What Were the Difficulties Faced by Farmers Before the Invention of the Haber – Bosch Process?

Before the Haber - Bosch process, farmers found that they constantly had to 
change farming land every few centuries. This was because the nitrogen in the 
soil would be absorbed by all the plants, for growth. With the natural process 
of fixed nitrogen, otherwise known as nitrogen fixation, not producing enough 
nitrogen for all the agriculture in the world, it was necessary that we began 
to produce nitrogen fertiliers. By the 19 century, almost no nitrogen rich soil 
was left on earth! Farmers could grow no more plants of good quality, most had

This plant displays nitrogen deficiency!

nitrogen defficiency.