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A global, unified dataset on Soil Organic Carbon (SOC) changes under perennial crops has not existed till now. We present a global, harmonised database on SOC change resulting from perennial crop cultivation. It contains information about 1605 paired-comparison empirical values (some of which are aggregated data) from 180 different peer-reviewed studies, 709 sites, on 58 different perennial crop types, from 32 countries in temperate, tropical and boreal areas; including species used for food, bioenergy and bio-products. The database also contains information on climate, soil characteristics, management and topography. This is the first such global compilation and will act as a baseline for SOC changes in perennial crops. It will be key to supporting global modelling of land use and carbon cycle feedbacks, and supporting agricultural policy development., Design Type(s)data integration objective • data collection and processing objective • factorial designMeasurement Type(s)amount of carbon atom in soilTechnology Type(s)digital curationFactor Type(s)climate • Species • experimental condition • ageSample Characteristic(s)Brazil • cultivated environment • Canada • United States of America • New Zealand • Italy • Germany • Cameroon • India • Sri Lanka • Venezuela • Kingdom of Denmark • Republic of Ireland • French Republic • United Kingdom • Kingdom of Spain • Costa Rica • Ethiopia • Ghana • Indonesia • Mexico • Nigeria • Republic of South Africa • Portuguese Republic • China • Malaysia • Turkey • Israel • Sweden • italy • Georgia • Puerto Rico • Tanzania • Australia Machine-accessible metadata file describing the reported data (ISA-Tab format)

The genesis of Planosols is a complex process since it can involve multiple cycles of soil formation, deposition of allochthonous materials and also past climate changes. Furthermore, this subject is still poorly studied in the humid tropics, thus hindering a proper appraisal of the potentials and limitations of Planosols. The objective of this research was to study pedogenetic processes and properties of Planosols formed from different parent materials in southern Brazil. Four soils were sampled: (P1) Hypereutric Luvic Albic Planosol, developed on lagoon plain sediments; (P2) Orthoeutric Luvic Albic Planosol, on Holocene alluvial deposits; (P3) Hypereutric Luvic Albic Planosol, on granite; and (P4) Orthoeutric Luvic Albic Planosol, on gneiss. All Planosols presented sandy horizons A and E, with low pH (

This study evaluates the dynamics of soil organic carbon (SOC) underperennial crops across the globe. It quantifies the effect of change fromannual to perennial crops and the subsequent temporal changes in SOCstocks during the perennial crop cycle. It also presents an empiricalmodel to estimate changes in the SOC content under crops as a functionof time, land use, and site characteristics. We used a harmonised globaldataset containing paired-comparison empirical values of SOC andincluding different types of perennial crops (perennial grasses, palms,and woody plants) with different end-uses: bioenergy, food, other bioproducts, and short rotation coppice crops. Salient outcomes include: a20-year period encompassing a change from annual to perennial cropsled to an average 20% increase in SOC at 0-30 cm (6.0 ± 4.6 Mg ha-1gain) and a total of 10% increase over the 0-100 cm soil profile (5.7 ±10.9 Mg ha-1). A change from natural pasture to perennial cropdecreased SOC stocks by 1% over 0-30 cm (-2.5 ± 4.2 Mg ha-1) and10% over 0-100 cm (-13.6 ± 8.9 Mg ha-1). The effect of a land usechange from forest to perennial crops did not have significant impacts,probably due to the limited number of plots; but the data indicated thatwhile a 2% increase in SOC was observed at 0-30 cm (16.81 ± 55.1 Mgha-1), a decrease of 24% was observed at 30-100 cm (-40.1 ± 16.8 Mgha-1); perennial crops generally accumulate SOC through time,especially woody crops; and temperature was the main driver explainingdifferences in SOC dynamics, followed by crop age, soil bulk density, claycontent and depth. We present empirical evidence showing that the FAOperennialization strategy is reasonable, underscoring the role ofperennial crops as a useful component of climate change mitigationstrategies.

Converting abundant agricultural residues to valuable products, such as biochar, is a pressing challenge for society. Here, our objective has been to produce biochar-based fertilizers (BBFs) with high carbon stability, high yield, and characteristics favorable for their use in soils. Thus, H3PO4 with and without MgO was co-pyrolyzed with coffee husk and poultry litter. Proximate analysis, total phosphorus and magnesium, biochar yield, carbon retention, and thermal and chemical carbon stability were assessed. The BBFs were slightly acidic (pH ∼6.0) and showed high contents of total P (146–206 g kg–1) and total Mg (96–98 g kg–1), similar to commercial fertilizers. Biochar yield increased up to 65% when treated with H3PO4 and H3PO4–MgO, resulting in up to 78% greater carbon retention. BBFs showed higher thermal stability, by thermogravimetric analysis and muffle oxidation, when compared to corresponding pristine biochars. Conversely, the addition of H3PO4–MgO decreased the chemical stability (higher H2O2 and...

The C:N ratio is the most widely used indicator of the quality of organic residues and soil organic matter, but little is known about how average soil C:N ratios change when pristine lands are converted to agriculture in the humid tropics. This work aimed to compile the literature on Brazilian soils and calculate percent changes in soil organic carbon (SOC), total N and C:N ratios, after conversion of native vegetation to different land use systems. The hypotheses tested were that land use change affects mean soil C:N ratios across a range of experiments, and that different land use types would affect C:N ratios differently. Overall, average changes for SOC and total N for the 0–20 cm standard depth interval were respectively −14.4 and −13.1% (p

T errestrial ecosystems, comprising vegetation and soil in uplands and wetlands, significantly impact the global carbon (C) cycle and, under natural conditions, are a sink of atmospheric carbon dioxide (CO2) and methane (CH4). However, conversion of natural to managed ecosystems (i.e., agroecosystems, urban lands, and mined lands) depletes ecosystem C stocks, aggravates gaseous emissions, and exacerbates radiative forcing. Thus, the onset of agriculture around 8000 BC presumably transformed these sinks into a source of greenhouse gases (GHGs) (Ruddiman 2003), mostly CO2, CH4, and nitrous oxide (N2O), and depleted the terrestrial (soil, vegetation, and peatlands) C stocks. Ruddiman (2005) estimated the depletion of the terrestrial C stock (soil and vegetation) by 456 Pg (502.65 × 109 tn) since the onset of agriculture. Of this, the historic depletion of soil organic carbon (SOC) stock is estimated at 130 to 135 Pg (143.3 × 109 to 148.8 × 109 tn) (Sanderman et al. 2017; Lal 2018). Therefore, recarbonization of some of the terrestrial biosphere (soil and vegetation) is an important strategy to mitigate the anthropogenic climate change (ACC) and enhance other ecosystem services because of the link between SOC stock and atmospheric concentration of CO2 (Trenberth and Smith 2005). Recarbonizing the terrestrial biosphere involves…

Despite a multitude of studies on fertility and physics of tropical soils, the effect of soil parent material on their genesis, chemical and mineralogical composition is not yet fully understood. Here, we studied a toposequence of four deep, well-developed soils along a basalt-sandstone transition, comprising two Ferralsols and one Luvisol on the summit and midslopes of a basalt plateau, and one Cambisol at a lower sandstone plateau. Basalt soils had high (42–77%) clay contents, and were mostly comprised by gibbsite, Fe oxides, and poorly crystalline kaolinite, whereas the sandstone soil had

In tropical humid conditions, soil organic carbon (SOC) concentrations have been reported to be proportional to clay, clay + silt and Fe/Al oxide contents. Typically, soil texture and mineralogy are strongly dependent on soil parent materials, but it is not known if SOC retention would also be affected by soil parent material. Such relationship, if established, could be useful to estimate regional SOC stocks, since geological maps are more numerous and often more accurate than soil maps. The objective of this study was to assess the effect of parent material, texture,and oxide content on SOC contents in tropical highlands. Thus, samples to 1-m depth were obetained for seven soils derived from quartzite, sericite-schist, itabirite, serpentinite, limestone, gneiss and phyllite. All soils formed under similar climate and native forest, and were located on the midslope position. Despite wide variations in soil texture and mineralogy, there were no valid correlations between SOC and clay, clay + silt or Fe/Al oxide concentrations. Similarly, SOC stocks did not differ significantly when computed for 0–20, 0–40 and 0–100 cm layers, and in all soils most SOC was associated with the clay fraction. We propose that such absence of effects of soil parent material, texture and oxide contents on SOC retention can be due to the overriding effect of altitudes of 900–1100 m a.s.l., which resulted in higher SOC stocks because of lower mean annual temperatures. These trends are in contrast to those reported for tropical lowlands where the textural and mineralogical controls of SOC retention were first described. Therefore, soils on tropical highlands (> 900 m) are likely to present similarly high SOC stocks, whereas soil parent material, by means of soil texture, mineralogy and oxide contents would affect SOC retention only at lower altitudes.

The identification of paleosols is difficult when no buried horizons or lithification occur. Here, we described the identification of a possible paleosol, its characterization, and which features supported its positive diagnosis. In a construction site, a vertical cut exposed an unusual red–yellow mottling with massive structure and channels (probably faunal), in contrast with the overlying homogeneous red Oxisol with fine granular structure. A similar but more deferrified section with white–yellow mottling also occurred nearby, and both were sampled as large clods. In thin sections, many oriented clay coatings occur along channel voids, suggesting illuviation, as well as dissolving Fe nodules and Mn coatings along planar and channel voids. X-ray diffraction showed a clay dominated by kaolinite, traces of illite, and absence of gibbsite, again contrasting with the gibsitic-kaolinitic clay of the Oxisol. We confirmed the diagnosis of a Paleoultisol due to the following incompatibilities with the overlying Oxisol: (1) massive, apedal structure, and higher bulk density, (2) clay coatings indicative of illuviation as key soil-forming process, (3) low clay contents in particle-size analysis due to cementation, (4) very low organic carbon consistent with long-term inhumation, and (5) kaolinitic–illitic clay. The unusual granular microstructure of the B horizon of the Oxisol is partly derived from disintegration and desilication of the Paleoultisol.

Despite the ancillary knowledge that soil N is chiefly retained as soil organic matter, little is known about how it is affected by other soil and environmental factors, especially in the tropics. In this study, we performed a comprehensive survey of soils under native vegetation in Minas Gerais, Brazil, aiming to (a) measure soil Kjeldahl-N concentrations to a 1-m depth, (b) identify the main affecting factors of soil N retention, and (c) predict N through soil profile based on organic C (SOC) and its main conditioning factors. Soils under 36 fragments of native forest and savanna were sampled at five depths (0–10, 10–20, 20–40, 40–60, and 60–100 cm) and characterized by physical and chemical analyses, including total N determined by the micro-Kjeldahl method. Single and multivariate regressions were used to predict N concentrations based on soil properties and climatic factors. The average N concentrations ranged between 0.12 and 7.54 g kg−1, decreasing with depth, and can be predicted using SOC concentrations (R 2 = 0.86). Multivariate regressions using more input data, namely texture, cation exchange capacity (CEC), and altitude increased slightly R 2 values (0.68–0.90) for separate soil depths, but not for the whole dataset (R 2 = 0.85). We demonstrated that N can be adequately predicted based on SOC concentrations, for any depth and forest type. The implications of the stable SOC/N relation and their coupled cycles and the environmental factors affecting N retention in Brazilian weathered soils are further discussed.

Soil internal drainage plays a major role in soil genesis, and it is mostly dependent on topography. However, the existence of sedimentary and meta-sedimentary rock strata with variable dip angle allows for strong differences in internal drainage for identical topographies, which result in a marked differentiation in the properties of overlain soils. This work aimed to investigate the micromorphology of soils formed from different dip angles of rock strata and their relationships to internal drainage, in Minas Gerais, Brazil. Over horizontal strata, a Xanthic Acrudox lacking hematite and with blocky structure has developed. Over strata with 45° dip angle, strong drainage has resulted in intense desilication, forming a Rhodic Acrudox having hematite and with strong fine granular structure. Micromorphological analyses showed that both soils contain relict nodules which are probably being dissolved in the current environment, whereas only the Xanthic Acrudox has nodules in current processes of formation due to slower drainage. The Cr horizon of both soils, but mainly the Xanthic Acrudox, presented a much slower saturated hydraulic conductivity than the respective overlying horizons, which was associated with a pattern of poorly connected fissural pores as seen in thin sections. The Cr horizon of the Rhodic Acrudox showed a matrix impregnated by Mn and Fe oxides in an unusual pattern of microlamination and hypocoatings that appear to be unstable, dissolving in the current, strongly drained environment. The soil color is a reliable indicator of such differential pedogenesis in these conditions. RESUMO A drenagem interna desempenha um importante papel na gênese de solos e é principalmente dependente da topografia. Contudo, a existência de estratos de rochas sedimentares e meta-sedimentares com ângulo de inclinação variável permite forte diferença na drenagem interna em locais de topografia semelhante, o que resulta em marcante diferenciação de propriedades dos solos acima. Este trabalho teve como objetivo investigar a micromorfologia do solo com estratos de rochas com diferentes ângulos de inclinação e suas relações com a drenagem interna dos solos, em Minas Gerais, Brasil. Sobre estratos horizontalizados, formou-se um Latossolo Amarelo ácrico típico sem hematita e de fraca estrutura média em blocos subangulares. Sobre estratos com ângulo de inclinação de 45°, a drenagem forte resultou em intensa dessilicatização, formando um Latossolo Vermelho ácrico contendo hematita e de estrutura forte muito pequena granular. As análises micromorfológicas mostraram que ambos os solos contêm nódulos reliquiais que estão provavelmente sendo dissolvidos no ambiente atual, enquanto somente o Latossolo Amarelo possui nódulos em processo de formação, devido à drenagem mais lenta. Os horizontes Cr de ambos os solos, mas principalmente do Latossolo Amarelo, apresentaram condutividade hidráulica saturada muito menor do que os horizontes sobrejacentes, em associação ao padrão de poros fissurais pouco conectados. O horizonte Cr do Latossolo Vermelho apresentou uma matriz impregnada por óxidos de Mn e Fe em padrão microlaminado incomum e hipocoberturas, aparentemente instáveis, dissolvendo-se no ambiente atual excessivamente drenado. A cor do solo é um indicador confiável destes diferentes sistemas pedológicos.

Metamorphic ultrabasic rocks are typically enriched in heavy trace elements, mostly contained within easily-weatherable silicate minerals such as talc and serpentine. In the humid tropics, such rocks can decompose rapidly, thus releasing trace elements (TE) at rates likely to create extreme soil environments that hamper plant development, but few studies are available on this issue in Brazil and most South America. We sampled eight soils formed on a 3.1 km2 steatite (a type of talc-schist) hill and its piedmont, with slopes ranging from 4 to 90%. The soils varied from shallow Entisols and Inceptisols to deep (>2 m) Oxisols, along a weathering continuum well described by increasing residual concentration of Fe oxides, which ranged from 15 to 69% total Fe2O3 (determined by X-ray fluorescence). Total Co, Cr, Ni, Ti and V were high in comparison to world soils´ ranges and averages, whereas Ba, Cu and Zr were relatively low or near average. Total concentrations of these TE except Ba were proportional to total Fe, and the same trends occurred when dithionite-extractable Fe and TE were considered. Thus, both primary (magnetite, chromite, hematite) and secondary (maghemite, hematite, goethite, amorphous phases) Fe oxides likely control soil TE contents, with much variation across TE, soils and horizons. Co, Cr and Ti were mostly comprised within the residual phases, i.e. mostly resistant primary minerals, whereas a larger part of Ba, Cu, Ni, V and Zr were included in pedogenic Fe oxides and other phases. The potentially plant-available (extracted with Mehlich-I) TE were mainly Ba, Co and Cu, and to a much lower degree, Ni. The environmental implications of the concentrations and partition of the studied TE are briefly discussed.

Despite recent efforts to assess heavy metal contents in soils in Brazil, little is known about the effect of parent material and sampling depth, both critical factors controlling soil geochemical composition, especially in areas with complex geology. We determined concentrations of Cr, Cu, Mn, Ni, Pb and Zn in soil profiles developed from eight contrasting rocks (quartzite, mica schist, gabbro, gneiss, limestone, phyllite, itabirite and ironstone after serpentinite) in a relatively small area under similar climate and native forests in Minas Gerais, Brazil. The hypotheses tested were that soil metal concentrations vary with parent material and depth. Soil samplings were done in triplicate at the 0–5, 30–40 and 90–100 cm depths, and metal concentrations assessed after nitric acid digestion and atomic absorption spectrometry determination. Generally, metal concentrations varied little with depth, and Pb concentrations were low and very similar among soils (always 75 mg kg−1), reaching 210–258 mg kg−1 in the soils derived from mafic and ultramafic rocks. Ni was generally

Steatite is a metamorphic, ultramafic rock composed by talc, serpentine, magnetite and other unique minerals. Soils developed from this rock is typically unproductive due to high Mg and low P contents, high concentrations of heavy metals, and the extent of such limitations in the humid tropics is still poorly known. Here, we aimed to study pedogenesis, morphology and composition of eight soils formed from steatite in Minas Gerais, Brazil. These soils were a) Lithic Udorthents (3 pedons); b) Oxic Dystrudepts (2 pedons); and c) Acrudoxes (3 pedons). All soils presented high particle density but low bulk density due to high packing void porosity associated to granular structure. Soil pH and exchangeable Mg+2 were relatively high, whereas Mehlich-I P and exchangeable Al+3 were very low. X-ray fluorescence data showed that Entisols and Inceptisols have high (94 a 200 g kg−1) MgO contents, whereas Oxisols are highly enriched in Fe2O3, although still bearing MgO contents as high as 30 g kg−1. The Entisols and Inceptisols were mostly composed by talc, but also had Fe oxides and small amounts of kaolinite, whereas the dusky red Oxisols contained mostly hematite. Although present in the parent material, serpentine was not detected in soils. The considerable amounts of MgO in Oxisols can be explained by rock fragments preserved by a dark Fe oxide coating, visible in thin sections. Magnetic susceptibility was high and increased strongly with increasing weathering stage. Local topography strongly controlled soil formation and composition, which allowed for the existence of three climax vegetations: canyon cloud forest, semi-deciduous forest and savanna, suggesting that soil limitations to native plants are lower than expected.

Little is known about how soil organic carbon (SOC) under tropical forests is affected by altitude. We investigated the effects of soil texture and altitude on SOC retention under native forests in Brazil, by sampling two pairs of soils of coarser and finer texture, developed respectively from quartzite and mica-schist. One soil pair was sited at altitude 1060 m, and the other at 1230 m, along a mountain range. For 1060 m, the soil with ~36% clay contained 227 Mg SOC ha–1 (0–1 m depth), the double of the soil with ~16% clay. Such effect of texture was negligible at 1230 m, where SOC stocks were 205 Mg ha–1 for the soil with ~12% clay, and 217 Mg ha–1 for the soil with ~21% clay. Furthermore, there were positive correlations between SOC concentrations with clay + silt contents and specific surface area for 1060 m but not 1230 m altitude, suggesting that SOC retention was affected by texture only for altitudes near 1000 m or lower. At 1230 m, lower temperatures were predominant in SOC stabilisation through slower decomposition. In addition, 65–80% of total SOC was associated with clays, indicating a high degree of organic alteration. Interestingly, at 1235 m, SOC concentration in clay fractions reached 17%, much higher than at 1060 m, strongly suggesting SOC saturation. Thus, at 1235 m the interaction of SOC with soil minerals was probably weaker than at 1060 m or lower, and so SOC stocks are more susceptible to decay.

Although particles >2 mm are not considered soil material, gravels composed of resistant secondary minerals can be useful records of past soil environments. We investigated gravels (2–8 mm) from a Plinthic Haplustox in central Brazil in order to assess their composition, fabric and genesis. Gravels were initially grouped into six macromorphological types, and investigated by mineralogical, micromorphological and microprobe analyses. The results suggest that gravels can be classified as pedogenic or lithopedogenic. Pedogenic gravels comprise indurated soil materials and include black magnetic gravels, black non-magnetic gravels and red earthy gravels. Magnetic gravels contained mostly quartz, hematite and magnetite–maghemite and were poor in kaolinite, gibbsite and goethite, whereas non-magnetic and red earthy gravels had the same minerals as in the surrounding soil. Lithopedogenic gravels are fragments of resistant rocks impregnated by iron (Fe), aluminium (Al) and manganese (Mn) oxides, including platy shales, quartzites and coarse quartz. The latter two showed oxide impregnations around internal pores, whereas the shale fragments included considerable mica, which contributed illite and potassium to the soil clays and, thus, the pedogenic gravels. These results point to multiple cycles of formation and incorporation of cemented materials into the soil, as well as their later impregnation by Fe, Mn and Al oxides. Thus, the conventional classification of all such gravels as ‘ironstone’ is questionable, and their potential role as indicators of past and present soil environments is demonstrated, which deserves further investigation.