Vincent de Leijster

62 Chapter 4 4.2 METHOD 4.2.1 Study site and field experiments This study was conducted in the eastern part of Andalusia, south-eastern Spain. Rainfed almond cultivation is rapidly expanding in this area, having increased by 18% between 2014 and 2017 (Junta de Andalucía, 2016). This expansion can be attributed to market opportunities and high prices, due to the failure in almond production in California (USA), which produces more than 90% of worlds’ almonds (FAOSTAT, 2019). This makes rainfed almond cultivation currently one of the most abundant agricultural land-covers in the high plains of the provinces Granada and Almería. Almond farms in this region are typically located at elevations between 700-1300 m. This region is characterized by low annual precipitation of 300-400 mm and extreme differences in temperature with a maximum average of 31–39 °C in summer and a minimum average of 0–4 °C in winter (Cruz Pardo et al., 2010). The soils of the experimental sites can be classified as Calcic Cambisols, Eutric Cambisols, and Calcic Regosols and had loam and sandy loam textures (De Leijster et al., 2019). 4.2.2 Agroecological experiments, yields and farmer surveys Agroecological experiments From 2016-2018 we conducted field experiments with four treatments on five experimental sites, located on private rainfed almond farms. The treatments were implemented in randomly assigned locations similar in slope, crop variety and visual soil conditions; each treatment containing a minimum of sixteen trees. The conventional tillage (CT) treatments were harrowed 2–3 times a year at 20-30 cm depth, using a chisel plough to remove the understory. The no tillage (NT) treatments were harrowed nor mowed, which allowed wild plant species to grow. The green manure (GM) treatments were sown with a legume– cereal mixture (common vetch, bitter vetch, barley; 50-50-20 kg ha -1 ) and then harrowed to incorporate the seeds in the soil. The compost (CM) treatments were fertilized with compost (fermented sheep manure and straw; type bokashi) applied manually near the almond trees at an approximate quantity of 6 m 3 ha -1 and incorporated in the soil by harrowing. In addition, the CM treatments were harrowed 1–2 times to remove weeds. Detailed information on the field conditions is provided by De Leijster et al. (2019).