When the solution is concentrated, there is strong possibility that the K : Ca will increase in arid region calcareous alkaline soils. Because upon conc., the Ca ions will tend to form first ion pairs and then precipitate as CO3 - compounds. Secondly Ca ions will enter into Stern Layer part of DDL which is not considered generally the part of  DDL. Both these factors will decrease Ca ions in soil solution while very very little change will occur in K conc. Hence the K : Ca ratio will widen. However, the clay mineralogy and contents of OM will affect the rate of change. 

Many thanks Sir,

whether the K-Ca activity ratio will doubled.

Could you clarify?

Dr.Manikandan,please read the following publications to better appreciate the concept of activity Ratio and Ratio law.Soil Conditions and Plant growth by Russell, Wiley Black well or revised edition. You may also read short 2-3 page brief description in Encyclopedia of Soil Science http://books.google.co.in/books 

Dr. Angamuthu Manikandan theoretically it could be assumed the 4-time conc of soil solution will double the activity ratio of K : (Ca)1/2 in arid regions calcareous alkaline soils, but practically might not possible. But there will an increase in ration. For example:

K = 4 mmol/L, Ca = 8 mmol/L, then activity ration of K : Ca = 4/(8)1/2 = 1.41, when conc increased 4-time, then

K = 16 mmol/L, Ca = 32 mmol/L, then activity ration of K : Ca = 16/(32)1/2 = 2.28.

  In the activity ratio computation for K,threre is square root  term for Ca or Ca plus Mg.

Activity Ratio of K=K/square root of Ca plus Mg.

Thank you Sir,

As per example provided by Abdul Sir and Subba Rao Sir Formula

I had solved the problem

Example

K = 4 mmol/L, Ca = 8 mmol/L, Mg= 6 mmol/ L then activity ratio of K -Ca  is = K/Square root of Ca+Mg = 4/Square root (8+6) = 4/3.74= 1.06

, when conc increased 4-time, then

K = 16 mmol/L, Ca = 32 mmol/L, Mg= 24 mmol/ L then activity ratio of K - Ca is = 16/square root (32+24) = =16/7.48= 2.13.

Hence we can say as doubled K-Ca activity ratio.

Thanks Dr Rao for suggesting correction, I have incorporated in the answer.

Thank you Debasis, I had gone through the page