Urgent!!!!..Advice: Puppy(6Ms old) eats dirt everytime I take him outside and introduce him to ground.

So I have a six months old puppy. He mostly stays inside. He acts ok..all quiet, sleeps normal, behaves well, just doesn't listen or follow me around if called, doesn't much tear stuff but occasionally when finds stuff that can go inside his mouth he eats it like insect,small black stuff or dirt on floor..it's all fine upto that…but the moment I take him outside and put him on ground of soil. He would descent his head down and begin licking and sometimes even bite chunks out soil and eats it..I stop him, gently lift his head up and say no..but when I remove my hands he again out his head down..I've tried rewarding him food one day or two to refocus his attention but the absence of food ,he returns again to eating dirt..the next day again same ….is it normal? Will he change? Is he deficient in something.