I endorse the comments from Dr Tapas, the best quality fruits like banana, citrus, mango, citrus ..all are produced despite subsoil acidity , which i emphasized in my  responses to almost similar question  flagged off by Dr Pal sir...stating that can we call acid soils chemically degraded..?

Soil pH is a useful indicator of the relative acidity or alkalinity of a soil. In the acidic soils of the tropics aluminium toxicity may become a serious problem and limit crop yield. Farmers may reduce manganese toxicity by liming and aerating fields. Subsurface tillage may be necessary to ameliorate subsurface acidity. Flooding in lowland systems as well as addition of organic matters also reduce the subsurface acidity. You may also use calcium carbonate equivalent of liming material. The subsurface acidity can also be reduced by neutralizing exchangeable aluminium.

You may also follow the below literature 

Biol Fertil Soils (1993) 15: 153-159.

May be a deep limestone amendment with drainage management.

Dear Teklu,

1. A repeated addition of lime will slowly reach the subsoil

2.Deap ploughing with application of lime and dolomite may help if ploughing is adviceable.

3. if there are drains to be constructed you may bring the lime into while making the drains.

4. You may inject lime, dolomite or alcaline salts in the appropriate depth.

Be carefull change of pH may reduce nutrient availability.

Yours sincerely

Karl Stahr

Hi!

And how you need to interpret? Can be different.

Interesting question and good comments by colleagues/ followers of the question.Amelioration of subsoil acidity is more problematic compared to surface soil acidity in leached and variable-charge acid soils.Vertical movement of lime is very slow and mechanical mixing of lime in deeper layer is difficult and may not be economical.I have come across some papers/reports on successful use of gypum in surface soil to ameliorate subsoil acidity.The following references may be consulted.

Publication No.01-024-090 Gypsum as an ameliorant for the subsoil acidity syndrome University of Georgia Department of Agronomy

www.soilsolutions.net/wp-content/uploads/2015/02/Effect-of-Gypum-on-Decreasing-Subsoil-Acidity.pdf

Long-term effects of gypum on crop yield and subsoil chemical properties.Toma,M. et al.  Soil Sci.Soc.Am.J. 39:891-895 (1999).

caes2.caes.uga.edu/commodities/fieldcrops/forages/events/SHC14/23 gypum/Toma Alfalfa Paper001.pdf

 Dr.Teklu,I have comeacross three papers addressing three different aspects of subsoil acidity and amelioration.

Causes and management of subsoil acidity by C.Tang

http://www.regional.org.au/au/asssi/supersoil/2004/s9/oral/1366_tangc.htm

https://www.researchgate.net/.../228493210

The second paper deals with the spatial variabilty of subsoil acidity and its characterization for proper planning of  amelioration for tageted (area) lime application. Targeting the subsoil to better manage acidity spatially by Oliver ,Y.M. et al.( 2015).

Proceedings of the 17th ASA Conference,20-24 September 2015,Hobart,Australia.Website www.agronomy2015.com.au

The third paper deals with the method for proper incorporation of lime at particular depth and mixing with soil.

Changes in soil pH as a result of lime addition as affected by rate,time and incorporation method by David Hall and Jeremy Lemon 2010

19th World Congress of Soil Science,Soil Solutions for a Changing World 1-6 August 2010,Brisbane,Australia.Available online.

Dear Dr. Teklu,

A very good question you raised and excellent answers by some scientist on ways and methods of treating sub-soil acidity were forward. While I agree with these answers, I would like to suggest additional or alternative means of treating sub-soil acidity and also for ameliorating surface acidity which is application of Zeolite minerals. Zeolite minerals naturally occurring alluminio silicate minerals which have very high cation exchange capacity and thus able to adsorb Al in  in strongly acid soils. By the way there are also synthetic minerals of diverse type which are very important in industry, medicine, environmental protection etc. Zeolites are the most important discoveries of 21 first century which are little exploited for the benefit of mankind yet. But definitely they will increasingly be used to solve many problems in agriculture, industry, medicine etc. in the future. 

Dear Dr.Wassie,I understand the importance of zeolites use in agriculture and environment.Because of their high CEC and binding strength they are being tested for decontamination of soils contaminated /polluted with heavy metals.As mentioned by you ,zeolites can adsorb the Al in acid soils.I think both lime and zeolites  together can be tested for amelioration of acid soils containing exchangeable Al  along with H ions.

Dear colleagues and fellow scientists,

Thank you so much indeed for your excellent insights. Your direct suggestions and the references provided would abundantly help towards my effort to develop the right strategy for acid soil management including subsoil acidity.

Kind regards,

Teklu

Dear Professor Subba Rao,

Thank you very much for strengthening my points on multiple benefits of Zeolites in addition to mitigating soil acidity. I fully agree with you that zeolites can be tested together with lime to ameliorate soil acidity. IN fact this will be my future area of interest.

With Best Regards

Wassie

Dear Dr. Teklu,

I believe that you are embarking on a very challenging and admirable project. The physical limitations of Vertisols are huge and ameliorating these limitations could make a huge difference to production and household food security in the Ethiopian Highlands and, indeed, other areas of the world where such soils exist.

However, I am somewhat concerned by your view that subsoil acidity is a probable problem. Almost by definition Vertisols, because of their clay mineralogy, high clay content and poor drainage --- the primary problem --- are generally regarded as being high pH soils to depth. The pH levels are usually well above 5, a level above which Al toxicity is not possible and Mn levels are greatly reduced. Unless you already have soil analyses to depth, which surprisingly show the opposite to what I have said, I would strongly recommend that you acquire such analyses from representative profiles.

If acid saturations are low, which I suspect they will be, subsoil acidity can be eliminated as a possible problem. This will help. I have spent more than six months in you wonderful country on contracts headed up by Dr. Bateno and Prof. Tekalign and we only found subsoil acidity in some of the Oxisols and Ultisols in southern and western areas of the country.

If you verify that subsoil acidity is a problem, there has been a lot of work published on the amelioration of the problem in Brazil and South Africa. I'm sure that this is listed in ResearchGate. We must also remember that pH elevation or self-liming is a prerequisite.

My apologies for perhaps sounding somewhat negative, but what I have said is not meant to be negative in any sense. Simply precautionary!!

All the very best in your endeavors.

Yours sincerely,

Mart Farina..

I would recommend adding biochar (1 or 2%), which usually has high pH and high CEC, so biochar could play the role of combined zeolite and lime. Mixing green manure with surface soil would enhance the movement of organic acids/anions from the manure into the subsoil, those in turn can effectively chelate and detoxify Al.

Send me your e-mail address and I will send you a digital version of the manual: Solving agricultural problems related to soil acidity in Central Africa's Great Lakes Region. Crawford, T.W., U. Singh & H. Breman, 2008. IFDC-CATALIST, Rwanda.

Be carefull when you start liming; too much lime, also locally, will lead to the loss of the single advantage of tropical acid soils: good water infiltration!

Dear Dr. Breman,

Thank you for the offer. Here is my private e-mail: [email protected]

Thanks,

Teklu

The excellent way to use lime to step by step ameliorate subsoil acidity.

Do we need to address soil acidity issue , first of the surface depth, thereafter going to subsurface , which i feel , will  not be the right way .In most of the tropical acid soils, sub-surface more acidic than surface layers. The other way could be the , amount of lime needed to ameliorate the depth of acidic soil,  based on root volume of the intended crop(s) to be grown . 

Gentlemen, I have no objection to your views on the topic of subsoil acidity, but how much is research based. If the problem exists in Ethiopian Vertisols, it will be a first in my admittedly limited experience. Much of what has been suggested is not supported by research numbers. We should not ignore published data!!

I will say, though, that field burning --- a practice I observed and got soil samples from --- suggested to me that P deficiency should not be ignored. The effects on P availability were huge. Under high pH conditions this would not be surprising.

Cheers all and my very best regards,

Mart Farina.

Dear Teklu,

If you have no objection, I shall tomorrow send you an email, including slides and soil and yield effects of subsoil amelioration. Many people, some of whom responded to your question, possibly have never encountered the problem. Tropical soils do not necessarily have acid subsoils. It depends on the particular soil and its position on the catena. Also the rainfall, of course. There are many arid areas in the tropics, and it  so happens that much of Ethiopia is above the tropics. Also true, however, that the problem of subsoil acidity is, perhaps, more severe in sub-tropical areas, because of the higher quantities of "reserve' acidity in sub-tropical, less highly weathered areas. For example, in Madagascar, where the soils are as highly weathered as those in Brazil, the lime requirements are much less than they are in South Africa. Quite simply, the reserve Al has long since been leached out of the system. Typically, at the same level of acid saturation, the lime requirements are about a third (at the same clay content) as they are in this country.

So sorry to hassle you, Sir, but exchange of data is what RG is all about and I believe that information I can give you is, perhaps, relevant. After all, prior to my visits to your lovely country, lime had never been used commercially in Ethiopia. Professor Tekalign and Girma Teklekidon would vouch for this.

Cheers for now and all the very best,

Mart Farina.

P.S. My email address is [email protected]

I would also recommend addition of biochar. Our recent work in acid sulfate soils (pH

Thank you Dr. Teklu that you have raised an offbeat problem of sub-soil acidity. This will not be an issue under forest ecosystem. So, the answer is phytoremediation to prevent and control sub-soil acidity. As for the arable lands where domesticated plants are cultivated, provision of space for perennial tree plantations would remedy the situation of sub-soil acidity. I also suggest extensive use of plant and animal residues to improve and sustain organic matter built up to feed soil sheltered micro and macro organisms and facilitate their growth and development. In a matter of three years, the problem of subs-soil acidity would vanish for sure. As a last word of caution, never attempt to lime the soils, since cure becomes worse than the disease. 

Thank you for the interesting question. 

As has been said, the mineralogy of Vertisols is conducive to high pH and a high pH buffer capacity (the change in pH per kmol of acidity per kg of soil). Therefore it is wise before suggesting remedies to establish the nature of the complaint. I'm no expert, but I would want answers to these questions at a minimum before deciding on a course of action: What is the surface pH? At what depth does the pH decline to a level at which toxicity occurs for acid-sensitive species (approx pH=5)? At what depth does the pH affect a wide range of species (pH of 4.2)? What are the levels of exchangeable Al and Mn in the acidic layers (% of ECEC)? 

Where I live and work in Australia we have some highly acidic, highly sodic, saline subsoils in Vertisols. Fortunately the soil layers above the acidity are unaffected. These soils are not common but some experiments have looked at their agricultural development. A search on "Warra" (the locality) and " Vertisol" should reveal some of those publications. 

Good luck with your studies.

Greetings Jeff,

I like what you have said, particularly with regard to the need for  a good soil analysis!!! It is a little premature to hear opinions on what should be done in the absence of good soil analytical data. Vertisols are most unlikely to have subsoil acidity problems!!!

Cheers for now,

Mart.

Martin, scientific  opinions also carry lot of weightage while debating scientific issues. This is how we progress in science, not necessary we should have always experimental data only. Let's be flexible in such discussion. 

Yes, i agree with Martin, Vertisols may  not have subsoil acidity issue.  How to arrive at  depth of subsoil limit with respect to root configuration of different crops. ..?

If the soil acidity is like that  Ultisols then one can follow what Prof. Stahr has indicated.

Lime requirement worked out on the basis of root volume of the given crop would be the best strategy to address subsoil acidity. 

 In terms of subsoil acidity the presence of compacted acid layers called plow pans can be a difficult situation. The mechanical resolution would be the fracture with plow points and the introduction of the lime to the subsurface layers. For liming in general it is important to first determine the appropriate liming material if the soil is low in Magnesium under 100 in the soil test the use dolomitic lime should be employed otherwise calcitic lime is the choice. For deep introduction of lime without deteriorating the soil mechanically the use of a large diameter disc plow is appropriate rather than mold board plows that tend to make compaction issues worse. The liming first and then deep plowing should introduce lime to subsoil. The use of tap rooted cover crops such as daikon oil radish and sudangrass can be effective in breaking up compacted layers also. The overliming of soils can result in marked reduction of micronutrients such as iron, manganese and zinc and this needs to monitored.  Deep rooted pasture mixtures grown perennially can greatly ameliorate the soil issues as they are key to improving soil organic matter. Many of the crop soil issues are alleviated when animal and crop systems are rotated and organic materials are recycled into production fields. For all these issues complete soil and plant tissue analyses are critical for getting the most of your soil and plant resources. 

Combinations of liming materials with gypsum and/or organic matter can hasten the penetration of the liming effect from surface applications down the profile -- assuming of course that there is sufficient rainfall or irrigation.  Unless your plants are very acid tolerant be wary of the gypsum applied alone, as it can push more exchangeable Al into solution. Ripping and incorporation may give rapid access of deep rooted plants to subsoil water.  

Selection and appropiate  use of acid- tolerant  crops and varieties is important as mentioned by Dr.Paul.For liming use of alternate liming materials especially the industrial byproduct sources deserves attention(if locally available) as liming materials are costly and limig is not a permanent solution.I endorse the good suggestions of Dr.Hepperly.

Dear Teklu.

I am agrre with Karl Stahr and using crops that tolerate acidity.  But before you have to know what acidity and textura do you have.

I work with organic agriculture, and we got improve some chemical attributes when we using manure tea and compost tea.

- We got more than half degree of pH in 2 years in foam sandy  (Fa) soils (USDA texture). pHo = 5,2, pHf = 5,8 (with cacao -  plantation - papaya). Using liquid organic fertilizer (manure tea).  Wen we used tea compost soil got improve phosforus, calcium, magnesium, etc.

- We got almost one degree when we applied 1 ton of lime per hectarea. pHo= 4,8; pHf = 5,6. after one year, foam clay (FA), (virgen soil, with natural vegetation).

-

Acid soils are not deleterious for the commonly grown crops, plantation trees etc.

Difference between surface and subsoil acidity are not much in the red soils of the lower Himalayas.

We have found that naturally-occurring 2:1 minerals act to sequester ex Al to buffer sub soil acidity in the Himalayas. Interestingly, acid soils in the Western Ghats again naturally ameliorated by Ca rich zeolites.  

We have to keep in mind that in spite of this sub soil acidity best quality plantation crops are seen around the world.

Regards

Biochar addition is a potential method.

It appears to me that there is limited information on subsoil acidity in India and we need to generate more information(taking into consideration the work done by Dr.Bhattacharyya and his team).The work should involve  subsoil acidity characterization,soil-plant interactions in those soils and amelioration/reclamation aspects.

I endorse the comments from Dr Tapas, the best quality fruits like banana, citrus, mango, citrus ..all are produced despite subsoil acidity , which i emphasized in my  responses to almost similar question  flagged off by Dr Pal sir...stating that can we call acid soils chemically degraded..?

The issue of sub-soil acidity projected as a problem has been driven to no significance as per the response of Dr. Anoop Kumar Srivastava, which deserves appreciation. It is a clear signal to those, not to worry about it unless there is evidence of crop failure or similar adverse situation. Thank you Dr. Srivastava. 

Dear Sir

Your response makes no sense to me at all. The fact that subsoil acidity seriously influences yield potential and sustainable crop production is undoubted!!! Just read the literature. Brazilians and others will be amazed at your response to a very well known and accepted problem in high potential areas. Read the literature please before making such a statement. It surprises me!!!

However, my kind regards,

Mart Farina.

After going through the discussion ,three questions came in to my mind

1.What will happen to acid soils if cultivated with annual agricultural crops  without  taking up any remedial measures? Will the remediation  become more problematic  and costly with time?

2.What is the effect of various cropping/farming systems and fertilizer practices(without liming) on soil acidity? Will they accelerate the soil acidity development?

3.With continuous cropping of acid soils, will the surface soil acidity enters into subsoil ,further complicating the situation?

Colleagues, a quick perusal of the published  literature revealed that soil acidity can  further increase with time  if no remedial measures are taken under undisturbed forestry system,pastures and under  cultivation of agricultural crops .Even subsoil acidity will increase with time if it is not monitored and remedial measures taken.In a long term study in south-west Sweden based on 90 profile samples measured in 1927 and 1982-1984 reaveled a general decrease in pH with 0.3-0.9 units.All soil horizons upto C horizon at 70cm had become more acid beneath all types of canopy(beech,oak,spruce).Futher details can be seen in the following paper

Changes in soil acidity from 1927 to 1982-1984 in a forest area of south-west Sweden by Hallbacken ,L.&Tamm,C.O. Scandinavian Journal of Forest Research ,1(1-4)

http://www.tandfonline.com/doi/abs/10.1080/02827588609382413

In  semiarid tropics of central and northern Queensland and the North TerritoryAustralia,accelerated soil acidification (0.2 to 10.l kmol H/ha.year for the  sites sampled)through the introduction of Stylosanthes spp.based pasture to a depth of 90 cm.

Evidence of accelerated soil acidification under Stylosanthes-dominated pasture by Noble,A.D. et al.Australian Journal of Soil Research 35(6):1309-1322 1997.

www.publish.csro.au/SR/S97053  http://dx.doi.org/10.1071/S97053

In some states of Australia like South Australia,Queensland and NSW soil acidity increased under different cropping systems,land use systems,products removed for market,fertilizer practices.Surface soil acidity further extended to subsoil if not taken care .The following references may be seen.Farming systems and soil acidity.Government of South Australia http://www.ruralsolutions.sa.gov.au

Soil acidification Queensland Government. http://www.qld.gov.au/dsiti/assets/soil/soil-acidification.pdf

Crop yield impacts and management of soil acidity in Central western NSW by Small,J.

https://grdc.com.au/Research-and-Development/GRDC-Update-Papers/2016/02/Crop-yield-impacts-and-management-of-soil-acidity-in-Central-Western-NSW

I believe soil acidity is largely undiagnosed and treated in both the so called industrial world and in developing economies. Working for top multiple national corporation we all did soil analysis but few ever pay much attention to fine tuning soil acidity issues. This I believe is both a big gap and opportunity as lime is very abundant and a low cost amendement which is not scarce and sulfur is also abundance as a by product and can remediate alkaline soil issues. Since much of the fertilizers used are acid generating the role of soil acidity is dynamic and needs attention proactively. 

Have a read of some of my papers on recent work we have done to treat soil acidity using organic matter. Organic matter is much cheaper, and, comparatively, readily available under many situations.

There is a reference in Tisdale and Nelson book entitled

Soil Fertility and Fertilizers on chapter entitled as Soil acidity and alkalinity application of gypsum can ameliorate sub soil acidity.

sulftae ion can replace exposed hydroxil group of layer silicate clay at sub soil, also it can bind Al as aluminium sulfate, and Ca from gypsum can also migrate to the subsoil to reduce subsoil acidity.But the requirement of gypsum will be high.