Nitrogen Reduction, Recycling and Reuse (Environment and Climate Change Committee Report)

Lord Krebs Excerpts

Tuesday 6th January 2026 Grand Committee

[Lord Krebs (CB)]

My Lords, I thank our chair for her excellent leadership in this inquiry, our clerk and our policy analyst for their excellent work and our specialist adviser, Professor Mark Sutton, for keeping us on the straight and narrow.

Our chair’s introduction was so excellent that I am tempted to simply say two words, “I agree”, and sit down. On the other hand, now that I am standing, the temptation to carry on speaking is too great. I am going to talk about agriculture. The noble Earl, Lord Leicester, having glanced nervously at me, I am glancing very nervously at him because he actually is a farmer while I have experienced farming only at second or third hand.

Agriculture, as we have heard, is the biggest source of nitrogen pollution, accounting for 87% of ammonia and 69% of nitrous oxide released into the atmosphere and 70% of nitrate leaching into water. The evidence that we heard, as has been said, suggested that nitrogen use in agriculture is inefficient and wasteful and creates unnecessary pollution, although of course that does not apply to the noble Earl, Lord Leicester. According to one estimate we heard, 45% of fertiliser added to crops is lost to the environment.

On our visit to the Netherlands, we saw that there are simple ways to reduce nitrogen pollution from farms. For example, farmers there showed us that dairy cattle can be fed on a diet with less nitrogen in it, which does not affect milk yield but reduces ammonia emissions to the atmosphere. We were also shown how the precision application of slurry, which is mandatory in the Netherlands but not here, reduces the leaching of nitrate into fresh water. In the Netherlands, research results from Wageningen University on how to reduce nitrogen pollution are disseminated to farmers via a peer-to-peer network. For some inexplicable reason, these and other equally effective and inexpensive measures are not mandated or widely adopted in this country. I therefore ask the Minister whether she agrees that we could learn lessons from, and indeed follow, the Dutch example.

We were told that farmers pay a price for their inefficient use of fertiliser. We have already heard some of the figures—Natural England estimated the cost as between £21 and £52 per hectare, totalling about £397 million per year for the agricultural sector, while the Sustainable Nitrogen Alliance, as we have heard from others, quoted a figure of £420 million of fertiliser wasted annually—but there are also much bigger costs to society and to the economy that are not paid for by farmers, the so-called externalities. As our chair mentioned, nitrogen pollution is damaging our ecosystems and the services they provide. According to the Joint Nature Conservation Committee, about 30% of the loss of biodiversity in the UK is attributable to nitrogen pollution, and 99.9% of sensitive habitats exceed the critical load for nitrogen deposition.

Secondly, nitrogen pollution is causing global warming, with all the costs and risks that result. Nitrous oxide is a potent greenhouse gas that is 270 times more powerful than carbon dioxide. As I have said, 69% of atmospheric nitrous oxide in this country comes from agriculture.

Thirdly, nitrogen pollution damages our health. Many of our city streets exceed WHO safety limits for fine particulate matter that arises in part from agricultural nitrogen pollution. When you step outside the Palace of Westminster and breathe in these fine particles, remember that it is estimated that between a third and a half of them result from ammonia pollution from agriculture; also remember that they will increase your chances of developing various forms of cardiovascular disease, respiratory disease, cancer and dementia.

All these impacts of nitrogen pollution impose costs on our economy. As a nation, we would be wealthier, as well as healthier, if we got a grip on the problem. Estimates of the total cost of nitrogen pollution from all sources vary widely, but the WWF quoted a central estimate of around £11 billion per year; agriculture contributes a significant fraction of this. To get a fix on what that looks like, I checked: it is about a sixth of our annual expenditure on secondary education in this country.

Having heard the evidence, I was puzzled. If farmers are generating unnecessary nitrogen pollution that is costly to themselves and even more costly to society in general, why do they carry on doing it? The puzzle is even greater when you learn, as we did, that applying less fertiliser appears not to reduce crop yields; this is described in box 1 of our report. Over the past 40 years, crop yields have tended to increase irrespective of the amount of fertiliser applied. Perhaps, as the noble Earl, Lord Leicester, said, many other factors—rainfall, temperature and so on—affect variation in crop yield. But when fertiliser application went down because of the price increase following Russia’s invasion of Ukraine, crop yields were apparently unaffected.

This suggests that factors other than fertiliser use are limiting productivity and, therefore, that farmers are applying too much fertiliser. Why would they do this? We were told by several witnesses that at least part of the problem may be that farmers do not have easy access to appropriate and trusted advice on nitrogen management. The Government agree with this conclusion that clearer advice for farmers is needed. In their reply to our report, they say:

“Defra are developing an online, free-to-use, nutrient management planning tool for Great Britain (NMPT-GB)”—


catchy title. They go on:

“NMPT-GB will be designed to help farmers and land managers in England, Wales, and Scotland to plan and manage nutrient use on their land”.


The tool, which was launched in a public beta version last month, sounds very good but, as far as I could ascertain, it does not contain any new information about fertiliser application. Instead, it uses the pre-existing Agriculture and Horticulture Development Board’s Nutrient Management Guide (RB209). This guide has been available since 2017, but I was not able to find out whether it has been successful in persuading farmers to reduce nitrogen pollution from fertiliser application. I therefore ask the Minister: has there been an assessment of the impact of the AHDB guide so far?

The guide does, however, provide clear advice on how much fertiliser to apply. This is set out on page 16 of the document in a section entitled “Principles of nutrient management and fertiliser use”. The guide states the following:

“The crop nitrogen requirement is the amount of nitrogen that should be applied to give the on-farm economic optimum yield”;


this is the point at which the marginal financial cost of adding more fertiliser would not pay for itself in the marginal financial returns of increased crop yield. In other words, the advice from the AHDB is to maximise net financial gain per hectare; of course, this ignores the other costs of producing the crops, such as machinery and labour. The detailed guidance also provides recommended inputs of nitrogen and other nutrients according to crop type, soil type and rainfall. So the information is out there; it is the just the case that, apparently, farmers either do not use it or do not know about it.

However—I return to the point made by the noble Earl, Lord Leicester—when we heard evidence from the fertiliser industry, it suggested an alternative metric: nitrogen use efficiency. This is the ratio of nitrogen input to nitrogen output. For me—this is the reason why I debated this measure with the committee—the problem with this measure is that it does not tell you about profitability per hectare, which is the thing in which I would have expected farmers to be interested and on which the AHDB guidance is based. Does the Minister agree with me that maximising net financial gain per hectare, as in the AHDB guidance, is a more appropriate guidance metric than maximising nitrogen use efficiency, as claimed by the fertiliser industry?

However, this is not the end of the story. As I have already mentioned, the societal cost of nitrogen pollution is borne not only by the farmer but by the rest of us. The “polluter pays” principle, which is one of the five environmental principles that Ministers should consider when making policy, suggests that these costs should be borne by those who produce the pollution. I therefore ask the Minister whether it would be appropriate to amend the guidance on fertiliser use in future to reflect not just the direct costs of the fertiliser to the farmer but the total cost to the country. Perhaps, if the costs of nitrogen pollution and fertiliser use reflected its true impact and cost to society, as well as the specific cost to farmers, we would see more judicious management of nitrogen and less damaging nitrogen pollution. I look forward to the Minister’s reply and to other contributions to this debate.