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Blog - New NVZ Rules

Last updated: 30 Jul 2013


NVZs have been around for some fifteen years and they say familiarity breeds contempt – well not contempt in this case but perhaps some complacency. Then just when you think everything’s settled down, the rules change. This is because the original EC Directive includes a requirement to review the rules at least every four years and the latest reviews in England and Scotland have just been completed. There have been some important changes which will catch out the unwary, especially as some of the changes don’t take effect until 2014.

Slurry Spreading


In England, changes that came into effect in May include narrowing the organic manure no-spread zone beside watercourses to 6m where precision spreading equipment is used. This will encourage the use of trailing shoe, trailing hose and shallow injection equipment which will bring benefits across the whole field by reducing N loss to the air. Certain compost can now be applied at 500 kg total N/ha every two years provided this is the only organic manure applied. This recognizes the slow release of N from compost.


Calculator and finances_275_183From January 2014, the method of calculating Nmax will change. All organic manures, not just livestock manures, will have to be taken into account. This has always been the rule in Scotland and it didn’t really make sense to include livestock manures but to exclude sewage sludge and compost. Also, Nmax will be extended to cover many field horticultural crops. Two changes will affect spreading of high-readily available N organic manures. The percentage of total N you must assume is crop available will increase – from 35% to 40% for cattle slurry and from 45% to 50% for pig slurry – and the closed period on medium or heavy soils will end two weeks later on 31st January. The first of these changes will encourage spreading in spring but the second will narrow the spreading window. Coping with the new Nmax will be a big issue next year.

The percentage crop available N in manures causes a lot of confusion because the values that must be used for Nmax calculations can be different to those in the Fertiliser Manual (RB209). For Nmax calculations, use the percentages in the NVZ guidance but for all other purposes, use those in the Fertiliser Manual.

There are other changes to the rules including some to record keeping, field manure heaps and grass for chlorophyll or protein. Some rules take effect later in NVZs that were first designated this year. Defra has produced guidance that is clear and well laid out but available in pdf only at A hard copy version would be good, even if priced. There is other information on NVZs at

There have been changes to NVZ rules in Scotland too though fewer than those in England. Changes to compost application, closed periods and crop available N in cattle and pig slurry are similar to those in England. Nmax now applies to some minor crops previously not covered (limits are the N recommendations in SAC Technical Notes). Records must be kept for three years instead of five years. Details of changes in Scotland are at