How technology lets crops turn pollution into fertiliser
© GNP A new technology that captures air pollution and uses sunlight to convert it into nitrate on the leaf surface of a crop has been developed by Lincoln-based Crop Intellect.
Called R-Leaf, it uses a process known as photocatalysis to break down nitrous oxide and turn it into an essential crop nutrient, offering the potential to reduce both farm emissions and the industry’s reliance on synthetic nitrogen.
See also: Video: Camera technology improves marketability for potato growers
Against a background of rollercoaster fertiliser markets and environmental concerns, the technology is being feted as a ground-breaking development that will allow farmers to make better use of nitrogen fertiliser and reduce the greenhouse gas emissions associated with its use.
Classed as a fertiliser, R-Leaf is based on titanium dioxide and comes in a liquid formulation that also contains manganese, molybdenum and zinc.
It can be applied through a standard farm sprayer to crop foliage, either on its own or as part of a tank mix.
Once applied, it uses sunlight to convert atmospheric nitrous oxide into nitrate, which the company says helps to provide the plant with a constant supply of the nutrient.
Daylight conditions
The patented photocatalyst technology contained in R-Leaf has been designed to work under normal daylight conditions, rather than needing high intensity light usually associated with such chemical reactions, Crop Intellect says.
This allows it to react with nitrous oxide in field conditions, breaking the pollutant down in to nitrate, carbon dioxide and water – all of which are required by the plant.
What is a photocatalyst?
A photocatalyst is a material that absorbs light to provide energy to a reacting substance, so that a chemical reaction occurs.
Well studied and understood, photocatalysts are used in many industries, as filters and decontaminants as well as for driving chemical reactions.
After application, it remains on the leaf surface for up to six weeks, providing nitrate in a slow-release manner and allowing farmers to manage the use of nitrogen fertiliser.
Having been tested on both combinable and root crops, and with further trial work ongoing, R-Leaf is described as a disruptive technology that enables the production of green nitrogen while reducing harmful air pollution.
Carbon credits
For growers wishing to reduce the carbon footprint of their business or with carbon trading in mind, R-Leaf’s potential to contribute towards reducing climate change has been validated at 5.4t/ha of carbon dioxide equivalent when used at a rate of 2 litres/ha, with verification coming from Climate Impact Forecast tool.
Crop Intellect
Crop Intellect is an R&D company based at Lincoln University, led by crop and soil scientist Dr Apostolos Papdopoulos.
The company has secured substantial funding to develop R-Leaf into a global solution to the sustainability and climate change challenges faced by the farming industry and wider society.
“This is a significant development for the industry’s net-zero ambitions,” says Jeremy Hitcham, commercial manager at Crop Intellect.
“Not only will it help to improve nutrient use efficiency on farms, it also has a role in reducing air pollution.
“In the future, its use should allow carbon credits to be produced, so that they can be monetised if required.”
On-farm use
He suggests two ways in which it can be used on-farm. “The first is to reduce your bagged nitrogen by 25% and let R-Leaf provide the rest, so that yields are maintained.
“The second is to stick to your normal farm practice and apply the same amount of nitrogen, with R-Leaf being used to give additional yield.”
Either way, R-Leaf costs £25/litre, with split applications of 2 litres/ha being recommended for cereals – giving a total cost of £50/ha. The current recommendation is to apply it at T1 and T2.
The second application is required because R-Leaf doesn’t move once it has been applied, explains Mr Hitcham, so a growing plant producing new leaves benefits from the follow-up as older, treated leaves become shaded.
Trials results
Already included in Tesco’s large scale commercial trial on nitrogen fertiliser use, R-Leaf is one of eight alternative fertiliser products being tested by the supermarket.
It has also received recognition from Tesco in the form of an Agri T-Jam Award for Innovation, as well as winning a Lincolnshire Technology and Innovation Award.
R-Leaf is available through Agrovista and Hutchinsons this season, as well as other suppliers.
Agrovista technical manager Mark Hemmant describes it as an exciting technology which has the potential to mitigate climate change.
“We’ve used diffusion tubes to show that it is taking nitrous oxide out of the atmosphere and we’ve measured more nitrogen in the leaf and in the grain where R-Leaf has been used,” he says.
“However, we haven’t done trials on reducing synthetic nitrogen rates by 25% yet, so can’t make any conclusions about that until we’ve done the work.”
Case Study: Frank Stennett, Genevieve Farms, Bury St Edmunds
Suffolk sugar beet grower Frank Stennett tried R-Leaf on some of his crop last year and recorded a 6% increase in yield.
Helped by the use of irrigation in a hot, dry growing season, untreated sugar beet gave an impressive yield of 106.15t/ha, while the portion of the crop that had received 2 litres/ha of R-Leaf had an average yield of 112.28t/ha.
The cost of using the innovative product at 2 litres/ha was about £40/ha, recalls Mr Stennett, which was easily covered by the additional 6t of beet at a 2022 price of £27/t.
“It can go on as part of a tank-mix so it doesn’t have to be an additional pass,” he says. “However, as it was the first time of using it, I decided to apply it on its own.”
He opted to stick to his farm standard of 120kg/ha of bagged nitrogen, then applying 2 litres/ha of R-Leaf, rather than using it to reduce nitrogen use.
“I wanted to see what it could do on our light soils, given the higher sugar beet price agreed with British Sugar for 2023.
“Foliar applications are a more efficient way of getting the nutrient into crops, so it gave us the chance to look at how it could help.”
Tissue testing carried out after application showed higher nitrogen levels in the leaves that had been treated.
These levels remained steady at about 5%, while the untreated crop showed a decline in nitrogen levels over time.
Given the results, Mr Stennett regrets that he didn’t put a second application on.
“Unlike many others and thanks to our ability to irrigate, the crop didn’t struggle with moisture stress.
“So a second treatment may have kept the leaves greener for longer and driven more yield from a later lifting date,” he says.
“It’s certainly a rain-fast product, as we were irrigating throughout the season.”
He also applied R-Leaf to winter wheat, but the combination of the farm’s light soils and the season’s high temperatures meant the crop burnt off before all the measurements could be taken.
He did, however, record his best-ever wheat yields in 2022 at levels in excess of 10t/ha, but is wary of drawing conclusions without data.
“I would like to try it on the oilseed rape too, but the timings are more tricky, as you have to get it all on with the sprayer before the crop gets too tall.”
He acknowledges that the R-Leaf development sounds too good to be true, but points out that it is a very timely development.
“Anything that has been shown to remove nitrous oxide from the atmosphere has to be a positive step.
“If it helps us to reduce the greenhouse gas emissions associated with growing crops and removes a potent pollutant from the air, it will have a place in sustainable food production.”