Vincent de Leijster

147 Synthesis and conclusion 7 gross and net revenues. Since we evaluated only short-term responses on agroecological interventions, it was not yet possible to conclude what the economic performance of a fully developed agroecological system will be, as costs and benefits may still develop further. Our findings concerning the short-term negative effects of vegetation cover on almond yield were similar to the findings in studies with a longer study period in Spain (Martínez-Mena et al., 2013) and Italy (De Giorgio & Lamascese, 2005). Agroecological management may also affect management costs, as costs for no tillage were lower than for conventional tillage, and costs for compost application were higher than for conventional tillage. For the coffee case study (Chapter 6), in which we assessed the effect of vegetation diversification and agroforestry, we found some similar outcomes (Figure 7-2). Implementing agroforestry also negatively affected the yield of the main crop; however, it positively influenced the quality of the main crop (Chapter 5). These effects did not result in changes in gross and net revenue compared to conventional monoculture coffee. Different from in our almond case study, the vegetation diversification here also resulted in income diversification and therefore additional benefits were obtained from fruit and timber. Furthermore, agroforestry was related to lower costs for harvesting and post-harvesting activities compared to conventional management. In both case studies we found that vegetation diversification affected the yield of the main crop, which has also been reported for similar agroecological practices in other studies (Jezeer et al., 2017; Knapp & Van der Heijden, 2018; Rosa-Schleich et al., 2019). The loss in yield of the main cropmay be caused by the competition for resources such as light, nutrients and water, although various resources have played a role. In almond orchards, ground cover vegetation may compete with almond trees for soil nutrients and water availability (Durán Zuazo et al., 2008b; Martínez-Mena et al., 2013). In the case of coffee, light is often the most important resource that is limited, due to shading by the canopy layer (Soto-Pinto et al., 2000); however, some trees may also compete with coffee plants for nutrients and water (Farfán, 2014). Potential reductions in the yield of the main crop may be compensated by lower management costs, higher market prices, and income from other products. For the latter, some studies have calculated the total economic returns or land equivalent ratio, so as to enable the comparison of monoculture systems and polyculture systems (Agegnehu et al., 2006; Schneider et al., 2017; Utomo et al., 2016). We studied income diversification through crop diversification in the coffee case study, but this option was not explored in almond farms. We found that the marketing of timber and fruit from the canopy layer provided substantial additional benefits; this was also found in several other studies (Jezeer et al., 2018; Schneider et al., 2017; Souza et al., 2011). We did not investigate the potential of crop diversification in almond systems, but here we present data from a comparable study