keeping nitrogen in the stable ammonium form for longer. This reduces losses through leaching or de-nitrification, leaving more available for the crop. 

Products, such as Instinct, which contains nitropyrin, should be used just before, or at the same time as, the main fertiliser dose, Chris advises.

“It is especially useful and an underused technology when applying slurries, organic manures and digestates.”

Urease inhibitors, often based on NBPT, reduce the release of ammonia into the atmosphere, leaving more nitrogen available for crop uptake. It is a requirement for Red Tractor assurance to use them when applying any urea from 1 April.

4. Consider methylated urea

Solid nitrogen fertiliser potentially can be replaced with more efficient foliar applied nitrogen products, such as MZ-28, Chris says.

MZ-28 is a controlled release nitrogen ­fertiliser containing 28% nitrogen – 11.5% ureic nitrogen and 16.5% urea formaldehyde.

It can be used on many crops, including winter and spring wheat, but is not recommended for use in barley.

“The nitrogen polymers are of ­variable chain length and so degrade at ­different rates to provide a sustained source of nitrogen,” he says. “High nutrient ­bioavailability typically results in 85-95% use efficiency.”

To maximise efficiency, apply 28 litres/ha between growth stage 32-33 to a good canopy following a base programme of at least 150kg N/ha on winter wheat, Chris advises.

“This will replace the last 40kgN/ha in feed wheats or apply 35 litres/ha to replace the last 50kgN/ha following a base of at least 150kgN/ha.”

5. What about biostimulants?

There is a wide range of biostimulants that can help improve nitrogen fertiliser efficiency, including amino acids.

“Making amino acids within a plant is energy intensive, so by applying them liberates energy to help improve growth and efficiency of nitrogen use.”

Biostimulants containing pidolic acid co-ordinate and regulate nitrogen assimilation and carbon fixation maximising the efficiency of applied nitrogen fertilisers.

6. Consider N-fixing products and photocatalysts

Microbial nitrogen-fixing products, such as Nuvenio or Smart Rotations by Plantworks, are a potential alternative source of nitrogen, according to Chris.

The free-living bacteria in Smart Rotations by Plantworks will fix atmospheric nitrogen in the soil into forms a crop can use, while Nuvenio contains a consortium of soil-dwelling, nitrogen-fixing bacteria and endophytes that colonise the plant allowing it to naturally fix up to 30-40kgN/ha.

Another alternative is the photocatalyst R-Leaf, which is applied with T1 and T2 fungicides. This new technology is sprayed onto leaves to capture and convert nitrous oxide into nitrate to be used for crop growth.

“Trials suggest that it can capture up to 20kgN/ha for the crop in a season,” Chris says.

7. Add a carbon source to fertiliser applications

Applying a carbon-based fertiliser, such as L-CBF Boost, can improve the performance of nitrogen fertiliser by providing a carbon source to ensure efficient production of amino acids.

“Trials suggest a 15-20% reduction in total nitrogen if applied by early April in winter crops.”