Because there were only a few scant varieties to choose from for farmers to grow. It's different nowadays, as farmers have far more cultivars and varieties to choose from to grow in their fields.
Soil and weather determines what is grown. The plains area are dry, windy, with little rain, but can get snow in the winter. Only a few crops can grow in conditions like that.
Silt deposits from the Nile and a long growing season allowed for a variety of crops.
To irrigate crops
Rainfall and growing season length determine crop production.
Barbed wire fencing.
Leaving fields unplanted allowed soil to recover from cash crops production, but it was impossible for poor farmers who needed the money from the sale of their crops.
It allowed the farmers to plant more crops and therefore increasing production.
Cyrus McCormack
Cyrus McCormack
It helped farmers all around the U.S. in the Great Depression era expand their varieties of main cash crops.
Farmers diversified their crops
The farmers' houses were usually located close to their fields and livestock for practicality. This proximity allowed farmers to easily tend to their crops and animals without having to travel far.