The organic movement touts the sustainability of their methods, but its claims do not withstand scrutiny. For example, a study published earlier this year in the journal Hydrology and Earth System Sciences found that the potential for groundwater contamination can be dramatically reduced if fertilizers are distributed through the irrigation system according to plant demand during the growing season. But organic farming depends on compost, the release of which is not matched with plant demand.
The study found that “intensive organic agriculture relying on solid organic matter, such as composted manure that is implemented in the soil prior to planting as the sole fertilizer, resulted in significant down-leaching of nitrate” into groundwater. Especially with many of the world’s most fertile farming regions in the throes of drought and aquifer depletion–which was the subject of a 60 Minutes segment on November 16–increased nitrate in groundwater is hardly a mark of sustainability.
Moreover, although composting gets good PR as a “green” activity, at large scale it generates a significant amount of greenhouse gases (and is also often a source of pathogenic bacteria applied to crops).
From "Why Organic Isn't 'Sustainable" on Forbes.