All depends, whether there is a need to overcome acidity, especially exchangeable acidity in soils; otherwise no need of liming!

My opinion is that since the pH of wetland rice soil remain around neutral, liming seldom bring positive results. Because main objective of liming is to increase the pH of acid soil.

It is possible that liming provides a boost to calcium supply that may be low if the soil is naturally acidic when not flooded (or highly leached).  The positive effect sometimes reported may be due to nutrient supply not a change in pH.

Absolutely right Dr. Butler. If there is any positive result of liming in wetland soil that may be due to the supply of Ca or Mg in the Ca or Mg deficient soil. Obviously that result was not for pH changes. Liming can show beneficial effect only in upland (dry land/aerobic) condition specially in vegetable crops.

A question more than an answer:  is there cation competition, e.g. with Fe 2+ ? might that be beneficial in some soils?

Thank you Paul Milham sir for your scientific response. I agreed to your comment that in wetland condition Fe3+ is reduced to Fe2+ and some times conc. of Fe2+ in soil solution become toxic to rice plant specially in Fe rich soil. Such a condition application of lime can play a positive role regarding nutrient availability.

In tropical soil we have vast area of acid sulphate soil which need high dose of lime applications. If the lime can increase the pH to 4.5 your rice yield will raise significantly. this was partly due to supressed Al concentrations apart from nutrient availability. Semi arid region I guest will be much different.

Kindly check..

http://scialert.net/fulltext/?doi=ijss.2014.1.15&org=10

See also..

http://search.proquest.com/openview/8571634f675c5aefd220723a8a4605ed/1?pq-origsite=gscholar&cbl=2032162

Explore here..

http://www.fao.org/docrep/x5872e/x5872e0a.htm

Also to be seen..

http://www.fao.org/docrep/x5648e/x5648e0e.htm

Sahibin Abd Rahim

Thanks for joining the discussion. Of course acid sulphate soil need to be limed rigorously. The pH of such soil is very low and Fe toxicity limits the crop growth. Paul Milham also wrote that positive response of liming in wetland rice soil can be recorded if the soil is rich in Fe2+.

Wherever it may be if the soil is highly acidic then liming is required.

Nice discussion on a very interesting question tossed up by Dr Aminul. As long as soil is acidic in nature , needs liming to be done , should be  done to make it more productive . At the same time , there is also a possibility , wetland soils getting buffered around neutral soil pH. 

Excellent comments by Anoop sir.

Dr.Aminul Sir,

I endorse Dr.Annop Sir answer.  Acid soils will be deficient in Ca.  Hence its supply will give response by the crop.

Thanks

Thanks Rajakumar for your comments. Actually acid soils and acid sulphate soils have some limitations for crop production. Excessive soil acidity associated with

1.leaching loss and low levels of Ca, Mg, K and Mo while toxic levels of Al3+, Fe3+  and Mn2+

2.Phosphorus fixation.

3.detrimental to plant growth and to microbiological process in soil specially nodulation process.

In this case liming with CaCO3, CaO, Ca(OH)2, MgCO3, and dolomite CaMg(CO3)2 can correct the soil pH. However, liming should be practiced in soils having pH below 5.5.

Some really very interesting points raised  about acidic soils by Dr Aminul. In perennial fruits being grown in and around northeastern India , which i feel, is  nothing but an extension of the same region while considering Bangladesh, especially Chittegaon, Morvibazar , Rangpur areas known for citrus  , there is hardly any practice of  lime addition , but still productivity can be compared with any of the best managed orchards globally...besides excellent quality as well...

Dear Anoop sir you rightly mentioned that in Bangladesh liming in fruit trees are not practiced. Here is some attachments for your review.

https://www.slideshare.net/sakiliubat/acid-soil-amendment-through-liming

Dear Aminul Islam

Fundamentally liming is the practice for acid soils irrespective of the crop. Acid sulfate soils do need liming for optimum production. Dr. Anroop Kumar Srivastava idea of buffering soils around neutral pH needs further explanation. However, deficiency of Ca in acid soils seems only when soils are too acidic (mostly pH < 5) and soils are rain-fed. In soils irrigated with surface water, Ca deficiency rare is recorded.

Excellent comments Dr. Abdul Ghafoor. I am very much pleased to read your comments. Like you I also am expecting elaborate discussion about soil's buffering.

Dr Aminul, you tossed up this question with an anticipation  , that  wetland rice might not need liming . We still believe that as long as soil pH remains within acidic range , we need do liming . The question of  experiencing any possible change in buffering capacity of soil  needs to be linked with soil mineralogy. Anticipating the soil mineralogy predominantly rich in low activity kaolinite clays , reaction products developing as a result of wetland characters of soil  , will be getting leached on a regular basis, thereby , maintaining the acidic soil pH  , and producing the positive response of lime application. 

Thanks Anoop sir for nice response. Actually I am going to establish some experiments in northern part of Bangladesh (Rangpur and Dinajpur regions) in which I like to the effect of liming and different macro and micro nutrients  (NPKSZnBMo) on rice productivity and nutrient availability in soil. Soil of those areas are acidic (pH 5.1-5.3) and light to medium textured. Experiments will be started in next wet season (Monsoon/T. Aman season) and will be continued up to Boro season (dry season). Can I expect a positive response of liming. I shall be grateful if any one give some suggestion with different treatment combinations.

Very interesting Dr Aminul. What an extent, liming alone can sustain the  rice crop..?