Tull was
an English farmer and agricultural writer.
He developed the horse hoe and seed drill and
published The Horse-Hoeing Husbandry 1633,
"which contained advice on plant culture as well as
ideas on plant physiology." He believed that the earth
was the plant's food and was absorbed and digested by
the plant, therefore, continued cultivation divided
the earth into small particles which the plant could
absorb. The air was useful to the plant only as a
place into which to throw off waste products. Roots
were the stomach and the intestines of plants. Leaves
were lungs and sap was blood. Manure he said caused
bad flavor in crops.
