If we take this through the term till:

To prepare (land) for the raising of crops, as by plowing and harrowing;

it does seem a little inconsonant, but, if we go on in the defintion past that semicolon and see

cultivate

perhaps it's not so inconsonant after all. Leave out that critical step of planting the seed and you haven't done much of a job of cultivating.

http://www.bartleby.com/61/42/T0214200.html