N2O Emission Due to Grazing Intensities of Marandu Palisadegrass During the Rainy Season.

This study aimed to quantify N₂O emissions due to grazing intensities of Marandu palisadegrass pastures in central Brazil during rainy season. The experiment was conducted at the Universidade Estadual Paulista “Júlio de Mesquita Filho” - Unesp, Campus of Jaboticabal, São Paulo, Brazil. The soil is classified as Oxissoils and climate as tropical with dry winter and rainy summer. The evaluation of the N₂O fluxes was performed using the static chambers. The experiment designer was completely randomized and the treatments were tree different grazing intensities (15 cm, 25 cm and 35 cm of canopy height) of Marandu palisadegrass kept under continuous stocking during the rainy season. Samplings of N₂O were made in the morning followed by gas chromatographic determination. The evaluation period was of  4 months and the total emission of the period was obtained by weighted average. The data was submitted to ANOVA. The highest fluxes were observed after the rainy events. N₂O consumptions were observed after a long time without rainy. The grazing intensities of 15 cm, 25 cm and 35 cm emittedin the rainy seasons 10.5 (± 8.7), 2.3 (±5.1), 1.7 (± 3.1) mg N-N₂O m^-2 respectively, among parentheses the standard error of the mean. The emissions was different due grazing intensities (P=0.023; α=0.05). In the 15 cm were quantified emissions of N₂O  greater than 25 cm and 35 cm. In the grazing intensities of 15 cm was observed a better distribution of the excretions and a faster N inputs in the soil due to higher plant grow than in the others grazing intensities and also due to the lower production of litter which contributed to the N losses as N₂O.