War in Iran has further increased pressure on fertiliser supplies and prices, compounding the effects of the EU Carbon Border Adjustment Mechanism (CBAM).
CBAM had already caused a sharp drop in fertiliser imports into the EU, leading to tightened supply and higher prices, including in the UK market, notes Chris Martin, Agrovista’s head of soil health.
The Iran conflict only intensifies those pressures with the near-closure of the Strait of Hormuz impacting supplies – around a third of global fertiliser trade passes through this narrow shipping lane in the Persian Gulf. The closure of the world’s largest liquefied natural gas (LNG) plant at Ras Laffan in Qatar has disrupted supplies of a crucial raw ingredient for nitrogen fertiliser, while the plant also produces sulphur, a key ingredient for phosphate fertilisers.
“While UK fertilisers may not come directly from the Middle East the reduced supply of Gulf State-produced fertiliser or raw ingredients increases competition for other sources and, as we’ve seen, quickly impacts UK prices,” Chris says.
The glib and unhelpful answer to mitigating the impact on farm is to have bought all your fertiliser requirements earlier in the season. “Many will have done so but unfortunately there will be some who haven’t been able to do that, whether it’s because of storage restrictions, cash flow or other reasons.
“Those 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, as in 2022/23, about the value of the last kgs of nitrogen applied, and the risk of whether specifications for crops like milling wheat can be hit.”
The old story of making sure nitrogen use efficiency is as high as possible will remain crucial, he adds, while noting there are potential alternatives sources of nitrogen to consider if necessary and as appropriate.
Tips to improve nitrogen use efficiency
Nitrogen efficiency doesn’t just depend on nitrogen
A wide range of other nutrients are required along the pathway from nitrogen uptake through its various guises to the formation of amino acids and proteins, Chris says. “If any of these are missing it can cause a bottle neck 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.
While it’s too late to do much about for this season, remember maintaining a suitable pH is essential for ensuring maximum nutrient efficiency.
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, Chris stresses.
“Variable rate application maps can be created to ensure nitrogen is applied where it is needed.”
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 such as Nitroshield or AdvaNshield, compete with the urease enzyme to create a chemical bond with the urea, reducing 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.
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 is most commonly used in maize, but can be used on many crops, including winter and spring wheat.
“The nitrogen polymers are of variable chain length and so degrade at different rates to provide a sustained source of nitrogen,” he explains. “High nutrient bioavailability typically results in 85-95% use efficiency, while the low salt and biuret content ensures excellent crop safety even at high temperatures.”
A specialised bio nutrition wetting system in the formulation improves spreading and sticking of the fertiliser, lowering risk of salting out of nutrients on the plant surface and minimising risk of volatilisation.
To maximise efficiency, apply 28 l/ha between GS32/3 to a good canopy following a base programme of at least 150 kgN/ha on winter wheat, Chris advises. “This will replace the last 40kgN/ha in feed wheats or apply 35 l/ha to replace the last 50kgN/ha following a base of at least 150 kgN/ha.”
MZ-28 is not recommended for use in barley as that crop sets its final yield much earlier, he adds.
What about biostimulants?
There is a wide range of biostimulants that can help improve nitrogen fertiliser efficiency. These include amino acids, Chris says. “Making amino acids within a plant is very energy intensive, so by applying them in products such as Terra-sorb Foliar Extra, liberates energy to help improve growth and efficiency of nitrogen use.”
Terra-sorb Foliar Extra can be applied through the growing season at 0.5-3.0 l/ha to reduce stress, improve pollination and nutrient uptake.
Biostimulants containing pidolic acid (PGA) co-ordinate and regulate nitrogen assimilation and carbon fixation maximising the efficiency of applied nitrogen fertilisers.
Consider N-fixing products & photocatalysts
Microbial nitrogen-fixing products, such as Nuvenio or Plantworks – Smart Rotations, are a potential alternative source of nitrogen, according to Chris.
The free-living bacteria in Plantworks – Smart Rotations 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 30-40 kgN/ha.
“Nuvenio is especially useful in dry conditions when nitrogen uptake through the roots of fertiliser is compromised.”
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.
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 readily available carbon source to ensure efficient production of amino acids. L-CBF Boost also acts as a microbial feed, improving nitrogen cycling.
“Independent trials suggest a 15-20% reduction in total nitrogen if applied by early April in winter crops,” Chris concludes.