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1. What definition of soil can you give ?

2. Why are humifiable organic matters so important ?

3. What difference is there between « humus » and « organic matters »?

4. What's the meaning of K1 and K2 ratios ?

5. Can humus better enhance fertilizers ?

6. Can the organic matter stock be calculated ?

7. What's to be done to have a desirable texture ?

8. Are green fertilizers always the best ?

9. Is microbial life so essential ? How improve it ?

10. I have learned that the C/N ratio was important. Why ?

11. The terms macro- and micro-porosity are often used. Can you give more precise details about the importance of voids in soil ?

12. On dry product or crude product amount ?

13. Do you say organo-mineral fertilizers ?

14. Simple urea or complex urea ?

15. Soil life plant benefit.

16. Respect for the consumer ?

1. What definition of soil can you give ?

There are a lot of definitions of soil. One can quote Aubert and Boulaine's ( 1980), «soil is the product of the alteration, the modification and organisation of the uppermost layers of the earth's crust, driven by the action of life, the atmosphere and energy exchanges taking place over it». According to some other sources, « soil is a natural formation, synthesized in profile from a variable mix of eroded minerals and organic matters in decomposition.. This formation provided with enough air and water can ensure mechanical support and nutrition to micro- organisms and plants».

In practice, let's remember that a good soil is a loose, friable soil without compacted or asphyxiated zones, well balanced in fertilizing elements. Aeration and useful water reserve of a soil are the major factors of its yield. In any kind of soil, the maintenance or improvement of its humus rate by the provision of organic matters (organic fertilizers manure) is a priority.

2. Why are humifiable organic matters so important ?

For a lot of reasons :
they generate humus;
they facilitate the formation of micro aggregates that give soil a desirable texture (a lumpy texture)
they allow to shelter and stimulate biological activity;
they have the capacity to hold a lot of water;
they permit to fix fertilizing elements;
they warm up soil;
they make soil lighter and give it body;
they allow a better use of fertilizers

3. What's the difference between «humus» and «organic matters»?

Humus is organic matter that has evolved. It is humus which, by getting mineralized provides plants with soil's nitrogen. A soil without humus is an inert or mineral soil. That's why one shouldn't go below 2% organic matter within an average soil (with 15 to 20% clay).
There are other types of organic matter : organic fertilizers, plant remains, fresh manure … that will then evolve differently (see K1) towards humus type … finally, the term
«organic matter» covers the whole types of various materials essential to a soil's life.

4. What does K1 and K2 rate mean?

The K1 rate or isohumic rate of organic matter corresponds to the proportion of humus obtained within the soil from that organic matter. According to Hénin and Turc (1957), the K1 isohumic rate is the expression of the amount of humus that is formed with regard to the amount of dry matter the soil is supplied with. This is experimentally determined on field by making comparative testing of humic measurements between plots supplied or not with organic provisions over a minimal period of three years. The K2 isohumic rate or mineralization rate corresponds to the proportion of humus lost every year (i.e. about 2 to 3% a year). Yearly losses amount to 1.2 tonnes (60txK2) for a
soil with 2% organic matter : (over 20cm, 3000 tonnes of soil x 0.02 = 60 tonnes OM). Yearly losses of humus can reach 1.2 tonnes (60t x K2)

5. What is a soil's desirable organic matter content ?

Humus is known to « make heavy soils lighter and give body to light soils». Thus lands containing 40% clay will need a lot of humus. In the same way, to increase their water holding capacity, light soils will need good humus content. Desirable organic matter contents read as follows :
10 % clay = 3 % organic matters
15 to 25 % clay = organic matters
30 % clay = 3 to 4 % organic matters
These rates are for general information. In fact, one should have a high rate of organic matter provided this didn't result from a bad evolution of organic matters. Indeed, the presence of high organic matter rate can come from a poor humic mineralization due to unfavourable environment conditions (aeration, temperature, moisture and pH).

6. Can humus better enhance fertilizers ?

Yes. The return to fertilizer supplies is more important in soils that are rich in organic matter and present favourable environment conditions.
Can soil organic matter stock be calculated?
It can through an analysis. In a soil containing 2% organic matter, the quantity of humus (60 to 75 tonnes within 20 to 25cm of earth) represents the product of the straw transformation that are said to come from a hundred years of cultivating cereals.
The accumulation of such capital is the fruit of centuries. It is therefore advisable to take the necessary steps for it not to be wasted but used in the best way, keeping its restoration in mind by means of organic manuring to maintain its soil in good state of fertility.

7. What must be done to have a desirable texture?

One should: provide soil with organic matter supplies (i.e. organic fertilizers), practise shallow tilling to prevent «diluting» organic matters, and that is to say avoid mixing the uppermost horizons that are rich in OM, with poorer, deeper horizons.

8. Are green fertilizers always the best ?

In some cases where texture is good and humic rate tends to decrease, green fertilizers are not advisable because they will activate the decomposition of this very humus even more. They provide very little humus themselves (see K1)
but they improve, texture thanks to transitory products and they limit nitrogen losses due to leaching.

9. Is microbial life really important? How can it be enhanced ?

Obviously it is very important because it is the function of micro-organisms to help evolve soil's elements to supply plant needs.
Micro-organisms are the microbes that convert all the supplies into humus. To facilitate life within soils, the quality of organic supply must be particularly looked after, as well as the working of the soil by trying to get a crumby, friable, aerated texture with a good stability.
Warming, mean moisture and pH close to neutral make up altogether with aeration the key factors that enhance active microbial life.

10. I have learned that the C/N ratio was important. Why?

The C/N ratio is a clue revealing a good or bad evolution of organic matters. The analysis of earth samples presents telling clues concerning the environment conditions that determine the evolution of organic matters.
The interpretation of the pH readings, of the organic matter rate, iron and manganese content can give a fair idea of the evolution conditions of organic matters. As a result, determining the C/N ratio is not essential. It can read as follows :

The high readings are to be linked to unfavourable evolution conditions. Naturally, these figures are to be read for soils managed as yearly cultivation. Permanent meadow soils present on the surface an important organic matter rate and the C/N rate is often high.

11. The terms macro- and micro-porosity are often used. Can you give some more precise details about the importance of voids in soil ?

1µ = 1 micron = 10-3 mm = 10-6 mm
Macroporosity can be subdivided as follows :
MAXIVOID : over 2mm space : earthworms and mesofauna.
MINIVOID : 0.2 to 2mm space visible to the naked eye
MACROPORE : 0.006 to 0.2mm space visible by macro photography.
Big macropores 60 to 200 microns
Average macropores 20 to 60 microns
Fine macropores 6 to 20 microns

Microporosity corresponds to 6 to 0.2 micron pores.
microporosity makes it possible to hold the major part of water reserve. 0.2 microns is the resolution limit of the optical microscope.

12. Amount on dry or crude product?

It is necessary to accurately check on the product sheets the nitrogen and organic matter rates that must be read on crude product, the same as regulations impose it on bag labels. The wording of rates on dry product increases their values deceptively.

For instance : granulated VEGETHUMUS. The 60% organic matter rate on crude product equals an 80% organic matter rate on dry product.

13. Do you say organo-mineral fertilizers?

Professionals well know that under the same labelling, organo-mineral fertilizer NFU 42001 standard, two agronomically opposed products can be found : organo-mineral pellet fertilizers containing over 50% plant compost and organo-mineral micro ball granules containing 10% animal organic base of leather meal type ( supplying a minimal 1% organic nitrogen).

14. Simple urea and complex urea

The AFNOR 42001 standard states that organic fertilizers and organo-mineral fertilizers are supposed to be free from synthetic organic nitrogen of formaldehyde urea type, crotonylidene diurea (CDU) and isobutylidene diurea (IBDU). By agreement, simple urea is not part of this class and can be incorporated to organic fertilizers in order to obtain more important nitrogen release.

15. Soil life to plant benefit

The transformations of the elements beneficial to plants; carbon, nitrogen, sulphur and phosphorus are closely linked to soils microbial life. Bacteria and fungi that exceed 1000 species play important roles in numerous processes :
. Release of nutrients from soil organic matter and minerals.
. Oxidation of ammonium into nitrates (nitrification process through action of nitrosomonas and nitrobacters).
. Production of growth hormones that stimulate root development.
. Competition with pathogenic micro-organisms that can thus limit risks of diseases.

16. Respect for the consumer ?

More and more big companies of the European agro food industry have banned the spreading of products
containing urban waste over crops to guarantee the quality of their production, for instance Bonduelle, Salade Minute, Producteurs de Champagne and Golf d'Evian, water capturing area at the Perrier spring, ...
Does it work in vine nurseries by soaking ? Just after stratification : OSIRYL is applied only as soon as plants are raised and as soon as roots start coming out so there is no consequence on naked plant by soaking - Osiryl must be absorbed by roots.