Manure in the organic garden


It’s a rhetorical question, I know, but I had to ask it. Obviously the answer is a resounding yes. There is a lot of difference between the different manures and now we are going to see the general differences between them. Let’s first look at some general guidelines for the application of manure in the garden. It goes without saying that although the word fertilizer, today is associated with sacks of chemical fertilizers, manure is the fertilizer par excellence since man has plowed the fields.


Commercial houses sell us compound fertilizers, with main elements such as NPK (nitrogen, phosphorus and potassium), sometimes enriched in some secondary nutrients (magnesium, calcium and sulfur) and even enriched with micronutrients (iron, manganese, zinc, boron, chlorine …). So we can think that if humanity has cultivated with manure, ash and by-products of daily life, we come to the conclusion that all these elements that plants need are contained in manure? And the next question is: do we need complex fertilizers then?

Too many questions that all have answers. In the first place we must have a historical dimension of time and space to begin to propose the appropriate answers.In the beginning of time, when man begins to cultivate and stops being nomadic, he finds virgin soils, provided with everything mineral and organic element necessary for its cultivation. Cultivate, cultivate and keep cultivating. So for thousands of years. Inevitably the soil is depleted . There’s no more. “Chickens that come in through those that come out.” If we extract nutrients from the soil to give them to the plant, we have to replenish them by fertilizing the soil.


Analyzing the various most common manures, certain amounts of the famous NPK triplet are found in all of them, but not in sufficient quantities for current industrialized production yields. In fact, almost all manures mainly lack an adequate concentration of phosphorus in its P 2 O 5 form .What a manure really contributes is a good fraction of fresh organic matter and nitrogen mainly but in organic form for the most part. Hence, a decomposition time is required for the organic fraction of N to become mineral. Normally for a garden, a replacement with composted manure, compost made from vegetable residues, etc., is usually good. Although at times many of us have had to add a little nutritional boost in the form of chemical fertilizer to get more tomatoes, more fruit, etc. etc. etc. Be careful, there is nothing wrong with it. It is a respectable decision like any other. Nitrogen is nitrogen, calcium is calcium, come from where you vegan. It is pure chemistry. In the periodic table of the elements there is no bad calcium and good calcium.


This is perhaps the most common question one asks oneself when a trailer with its characteristic “ pi pi pi pi” in reverse, dumps a few hundred kilos of manure onto the farm. In the books everything is beautiful, but then we have that lot of m…. we don’t know what to do with it.

[pullquote align = »right»] Composting manure is the best thing to do. [/ pullquote]

We must bear in mind that the direct application of fresh manure on the most superficial horizon of our land will change the characteristics of our soil in the short term : sponginess, conductivity, pH, even temperature! And many of these manures come with certain gifts that we will suffer later (seeds of adventitious plants). Yes friends, all that glitters is not manure. Then what do we do? First and only rule to follow: it should not be planted immediately after applying the manure. It is highly recommended to allow between 1 and 4 months depending on the type of manure before sowing to achieve an adequate degree of decomposition.


In a certain way, yes, and therefore, composting with manure is the most suitable method in orchards and not so orchards (it is preferable to direct application). Industrial composted manure fertilization is increasingly applied. A cherry tree farmer recently told me that he was adding composted manure to several hectares of his farms and it is doing great.


Of course there are limits, especially from an environmental protection point of view on the nitrification of aquifers. In Spain the normal imposed limit is 170 kg of Nitrogen per hectare of land and year . This is done mainly for chemical fertilizers that are much more concentrated in Nitrogen than manure, although the use of manure such as pig manure or chicken manure are also in the spotlight due to this excessive nitrification. You can see it in the European regulations.



The average amount of nitrogen in manure can be quickly established at 0.5-0.7% (excluding chicken manure), without going into further calculations on the organic fraction, mineral fraction, moisture status or fertilizer units. . It is a somewhat rough calculation but for our purposes it may be worth it. This means that each kg of manure has 6g of total Nitrogen. By a simple rule of three throughout life, to reach 170kg of N / ha · year we would need on the order of 28,000 kg of manure / ha as an average value to exceed the legal limit. These figures, taken to a small orchard of 100m 2 , yields a maximum of 280 kg of manure.


[pullquote align = »right»] The most important contribution of manure is organic matter [/ pullquote]

Two words, one concept: Organic matter. In the end, in highly industrialized crops, the soil becomes a mere physical support to which specific doses of X restitution elements are applied in the form of mineral elements provided by macro-fertilizers (NPK) and microelements. What about organic matter? Today, it is considered that an adequate level of organic matter present in agricultural soil should be between 2 and 3%.Many intensively exploited soils do not reach 1%. The most direct consequence is a soil without structure, without fluffiness and with many deficiencies. A soil that becomes mere physical support for plants, without what is necessary for their growth. Consequence? Need for fertilization. For this reason, the soil has to be recovered, not simply fertilized for the next crop. We are going to list some advantages of organic matter in the soil:

  • Improves the colloidal structure of the soil.
  • Improves drainage.
  • Heat the earth.
  • Reduces waterlogging (as a consequence of improved drainage).
  • It improves the buffer capacity against changes in pH (although a priori the most superficial horizon may vary).
  • Reduces erosion.
  • Better use of water.
  • And above all, it favors the microbiological life of the soil.

In the article dedicated to soil organic matter you will see each of these points well developed.

If we have managed to clarify some things about manure, we are going to see the characteristics of the most common ones and a table with the concentrations of each nutrient that can be very very useful to know what we have in hand … with clear gloves xD. It must be said that the figures should never be taken as absolute. We must bear in mind that the composition of a manure of an animal species can vary with age, diet (which affects the most) and other factors.


Beef (fresh)
Beef (dry)160.580.010.490.010.040.13
Sheep (fresh)130.550.010.150.460.150.16
Sheep (dry)351.950.311.261.160.340.34
Equine (fresh)241.550.351.500.450.240.06
Equine (dry)100.550.010.350.150.120.02
Porcine (dry)180.600.610.
Chicken manure (dry)476.115.213.20
Camelids (dry)373.61.121.20

Source: FAO



It is a manure with a high water content and in general balanced, although somewhat lacking in Nitrogen and Potassium. It is not considered bad at all, but it takes more quantity and it is usually better to compost it to balance it a little more. As we can see in the table above, the N fraction is the lowest of all due mainly to the fact that the extract in dry matter is the lowest of all (fresh). Having a lot of water, the proportion of nitrogen decreases.


Very balanced in nutrients and with a very good amount of each one. It is the most appreciated of the manures (among the most common in Spain) along with horse manure, mainly for its potassium content and its best phosphorus value, although this is still sometimes insufficient. As it has almost 35% dry matter, it is a manure with low humidity, very compacted and therefore requires a proper composting process before adding it. It is a very good manure for the activation of the compost heap (increases the temperature of the heap). Sometimes it is necessary to add cellulosic components (straw) to promote aeration and avoid anaerobic fermentation. Our friend Germán Tortosa from Composting Science, shows us thechemical characterization of sheep manure.


Similar to sheep, with slightly less secondary nutrients (Ca, Mg, S) but still very good. It has a little more moisture than that of sheep but its dry fraction (24% dry) is still much higher if we compare it with that of beef (16% dry). Horse manure is usually accompanied by the straw beds of the stables so it will not be necessary to add fibrous component in the compost as in that of sheep. And here the chemical characterization of horse manure .


Due to the type of mebaolism of birds, compared to that of ruminants (sheep, horse, cow), manure or rather bird droppings have the highest percentage of dry matter (about 50%) and therefore some Very high NPK contents compared to the previous ones. It is not good to abuse chicken manure as manure. They have a lot of nutritional capacity and are also assimilable, although all the improvements of the soil that we mentioned before (drainage, structure, aeration), are better achieved with the previous ones. In addition, we have to bear in mind that this type of manure is not very suitable in limestone soils with a pH that is closer to the basic zone since its high calcium content will further increase this value.


Pork purines are an element of controversy and debate regarding their management given the millions of tons of this waste that are generated annually and their excessive and almost uncontrolled addition to agricultural land. In many cases they are causing the nitrification of aquifers precisely because of the surplus that ends up exceeding the legal limits that we talked about above. It is a manure that is difficult to handle, dense and by itself it is not convenient to use or abuse it. In case of having it for an orchard, it is possible to use it mixed with quite a fraction of straw, other manures in order to balance its structure a bit and facilitate handling.


In Spain it is not common, it is evident that camels are not abundant in our country, but if we look at the dry matter and nutrient fractions, we are facing manure as good as sheep or horse manure (there is no data on secondary elements). We see that it has a very high dry fraction so it will be a dry and compact manure. A camel cannot afford to generate water-rich manure for obvious reasons. It is not widely used here but I wanted to add it as a curiosity …

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