Abstract
Were quantified the plant residues on the soil, total soil organic carbon (TOC) and nitrogen (TN) contents and the different soil organic matte (SOM) fractions and to determine 13C and 15N isotopic soil composition and plant residues in the crop–livestock integration system (CLIS), pasture and Cerrado areas, in Goias, Brazil. TOC and TN, C and N light organic matter content (C-LOM/N-LOM); C and N of particulate organic matter (C-POM/N-POM); and mineral organic matter (C-MOM/N-MOM) were evaluated. δ13C and δ15N of soil and LOM, POM, and MOM fractions, as well as the δ13C of plant residues, were also determined. Plant residues from pasture were more enriched with nutrients and C, and CLIS which are richer in N. δ13C of pasture and CLIS soils indicated that the C from the Cerrado vegetation (typically C3) was replaced by vegetation with C4 photosynthetic mechanisms. CLIS accumulated more TOC than the pasture, and provided higher C-MOM and N-MOM values than pasture, and higher N-LOM levels than pasture and Cerrado. δ13C of LOM is associated with more recent origins of carbon. δ15N of POM and soil of the CLIS and pasture indicate greater mineralization of SOM.
Highlights
IntroductionThe Cerrado biome is the largest savanna region in South America
Plant residues differed among samples, with higher values for the Cerrado and crop–livestock integration system (CLIS) areas and lower values for the pasture area (Table 2)
The δ13C values of CLIS and pasture areas up to the 80 cm depth were compared with those obtained for the Cerrado area, showing an isotopic enrichment in CLIS and pasture areas (Figure 4). These results indicate the substitution of carbon from the Cerrado vegetation by a new carbon, from vegetation with C4 photosynthetic mechanisms, such as Brachiaria and corn
Summary
The Cerrado biome is the largest savanna region in South America. It is located in the central portion of Brazil and is the second largest biome within the country, with an area of approximately 200 million hectares. Almost 55.0% of Goiás is used for human activities (Sano et al, 2008), of which 27.7% holds agricultural crops, 71.0% has cultivated pastures, and the remainder is occupied by forest plantation and urban areas. Regarding land use systems commonly used with agricultural crops and pastures, the no-tillage system (NTS) and crop–livestock integration system (CLIS) are the most used, respectively. Both systems have the potential to accumulate carbon in Cerrado soils. In CLIS, the use of forage increases haystack production, especially during the dry season, promoting an efficient development of NTS and the subsequent accumulation of organic matter in the soil (Carvalho et al, 2010; Loss et al, 2012a, 2016; Sant-Ana et al, 2017)
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