Reducing reliance on synthetic nitrogen is at the top of most grower’s agendas given the current supply and pricing challenges, as well as environmental concerns over its use.
With a global nitrogen market worth about $193bn (£178bn) in 2022, the opportunity is huge for those who can provide successful alternatives and has already led to a huge amount of investment in research and development of new solutions.
See also: How a grower is aiming for a 10% yield raise using a data tool
At the recent World AgriTech Innovation Summit in London, a number of promising technologies were discussed.
One of the biggest investment areas has been in biological or microbial products with the potential to provide nitrogen directly for plants.
US-based Pivot Bio’s technology uses gene editing to programme the DNA of bacteria to convert atmospheric nitrogen into plant-available ammonia in the soil.
The bacteria, which are naturally occurring in the soil, can fix nitrogen but it shuts down when the microbe identifies there is enough ammonia in the immediate surrounding area.
Pivot Bio has “flipped the switch” so the microbe still fixes nitrogen even when high levels of nitrogen surround them.
“There are many bacteria that can take nitrogen out of the air to make ammonia and feed themselves, and make proteins and grow,” explains Ernie Sanders, Pivot Bio vice-president of product development.
“We isolated those microbes and reprogrammed them to make more ammonia than they need themselves and excrete it out.
“Our product grows on the outside surface of the plant roots and the ammonia is immediately taken up by the plant.”
The firm has developed a couple of products – Pivot Bio Proven 40 for maize and Pivot Bio Return for wheat and barley.
Both are designed to be applied on the seed, with the microbes providing the opportunity to replace 40kg N/ha in maize and 25kg N/ha in cereals, says Mr Sanders.
“As soon as the seed germinates and sends out roots, our bacteria colonise the roots and grow, using the exudates that come from the plant as a food source.
“Our product delivers the most nitrogen when the maize or cereal plant needs it the most.”
The products were used across 1.2m ha in 2022 at a cost of £47/ha ($21/acre), with the vast majority of growers using it to replace synthetic nitrogen application rather than as an additional source of N, Mr Sanders says.
Future developments will continue to aim to increase the amount of synthetic nitrogen that can be replaced.
No testing has so far taken place in the UK, but trials are ongoing with different strains – developed without gene editing because of the more restrictive regulatory environment – in Poland, Germany and France, he adds.
What makes UK-based Azotic Technologies nitrogen-fixing bacterial product different is that it multiplies and grows within the cells of the plant.
Gluconocetobacter diazotrophicus bacteria were originally found in sugar cane. They have been sold as Envita in the US since 2019, with millions of acres treated in 2021, says Nolan Berg, the firm’s head of global marketing.
That footprint is set to expand with the product also now available in the UK and Europe, under the brand name Encera.
The technology is non-gene edited or modified and is crop-agnostic, with the focus on crops such as maize, potatoes, rice, wheat and barley. It’s usually applied as a post-emergence foliar spray, although it can be used as an in-furrow application or seed treatment, says Mr Berg.
“Once the bacteria gets into the plant, it will grow as the plant grows.
“By physically getting into the plant cell where photosynthesis is taking place, it creates a natural source of nitrogen filling the gap between what the crop needs and what the crop can get from the soil and roots.”
In North America, many growers have used it as an additive to usual nutrition programmes with about 5-10% increase in yield in crops from a treatment costing about $15/acre (£37.50/ha).
Alternatively, it can be used to replace about 25% of the synthetic nitrogen fertiliser requirements in maize – about 55kg N/ha – or up to 50% in rice, without any drop off in yields, Mr Berg says.
“We’ve also seen consistent 5-10% yield increases in wheat and barley in trials when used with a full nutrition programme.
“We’re still working on quantifying how much N it can replace in these crops, but early results suggest potential for reductions of 10% or more.”
The firm is planning an introductory demonstration programme where product is provided to farmers free of charge to establish the product’s efficacy across Europe, including the UK, Mr Berg adds.
Digital tools, in conjunction with more efficient forms of nitrogen fertiliser, have shown the potential to reduce applied N requirements in BASF’s Better Barley project.
The project was run on a 50ha field of malting barley on a German farm. It compared the use of variable rate applications of urea fertiliser treated with nitrification inhibitors driven by data insights from BASF’s digital platform, xarvio, with flat-rate applications of uninhibited fertiliser.
The aim was to maintain or improve yield and malting quality while minimising fertiliser inputs and carbon dioxide equivalent emissions, explains Matthias Nachtmann, BASF European business development manager.
Nitrification inhibitor added to fertilisers protect N against losses due to nitrate leaching and nitrous oxide emissions. As a result, more N is available for the plants.
“We give the plant support in the race for nitrogen uptake of the plant so, depending on the weather, the plant can take up nitrogen over a longer period,” explains Mr Nachtmann.
“That gives a higher nitrogen use efficiency and lower emissions.” Using variable rate applications further improves efficiency, he adds.
In this trial, xarvio field manager analysis of the previous 15 years of plant biomass development, overlaid with yield maps, provided the basis to create xarvio powerzone maps to identify areas of higher and lower field performance.
These were used as the basis for the variable rate applications.
Results from the trial are still being analysed, but the preliminary outcome suggests target grain nitrogen levels were achieved while saving about 20-30kg N/ha and improving yields by about 1-2%.
“We’re keen to run the Better Barley project on more soil types, including in the UK,” Mr Nachtmann says.
Yara’s digital tool AtFarm, which was launched in 2018, also uses satellite data to create variable rate application maps based on the N-Sensor algorithm.
“We’ve been able to improve yields by 6% by using this tool and also reduce nitrogen fertiliser use by 12%,” says Monica Andres Enriquez, Yara’s executive vice-president in Europe.
To encourage farmers to use this type of precision farming tool, Yara made the AtFarm free this year. The company has also been lobbying for further support to improve access to digital tools for European farmers, she says.
Gene-editing company Inari is aiming to reduce the amount of N needed to grow maize by 40% through its SEEDesign technology platform.
It is also targeting a 40% reduction in water requirements for the crop, while increasing yields by 20%.
Reducing N requirements by 40% is an audacious goal, admits Inari chief executive officer Ponsi Trivisvavet.
“Crops’ nitrogen use efficiency is determined by a system of genes and gene networks that are incredibly complex.
“There is not a trait that can be added or a single gene that can be knocked out to deliver the systematic changes in plants needed to improve nitrogen uptake, which is why it has historically not been addressed.”
But recent advances in artificial intelligence, genomic sequencing and gene editing have unlocked new tools and knowledge, she says.
Inari pairs predictive design with advanced multiplex gene editing.
“Predictive design works to create a deeper understanding of the unique pathways and genomic interactions within the plant.
“These insights can deliver editing ‘blueprints’ to guide our breeders and scientists in making a range of gene edits with the plant’s own DNA.”
Making multiple edits to the plant at the same time is necessary to address the natural complexity of plant gene networks, such as resource use efficiency, she says.
But gene editing is still in its infancy – it’s just 10 years since the discovery of a ground-breaking technology – clustered regularly interspaced short palindromic repeats (CRISPR) was published.
Initial products such as browning-resistant mushrooms and tomatoes containing higher amounts of gamma-aminiobutyric acid, which can help support lower blood pressure, are the result of single-gene edits.
“Given the complexity and depth of knowledge necessary to address gene networks, the first multiplex gene-edited products have not yet hit the market,” Ms Trivisvavet says.
“But given the speed at which technology is advancing, we expect that to change in the next couple of years.”
However, accessibility to this technology will depend on regulatory approvals, she stresses.
“It is crucial to have a clear regulatory path accessible to companies and organisations of all sizes, to allow multiplex gene-edited products to get to market at a speed that keeps pace with both our growing global population and our fast-changing climate.”
A global round-up of other alternatives to nitrogen fertiliser
The US firm’s Source product is based on plant root signalling compounds strigolactones. It imitates signalling between plants and the soil microbiome, which wakes up nitrogen-fixing bacteria and phosphorus solubilising microbes, improving nutrient availability.
The firm claims to be able to replace up to 55kg/ha in various crops including maize, wheat, and soya beans, or to increase yields.
UK-based Biolevel PhosN and GramaxNP products contain a mix of nitrogen-fixing and phosphorus solubilising bacteria, which can be applied as a seed treatment or in-furrow application in potatoes, vegetables and oilseed rape (PhosN) and cereals (GramaxNP).
Most initial research has concentrated on increasing yields, but there’s growing evidence from independent trials in the UK and abroad of being able to reduce nitrogen requirements by 20% with no impact on yields.
Anuvia Plant Nutrients
The company converts food, animal, industrial and waste water organic waste into a slow-release biofertiliser, SymTRX. The product feeds crops for up to eight weeks, while also improving soil health by returning up to 16% organic matter to the soil.
Nutrients bind to the organic components, which slows their release in the soil. Soil microbes then break the bonds to gradually release nutrients for plant uptake.
Nitrogen leaching is reduced by up to 50% compared with urea.
A further area of development is to integrate Novozymes biological products into each fertiliser granule to enable additional reductions in synthetic nitrogen use.
Ghent firm Aphea.Bio is targeting nitrogen use efficiency through identifying novel soil microbes, which it then formulates as seed treatments.
Backing its efforts is a collection of more than 15,000 microbes and a bundled technology platform that helps it analyse beneficial plant-microbe interactions and evaluate them quickly for potential use as biostimulants and biocontrols.
Its first products are expected to be launched in 2023.
Nitricity makes fertiliser from air, water and renewable energy at the point of use. The startup has found a way to mimic lightning, which splits nitrogen atoms in the air.
The free nitrogen combines with oxygen to form nitrogen dioxide before dissolving in the water in clouds and making its way to the soil in rainwater.
Nitricity has found a way of containerising lightning, creating a low-cost, plasma reactor powered by solar panels, which fixes nitrogen and substantially reduces the amount of carbon dioxide emitted compared with the Haber-Bosch process.
In its pilot projects in California, the fertiliser is injected into irrigation systems.
Another nitrogen-fixing bacteria, Methylobacterium symbioticum, is being marketed by Corteva as Utrisha N in the UK.
This shares some similarities to the Azotic product in that it is foliar-applied.
It enters the plant through stomata and colonises around the leaf cells, converting nitrogen from the air into ammonium. This constant supply of ammonium enhances nitrogen use efficiency.
Corteva recommends one application is applied when temperatures are between 10-30C and the crop is actively growing.
This startup has energised naturally occurring nitrogen-fixing bacteria by providing them with a carbon-rich energy source, helping them build up larger-than-normal stores of energy and nutrients.
The bacteria, when applied to the soil, communicate with plants to produce ammonia on demand, but with larger stores of energy, they can survive and thrive for weeks rather than days. This gives plants a slow-drip of nitrogen to maximise growth.
The firm claims it can replace up to 50% of nitrogen demands.
Synthetic biology startup Switch Bioworks is aiming to boost biofertiliser performance using a novel approach developed by researchers at Stanford University.
Usually there is a trade-off between a microbe’s ability to grow in soil and produce nitrogen due to basic energy and nutrient constraints.
Switch Bioworks aims to disrupt this trade off by engineering bacteria to first optimise for growth, then switch to optimise fertiliser production.
The company uses captured carbon dioxide from industrial power generation to stabilise materials, such as ammonia and phosphates from agriculture and industrial waste streams, to create slow-release fertiliser products with significantly lower carbon footprints.
Trials with PepsiCo, Niab, WWF and Velcourt suggest 10-20% saving in nutrients required to produce the same yields.