137 Granddad s walking stick obviously isn t humus the ground would be identified as soil organic matter us ing this carbon analysis method But Granddad s walking stick obviously isn t humus Humus understood in a narrower sense is called perma nent humus which is a small subset of soil organic mat ter that develops over decades and centuries really It consists of myriad complex organic compounds which endure for a long time in the soil closely bound to clay minerals To use a modern term humus is a fuzzy struc ture We still can t exactly describe its complex compo sition or the processes that create it even though humus plays a such a vital role in soil functions system stability and the buffering capacity of the soil Is it fair to say that non organic agriculture does not depend on soil quality as much as organic agriculture Yes I don t mean to suggest that the condition of the soil is not considered at all but it plays a much smaller role than in organic farming If soil fertility is lacking for ex ample when structural damage to the soil impairs root growth or when the soil contains too little organic mat ter and humus the quick non organic fix is to apply more fertiliser especially mineral nitrogen Is there a problem with resorting to a bag of fertiliser Applying readily soluble fertiliser can seriously disrupt bi ological and microbiological processes We are all familiar with a similar phenomenon in our own bodies If you don t exercise for instance your muscle mass will decline Use it or lose it That s a law of Nature What are the consequences Nitrogen boosts crop yields more than any other nutri ent In organic agriculture limited amounts are supplied Nature through the targeted cultivation of legumes which bind nitrogen from the air But mineral nitrogen fertilisers are comparatively cheap so they tend to be too liberally ap plied in non organic agriculture with less efficient re sults The consequences for the environment are dire Surplus nitrogen that can t be absorbed by crops con taminates the aquifer as nitrate And it evaporates into the atmosphere as nitrous oxide which is a greenhouse gas with a 300 times greater effect than carbon dioxide at the molecular level A previous and more extensive interview with Prof Dr Köpke is available in German at www lebensbaum de koepke

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