Efeitos nas fra??es da mat?ria org?nica do solo pela aplica??o de N- fertilizante em cana crua com deposi??o da palhada

• Autor(a) principal: Assun??o, Shirlei Almeida
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/1409
• topic: Humic substances; Sugarcane management; Spectroscopy; Subst?ncias h?micas; Manejo da cana-de-a??car; Espectroscopia; Agronomia

Brazil is the biggest sugarcane producer of the world with cultivated area superior to nine millions hectares. To reach economically viable productivity levels it is necessary to make use of high amounts of N fertilizers. These fertilizers are high cost and they also can contribute to emission of greenhouse gases and pollution of watercourses, as well as, to influence directly on the decomposition of the soil organic matter (SOM). In this context to understand how interactions between nitrogen and SOM occurs in sugarcane fields is important from both economic and environmental points of view. Therefore, the objective of this study was to evaluate quantity and quality of soil carbon when different doses of nitrogen are added in the form of ammonium sulphate in a sugarcane raw agro-ecosystem in an ultisol from Coastal Plains. The experiment was conduced in sugarcane fields renovated in 2009 in area of the company LASA alcohol distillery, in Linhares - ES, in an Ultisol with sandy to medium texture, from Coastal Plain environment. The variety of sugarcane (Saccharum spp.) used was RB918639. There were evaluated five treatments of N ammonium sulphate doses: 0 (control), 80, 100, 120 and 160 kg of N per ha-1 with four repetitions, established under experimental design of randomized blocks. Each experimental unit (plot) was 70 m? (5 lines with 10 m, spaced by 1.4 m between lines). Samples of plant and soil were collected in September 2013 and 2014, corresponding to 4th and 5th harvest. The results indicated that among the N doses evaluated, the doses of 100 and 120 kg were the most efficient on accumulating carbon on the humic fractions, particle size, densimetric and oxidizable carbon fractions. The dose of 160 kg was the less effective to carbon accumulation on the humic fractions, particle size, densimetric and oxidizable carbon fractions. Total nitrogen, natural abundance of 13C and 15N, stem and straw production were not influenced by N rates, with no differences on any of the seasons. About the elemental composition of humic acids (HA), the quantities of chemicals were very similar between doses and coherent with results in the literature for the HA. In the E4/E6 ratio, the dose of 160 kg of N was the one with the lowest E4/E6 ratio. Regarding the infrared with Fourier transformation it was observed the predominance of aliphatic groups, and the analysis of major components enabled the clear separation of the effects from different N doses. In the 13CNMR prevailed larger amounts of aliphatic carbons, it was confirmed with the aliphaticity index of the samples, the results were above 80% for all samples. It was also verified through the 13 CNMR that the control area and the dose of 160 kg had the lowest aromaticity rates. Therefore, it was concluded that different fractionations of organic matter along with spectroscopic techniques were effective on evaluating the influence of different nitrogen doses to the decomposition of SOM.