Impact of farming systems on soil ecological quality: a meta-analysis

The productivist model implemented after the second world war has succeeded in improving production to meet growing demands for food, but it has also deeply affected soil physicochemical properties, as well as of aboveground and belowground biodiversity. Alternative farming systems such as organic farming, biodynamic farming and soil conservation farming are actually developing to enhance the sustainability of farming systems. Although the impact of agricultural practices on soil ecological quality is well known, there is little knowledge on the impact of the different farming systems as a whole. Here, we analysed the impact of the main farming systems on soil biodiversity and functioning, reported in about 100 scientific publications. We found that conventional, organic, and biodynamic systems are the most widely studied, whereas soil conservation farming is poorly documented. Soil biological indicators are improved by ca. 70% in organic farming and biodynamic farming relative to conventional farming. 43% of soil bioindicators are improved in biodynamic farming relatively to organic farming. Soil conservation farming scores better than conventional farming for 57% of the indicators. Therefore, biodynamic farming displays the highest soil ecological quality, followed by organic farming, soil conservation farming and, last, conventional farming. Organic fertilisation and longer crop rotations are the most favourable practices, whereas pesticides and soil tillage are the most deleterious ones. The review also evidences a lack of studies on soil conservation farming and on bioindicators of the soil fauna.