Over the past nine months fertiliser prices have skyrocketed, and with summer gas futures still indicating four times to five times higher than in previous years, the trend looks set to continue.
What goes up must come down eventually, but even for growers who bought nitrogen for a good price this year, next season prices are still likely to remain higher, says Jo Gilbertson, AIC head of fertilisers.
Can we see light on the horizon? “Obviously as gas prices eventually come down, it will become more economic to manufacture fertiliser, but at the moment a lot of fertiliser plants in Europe have reduced or stopped production because they cannot afford to manufacture it,” she says.
“Similarly, it is about supply and demand – farmers are not buying at the moment because the ones with crops in the ground have bought and are covered and farmers are putting off making a decision, hoping the price will come down – the gas price might be an indicator to suggest this might not happen soon.”
Europe’s dash to reduce its carbon dioxide profile has left British farmers highly sensitive to gas price movement and with such high dependency on low-price fertilisers, they are in a vulnerable position.
Break-even ratio Amid the high prices, AHDB and ADAS have been working to create new recommendations for nitrogen management.
This starts with accommodating a new break-even ratio – beyond which the value from the extra grain produced does not pay for the extra nitrogen applied to achieve it (see graph, below, right).
Since 2008, the recommendations have used a break-even ratio of 5kg of cereal grain paying for 1kg of fertiliser nitrogen, but the high fertiliser prices mean a new, larger break-even ratio has been created.
Prof Roger Sylvester-Bradley, head of crop performance at ADAS, says: “It will depend on how much you paid for the fertiliser, but generally we’ve worked out if the price ratio has gone from 5kg of grain to 10kg, which is the current ratio, you need to reduce nitrogen applications to cereals by 50kg per hectare.
For oilseeds the ratio has changed from 2.5kg of seed paying for 1kg of nitrogen, to 4kg so that would mean also reducing nitrogen applications to OSR by 50kg/ha roughly.”
This should be taken from the least effective timing which, for feed cereals and malting barley, tends to be the latest application, says Prof Sylvester-Bradley.
“For milling wheat, there is a question of whether you should be cutting back at all because you stand to risk losing your premium if you’re committed to a certain spec, such as 13% protein.
“If you’ve got a very forward OSR crop then you don’t need to apply nitrogen early.
Pull back across the board – then you are just pulling back from that last little bit of yield you would have gained by applying the last 50kg/ha nitrogen.”
Yield effects of reducing nitrogen can be modest (see table, top right).
This is because most nutrition programmes operate around the flatter part of the nitrogen response curve, meaning there can be quite big changes in nitrogen rate around the optimum ratio which only have a moderate effect on the overall yield.
Alternative sources of nitrogen will also find their value this season, with products that boost nutrient uptake becoming more cost-effective.
However, although there are a number of mainstream fertiliser options available which can help to replace bagged nitrogen, Agrovista has never found anything in its trials that would substitute more than around 40-50kg/ha of nitrogen, says head of soil health, Chris Martin.
Slow-release “So, we still need around 150kg/ha as a base level from traditional sources.
“One of the most popular options is slow-release fertilisers such as MZ28 which is foliar urea with different polymer length chains – this means the N is released at different stages into the crop.
“Agrovista started looking at this about 20 years ago, not as a cheaper form of nitrogen but as a more environmentally-friendly form of nitrogen to reduce nitrate and greenhouse gas emissions – it works out several times lower in its carbon footprint than traditional fertilisers.
“Current costs mean it is very cost-effective too. In the current market we will be looking for the last 40-50kg/ha on a feed wheat with 28-35 litres/ha of MZ28 at roughly around growth stage 32.”
For growers applying digestate or slurries, a nitrification inhibitor is well worth considering, Mr Martin adds.
“Particularly for digestates, where a lot of the N is in the ammonium form, which is very stable, the idea is to keep it in that form for as long as possible and slow down conversion to nitrate where it can be lost through leaching or as nitrous oxide.”
Bacteria These include products such as N-Lock and Instinct, which inhibit the multiplication of the bacteria that convert ammonium to nitrate.
“This is nothing new, but 30 years of research has shown reductions of 50% in nitrous oxide emissions and 16% in leaching – that means you’re getting more value from your organic fertilisers, so it would be a sensible approach this year,” Mr Martin says.
Another product Mr Martin has explored, namely from a soil health point of view, is molasses and yeast extract-based L-CBF Boost.
“It’s basically a carbon source. We’re seeing quite clearly that because you’re putting a carbon source alongside your nitrogen, the amino acids are being formed more efficiently so you’re getting better value for your nitrogen.
“With a standard rate of about 40 litres/ha on a cereal crop across the season, you could be looking to reduce your nitrogen by 30-40kg with the same yield results.”
And finally there is the increasingly popular biologicals route, utilising free living bacteria that can fix nitrogen.
Mr Martin says: “There is plenty of nitrogen in our soils and around 70,000 tonnes of inert N gas above every hectare that we can’t use, but we can try and reach it like a legume crop would.
Significant “There are free living bacteria specific to each crop that can convert some of that into plant-useable sources. With the likes of Smart Rotations and Plant Works, we’re looking at some products where significant nitrogen can be fixed from the right bacteria.”
While these products could hold merit in some systems, the starting point should be ensuring plants have access to the whole ‘cocktail’ of nutrients needed for optimal growth.
“If one nutrient is missing it is going to impact the rest of them.
Molybdenum is an element we barely consider on cereals, but it is really important for nitrogen metabolism.
You may only need one atom of molybdenum for every million atoms of nitrogen, but if you haven’t got it, you are compromising the nitrogen because it won’t metabolise efficiently.”
Mr Martin recommends soil testing followed by in-season tissue or sap testing to match nutrition to the crop’s direct need.
“In-season tissue testing is really useful because it tells you where you are on that day, where you should be on that day, where you should be at the next growth stage and how to get there.
It is one of the most comprehensive ways to match nutrition to need.
Another options is to do a ‘post-mortem’ with a grain test.
“That will tell you how successful your nutrition programme has been.
Although it is hindsight, you can learn from it next year if there are areas you are getting horribly wrong,” says Mr Martin.