Determinação de fósforo microbiano: comparação entre métodos e coberturas florestais
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Data
2009-08-01
Autores
Villani, Ecila Mercês de Albuquerque
Barros, Nairam Félix de
Novais, Roberto Ferreira
Mendonça, Eduardo de Sá
Zocolo, Guilherme Julião [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Ciência do Solo
Resumo
Muitos trabalhos mostram a importância da biomassa microbiana do solo (BMS), principalmente como fonte/dreno de C e de N em plantações florestais; contudo, são escassos os trabalhos relacionados ao fósforo microbiano (PBM), sobretudo aqueles relativos aos métodos de determinação do PBM nesses ecossistemas. O presente trabalho foi realizado com o objetivo de avaliar métodos de determinação do PBM em solo com diferentes coberturas vegetais. O trabalho consistiu da análise de amostras de Latossolo Vermelho-Amarelo distrófico muito argiloso (LVAd) localizado no município de Viçosa (MG), coletadas nas profundidades de 0 a 5 e 5 a 10 cm, em áreas com as seguintes coberturas vegetais: pínus (Pinus taeda), eucalipto (Eucalyptus grandis) e floresta nativa. Para determinação do P microbiano, foram empregados os métodos fumigação-extração (FE), irradiação com micro-ondas-extração (IE) e irradiação com micro-ondas-extração com membrana de troca aniônica (EMTA). em termos gerais, menores teores de PBM foram obtidos com o método irradiação-extração. Considerando a cobertura vegetal, foi detectada diferença significativa entre os três métodos sob floresta de eucalipto e floresta nativa, principalmente na camada superficial. Sob pínus, apenas o método IE diferiu dos demais, na camada subsuperficial. Menores coeficientes de variação (CV) foram obtidos com o FE, retratando maior precisão do método. Entretanto, o método IE mostrou-se, em termos operacionais, o mais adequado à determinação do PBM quando se tem maior número de amostras. Com relação às coberturas vegetais, a grande variabilidade observada nos CVs obtidos para cada cobertura, nos três métodos testados, inviabiliza a escolha de um único método que apresente maior precisão na avaliação do PBM.
Many studies have shown the importance of the soil microbial biomass, mainly as source/sink of carbon (C) and nitrogen (N) in forest stands. However, there are few studies focused on microbial P (MPH), especially in relation to the determination methods of MPH in these ecosystems. For an evaluation of the methods used to determine microbial P (MPH) in soils, three methods were evaluated: fumigation-extraction (FE); radiation with microwave-extraction (RE); and radiation by microwave-extraction with a membrane for anionic exchange (EMAE). Samples of a very clayey dystrophic Red-Yellow Latosol (LVAd) were collected at depths of 0-5 cm and 5-10 cm in soils under pine (Pinus taeda), eucalypt plantations (Eucalyptus grandis), and native forest, in Viçosa, state of Minas Gerais. In general, lower MPH contents were obtained by the RE than by the FE method. The MPH contents established by the three methods in the areas with eucalypt and native forest varied significantly in the surface layer. Under pine, only the RE method was significantly different in the 5-10 cm layer. The lowest coefficients of variation (CV) were obtained by FE, expressing the greater precision of this method. Under the studied conditions, however, where a large-scale analysis of samples is required, the RE method turned out to be, in terms of functionality, most adequate for the MPH determination. In relation to the stands, none of the three tested methods could be indicated as uniquely most precise method for the evaluation of the MPH, due to the great variability in the CV for each forest type.
Many studies have shown the importance of the soil microbial biomass, mainly as source/sink of carbon (C) and nitrogen (N) in forest stands. However, there are few studies focused on microbial P (MPH), especially in relation to the determination methods of MPH in these ecosystems. For an evaluation of the methods used to determine microbial P (MPH) in soils, three methods were evaluated: fumigation-extraction (FE); radiation with microwave-extraction (RE); and radiation by microwave-extraction with a membrane for anionic exchange (EMAE). Samples of a very clayey dystrophic Red-Yellow Latosol (LVAd) were collected at depths of 0-5 cm and 5-10 cm in soils under pine (Pinus taeda), eucalypt plantations (Eucalyptus grandis), and native forest, in Viçosa, state of Minas Gerais. In general, lower MPH contents were obtained by the RE than by the FE method. The MPH contents established by the three methods in the areas with eucalypt and native forest varied significantly in the surface layer. Under pine, only the RE method was significantly different in the 5-10 cm layer. The lowest coefficients of variation (CV) were obtained by FE, expressing the greater precision of this method. Under the studied conditions, however, where a large-scale analysis of samples is required, the RE method turned out to be, in terms of functionality, most adequate for the MPH determination. In relation to the stands, none of the three tested methods could be indicated as uniquely most precise method for the evaluation of the MPH, due to the great variability in the CV for each forest type.
Descrição
Palavras-chave
fósforo microbiano, precisão, solos ácidos, microbial phosphorus, precision, acid soils
Como citar
Revista Brasileira de Ciência do Solo. Sociedade Brasileira de Ciência do Solo, v. 33, n. 4, p. 1061-1069, 2009.