Investigating the Optimal Day for Nitrogen Fertilization on Piatã palisadegrass and Quênia guineagrass after Defoliation

Considering that nitrogen is the main macronutrient limiting pasture productivity, the aim of this study was to investigate the most appropriate day for nitrogen fertilization of the grasses Brachiaria brizantha BRS Piatã and Panicum maximum BRS Quênia. The experiment was conducted in a greenhouse in the city of Rondonópolis, located in the state of Mato Grosso, Brazil, using a completely randomized design. The treatments consisted of five nitrogen fertilization periods: 0; 2; 4; 6 and 8 days after defoliation. The dry mass of the leaf blade (DMLB), dry mass of stem + sheath (DMSS), dry mass of residue (DMRES) and root dry mass (RDM) were evaluated. The non-structural carbohydrate of the grass roots was also quantified. The later nitrogen fertilization after defoliation reduced DMLB (P< .01) and DMSS (P< .01) of the BRS Piatã palisadegrass, and DMRES of both grasses (P< .01). Higher levels of water soluble carbohydrates were observed when nitrogen fertilization was performed on grass cutting (day 0). Nitrogen fertilization of the BRS Piatã palisadegrass close the time of defoliation is recommended. For Quênia guineagrass, nitrogen can be applied between the cutting day and the eighth day after defoliation. For the root system, there is a higher content of water soluble carbohydrates in the BRS Piatã palisadegrass and greater accumulation of starch in the BRS Quênia guineagrass.