Organic Farming Manure Calculation: 170 kg/ha N Limit

1) 170 kg/ha “pure nitrogen” limit: What do the EU and Turkish Regulations say?

EU Organic Regulation

According to Regulation (EU) 2018/848 (consolidated text) Annex II, Chapter III,  Part I;

1.9.4 The total amount of livestock manure, as defined in Directive 91/676/EEC, used in the in-conversion and organic production units shall not exceed 170 kg of nitrogen per year/hectare of agricultural area used. That limit shall only apply to the use of farmyard manure, dried farmyard manure and dehydrated poultry manure, composted animal excrement, including poultry manure, composted farmyard manure and liquid animal excrement.

1.9.5. Operators of agricultural holdings may establish written cooperation
agreements exclusively with operators of other agricultural holdings and undertakings which comply with the organic production rules, for the purpose of spreading surplus manure from organic production units. The maximum limit referred to in point 1.9.4 shall be calculated on the basis of all of the organic production units involved in such cooperation.

According to TR Regulation No. 27676
Article 9(1)(c)(2);It is permitted to use animal manure from organic production or organic materials, preferably both composted. In order to prevent agricultural nitrogen from causing water pollution, the total amount of livestock manure to be used in organic plant production cannot exceed 170 kg N/ha/year. This limit applies only to the use of farmyard manure, dried farmyard manure, dried poultry manure, composted animal excreta including poultry manure, composted farmyard manure, and liquid animal excreta.

Article 16(1)(ç); Animals must have access to pastures, open-air play areas, or open spaces. The number of animals per unit area in pastures and open spaces must be limited to provide sufficient animal manure for the crop production in the production unit. Animal density is determined by the amount of nitrogen emitted, not to exceed 170 kg/N/ha/year on the agricultural land used. If this amount is exceeded, the entrepreneur must acquire another area in the same area or, with the knowledge of the authorized institution, obtain this opportunity from neighboring businesses. The authorized institution may reduce animal density for environmental protection purposes.

So both Regulations deal with the issue almost in the same way. In this case, how will the producer know how much manure can be used without exceeding the 170 kg/ha/year limit?

2) Nitrogen Ratios According to Animal Species

Naturally, the nitrogen ratio in manure must be known, but as you might guess, the amount of N in manure differs depending on the animal species. So how or where can we find the N ratios according to animal species?

Here we have a small problem: the regulations have set a restriction regarding the amount of N, but they have not provided a universally applicable source that shows “N percentages by animal species” which would allow this rule to be applied in a standardized way.

It is possible to find some information on N percentages by animal species on the internet. For example, you can check the following links:

Utah State University source – See Table 1

*Minnesota Department of Agriculture (MDA) – See Table 3

*Pennsylvania State University – See Table 1

*: In these two examples, the unit lb is used. When reviewing the figures, you need to make the conversion “1 ton = 2000 lb”.

Also, when you ask ChatGPT this question, it provides an answer consisting of average values, but it is almost impossible to accept any of this information as universally valid. The reasons are:

  Great variability: N content varies significantly depending on animal species, ration/diet, bedding type (straw, sawdust), housing conditions, storage/maturation, dilution with liquids, and method of application.

  Losses: During storage and application, N losses occur through ammonia volatilization and other means; literature reports that the plant-available N in the first year may vary between 10–80%.

  Table values are averages: Expert sources provide average N values (e.g., “cattle solid manure ~5–10 kg N/ton”), but without field-specific analysis, uncertainty remains.

3) Calculating the Nitrogen Content of Manure Applied to Land

With this limited information, let us calculate whether the N content of a planned manure application exceeds the 170 kg/ha/year limit.

In some field practices, for cattle manure an approximate assumption of 0.5% N is common.
(Note: The Samsun Provincial Directorate’s booklet “Organic Fertilizers and Their Importance” reports 0.29% N in fresh cattle manure as an example; depending on conditions, it may be lower/higher.)

Example 1: Assuming 0.5% N in cattle manure — does 10 tons of manure exceed the limit on 24.7 decares of land?

Givens

• Land: 24.7 decares = 2.47 ha
• Manure amount: 10 tons (10,000 kg)
• Total N percentage assumption: 0.5%

Steps

• Total N (kg) = 10,000 kg × 0.005 = 50 kg N
• Nitrogen per hectare = 50 kg ÷ 2.47 ha ≈ 20.24 kg N/ha
• Decision: 20.24 kg N/ha ≪ 170 kg/ha, so the limit is not exceeded.

Example 2: Poultry manure — quickly exceeding the limit

Scenario

• Land: 1 ha
• Manure: Broiler litter (solid) 10 tons
• Typical total N assumption: 3% (0.03) — in the literature, poultry manure has significantly higher N than cattle manure.

Calculation

• Total N = 10,000 kg × 0.03 = 300 kg N
• Nitrogen per hectare = 300 kg N/ha → 170 kg/ha limit exceeded.

4) How does USDA NOP (US) organic regulation address animal manure?

USDA NOP (7 CFR §205.203) does not set a numerical limit such as 170 kg/ha N. Instead, it introduces the “90/120 day” harvest interval rule for raw (uncomposted) manure applications:

• For edible crops in direct contact with soil: harvest at least 120 days after application.
• For edible crops not in contact with soil: harvest at least 90 days after application.

Technical criteria are also provided for compost and processed materials; composted plant and animal materials produced by performing the following operations:

(i) Established an initial C:N ratio of between 25:1 and 40:1; and

(ii) Maintained a temperature of between 131 °F and 170 °F for 3 days using an in-vessel or static aerated pile system; or

(iii) Maintained a temperature of between 131 °F and 170 °F for 15 days using a windrow composting system, during which period, the materials must be turned a minimum of five times.

5) Nitrogen Limits According to Standards
KRAV:
You may add a maximum of 170 kg nitrogen per hectare of spreading area and year with fertiliser. (does not apply to greenhouses)
You must calculate the addition as an average total amount of nitrogen in the manure. You must report the calculation per hectare as an average value for your KRAV-certified arable land area. (For more detailed information, see the KRAV standard. 4.6.8)

BİO SUISSE:
The amount of fertiliser applied must be adapted to the site and to climatic conditions. The total nutrients applied per ha under optimum conditions may not exceed the equivalent of 2.5 livestock manure units/ha of fertilisable land in lowland areas. To calculate the average number of animals on a farming operation, the stocking intensity of the various plots must be taken into account. In covered cultivation, more than the equivalent of 2.5 livestock manure units/ha FL(10) (i.e. 135 kg available nitrogen) may be applied if it can be demonstrated that the crops require a higher input (in conformance with the Suisse-Bilanz method). (For more detailed information, see the BioSuiise standard. 2.4.2.1)

DEMETER:
For Arable farming – up to 112 kg N/ha/yr
For Market Gardens– up to 112 kg N/ha/yr
For Perennials – The total amount of nitrogen applied from all types of fertilisers used, may not exceed 96 kg N/ha/y in general, 50 kg N/ha/y for viticulture (calculated as an average over three years) and 170 kg N/ha/y for perennials in the (sub)tropics – based on the total area of the farm.  (For more detailed information, see the Demeter Standard. 6.1.3.1)

NATURLAND:
When growing vegetables in the open, nitrogen fertilization must not exceed 110 kg N/ha per year on average in vegetable cultivation areas. For greenhouses, due to the higher degree of nutrient decomposi-tion in the soil on account of a higher degree of cultivation intensity, more concentrated manure applica-tion (over 110 kg/ha per year) may be permissible in some cases after consultation with Naturland. In or-der to prevent over- or undersupply, the soil’s or substratum’s nutrient and soil organic matter content must be analysed at least every third year. (For more detailed information, see the NATURLAND Standard. PART B,III,1.1.)