Calendula officinalis L. presents ornamental, culinary and therapeutic use. Its inflorescence is used to heal and as an anti-inflammatory. This study analyzed the effect of four different irrigation depths under field conditions on flavonoid production in marigold plant (Calendula officinalis L.). The water depths were estimated based on the class A pan evaporation (CPE): 0, 50, 100 and 150% CPE; they were applied from the beginning of flowering to the end of the culture cycle. There were no statistical differences in flavonoid content. The highest values of flower dry weight and flavonoid yield were obtained with the treatment without irrigation. The highest proline content was found in the plants subjected to overwatering stress. The accumulated water deficit for the treatment without irrigation signalized possible death due to water deficit. As precipitation occurred in the pre-flowering, the plant, originated from Mediterranean, responded with an abundant flowering in mass and number of flowers. Thus, for Presidente Prudente (São Paulo State, Brazil), if there is no water replacement through precipitation, supplementary irrigation with 200 mm will be necessary only in the pre-flowering to induce maximum flowering and maximum flavonoid yield per hectare.
Calendula officinalis; irrigation scheduling; class A pan evaporation
