Manure

Role of manures

To achieve the process of their vegetable life, the plants need water, of almost twenty nutritive elements which they find in mineral form in the ground, of carbon dioxide (CO₂) brought by the air, and of solar energy necessary to the chlorophyllian synthesis.

Manures bring:

of the basic elements, Nitrogen (NR), Potassium (K), Phosphorus (P); one speaks about manures of the type NPK if the three are associated unit. If not one also speaks about NR, NP, NK, km No;
of the secondary elements, Calcium (Ca), Soufre (S), Magnésium (Mg),
of the Oligo-élément S such as the Fer (Fe), the Manganèse (mn), the Molybdène (Mo), the Cuivre (Cu), the Bore (B), the Zinc (Zn), the Chlore (Cl), the Sodium (Na), the Cobalt (Co), the Vanadium (Goes) and the Silicium (If).

These secondary elements are usually in sufficient quantity in the ground, and they are added only in the event of Carence.

The plants need relatively large quantities of the basic elements. The nitrogen, phosphorus and potassium are thus the elements which it is necessary to generally add on the ground, and they constitute the base of the majority of manures sold nowadays. the nitrogen most important among them, and the most are discussed because of the phenomenon of scrubbing, bound strong solubility in water of nitrates. By the proceeded Haber-Bosch a percent of the power consumption by the human ones produces Ammoniac which provides half of nitrogen necessary to agriculture.

Calcic lime is a source of calcium and dolomitic lime provides calcium and magnesium. Sulfur is generally present in sufficient quantity in the ground.

Types of manure

Manures can be of three types: organomineral organics, minerals and.

Organic manures

The organic Engrais S are generally of animal or vegetable origin. They can also be synthesized (Urée for example).

The first are typically industrial waste such as waste of slaughter-houses (desiccated blood, torrefied Corne, fish scrap, muds of purification of water). They are interesting by their nitrogen contribution with relatively slow decomposition, and by their action supporting the fast multiplication of the Microflore of the ground, but hardly enrich the ground in stable Humus.

The seconds can be vegetation wastes (green Résidus), Compost be or not. But it can be also crop plants especially like Manures green or prepared to this end (Purin of nettle, Algue S). They are also by-products of the breeding, such as Fumier S (composition of the majority of the manures: vegetable litter and dejections - which are not animal matters but more or less digested plants), Lisier, Fiente S, etc

The principle of the green manure takes again the ancestral practice which consists in hiding the Mauvaises grass . It rests on a intercalated Culture, which is hidden on the spot. When it is about Légumineuse S such as the alfalfa or the Trèfle, one obtains in more one enrichment of the ground out of assimilable nitrogen because their system racinaire associates Bactérie S, kind Rhizobium, able to fix atmospheric nitrogen. To make this technique more effective, one sows beforehand seeds with the associated bacterium.

Mineral manures

The mineral manures are substances of mineral origin, products either by chemical industry, or by the exploitation of layer natural (phosphate, potash).

Chemical industry intervenes especially in the Production of the manures nitrogenized, which passes by the synthesis of the Ammoniac starting from nitrogen of the air, with the help of an important contribution of energy provided by the Natural gas (which also provides the Hydrogène). ammonia is derived the Urée and the Nitrate. It also intervenes for the manufacture of complex manures, which are consisted salt S resulting from the reaction of a bases with a Acide. Made up manures can be simple mixtures, sometimes carried out by the distributers (co-operatives or traders). One calls these mixtures of the Bulk Blending.

One distinguishes simple manures (containing one nutritive element) and made up manures (which can contain two or three of them). The name of mineral manures is standardized, by reference to their three main components: NPK. Simple manures can be nitrogenized, phosphatic or potassic. Binary manures are noted NP or km No or NK, the ternary NPK. These letters are generally followed figures, representing the respective proportions of the elements. The industrially produced artificial fertilizers contain a guaranteed minimal quantity of nutritive elements, and it is indicated on the bag.

For example, formula 5-10-5 indicates the proportion of nitrogen (NR), phosphorus (P) and potassium (K) present in manure, that is to say 5% of NR, 10% of P₂O₅ and 5% of K₂O.

the nitrogenized contribution is expressed in Azote NR and is brought either in the form of Nitrate NO₃, of ammonium NH₄ or urea. The constraints of storage of the form nitrate encourage the muck-spreaders to turn to ureic ammoniacal forms.
the Phosphore is expressed in the P₂O₅ form but is brought in the form of Phosphate S of calcium or ammonium.
the Potassium is expressed in the K₂O form but is brought by Chlorure, Nitrate and Sulfate of potassium.

Organomineral manures

Organomineral manures result from the mixture of mineral manures and organic manures.

Composition of manures

See also List of manures

Some examples of simple manures

the urea (nitrogen 46%), the ammonia sulfate (SA, nitrogen 21%), the ammonitrate (YEAR, 33.5% of nitrogen) and nitrates it lime (CAN/NAC, up to nitrogen 27%) do not contain that nitrogen (NR);
simple superphosphate (SP, 18% of phosphorus) or triple superphosphate (TSP, 46% of phosphorus) contains only phosphorus (P₂O₅)
the chloride potassium (potassium 60%) contains only potash (K₂O). The potassium sulfate (SOP, 50% of K₂O) also contains sulfur 18%.

Among other current manures which, in addition to the principal nutritive elements, contain sulfur (S) one can quote simple manures: sulfate of ammonia or SA which has sulfur 24% and the SSP which has 12% of them.

Some examples of made up manures

the diammonium phosphate contains at the same time NR and P. the most current formulas are the 18-46-0 and 20-20-0.
the potassium nitrate contains at the same time NR and K.

Application of manures

Generally, manures are incorporated in the ground, but they can also be brought by the water of Irrigation. This last technique is employed as well for the cultures in ground (traditional), as except ground (on more or less inert substrate, such as composts, peats, rockwool, pearlite, Vermiculite, etc). Another particular technique, the hydroponic culture, makes it possible to nourish the plants with or without substrate. The roots develop thanks to a nutritive solution - water plus manure which circulates with their contact. The composition and the concentration of the nutritive solution must be constantly readjusted.

In certain cases, part of the fertilization can be realized by foliar way, in pulverization. Indeed, the sheets are able to absorb manures, if they are soluble and if the surface of the sheet remains wet long enough. This absorption remains however limited in quantity. In fact thus rather the Oligo-élément S can be brought thus, taking into account the small quantities necessary to the plants.

On acid grounds, one can proceed to the Chaulage to increase the pH. This measurement increases the effectiveness of manures by supporting the assimilation by the plants of the nutritive elements present in the ground.

Manures must be used with precaution. It is generally suggested

avoiding excesses, because beyond certain thresholds the additional contributions not only do not have any more any economic interest, but moreover are likely to be toxic for the plants (in particular trace elements), and to harm the environment;
to control their effects on acidity of the ground;
to take account of the possible interactions between the chemical elements;
to take account of the limits imposed by the other factors of production.

Proportion manure

The amount of manure is the quantity of manure to be brought for a certain surface or a certain number plants. Ideally, the quantity brought would have

to be sufficient to meet the needs for the plant (in order to guarantee the output, quality, growth rate, even the beauty, wished),
without however exceeding them (in order to limit the cost of the fertilization, as well as the environmental impact. A too high amount can also damage a culture).

The fertilizer user will often base himself on the concept of amount recommended

The amount recommended is the amount of application suggested by the agricultural, public or deprived research institutes, certain associations or ONG, or by the companies of marketing. It will be given either in term of many bags to use (with indication of proportions NPK contained in a bag), or directly in terms of quantity of each element to be brought to the hectare, or in quantity to be brought by plant or hole of plantation.

The amounts recommended vary according to the culture, of the variety used, the type of ground, climate etc…

Is Which the means simplest to calculate the quantity of the nutritive elements contained in a bag of manure?

The simplest means is to divide the numbers printed on the bag of 50 kg by 2 and those marked on the bag of 25 kg by 4. Thus in a bag of 50 kg whose formula is 15-5-20, we will have the following quantities of nutritive elements:

15/2: 7.5 kg NR (quantity of nitrogen)

5/2: 2.5 kg P₂O₅ (quantity of phosphate)

20/2: 10 kg K₂O (quantity of potassium)

On the whole 20 kg of element for a bag of 50 kg manure.

Some examples:

1. The recommendation is: application of 60 kg NR per hectare in the form of urea, which contains 45% of NR. How much bags to envisage?

46 divided by 2 is equal to 23: division by 2 corresponds to the weight of the bag: 50 kg. Each bag thus contains 23 kg of nitrogen.

60 divided by 23 is equal to 2.6. Thus, about two bags and two thirds of a bag of the product are necessary to cover one hectare

2.6 sacs*50 kg: a total of 130 kg urea, must be applied per hectare.

2. Which quantity urea to use for a field of 500 m ²?

If the surface of the field is of 500 m ² the necessary quantity of urea is one twentieth of that for one hectare either 6 ½ kg (for recall, one hectare made 100m * 100m (or 10.000 m ²).

3.Quand the recommendation a manure 60-30-30, that happens T it is to use if you use a manure 15-15-15?

If you use only this manure, you will twice apply

either too much phosphorus and potassium (economic loss and risk for the environment)
or only the half of nitrogen necessary (from where deprives)

In this case

either buy a manure 60-30-30 to fertilize your culture
or apply only half in the form of manure 15-15-15, and buy another manure not containing that simple nitrogen.

Effects on the environment and health

The use of manures involves two types of consequences which can involve health hazards (reached with the health of the man) or risks environmental (damage on the ecosystem S).

The most known health hazard is that relating to the water consumption rich in nitrate (nitrogen fertilization) by the Nourrisson.

The environmental risk more quoted is that of the Pollution of the Drinking water or the Eutrophisation of water, when manures, organics or minerals, are widespread in too great quantity compared to the needs for the plants and with the holding capacity for the grounds (function in particular for its texture), and that the soluble elements are involved towards the Ground water by infiltration, or towards the River by Ruissellement.

More generally, the consequences of the use of manures, which can involve risks and which are subjected to criticism, are the following ones:

effects on quality of the ground S, their fertility, their structure, the Humus and biological acitivity;
effects on the erosion;
effects related on the cycle of the Nitrogen and the toxicity of the Nitrate S in drinking water;
effects related to degradation of unutilised manures, which emit gases with greenhouse effect (nitrogen oxides and) in the atmosphere;
effects related to the cycle of phosphorus;
effects related to the other nutritive elements (Potassium, Sulfur, Magnesium, Calcium, Trace element S);
effects related to the presence of heavy metals (Cadmium, Arsenic, Fluorine) or of radioactive elements (significantly present in phosphates, and the liquid manures of pig for heavy metals);
effects on the parasites of the cultures;
Eutrophication of fresh water and marines;
effects on quality of the products;
pollution emitted by the industry of production of manures;
use of energy nonrenewable;
exhaustion of the mineral resources;
indirect effects on the environment, because of mechanization for the intensive agriculture and spreadings.

Worldwide consumption of manure

Between 1972 and 1992, the world use of manure passed from 73,8 to 132,7 million tons. To Canada, the use of manures passed from nearly 1 million tons in 1960 to approximately 4 million tons in 1985, while the percentage of the grounds having received manures passed from 16% in 1970 to 50% in 1985.

The worldwide consumption of manure rose to 141,4 million tons in 1999 (source FAO). The principal consumer countries are the following (in million tons nutrients):

See too

durable Agriculture
Engrais with slow diffusion
Produces plant health
Régression and impoverishment of the soil
farming Rotation
Transfert of fertility
Humus, Compost

External bonds

Graph: Consumption of manure in the world (UNO,
Report/ratio GEO 3

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