Data/hora: 04/06/2024 03:20:39

Biblioteca(s): | Embrapa Pantanal.
Data corrente: | 31/07/1995
Data da última atualização: | 31/07/1995
Autoria: | TAN, K. H.
Título: | Effects of humic and fulvic acids on release of fixed potassium.
Ano de publicação: | 1978
Fonte/Imprenta: | Geoderma, v.21, p.67-74, 1978.
Idioma: | Inglês
Conteúdo: | Release of potassium fixed by expanding silicate clays is considered of practical importance in soil fertility. Humic and fulvic acids are expected to play a definite role in liberating this fixed K, because of their chelating power, but not much is known in this respect. The following investigation was conducted to study release of fixed K by mont- morillonite and illite, using humic and fulvic acids isolate from the surface horizon of a Cecil soil (Typic Hapludult, Red Yellow Podzolic soil) as extractants. For comparison, extraction was also done with 1 N neutral NH4 -acetate, a mixture of 0.05 N HCL and 0.025 N H2SO4 or H2O. Supporting analyses of clays were carried out with X-ray diffraction to establish changes, if any, in crystal structure due to fixation, release of K, or asorption of humic compounds. The results indicated that humic and fulvic acids released some of the K fixed by montmorillonite or illite. In terms of percentage of the total K fixed, 9 to 28% were released by the various extractants. The percentage K released by humic and fulvic acids were similar from both montmorillonite and illite, but based on absolute values, humic and fulvic acids extracted less K (mg/100g) from illite than montmorillonite. Although statistically significant at the 5% level of probability, the capacity of humic compounds to liberate fixed K was not different markedly from those of NH4 -acetate and the double acid mixture. Differences in pH of humic solutions had no influence on extraction of fixed K. X-ray diffraction analysis yielded curves showing an increase in spancing from 10.4 for K- montmorillonite to 13.2 as a result of extraction with the double acid mixture.
Palavras-Chave: | Fertility.
Thesagro: | Fertilidade; Potássio; Solo.
Thesaurus Nal: | potassium; soil.
Categoria do assunto: | --
Registro original: | Embrapa Pantanal (CPAP)
Exemplares: | CPAP - (28830-1) - ADD - SP - -- - SP0524 -  - 0524 - DIS