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Author Topic: Are govt nitrogen limits for compost/mulch application a threat to no-dig?  (Read 113001 times)

jonnygutteridge

  • Joined Sep 2023
Hi

I'm thinking about starting a no-dig market garden and I've just come across the issue of UK government rules (https://www.gov.uk/government/collections/nitrate-vulnerable-zones) on the amount of nitrogen fertilizer that can be applied per hectare.  Given that no-dig methods rely on adding and growing in a thick layer of compost/manure the government rules seem to prevent no-dig at the scale required for a market garden.  For example I calculate that applying Earthcycle Compost Mulch in 15mm deep beds of 20m x 0.75m, I'd be limited to between five and ten beds per hectare, which just isn't enough for a viable business.

This does seem to be a genuine issue. This academic article is a useful explainer: "Excessive Nitrate Limits the Sustainability of Deep Compost Mulch in Organic Market Gardening" https://www.mdpi.com/2077-0472/13/5/1080.

The article states that commercial no-dig specialist Richard Perkins says it's not an issue because the excess nitrates don't run off. If true, perhaps UK legislation needs to catch up with the science.

What do you think?  I'd love to hear from anyone who can give me confidence that it's OK to go ahead with my market garden.

Jonny

Steph Hen

  • Joined Jul 2013
  • Angus Scotland.
I think in terms of the calculations you could be right.
However in theory nitrogen doesnít leach from compost much. Charles Dowding claims it doesnít leach. I donít know whatís been described in the scientific literature.

Farmers are regulated in how much they can apply whereas no oneís asking gardeners, smallholders and market gardeners for the moment at least. 


Fleecewife

  • Joined May 2010
  • South Lanarkshire
    • ScotHebs
I used to run my brother's farm which is in a nitrate sensitive zone. I was petrified whenever I got letters from them!


For farms, the amount of fertiliser applied will be reflected in the run-off and the proximity of streams and rivers will affect how badly the environment is impacted.  The amount of humus in the soil will be reflected in run-off too, where seriously depleted soils will have a lot more run off than healthy, humus rich soils.


For vegetable growing, I suggest you don't overdo the application of manures and feeds which are very rich in nitrogen.  In fact that's part of organic growing, you just apply what is needed, no overdosing, and you apply it to the soil where you will be growing those plants that need it when they need it. That sounds as if I'm meaning liquid feeds but I mean feeding the soil.  You will know which groups of plants need nitrogen, such as brassicas, which need potassium such as tomatoes and so on.  So by careful crop rotation and mulching with appropriate manures, green manures, garden compost, then by giving manure tea, comfrey tea, nettle tea or whatever is needed as an occasional boost, you should be able to match feeding to take-up and keep leaching to a minimum. Green manures over winter are important for the prevention of leaching and if you don't use them now they are well worth investigating.
So don't go OTT with the depth of the manure in your initial no-dig areas but match it to the crops you intend to grow there.
Another point I heard of a few years ago, when the government was introducing rules on drainage from muck heaps, is that the problem is mainly for heaps on concrete where there is visible runoff.  Gardeners were up in arms, but it doesn't seem to be a problem with domestic garden compost heaps on soil.
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