Farm Book, page 79
by Thomas Jefferson

VI. Preparation of ground.
Young's experiments shew that ploughing in fall gives from one to three bushels per acre
produce more than ploughing in the spring. 4. Exp. agr. 206-211
they shew that 2 ploughings produce 1/4 more than 1. in barley which is a spring grain
3. 1/5 more than 2.
5 1/3 more than 4.
6 no more than 5.4. Exp. agr. 213. 216
he found ploughing deeper than 5. I. of no utility to wheat or barley the first year, but supposes it would become useful in 2. or 3. years. trench ploughing 10. or 12. I. deep produced immediate benefit to turneps & carrots, but not deeper. 4. exp. agr. 223.