Leys in sustainable farming systems

A grass ley is defined as a temporary grassland that is integrated in a crop rotation. It has its origin in the 16^th century in Brabant and Flanders, where red clover replaced the fallow period in the crop rotation. Today, the main reasons for the use of leys have remained very similar; next to weed and pest control, leys are used for improving soil quality, fertilisation and feed for livestock. Where leys originally consisted of mainly red clover, they have evolved to leys with lucerne, grasses and mixtures with grassclover and grass-clover with forbs. Grosso modo, three types of farming systems in which leys are used can be distinguished: (1) dairy/beef farming systems with leys in rotation with fodder crops; (2) mixed dairy/ beef and arable farming systems (on one farm or regionally cooperating farms) using leys in the arable rotation for forage or biomass for energy; and (3) arable farming systems using leys for internal input as cut and carry fertilizers (C&C) or ‘green fertilizer’. In this paper these three types of farming systems are described and illustrated with case studies. The role of a ley, consequences for species choice, ley duration and percentage of leys in the system are discussed.