Agroscope, Institute for Sustainability Sciences ISS, Switzerland

Effects of many years of organic agriculture

More and more farmers consider to switch from conventional to organic production. What effect, then, does this have on yield and environmental performance? In particular, the question of how the duration of organic management affects plant yield, weed populations, biodiversity and soil fertility has rarely been investigated. To investigate this question, we compared 34 plots distributed over four farm categories – conventional, recently converted, and «new» and «old» organic farms. Our study shows that crop yield and soil fertility remain constant as length of time under organic management increases. Similarly, weed pressure has not increased along with duration of organic management. Weed abundance did, however, vary strongly among fields, with problematic weeds being highly abundant at specific field sites. This study demonstrates that duration of organic management does not have a negative impact on either plant yield or soil fertility on mixed-economy farms under Swiss conditions

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