You are an NRI . You cannot purchase  agricultural land in Karnataka or in any state in India 

You need RBI permission which would not be easily granted

In Karnataka you need to be a farmer to buy a farm land if you are non farmer then buying a farm land needs ceiling of income up to 25 lakh per annum.  Earlier it was only 2 lakhs

See firstly a NRI cannot purchase agriculture land in India.

Secondly if you are not NRI and your family Income is below 25 lakh PA then you can with permission from commissioner can purchase the agriculture land in Karnataka.

If your annul income is less than 25 lacs you can buy.

You can jointly purchase the agricultural land with another person who comes within the category of "Farmer”. some laws are differ from state to state better consult a local property lawyer. 

You need to be an agriculturist or belong to an agricultural family to buy agricultural land in Karnataka state especially if you would like to buy in partnership, then all the partners until it is not a firm, need to belong to the above category.

Since you own an agriculture land elsewhere, you can buy agricultural landed property in Karnataka, provided you comply with the other formalities as envisaged in law for the purpose. The Karnataka Land Reforms Act now does not allow non-agriculturists whose income is more than Rs 25 lakh per annum to buy farm land.

However please note that if you are a NRI you cannot buy agricultural land anywhere in India.

1. For buying africultural land in Karnataka, you shall have to be an agriculturist or from an agricultural family.

2. Let the said lanjd be bought by some one who belongs to an agricultural family and all other5s can join the partnership firm wherein the said agriculturist will invest his land while others will invest money.

1. As per the information mentioned in the present query, makes it clear that you want to buy a farming land, but not surely not from a farmer family as you yourself have stated that have no idea about the land of front with grandfather.
2. You can buy it, but with some government formalities.
3. You will have to get the certificate or permission from the Tehsildar of the district where the land is situated.
4. And also will have to give the undertaking in affidavit that you won’t use the land for some other purpose.

Dear

If you are NRI then you cannot buy farm land in India.

And if not then you can go ahead with the purchase by permission of tehsildar of that area. 

you can purchase on your wife's name only if the agrilcute land exists on her fathers name. 

Yes if the wife is from agricultural family then you can purchase the land on her name.  

purchase agricultural land in wife name if she has agricultural back ground 

Then she has to buy the same

Yes, your wife can buy the agricultural land provided all other criteria like her income from non agricultural source is within the prescribed limit.