Análises fisiológicas em capim-elefante BRS Capiaçu (Pennisetum purpureum Schum) submetidos a diferentes doses de nitrogênio

Abstract

Elephant Grass (Pennisetum purpureum Schum) is one of the most widespread and important grasses in Brazil, and can be used in different ways and achieving good levels of animal production, when well managed, due to its nutritional value and good acceptability by animals. Knowledge about the physiological responses in relation to fertilization, especially nitrogen, is extremely important so that the species can be properly managed. Therefore, the objective of this work was to evaluate the gas exchange response of Elefante Grass BRS Capiaçu subjected to different doses of nitrogen (0, 100 and 200). Therefore, the experiment was carried out on the Menezes farm, located in the municipality of Capanema, close to the district of Tauari. A completely randomized design (DIC) was adopted, in a 3x3 factorial arrangement, with four replications for each treatment. The treatments were composed of three doses of N (0, 100 and 200). Data collection took place between January 26, 2023 and May 31, 2023, after the leveling cut close to the ground. Monitoring gas exchange through photosynthesis, transpiration, stomatal conductance, system II photosynthetic efficiency, electron transport rate, non-photochemical quenching and the relative chlorophyll index. Gas exchange analyzes were carried out using IRGA, with 30, 45 and 60 days after leveling and fertilization. The relative chlorophyll index was taken using a chlorophyllometer (SPAD-502, Minolta), from 8 am to 12 pm. Analysis of variance (ANOVA) of the treatments was performed. The significant means were compared by the Tukey test, considering p<0.05, using the statistical program R. Based on the gas exchange of BRS capiaçu, the gas exchange and the relative chlorophyll index had physiological efficiency, with the gas exchange was from 45 days onwards at a dose of 200 kg/ha of N and the relative chlorophyll index had its greatest efficiency from 30 days of collection on increasing doses of N, that is, doses of 100 and 200 kg/ha of N are recommended.