Manure is a natural fertilizer consisting of the excrement (feces and urine) of livestock and litter, while bird manure, consisting of poultry manure, comes from a litter-free animal husbandry system.
In the so-called “shallow litter” system of livestock farming, in addition to solid manure, a slurry is produced, i.e., fermented urine with a tiny fraction of faeces penetrating the litter layer and collected in special containers.
The liquid manure is produced in non-cage systems and is a mixture of animal manure and water from cleaning stalls and watering.
The chemical composition of manures is variable and depends on the species, age, the direction of use, and feeding of animals, as well as on the conditions of manure storage.
For the rational and lawful use of natural fertilisers, it is necessary to determine the permissible and optimal dose of fertilizers. An acceptable rate is one in which the amount of nitrogen input does not exceed 170 kg N/ha. Depending on plant nutritional requirements and the abundance of soil, the optimal dose may be lower than the acceptable one. When applying natural fertilizers frequently and in large amounts, particular attention should be paid to the abundance of phosphorus in soils, whose excessive accumulation may threaten the aquatic environment.
The most accurate method of estimating the composition of natural fertilizers is laboratory analysis.
For the above purpose, a fertiliser sample (taken in a representative way) should be delivered to the laboratory of a district chemical and agricultural station or another agrochemical laboratory. The most critical parameters to be determined in the fertiliser are the content of nitrogen, phosphorus, and potassium. Based on the results obtained, calculate the rate of fertilizer that can be used not exceeding the allowable amount of nitrogen ( 170 kg N/ha). Next, calculate the amount of phosphorus and potassium contained in the fertiliser.

Another method of fertiliser composition estimation and the amount of fertilizer production in a farm is to implement a natural fertiliser production model elaborated by IUNG-PIB, available online (polish version) as an internet calculator. The same model is also incorporated into computer-based fertiliser advisory programs.

If no fertiliser chemical analysis or modeling results are available, standard fertiliser mineral components (tables below) can be used for fertilisation planning.

The maximum permissible fertiliser rate is calculated by dividing the allowable nitrogen rate by the content of the component in 1 ton or 1 m3 of fertiliser. E.g. 1 tonne of cattle liquid manure according to the table contains 3.4 kg N, therefore the permissible fertiliser application rate for 1 ha is: 170 kg N/ha : 3.4 kg N/t = 50 t/ha = 50 m3/ha.

• The weight of 1 m3 of slurry and liquid manure is assumed to be about 1 t (1000 kg)

Poultry manure, also known as bird manure, is a natural fertiliser composed of poultry excrements and litter. Ammonia-reducing agents may be added to the manure. Poultry manure is used to fertilise soils and produce various organic substrates, e.g., for mushroom growing. The chemical composition of above mentioned manure varies depending on the species. The hen manure contains on average 1.6% N; 1.5% P2O5; 0.8% K2O; 2.4% CaO and 0.7% MgO with 56% water content. Waterfowl manure (ducks and geese) contains 0.5-1.0% N; 0.5-1.4% P2O5; 0.6-0.9% K2O; 0.8-1.6% CaO and 0.2-0.3% MgO at 70% water content. Nitrogen in poultry manure is predominantly in the form of uric acid, which rapidly breaks down to ammonia. Poultry manure is recommended to be applied in rates of 10-15 t/ha, to the same plants and at the same timing as conventional manure.

In addition to nitrogen, it is also necessary to control the input of phosphorus and potassium in manures. The amount of fertiliser intended to be applied, expressed in t/ha or m3/ha should be multiplied by the content of P2O5 and K2O in 1 ton or 1m3 of fertiliser in order to calculate the amount of phosphorus and potassium input.

In the example provided above, the amount of phosphorus input is: 50 t/ha  * 2.0 kg  P2O5/m3 = 100 kg P2O5/ha, and potassium: 50 t/ha * 3.7 kg K2O/t = 185 kg K2O/ha.

The calculated amounts of nutrients, especially phosphorus, may be excessively high in soils rich in the element. In such cases, it is recommended to reduce the application rate of manure and adjust it to the needs of fertilisation in a given field.

Plant uptake of nutrients from natural fertilisers, and in particular from manure, is lower than from mineral ones. Therefore, for fertilisation planning, the input of nutrients from natural fertilisers is converted into so-called active ingredients through appropriate nitrogen fertilisation equivalents and phosphorus and potassium conversion factors.

Nitrogen fertilisation equivalents and phosphorus and potassium conversion factors.
(Journal of Laws 2020, item 243, Annex 8, table 11)

The amount of active ingredients is calculated by multiplying the total amount of an element carried in manure by the appropriate value from the table. The value obtained indicates by how much the rate of mineral fertilisers (resulting from the needs of fertilisation in a given field) should be reduced after the application of natural fertilisers.