Winter Cover Crops as Sustainable Alternative to Soil Management System of a Traditional Durum Wheat-sunflower Rotation in Southern Spain

Abstract

Durum wheat (Triticum durum)-sunflower (Helianthus annuus) rotation is a common practice in rain-fed arable areas in southern Spain. However there is a need to modify the current crop management due to the stagnating products prices and the achievement of the CAP environmental requirements such as erosion control and reduce fertilizer and pesticides, in keeping with the principles of cross-compliance.In response to all CAP requirements, we propose the introduction of winter cover crops preceding sunflower sowing. Several brassica and legume species have been used as winter cover crops in different agro-systems worldwide due to their high potential for weeds and diseases control and capacity of N fixation respectably (Hartwig and Ammon, 2002). White mustard (Sinapis alba subsp. mairei) and narbon bean (Vicia narbonensis) are species well known for fast growth and high biomass production and their adaptation to Mediterranean conditions (Alcantara et al., 2011, 2009; Nadal and Moreno, 2007), however, the most limiting factor for the introduction of winter cover crops and soil management in the Mediterranean region is water availability (Lopez-Bellido et al., 2007). This study, which is part of a long-term experiment, aims at examining the effect of white mustard (CCC) and narbon bean (LCC) cover crops on soil moisture content (%), compared with a bare soil managed by conventional tillage (CT) adapted to the cross-compliance regulations and no tillage (NT), despite the low adoption of this latter soil management practice (0.5%) in Southern Spain. Trial was conducted at two locations with Vertisol and Inceptisol soils starting in 2012 in southern Spain. Soil water contents were measured by gravimetric analysis in two samples per plot at three depths (0-10, 10-30 and 30-60cm). Results suggested that CCC and LCC could be used as alternative to CT in different soil types with changing rainfall patterns. However, cover crops only could be an alternative to NT in different types of soils in years with precipitation higher to average rainfall of the area, or in soils with high water holding capacity in years with normal precipitation while in soils with poor water holding capacity and lower rainfall years the management of CCC and LCC should be improved (probably early sowing and early mowing).