Abstract
The crop-livestock integration system significantly increases the carbon content in chemical fractions of soil organic matter (SOM). This study aimed to evaluate chemical indicators of SOM attributes for sites under brachiaria/livestock and pearl millet/no livestock in Goias, Brazil. A third area covered with natural Cerrado vegetation (Cerradão) served as reference. Soil was randomly sampled at 0-5, 5-10, 10-20 and 20-40 cm. Total organic carbon stocks (TOC), oxidizable carbon fractions (OCF) (F1>F2>F3>F4), carbon content in the humin (C-HUM), humic acid (C-HAF) and fulvic acid (C-FAF) fractions were evaluated. F1/F4, F1+F2/F3+F4, C-HAF/C-FAF and (C-HAF+C-FAF)/C-HUM indices were calculated, as well as stocks chemical SOM fractions. Brachiaria/livestock produced greater TOC stocks than pearl millet/no livestock (0-5, 5-10 and 10-20 cm). In terms of OCF, brachiaria/livestock generally exhibited higher levels in F1, F2, F4 and F1/F4 than pearl millet/no livestock. C-HUM (0-10 cm) and C-HAF (0-20 cm) stocks were larger in brachiaria/livestock than pearl millet/no livestock. Compared to the Cerradão, brachiaria/livestock locations displayed higher values for TOC (5-10 and 10-20 cm), C-HAF and C-HAF/C-FAF (5-10 cm) stocks. TOC, C-HAF stock and OCF show that land management with brachiaria/livestock was more efficient in increasing SOM than pearl millet/no livestock. Moreover, when compared with pearl millet/no livestock, brachiaria/livestock provided a more balanced distribution of very labile (F1) and recalcitrant (F4) carbon throughout soil layers, greater SOM humification. Brachiaria/livestock leads to higher values of F1 and F4 in depth when compared to pearl millet/livestock and provides a more homogeneous distribution of C-FAF and C-HAF in depth compared to Cerradão.
Highlights
The Cerrado, after Amazon biome, is the second largest Brazilian biome, exhibiting complex dynamics that are strongly affected by seasonal fluctuation and anthropic activity (Bolliger et al, 2006; Sano et al, 2007)
In Cerradão combined with the lack of anthropic activity
The largest Total organic carbon stocks (TOC) stocks in depth in cropped areas can derive from a consistent root development, i.e., pearl millet and brachiaria grasses
Summary
The Cerrado, after Amazon biome, is the second largest Brazilian biome, exhibiting complex dynamics that are strongly affected by seasonal fluctuation (wetdry savannah) and anthropic activity (Bolliger et al, 2006; Sano et al, 2007). The Cerrado is characterized by a tropical savannah-like native vegetation of low trees, scrub brush and grasses. It covers approximately 204 million hectares (Mha) or 23% of Brazil’s land area (Bustamante et al, 2006; Rodríguez Pacheco et al, 2012). About 62% of this area (127 Mha) is suitable for agriculture (Lilienfein & Wilcke, 2003). Cultivated pastures in the Cerrado region cover about 66 Mha An estimated 50 Mha are subjected to a process of degradation by excessive grazing (Silva et al, 2004a; Klink et al, 2008)
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