Peas provide promise for fewer fertilisers

Can the nitrogen fixing abilities of peas be transferred into other crops?
07 February 2023

Interview with 

Giles Oldroyd, University of Cambridge


Nodules on roots


Crossbreeding is one way to get crops to produce better yields, but it’s not the only way. And scientists at the University of Cambridge are approaching the issue from a slightly different angle. Giles Oldroyd is the director of Crop Science Centre where they’re engineering grain plants to take advantage of naturally occurring interactions with microorganisms in the soil, in the same way legumes like peas do.

Chris - Giles, do tell. What have peas therefore got the corn, wheat, barley, et cetera, doesn't.

Giles - Yes. So peas and beans have learned to engage with these nitrogen fixing bacteria that can colonize the roots of the peas, and they're able to convert nitrogen from the atmosphere into a reactive form of nitrogen that plants can use and then incorporate into amino acids, proteins, DNA, and RNA, et cetera.

Chris - How good are they doing that, Giles? As in, if you compared a bag of fertiliser and a pea plant, how much better is the fertiliser than the pea or vice versa?

Giles - Well, the pea plant doesn't need any fertilisation, so that's how good they are. They get all of their nitrogen from the air through this interaction with the bacteria. And if you compare that to a wheat or maze, you're getting most of the nitrogen through fertiliser application.

Chris - And your goal then is to say, well, we learn how the pea does it, we then borrow from the biology and we endow the wheat with the way the pea does it.

Giles - That's right. So for the last 20 years, myself and many others in the research community have been trying to understand how peas are actually engaging with these nitrogen fixing bacteria and identifying the genetic components that are present in peas and beans that allow them to recognize the bacteria in the soil and attract those bacteria into those roots, and then also create the environment for nitrogen fixation.

Chris - Would this be genetic engineering?

Giles - Correct.

Chris - And then you take the genetic elements from the pea and insert those into the wheat so that it can produce the right sort of factors and environments. So those microorganisms that are there get recruited into the wheat roots.

Giles - That's right. So we now have a really good understanding of how peas are able to engage with these nitrogen fixing bacteria. We know pretty well, at least a lot of the genetic components that are involved in that process. And so now we're in the process of putting those genes from taking them from peas, putting them into our cereal crops and trying to get our cereal crops to engage with these nitrogen fixing bacteria. Such that we can grow those cereal crops without the need for adding nitrogen.

Chris - Does it work?

Giles - We are in the process of doing it, so we just got the money to do that, to do all of that engineering. We've been working for a long time using funds from the Bill & Melinda Gates Foundation to understand that process in legumes. And we're really now pushing into that sort of product concept of how we actually make that system work and get the cereals to actually fix their own nitrogen.

Chris - I suppose that if you are able to do this and plants effectively become self fertilising, it means we are dosing soils less, which has got to be good for farmer's pockets. It's gotta be good for the environment. But it presumably also means that people who live in areas where the soils are naturally poorer and would have to use more fertilisers, presumably they're gonna be extremely pleased with your work because it means that they'll get a better yield out of their crops too.

Giles - So when we look at nitrogen, it's like a two-sided coin. Here in high income countries like the UK and particularly here in Cambridgeshire, we are applying fertilisers at high concentrations to support our crop productivity. That's essentially the green revolution and that green revolution, which allowed us to apply these nitrogenous fertilisers. It's tripled the yields of our cereal products. So we are really heavily reliant on the use of inorganic fertilisers to maintain our crop production. But the use of those fertilisers is very polluting. It's one of the major pollutants deriving from agriculture, both washing into our aquatic systems and causing biodiversity collapse, but also causing greenhouse gas emissions. So here in the UK and then for instance here in Cambridgeshire, if we could stop using those nitrogenous fertilisers have a much more sustainable way of growing our food. On the other side of the coin, if you look at much lower income countries like Sub-Saharan Africa, the farmers there don't have the financial resources to buy these fertilisers. And because of that, their crop production is really atrocious. I mean, we're talking about 20% of the potential production that they could actually be achieving, in part because of the lack of these inorganic fertilisers. So we can find ways of getting nitrogen into those systems, and particularly sustainable ways of getting nitrogen into those systems. We can massively raise up crop production for smallholder farmers. So really, if we can make this work, it could be truly transformative of our food production systems. Driving sustainability in high income countries and driving equity of global food production, particularly for smallholder farmers.

Chris - And just in the last minute, will this work everywhere? Because if the microbes are coming out of the soil and forming those relationships with pea plants, if you try and grow plants in places where peas wouldn't normally grow, will it work? In other words, are these microbes sufficiently universal that if you go and plant your modified plants in sub-Saharan Africa, those, uh, bacteria are there and the plants can use them?

Giles - So we know these nitrogen fixing bacteria are ubiquitous in soils across the world. But there are specialized bacteria that associate with peas and different bacteria that associate with beans. So it might be that you'd have to use inoculants and certainly in soil production in the US they're using inoculants. But once you've used those inoculants and got that, you actually plant the seed there.

Chris - That's where you physically add the stuff to the soil.

Giles - Yeah exactly. You plant the seed and you bring the bacteria with it. But often when you've done that inoculation, those bacteria then present in the soil and they're maintained in the soil. So you don't have to inoculate every year the bacteria reside within the soil and the next time you plant the, the crop, the bacteria there, the crop can find them and form that nitrogen fixing back association.


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