Organic amendment will have two major impact on soil properties,. It will increase the soil water holding capacity whish will more water to plant and it will increase the cation exchange capacity (CEC) which will allow to reduce the the concentration of some toxic element (Na) in soil solution. beside as Dr Rao said its decomposition will supply nutrients and humic and fulvic acid whish contribute to the alleviation of salt effect complexion of monovalents ions and may also stimulate root growth. Also the decomposition of organic matter will acidify the soil medium releasing calcium whish will interact with Na absorption and reduce its uptake by the plant

Dr.Azim,practical but difficult question.As you are quite aware,we amend sodic soils or some times saline-sodic soils with farmyard manure..It has both reclamation effect and nutrient supplying power.The manure if it is properly decomposed may contain  good amount(say 30%) of humus.However, the humus in dilute phase may prefer the di or trivalent cations to adsorb.But in concentrated phase like saline water it may complex the monovalent cations like sodium.When sodium is adsorbed ,other cations can be released from humus.Let us hear from other colleagues.

Organic amendment will have two major impact on soil properties,. It will increase the soil water holding capacity whish will more water to plant and it will increase the cation exchange capacity (CEC) which will allow to reduce the the concentration of some toxic element (Na) in soil solution. beside as Dr Rao said its decomposition will supply nutrients and humic and fulvic acid whish contribute to the alleviation of salt effect complexion of monovalents ions and may also stimulate root growth. Also the decomposition of organic matter will acidify the soil medium releasing calcium whish will interact with Na absorption and reduce its uptake by the plant

Khalid  your question is other way round. Application of organic amendments to clay soils will surely bring some distinct changes in sorption behaviour such fine textured soils by increasing the surface area of exchange sites . But there wil be faster and supposedly  easier exchange  of Na from the exchange complex compared to the clay soil without any treatment with organic amendment , since Na binds more strongly to clays than  protonated organic acids. And in all possibility , the effect of salinity in irrigation water is also expected to be masked by application of organic amendments.   

You  have got the best answer from Dr Rao

The addition of organic compounds results in improved microbial activities and release of many ions like Ca, Fe and Mg etc , which can replace sodium on soil exchange complexes. The released sodium will percolate down into the deeper soil layers, thereby not affecting the plant growth. In India, we often collect the fresh rain water in these amended fields for growing salt tolerant variety of rice, which results in further flushing of released salts down into the deeper soil layers. 

I think , cleansing effect of organic amendments on clays( Increased surface area due to coating of clays  with humic acid or through formation of clay-humus complex )  will surely keep the process of sodiumization   of soil at a much slower rate , despite using saline water.

Very good replies by scientists.

Dear Azim, I understand that OM, in addition to nutrient supply, much more effect to alleviate saline water effects: through increased CEC of soils, enhanced soil drainability, soil aeration, in-situ mineral weathering (like lime etc.) during and upon OM decomposition. All these combine to mitigate the adverse effects of saline water irrigation in favor of crop production.

Thank you all for your valuable contributions, I believe that added OM will have a positive effect on soil CEC that will buffer more the sodium ions from irrigation water. The fact stated by Dr Srivastava "Na binds more strongly to clays than protonated organic acids" is quit worrying. So my question will be the following: how clay-humus complex is alleviating sodium stress? what are the mechanisms involved? thank you for your knowledge sharing!

When it comes to salinity most emphasis is on the displacement of Sodium which binds with the clay and seals the soil structure. Displacement of excess sodium is accomplished by using a combination of Calcium sulfate gypsum with the application of excess water to drain off the excess salts. In many saline soils the alkaline pH is combined with excess salts and beside the Calcium treatment and drainage I suggest the implementation of Sulfuring to pH 7.3 to 7.0 which will eliminate many of the soil issues.

in terms of organic materials the organic materials will bind and complex after the salt is reduced and adequate Calcium is available. In terms of resources raw manures can be quite high in salts and may contribute to salt issues. Preferred is aged compost which has lowered salts and gives a longer term beneficial effect. Compost using raw manure needs to have liberal amounts of woody or strawy material and the use of silt and clay is quite useful as well, The lasgna layering of the compost is used to ensure the manure and claysilt amend retard losses. In arid semi arid regions compost is best accomplished in trenches to capture and retain water and in all situation the turning of compost is based on accomplishment of peak temperature and done only until the pile heats no more.

While I would not recommend direct use of manures in saline conditions I would recommend use of stabilized amended compost which will avoid potential contribution to soil saltiness and optimize soil organic matter retention which will be useful in multiple areas not least being soil structure and water capture and recycling potential.

Recommendation 1) consider the application of gypsum combined with soil leaching 2) address soil pH issues with sulfuring 3) use raw manure for composting but not for direct application  4) compost to maturity and use clay silt amendment which will help eliminate the rapid loss of organic matters.

Good luck.

 Very interesting discussion on a topic very practical importance.We know that if we irrigate a clay soil with insufficient drainage(slow permeability and limited leaching) initially salinity may build up and after some years  sodicity will  develop.In the initial years we have to take care of sodium salts in water.We recommend  leaching with good quality water for saline  soils and gypsum application  and leaching in sodic or saline sodic soils.Composted manures are also recommended for sodic soils.The benefits of manure application are humus addition(increase in CEC of soil),increase in water holding capacity through aggregation ,increase in aeration,water conducting property (increased permeability),and addition of several nutrients including Ca.Main problem is how to tackle the Na.If Na is already on the exchange complex we have to dislodge and remove or leach it.If it has not gone to exchange complex and present in soil solution  and we have to leach it down not allowing to build up its concentration.If the soil  inorganic colloids and humus have relatively high CEC(as in clay soil with addition of composted manure) and the soil solution is dilute, Na is not is not allowed to go to the exchange complex and rather Ca is preferred or selectively adsorbed.  In that case the Na is safely leached from root zone.If the Na ion concentration is high in solution phase,it can exchange with ions like Ca,Mg or K.We have to see how far the reaction can be stopped through addition of Ca,Mg ,K and protons through manure?.How far the aggregation and improved physical conditions favor the free leaching of  Na from root zone?.Even the crop will have ameliorating capacity through better root system,addition of root exudates,stubble etc.So it appears that,as mentioned by some colleagues,through chemical ,physical and biological means it may be possible to use composted manures where saline water irrigation  is a necessity.

Very good Rao! Clay plates participate in triple-layer bonding to a very high degree which in turn makes the soil even less permeable. Fertilizer salts then are bonded, to the triple layer,  and so the entire balance of nutrients is lost. True also that sodium is a persistent element in clay soils.

But one point not being clarified well is the difference between humus, organic matter and organic material. Humus is the by-product of long periods of break-down of organic matter. But organic material is the fresh vegetative, animal and sea materials put into the ground.

Each version performs different functions. Organic materials are more roughage, creating pores in soils by bulk materials....stems, leaves, roots.

From there it is weathered/decomposed by soil organisms and becomes organic matter: less bulk, less physical changes; more of the impact to elemental soil bonding.

Humus is the completely weathered decomposed remaining material of ligins/polysaccharides and has little benefit when applied as an end product on clay soils because it is once again very small electro-charged particles and now subject to triple-layer bonding principles. Meaning humus, as an applied product, (humates), only bonds once again with clays. Well, unless you apply tons and tons per hectare. Even worse, many companies use NaOH as the extraction material for humic acids from humates increasing the amount of Na in the product!!

Some very good plants have been shared. I will just add that organic matter increase floculation of soil particles which were dispersed due more Na on exchange site. Therefore, porosity of soil will increase that will help in leaching of salts, especially in case of clay soils.

The salt overcoming mechanisms pointed out are leaching with Calcium substitution with gypsum  and the improvement of plant nutrition through stabilized organic matters. Usually multiple approaches will need to taken not just looking at organic matter. For instance please remember that plants such as barley have good salt tolerance and can utilized in your rotation with good effect and that mycorrhizae has proven very useful. Do not forget to get very complete soil analysis and consult your plan with local and regional experts. Although Organic Matter can have many great attributes some organic matter especially raw manures are high in salts this may be a consideration to keep track of.

Trials done in the Nile download soils back in the 1990s showed that extracted humic acid, when extracted using KOH, exchanged the K for Na in the soil environment, tying up the Na and reducing sodium damage to the crop. However..... it did not tie it up forever, nor did it help move it, (leach) from the crop-soil-zone. In the end, it added to the soil-salinity levels. The project, one I was part of, both succeeded and failed. Temporary impact, not the long-term solution.  Annual flooding down the Nile washed clean the salt residues from the crop soils and in some cases deposited new silt. The Aswan High Dam changed all of that, maybe not for the better.

Thank you very much for your high level contribution, I understand more the role of organic matter as a solution for salt alleviation. Dr Nazir pointed two facts that can be assessed: 1-Soil particle floculation and 2-Soil porosity. How can they be measured (aggregate stability?...).

Dr Hepperly also pointed the practical approaches in the farm, meanwhile I'm interested in how can I follow those changes in pot experiments prior to open field trial with organic vegetables. Thank you again for those contributions. I hope to receive more insights and more deep discussions.

In growing plants in pots using of unamended soil will often cause issues with chronic soil borne fungi due to lack of sufficient internal drainage.

The soybean for instance with succumb to Pythium and Phytophthora fungi but if the local clayey soil is cut by mixing it with an equal volume of sand sufficient drainage is favorable for the plantings.

In Morrocco where you live I bet there is a local and large resource of sand. If you transport and mix into your production areas it might be very useful. Many old soils are deficient in Silicon and the addition of sand silicate might be useful structurally and chemically and sand could also be a useful addition into compost medium.

Interestingly Silicon in optimum quantitites increases the resistance to pests and diseases and reduces the evapotranspiration which might be very useful.

Khalid In terms of measuring soil stability. It is generally achieved by sieving out soil aggregates of different size classes getting a dry weight then exposing them to water reisolating them and determing the loss in dry weight by dissolution. The less the loss the greater the soil aggregate stability.

In terms of stability soil organic matter and clay both have negative overall charge when multiple valent cations are present in solution they will build with clay and organic matter aggregating the structure and stabilizing it.

When soils are replete with Sodium it replaces Calcium and this is at the root of the poor soil structure in sodic conditions. Many sodic soils are alkaline and Calcium carbonate would be problemsome in contributing to micronutrient deficiencies by inappropriate pH the use of Calcium sulfate is favored as it does not contribute to alkalinity issues as it changes the soil equilibrium to help substitute out Sodium.

As pointed out by Hepperly , addition of sand to a clay soil would definitely help in improving soil conditions especially drainage and aeration ,in addition to points mentioned by Dr.Hepperly.Matured and salt free compost and gypsum application will also have  good ameliorating effects,as both will improve  soil aggregation in addition to other benefits.

Very interesting discussion . Appreciate the view of Dr Hepeprly . Lets also consider the additional buffering capacity offered by addition of organic amendments   to clay  soils which is already having the high buffering capacity  . Coating of clay particles with humates/fulvates  and formation of clay-humus complex   in eventual terms will keep such clay soils from secondary sodiumization ,   a very strong potential   prospect in clay soils irrigated with saline irrigation water.

Thank you all for your inputs, I really appreciate!!

Do you have some papers related to this questions, please share

Many thanks