An easy and fast method to estimate Cynara cardunculus seed yield based on head weight and number

This paper aims (a) to derive empirical relationships to predict cynara seed yield per head and per unit area, avoiding laborious extraction of seeds from its complex inflorescence structure; (b) to determine the head­weight distribution per unit area; and (c) to estimate the range of Cynara cardunculus seed yield. We analyzed 16 field experiments, varying in crop age and environmental conditions in Greece. Seed yield per head (SYhead) can be accurately predicted as a linear function of dry head weight (Hw): SYhead = 0.429 · Hw– 2.9 (r 2=0.96; n=617). Based on this relationship, we developed a simple two-parameter equation to predict seed yield per unit area (SY): SY = HN · (0.429 · µ – 2.9), where HN is the total number of heads per unit area and µ is the mean head weight (g head-1), respectively. The models were tested against current and published data (n=180 for head-level; n=35 for unit area­level model), and proved to be valid under diverse environmental and management conditions. Attainable cynara seed yields ranged from 190 to 480 g m–2 y–1, on dry soils and on aquic soils (shallow ground-water level). This variation in seed yield was sufficiently explained by the analyses of head-weight distribution per unit area and variability of seed/head weight ratio at head level. This work provides basal information of crop reproductive effort and reveals the great potential of cynara as a biomass and oil crop for bioenergy production.