Preethikha you asked your question on behalf of your friend Johan who appeared to be having trouble in growing his corn seeds in clay. I asked my friends about this and these were the ideas that they arrived at.
The roots of the corn plant are very complex like most plants and they NEED oxygen . Clay is an important soil, it is full of nutrients which are important in providing the growing plant with food , HOWEVER it is very different from most of the soils that we meet in our gardens.
Soils are composed of three types of particles: sand, silt, and clay.
The size of the particles varies, with clay having the smallest size and sand the largest.Smaller sized particles pack more closely together and slow the flow of water through the soil.The composition of a soil can affect the permeability (flow) of water through it.
There is the possibility that your friends corn seeds produce roots which are then ‘drowned’ in the surrounding clay soil. Investigate your friends soil and compare it to other soils in your neighbourhood. My next question for you is how would you go about investigating it ?