Soil organic matter in podzol horizons of the Amazon region: Humification, recalcitrance, and dating

Abstract

Characteristics of soil organic matter (SOM) are important, especially in the Amazon region, which represents one of the world's most relevant carbon reservoirs. In this work, the concentrations of carbon and differences in its composition (humification indexes) were evaluated and compared for several horizons (0 to 390cm) of three typical Amazonian podzol profiles. Fluorescence spectroscopy was used to investigate the humic acid (HA) fractions of SOM isolated from the different samples. Simple and labile carbon structures appeared to be accumulated in surface horizons, while more complex humified compounds were leached and accumulated in intermediate and deeper Bh horizons. The results suggested that the humic acids originated from lignin and its derivatives, and that lignin could accumulate in some Bh horizons. The HA present in deeper Bh horizons appeared to originate from different formation pathways, since these horizons showed different compositions. There were significant compositional changes of HA with depth, with four types of organic matter: recalcitrant, humified, and old dating; labile and young dating; humified and young dating; and little humified and old dating. Therefore, the humification process had no direct relation with the age of the organic matter in the Amazonian podzols.

Evaluation of the roles of metals and humic fractions in the podzolization of soils from the Amazon region using two analytical spectroscopy techniques

“…In previous work by Tadini et al [13], involving the dating of these Amazonian Spodosols and determination of the humification indices, it was observed that soil P1 presented an accumulation of young organic material with a low degree of humification, which was displaced with depth, due to physical and chemical processes. The highest values for humification of the whole soil and for the humic acid fraction were obtained for the Bh-C horizon, at 240 cm.…”

“…Sample P4 was from a well-drained podzol under rainforest vegetation, with no influence of groundwater. Further details of the study area can be found in Tadini et al [13].…”

“…Therefore, the results indicated that the transfer of iron and aluminum to deeper profiles of soil P1 involved the participation of young and less humified organic matter. Transfer of the metals in soil P4 involved older organic matter with a low degree of humification, which could be attributed to the presence of more recalcitrant compounds derived from lignin [13].…”

Solidification of High Organic Matter Content Sludge by Cement, Lime and Metakaolin

“…On one hand, the organic matter wraps the clay particles and hinders the reaction between the solidification agents and the clay particles. On the other hand, since the organic matter is acidic [17][18][19], it will produce neutralization reaction with alkaline substances produced by solidification agent hydration reaction, which will reduce the pH of the solution, and then hinders the hydration reaction of solidification agents [20][21][22]. So for S/S sludge with high total organic content (TOC), the solidification effect is often poor.…”

Aplikasi pupuk organik limbah rumah potong hewan untuk meningkatkan kesuburan tanah dan produktivitas padi

“…Bahan organik tanah dalam pengelolaan lahan berkelanjutan berperan dalam pengaturan dinamika unsur hara tanah (Tadini et al, 2018). Bahan organik di samping berpengaruh terhadap pasokan hara tanah juga tidak kalah pentingnya terhadap sifat fisik, biologi dan kimia tanah lainnya (Suminarti & Susanto, 2015).…”