The concept of mull, moder, mor is applicable for forest covers. But for agriculture crops humus is also equally valued by farmers and gardeners because it provides nutrients essential for plant growth, increases soil water absorption, and improves soil workability. Above ground organic matter comprises plant residues and animal residues; below ground organic matter consists of living soil fauna and microflora, partially decomposed plant and animal residues, and humic substances. The C:N ratio is also used to indicate the type of material and ease of decomposition; hard woody materials with a high C:N ratio being more resilient than soft leafy materials with a low C:N ratio. Most of our productive agricultural soils have between 3 and 6% organic matter. 

The concept of mull, moder, mor is applicable for forest covers. But for agriculture crops humus is also equally valued by farmers and gardeners because it provides nutrients essential for plant growth, increases soil water absorption, and improves soil workability. Above ground organic matter comprises plant residues and animal residues; below ground organic matter consists of living soil fauna and microflora, partially decomposed plant and animal residues, and humic substances. The C:N ratio is also used to indicate the type of material and ease of decomposition; hard woody materials with a high C:N ratio being more resilient than soft leafy materials with a low C:N ratio. Most of our productive agricultural soils have between 3 and 6% organic matter. 

Dr. Thomus,  in most of the agricultural soils the bulk of the soil organic matter occurs as stable humus. The percentage of the humus that occurs in the various humic fractions varies considerably from one soil to another. Alfisols, Spodosols, and Ultisols generally have  lower humic acid/ fulvic acid ratios than the humus of peat and grassland soils ( Mollisols). But  I think, even 1-3% organic matter in agricultural soils are also sometimes very productive. Productivity is not only depends on the organic matter content, but many more other factors...

Humus as humic acid applied to the agricultural cultivated soil for sustainable agricultural production..

Yes gentlemen, but my question is precisely about humus categories : mull, mor, moder

Dr. Fungenzi, in agricultural soils Humus (organic matter) categories are: Humin, Humic acid, Fulvic acid fractions which have the almost same elemental composition ( C, O, H, N, S) as your mull, moder and mor in forest soil. They have also the similar functional groups like COOH, acidic OH, weakly acidic alcoholic OH, C=O etc. So, one can expect similar type of function in agricultural soils only the names are different.

Cation and anion exchange phenomena governed by mass flow,diffusion and root interception  from soil to plant for all the essential plant nutrients..

Dear Thomas,

you're right, in Agrosystem the Mull, Moder and Mor humus form are strongly disturbed, that's why in the framework of Humusica projet lead by Pr Zanella Augusto, Agricultural topsoil have been separate in the Agro and Techno system

I strongly recommend  the following papers.

Cheers

Article Humusica 2, article 14: Anthropogenic soils and humus system...

Article Humusica 1, article 3: Essential bases – Quick look at the c...

Article Humusica 1, article 7: Terrestrial humus systems and forms –...

HUMUS IS COMPOSED OF LIGNITE CARBON AND PROTEIN AS ENZYMES OF MICROORGANISMS WHICH TRANSFORM   ESSENTIAL NUTRIENTS FROM SOIL THROUGH ROOT HAIR OF PLANT IN IONIC FORM FOR NUTRITION AND  COMPLETE THE FOOD CHAIN OF THE ECOLOGY OF NATURE FROM LOWER TROHPIC SMALL MICROORGANISMS TO HIGHER TROPHIC ANIMAL AND HUMAN.

I actually think it would be possible to apply the mor/moder/mull definitions in all natural soils, grassland included. In alpine grassland, for example, Moder humus above Umbric A horizons are absolutely common, even if normally grassland soils are normally considered "Mollisols". Mor humus forms are locally developed as well, below Carex curvula grassland on the Alps, particularly in humid sites.

And what about agricultural soils? Do the underlying principles still to describe the transformation of soil organic matter?

Thank you for all your answers gentlemen.

In grasslands the mor/moder/mull categories may appear but as soon as management practices disturb the top soil this kind regularly of classification doesn't quite work out anymore. Mor and moder humus usually form organic horizons above the mineral soil as you might be aware of. When the soil is plowed these horizons are mixed up and the soil structure is altered. Usually this results in a faster decomposition of organic matter and significantly alters the soil fauna. You could probably try classifying your soil according to these categories nevertheless, but if you are doing that by the classic caracteristic horizon morphology all plowed soils are going to be caracterized as mull, as the top soil is mixed up as mentioned before. Therefore I believe there would be no benifit in doing so. As many others mentioned before, you could also use C stores as well as C/N and C/P ratios to caracterize agricultural soils. That can be done with forest soils as well faciliating a comparison of soils independantly of the vegetation. As C/N And C/P ratios are directly influenced by fertilization, I suggest C stores in combination with the ratios of humin, humic acid and fulvic acid, may actually be the best way to caracterice the soil organic matter and its transformation processes in plowed soils.

All of this is more opinion than anything else but I think a lot of it is obvious logics based on my student knowledge, so I hope it helps.

Any kind of organic matter become HUMUS in system of soil known as and composed of lignite- carbon and protein as enzymes of microorganisms .Carbon of humus part maintain carbon sequestration for soil microorganisms . This is a unique process in the ecology of living soil in nature. So,organic matter as mull,moder,mor of humus category may be applied be applied in soil to maintain sustainable soil fertility and productivity of crop.

8 articles of The Humusica project (Humus Classification key and more) edited as Special issue of Applied Soil Ecology are available for free until January 25, 2018.

Humusica 1, article 1: Essential bases - Vocabulary

https://authors.elsevier.com/a/1WAk53JGmQvIt8

Humusica 1, Article 2: Essential bases - Functional considerations.

https://authors.elsevier.com/a/1WAk53JGmQvJ4N

Humusica 1, Article 3: Essential bases – Quick look at the classification

https://authors.elsevier.com/a/1WAk53JGmQvJJj

Humusica 1, Article 4: Terrestrial humus systems and forms – Specific terms and diagnostic horizons.

https://authors.elsevier.com/a/1WAk5_L84ruxYV

Humusica 1, Article 5: Terrestrial humus systems and forms – Keys of classification of humus systems and forms.

https://authors.elsevier.com/a/1WAk53JGmQvJUd

Humusica 1, Article 6: Terrestrial humus systems and forms – Hydro intergrades.

https://authors.elsevier.com/a/1WAk53JGmQvJWF

Humusica 1, Article 7: Terrestrial humus systems and forms – Field practice and sampling problems.

https://authors.elsevier.com/a/1WAk53JGmQvJWg

Humusica 1, article 8: Terrestrial humus systems and forms – Biological activity and soil aggregates, space-time dynamics.

https://authors.elsevier.com/a/1WAk53JGmQz5ov

I recommend Jérôme's answer

Best Regards

The links of Jérôme have expired, but I will use the titles ;)

Thanks