Dear Dr Nazir , it is an excellent question . let me respond to it ;

Saline water limit :  Electrical conductivity 11.5-2.0 dS/m; Sodic water limit: 1.0-1.5 RSC ( Residual sodium carbonate ) 

Saline soil limit : Electrical conductivity  2.5-3.0 dS/m ; Sodic soil limit: 8-10 ESP  (  Exchangeable sodium percentage ) and 5-7 SAR ( Sodium adsorption ratio )

But Dr Nazir , we need to define these limits , especially the soil salinity and sodicity  on the basis of soil texture . As soil texture goes finer , the tolerance limits will be much lower  . And , another very important factor is , to what an extent , there is a reduction in fruit yield , whether such limits are restricted upto  25 per cent reduction or 50 per cent reduction in fruit yield. These limits will again be dictated by soil texture . Interesting

Notwithstanding the  greater threshold value  salt tolerance level of Guava, it is essential to take up corrective measures to reduce significantly salinity and/ or sodicity in soils. In a textural context, it is easier to manage coarse textured soils than fine textured soils for their salt problems as the latter suffer from restricted drainage and saline waters aggravate the problem. To live with saline water problem for irrigation, just  add one kg of fresh cow dung to 1000 liters of saline irrigation water before irrigating the crop as this measure would reduce salinity of water. 

Good response from two specialists; Anoop Kumar and Reddy. Yes, Guava plant is not high tolerant of salinity and sodicity. Sodic water and sodic soils do more damage compared saline water and saline soils because of degradation of soil physical properties in case of the former. Water infiltration, decrease porosity and root aeration are the major problems emerging when sodic water is used for irrigation or the soil is sodic. Soil texture is very important factor for salinity and sodicity tolerant of almost all plants. There is high level of tolerance in sandy and loamy soils compared to clayey soils, especially to that of sodicity. My aim of this question is to get information and data specifying tolerance level of Guava plant to each type of water and soil salinity/sodicity with respect to soil texture. Mostly such details are not available in many countries. Sharing of information and data will help researchers, if it is available. In case of absence of such data, it is time to go for investigations to so much details. Time has reached to surpass to mention just the general and average conditions. 

Pl see following RP(s):

http://edis.ifas.ufl.edu/mg045

http://conference.ifas.ufl.edu/gardener10/Presentations/Monday/pm/0230%20J%20Crane.pdf

Another very important issue , I missed in my previous response , is the stage of screening , how old seedlings/buddlings of guava , you are  subjecting them to screening against salinity/sodicity tolerance .

Thank you Anoop Kumar and Riaz Waheed for your valuable addition. Yes, the stage of plant growth and the age of plant are very important considerations. Even the climatic conditions are very important because response of plants will not be similar in cold and hot climates. I want that the recommendations should now be so refined to mention all details and the end users should be able to believe it confidently.  Now there is need to move forward. For example I repeat the information I have taken from the reference given by Riaz Waheed.

  "Guava trees are moderately tolerant to saline soils and water however growth and fruit production decrease. Symptoms of salinity stress include marginal and tip browning of leaves, leaf drop, stem dieback, small fruit size and fruit drop."

Presently, we are having information like above. 

I am emphasizing that information should be like as under.

"Guava plant can tolerate .... dS/m  or ......SAR ..... RSC when grown in sandy soil/ loam soil/ clay loam soil (There should be one option) up to the age of ... or as mature tree under climatic conditions of (Rainfall, temperature and humidity)."

I hope that my point/ consideration will be well taken.

Guava is salt sensitive plant and water salinity more than 1.5 dS/m can hinder the plant growth and productivity.  More importantly, salinity in seedling stage  can have serious impact in term of establishment. if you want to do experiment you can set water salinity concentration like this 0.5, 1.5, 2.5,  4.5 ( dS/m) and do the experiment . But it may depend on the soil types and  irrigation methodology. Drip irrigation is suitable for saline water irrigation. Hope it helps

Suresh Panta! thanks but try to understand the discussion. Your answer is that guava plant growth and productivity is reduced if water EC is more than 1.5 dS/m. I have questions to this statement:

How much productivity is reduced?

In what type of soil texture is this reduction? whether it will be same in sandy soil, loamy soil and clayey soil?

Which cultivar/ variety will indicate this response? Will it be same in all varieties?

What are the climatic conditions under which this result will be reproducible? Will the results be the same under cold and hot climates?

I am just talking of generation of detailed and refined recommendations which are now need of the day. 

Dear Dr Nazir Hussain, there is nothing like fine tuning in applied sciences like soil science and plant physiology to get a reproducible data on salt tolerance limits and crop yields as both soil and plant are extremely dynamic systems affected by diverse factors including climate. This is not the case with pure sciences where the data can be perfectly reproducible to a precise values and all experiments are repeatable to verify the data for its reliability. Even for that matter, soil texture, who can specifically and accurately state with precision that the texture is uniform throughout the soil sampled and analysed. The data in applied sciences are always relative but can not be accurate and precise for obvious reasons.

Dear Dr Nazir Hussain, there is nothing like fine tuning in applied sciences like soil science and plant physiology to get a reproducible data on salt tolerance limits and crop yields as both soil and plant are extremely dynamic systems affected by diverse factors including climate. This is not the case with pure sciences where the data can be perfectly reproducible to a precise values and all experiments are repeatable to verify the data for its reliability. Even for that matter, soil texture, who can specifically and accurately state with precision that the texture is uniform throughout the soil sampled and analysed. The data in applied sciences are always relative but can not be accurate and precise for obvious reasons.

All right Dr. Reddy, by reproducible I do not mean that it should be 100 % the same. But I mean in this discussion is that we should recommend like that .... so much tolerance level of guava is under sandy soil under hot conditions. The end user will be clear to decide if he want to grow guava in sandy soil, it will be OK to him for that salinity level. But if he grows it in clayey soil he can get still higher reductions in fruit yield etc.

Agricultural Science, frankly speaking is nothing short of a shadow boxing thrives on relativity and approximations and as you rightly sought for Dr Nizar Hussain. As such, I only suggest to a Guava farmer to grow guava as a test crop with very limited extent and observe the crop for its performance, having already said that corrective measures have to be adopted to get rid off the salt problem in soils. Why should Guava or whatever crop be put to suffering with salt problem as if it is next to impossible to get over the problem adopting chemical and/or biological techniques. Humans I consider as highly selfish expecting plants and animals to behave to their order and dictates and still get adequate income for humans. Let the plants and animals be treated as the best and dependable friends on Earth unlike human species whose greed is never ending.

Please go through link given below

http://www.fao.org/docrep/005/y4263e/y4263e0e.htm

Agreed with the answer of members

Thank you Sarvada and Shukla.

Thank you Hassan for sharing a valuable reference.