Capital, Vol. 3, Chapter 6: http://www.marxists.org/archive/marx/works/1894-c3/ch06.htm
<quote>
The moral of history, also to be deduced from other observations
concerning agriculture, is that the capitalist system works against a
rational agriculture, or that a rational agriculture is incompatible
with the capitalist system (although the latter promotes technical
improvements in agriculture), and needs either the hand of the small
farmer living by his own labour or the control of associated
producers.
<unquote>
Michael