ABSTRACT
Agricultural land under organic management globally constitutes around 30.4 million hectares out of 4676.9 million hectares total agricultural land (0.64%; Willer et al. 2008), and wheat was fourth among crops in world production in 2008 (FAOSTAT 2011). The term organic farming dates back prior to 1940, when it was deŸned as a way to improve soil
5.1 Wheat-farming systems and soil organisms ................................................................... 89 5.1.1 Organic farming....................................................................................................... 89 5.1.2Taxonomic sufŸciency .............................................................................................90 5.1.3Effects on soil organisms ........................................................................................ 91
5.1.3.1Bacteria and Fungi .................................................................................... 91 5.1.3.2 Nematoda ................................................................................................... 92 5.1.3.3 Enchytraeidae ............................................................................................ 93 5.1.3.4Generalist predators ................................................................................. 94
5.2A case study .......................................................................................................................... 94 5.3Discussion ........................................................................................................................... 103 References ..................................................................................................................................... 105
fertility through the application of animal feces (Heckman 2006). Today, organic farming refers to management strategies that avoid the use of inorganic fertilizers, pesticides, and growth regulators to minimize environmental impact. These management strategies have therefore been promoted as ecosystem-oriented agricultural production systems and may contribute to a sustainable agriculture in the future (Häni et al. 1998). A long-term study by Mäder et al. (2002) in Switzerland suggested that the proŸt under organic farming is comparable to conventional farming for a number of row crops, while associated environmental impact and soil degradation are reduced. Yields were on average 20% higher in conventionally managed crops, but costs for pesticides and inorganic fertilizers adjusted farmers’ proŸts to the same level. The extrapolation of results of such small-scale studies and related reviews to the potential of organic farming for sustaining a global food supply (Badgley et al. 2007; Badgley and Perfecto 2007) has been challenged (Avery 2007; Cassman 2007). However, consumer awareness is increasing in several countries, and there is a growing demand for environmentally sound agricultural products (Tilman et al. 2002; Willer and Kilcher 2010). One of the mechanisms that have been put forward to explain the relatively high yield in organic farms without making use of pesticides and inorganic fertilizers is that organic crops are associated with more complex soil food webs (Haubert et al. 2009; Crowder et al. 2010). These food webs can ensure sufŸcient nutrient availability through decomposition of organic matter by soil organisms and may maintain pest densities at low levels (Zehnder et al. 2007; Birkhofer, Bezemer, et al. 2008).
