Dear Mr. Dadamouny,

Regarding your question there are several soil properties used in its classification and identification. Some of them are the soil water content, soil bulk density, relative density, particle size distribution, consistency limits, plasticity index, etc.

A very good text in which you will find the description of methods to calculate the properties indicated above and the factors that affect them is the "Methods of Soil Analysis. Part 4. Physical Methods (Soil Science Society of America Book Series, Vol. 5), 2002, by Jacob H. Dane and Clarke Topp".

Regards.

You have a good question, however, it is not completely clear as to the specific "index" to which you refer. Certainly as Dr. Pires indicates, several physical properties can be used in characterization and classification of soils. But if you wish to derive an index for assessing soil conservation or soil management, several other approaches including the soil conditioning index, soil management assessment framework, etc. can be used. These indexes include soil organic matter (or soil C) as a major property or indicator as well as many other physical, chemical, and biological properties. A bit more detail included in the question will allow a better and more useful answer for your purposes.

The question is not clear.

However I would suggest you to read the articles (especially Ray et al and Chatterjee et al ) in the sp section of Current Science (Bangalore, India) published in Nov, 2014 as Georeferenced soil information system.....

Please read the articles first and then write to me if you need to put the soil parameters in spatial domain for developing theme maps on different soil parameters.

Regards

Dear Mr. Dadamouny,

This works could help to you!

https://www.researchgate.net/publication/263152153_The_influence_of_grazing_intensity_on_soil_properties_and_degradation_processes_in_Mediterranean_rangelands_%28Extremadura_SW_Spain%29

https://www.researchgate.net/publication/263152128_Evaluacin_de_la_calidad_del_suelo_en_dehesas_y_pastizales_del_suroeste_de_Espaa

Best regards,

Conference Paper The influence of grazing intensity on soil properties and de...

Conference Paper Evaluación de la calidad del suelo en dehesas y pastizales d...

Thanks for all!

Many thanks to Dr. Luiz Fernando Pires, Dr. Robert J Kremer, Dr. Tapas Bhattacharyya, Dr. Judit Rubio Delgado, and Dr. Shaban Ahmed!

Understanding the properties of soil is very important not only for plant, but for the conservation and sustainable management of the land, many coastal projects under the risk of non-suitable soil, increase the rate soil erosion and other factors like impact of climate change on soil properties should be considered before starting in any project.

Yes, the soil properties on which their classification and identification are based are known as index properties, which may are:

1. Grain size distribution, 2. Consistency limits, 3. Plasticity Index.

Grain size distribution: by many methods for example the sieves method.

Consistency of Soil: which is the physical state of soil with respect to moisture content present at that time.

It means the relative ease with which water can be deformed. Consistency is related to the fine grained soil.

Consistency Limits or (Atterberg Limits): the moisture content at which the soil change from one state to another state.

When water is added to the dry soil mass its change from solid state to liquid state passing through semi solid and plastic state.

The plasticity index: is a measure of the plasticity of a soil, it is the size of the range of water contents, but which water? where the soil exhibits plastic properties. The PI is the difference between the liquid limit and the plastic limit (PI = LL-PL). Soils with a high PI tend to be clay, those with a lower PI tend to be silt, and those with a PI of 0 (non-plastic) tend to have little or no silt or clay.

Finally, my question was if one has these parameters and other soil parameter and wants to explain these parameters in an index, how? It is a new and an interesting point for me.

What are the main properties used for determining index soil properties for an area? How can one calculates it?- a tricky answer to a tricky question.

index of soil properties for an area is better judge by local conditions mainly of topography, degree of soil development , climate and vegetation. 

any index calculation in an area needs to clculate topgraphic index, soil development index, climatic index and vegetation index and integrate all these indices to derive local indices of different soil types existing in an area.It is not simply soil properties alone , the other soil forming factors must be included in deriving regional indices. It is only an opinion.