Fertilisation with organic matter : soil enrichement for the pasture

What is organic matter?

Organic matter is made up of carbon molecules (C : Carbon) associated to the folowing chemical elemnts : H (hydrogen), O (oxygen), N (Nitrogen). Organic matter is produced by animals and plants, and is made up of decomposing residual waste from animals and plants, or macro-molecules from structurally evolved matter such as humus.

What is organic soil enrichment ?

Organic enrichment is a stable product from composting, or from a mixture of plant waste, and fresh more or less stabilised products such as  farm effluents (liquid manure, manure….)

The action is threefold :

• Soil enrichement: The effect is to add structure to the soil. It increases the Capacity of Exchange of Cations (CEC) and the useful reservoir (Capacity of the soil to retain water). It contributes to soil fertility.
• Fertilising: It provides the elements N, P and K, as well as the micro-nutrients the plant needs to develop and grow.
• Living matter: it is composed of micro-organisms (bacteria, fungus,….) which will contribute by mineralising organic matter, i.e transforming it into nutritive ions  (NO3-, HPO42-) for the plant.

Manure is best spread on mowed  fields used for hay, as fodder exports mineral elements, whereas grazing animals will restitute organic matter in the form of droppings and urine.

The main humus-rich enrichements which can be spread on fields, are manure and manure compost. The level of decomposition of plant or animal waste used as soil-enrichement is variable. A laboratory chemical analysis (~30 to 50 €) is advisable, to have a good idea of the agronomical worth of the product to be spread.

Spreading manure

Manure is a heterogenous compound of droppings and straw, more or less soaked in urine. The composition, and fertilising value depends on the type of bedding used, the proportion of straw, the way the horse is stabled, and the way the manure is stored in a manure pit.

Spreading manure entails less work than implementing a compost heap. Nevertheless there are more drawbacks:

• The produit has not been de-odorised. It can contain pathogens (eggs of digestive parasites).
• Ammonia loss when spreading manure is greater than when spreading compost.
• It is difficult to break down manure in a homogenous fashion, and straw decays slowly on the ground. This can give rise to a deterioration of the plant cover, and loss of palatability for the animals. The distance from third party dwellings is regulated to 50m.

Spreading compost

Compost is a soil enrichment made up from stable humus and fertilising elements (N, P, K, Ca, Mg). It is de-odorised and there are no problems relating to palatability of the pasture for animals. Animals can be returned to the pasture 3 weeks after spreading.

It is also exempt from pathogens (such as Parascaris and Rhodococcus) and seeds from weeds. This is due to sanitising which occurs through increased temperatures, and the fermentation process.

Compost has a finer texture, which allows for regularity in spreading, and fast penetration into the soil. Compost is less bulky,and easier to spread than manure.

Appropriate type of horse manure for compost

Horse manure is the only manure suitable for composting, providing it contains enough fecal waste ( « Ripe » manure, soaked in urine and droppings). 

Examples of agronomical values of horse manure and horse manure compost

Spreading 15 to 20 tons/ha of manure or compost is required to cover the needs to upkeep average natural pasture land, producing 6 tons of dry matter. This is for a compost based on horse manure, with the following agronomical values (kg per ton of gross product):

• N : 5,2
• P : 3,7
• K : 7,9
• Ca : 12,1
• Mg : 1,6

When spreading 15 tons per hectare, the value measured in agronomic units is the following :