Photochemical efficiency of Brachiaria brizantha under Eucalyptus canopies in an ILF system.

Brazilian livestock farming is an essential part of the country's economy, standing out as one of the largest sectors of national agribusiness. Challenges such as the search for environmental sustainability require appropriate management for soil conservation and the development of the livestock sector. The integrated livestock-forestry (ILF) system is a sustainable technique that aims to integrate different production systems in the same area, making better use of natural resources. The choice of tree species to be implemented in the system is highly relevant, as it affects the luminosity available to the species that grow under its canopy, affecting determining characteristics associated with the productivity and quality of the pasture. The aim of this study was to evaluate the influence of luminosity in the understory of an ILF system on the photosynthetic activity of the Brachiaria brizantha species in an Atlantic Forest region. To do this, chlorophyll a fluorescence analyses were carried out on forage plants grown in a consortium with Eucalyptus urograndis (Clone 1407), with spacing between the trees of 4m and 24m between the crop rows. The treatments were established according to two lighting conditions: the control treatment corresponding to the condition with the highest lighting (between the planting rows) and the treatment with the lowest lighting corresponding to the area under the canopy of the eucalyptus trees (in the crop row). The results show that the low light supplied to the B. brizantha forage promotes low efficiency in the electron transport chain, indicating a possible stress situation.