HUMIC-FULVIC ACID RATIO, Al, Fe AND C IN PYROPHOSPHATE EXTRACTS AS CRITERIA OF A AND B HORIZONS

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Abstract
The ratio of carbon in humic to carbon in fulvic acid (Ch/Cf) in 0.1 M pyrophosphate extracts of soils was useful in differentiating certain A horizons from the associated B horizons. A Ch/Cf ratio of less than 50% was characteristic of Bf and Bh horizons, and the ratio was greater than 50% for nearly all of the A horizons. The ratio varied widely for Bm horizons and for the two Bg horizons tested.The ratio of carbon extracted by pyrophosphate to total carbon (C ext/C) was greater than 50% for the B horizons of acid Brunisolic soils and Podzols, and less than 50% for the A horizons. The ratio of carbon in fulvic acid to total carbon (Cf/C) was greater than 30% for the B and less than 30% for the A horizons of the same soils. Neither percentage extractable carbon nor Cf/C clearly differentiated between Bm and Ah horizons.Ratios of Al + Fe to fulvic acid in the extracts of the B horizons were as high as or higher than those of some insoluble synthetic complexes.