The question of agriculture is a question of art. [...] Agriculture basically just deals with the things that are there: the topsoil is principally chalk, silica and then of course one must make sure that there is humus, ensure the soil is well aired and that no substances that muck up this process enter the soil such as artificial fertilizers, minerals, etc. 

Agriculture is a question of art, which for me is the engagement with substances. In other words, if one understands the spirit of substances, one can only really do agriculture. 

Joseph Beuys, Conversation with Joseph Beuys, 2004