sale of farm land

I am resident alien for tax purposes. I have an unused farm land in my home country that I want to sell. I had been the owner of the land for almost 20 years. How is the income from the sale of such land taxed in US. Also, does the final sell price that i report consider the amount that i invested in purchasing the land and the period for which  i had held? Will this income be taxed separate from my US income or will it be added to my US income and then taxed? Thanks