首页|Conversion of Brazilian savannah to agricultural land affects quantity and quality of labile soil organic matter

Conversion of Brazilian savannah to agricultural land affects quantity and quality of labile soil organic matter

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  • NSTL
  • Elsevier
Most studies assessing land-use change (LUC) and management impacts on the soil organic carbon (SOC) budget mainly focused on total soil organic matter (SOM), neglecting its functional fractions such as water-extractable organic matter (WEOM). This may limit a better understanding of SOC dynamics along the soil profile as WEOM plays a key role in several soil and microbial processes. Here, we aimed to obtain a quantitative and qualitative assessment of WEOM dynamics to 1 m depth in areas after native vegetation conversion to long-term agriculture in Brazil. For this purpose, cropland areas under no-tillage (NT; similar to 23 years old) and native vegetation (NV; i.e., Cerrado vegetation) were evaluated across a transect of 1000 km within Brazil's new agricultural frontier - the so-called MATOPIBA region. We combined spectroscopic analyses (UV-Vis and DRIFT spectroscopies), C and nitrogen (N) determination in different SOM pools (i.e., bulk SOM, WEOM, and microbial biomass), and microbial measurements [e.g., microbial biomass C (MBC) and N (MBN), and p-glucosidase activity] to better understand changes in WEOM dynamics induced by LUC. We observed that although SOC decreased along the soil profile after NV (4.2-20.7 g kg(-1)) conversion to NT (3.8-14.2 g kg(-1)), water-extractable organic C levels (3.6-79.3 mg L-1) were similar between land uses. On the other hand, an increase in water-extractable total N was observed after NV (0.4-4.6 mg L-1) conversion to NT (0.5-19.3 mg L-1). Although MBC and MBN levels decreased for most study sites, beta-glucosidase activity increased after LUC indicating intensive microbial processing of SOM. As a result, WEOM had lower aromaticity and molecular weight (i.e., low values of SUVA254 and A2/A3) in NT than NV; and a relative decomposition of aliphatic and polysaccharides over aromatic and amine/amide was observed after LUC through DRIFT spectroscopy. Our study indicates that LUC had stronger impacts on WEOM quality than its quantity, with agricultural areas having more biochemical changes in WEOM than NV.

Soil organic matterWEOMUV-Vis spectroscopyDRIFT spectroscopyNo-tillageOxisol

Santos, Rafael S.、Wiesmeier, Martin、Oliveira, Dener M. S.、Locatelli, Jorge L.、Barreto, Matheus S. C.、Dematte, Jose A. M.、Cerri, Carlos E. P.

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Univ Sao Paulo, Dept Soil Sci, Luiz de Queiroz Coll Agr, Ave Padua Dias 11, BR-13418260 Piracicaba, SP, Brazil

Tech Univ Munich, Sch Life Sci Weihenstephan, Chair Soil Sci, D-85354 Freising Weihenstephan, Germany

Univ Fed Vicosa, Inst Ciencias Agr, Campus Florestal,Rd LMG 818 Km 06, BR-35690000 Florestal, MG, Brazil

Mohammed VI Polytech Univ UM6P, AgroBiosci Program, Lot 660 Hay Moulay Rachid, Benguerir 43150, Morocco

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2022

10.1016/j.geoderma.2021.115509

Geoderma: An International Journal of Soil Science

Geoderma: An International Journal of Soil Science

ISSN：0016-7061
年,卷(期)：2022.406
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