Comparação de métodos de análise química de K, Ca, Mg e Al, em folhas de erva-mate (Ilex paraguariensis St. Hil.)

Abstract

This study was carried out in order to test five chemical methods for leaf analysis and their interrelationships in the analysis of K, Ca, Mg and Al in tea leaves. The samples were collected in a liming experiment, with different base saturation levels, laid out in the field with planted erva-mate (Ilex paraguariensis St. Hil.), located at Pinhais County, Paraná State. The evaluated methods were as follows: Wet digestion with nitro-perchloric acid, dry ashing in porcelain crucibles, dry ashing in platinum crucibles, wet extraction (non digestion) with 1 mol/L HCl and wet extraction (non digestion) with 1 mol/L HCl+d (d=further 1:3 dilution of the extract). In the laboratory, the samples were ordered according a split plot design, being factor A, the five tested methodologies and as factor B, the different base saturation levels of the field. All tested variables presented statistical significance(P<0,01) for variation source and methods. High solubilizations were achieved for most of the tested elements with the nitro-perchloric, dry ashing in porcelain crucibles, and both HCl wet extractions methods. The non digestion methods with HCl showed to be highly promising. High significance was observed for the correlation among methods for K, Mg and Al. Ca showed the poorest correlations among methods.