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We evaluated the effect of Azospirillum brasilense strain HM053 inoculation on maize seeds, a spontaneous mutant that excrete ammonium and fix nitrogen constitutively. Maize was grown with different nitrogen (urea) concentration and inoculated with A. brasilense Ab-V5 (Brazilian commercial strain) or HM053 strain in four field experiments, in three regions of Parana State, Southern Brazil. We evaluated yield components, nutrient content on leaves and grains and productivity during the crop cycle. Inoculation with A. brasilense strain Ab-V5 and HM053 associated with base fertilization (30 kg ha−1 N) improved crop yield in all trials. Ab-V5 increased production between 2.2 to 10.4%, or 178.0 to 759.9 kg ha−1, respectively. HM053, by itself, increased production between 4.7 to 29%, or 460.5 to 1769.3 kg ha−1, respectively. The new strain HM053 showed to be a great biofertilizer for maize seeds and a new alternative for a more sustainable agriculture.

Soil organic matter (SOM) is a critical ecosystem variable regulated by interacting physical, chemical and biological processes. Collaborative efforts to integrate perspectives, data, and models from interdisciplinary research and observation networks can significantly advance predictive understanding of SOM. We outline how integrating three networks – the Long‐Term Ecological Research, with a focus on ecological dynamics, the Critical Zone Observatories with strengths in landscape/geologic context, and the National Ecological Observatory Network with standardized multi‐scale measurements—can advance SOM knowledge. This integration requires improved data dissemination and sharing, coordinated data collection activities, and enhanced collaboration between empiricists and modelers within and across networks.

Soils can be a source or sink of atmospheric CO2, depending on the historic and existing land use and management. We used long term soil management database of a production farm that is based on principles of conservation agriculture such as: a) eliminate soil disturbance; b) maintain permanent soil surface cover; C) adopt crop diversity with high biomass-C input; for 30 years and agroecosystem models to study the potential of different management options to sequester C in soils. Using Century and Roth-C models we simulated the carbon stocks evolution in the farm and four subtropical soil management scenarios and studied C sequestration potential. The scenarios were: a) existing farm biomass input (14.5 Mg ha−1 year−1) or C input (6.5 Mg ha−1 year−1); b) 15% increase of farm biomass input (16.7 Mg ha−1 year−1) or C input (7.5 Mg ha−1 year−1); c) 15% decrease of farm biomass (12.3 Mg ha−1 year−1) or C input (5.5 Mg ha−1 year−1) and, d) 30% decrease of farm biomass input (10.1 Mg ha−1 year−1) or C input (4.5 Mg ha−1 year−1). Our results demonstrate that soil organic carbon continuously increased after conservation management practices adoption in 1985 until 2015, and currently soil organic carbon is in equilibrium. We found that an increase of 2.2 Mg ha−1 year−1 biomass-C input for 60 years resulted into increase of 12 Mg ha−1 soil organic carbon stocks. The same way, crop yields increased with time, and were more pronounced for maize compared to soybean and wheat. The scaling up of model results to similar climate and soil types indicated that conservation management practices has the potential to sequester 2.7 ± 0.02 Pg C at 0–20 cm and 4.8 ± 3 Pg C at 0–100 cm soil depth in 43 million ha area globally. In the 30% and 15% decrease scenarios the sequestration were 2.2 ± 0.02 and 2.4 ± 0.02 Pg C at 0–20 cm an in 15% increase scenario it goes to 3.2 ± 0.02 Pg C. This equilibrium soil organic carbon stocks considering the currently adopted system are equivalent to 3.5–4.5% of the world SOC stocks in 3% of the world croplands and correspond to 6 years of global land use and land use change emissions, indicating that conservation management practices can lead the soil be a sink and a promising tool to promote C sequestration in subtropical soils.

Understanding the influence of environmental factors on soil organic carbon (SOC) is critical for quantifying and reducing the uncertainty in carbon climate feedback projections under changing environmental conditions. We explored the effect of climatic variables, land cover types, topographic attributes, soil types and bedrock geology on SOC stocks of top 1 m depth across conterminous United States (US) ecoregions. Using 4559 soil profile observations and high-resolution data of environmental factors, we identified dominant environmental controllers of SOC stocks in 21 US ecoregions using geographically weighted regression. We used projected climatic data of SSP126 and SSP585 scenarios from GFDL-ESM 4 Earth System Model of Coupled Model Intercomparison Project phase 6 to predict SOC stock changes across continental US between 2030 and 2100. Both baseline and predicted changes in SOC stocks were compared with SOC stocks represented in GFDL-ESM4 projections. Among 56 environmental predictors, we found 12 as dominant controllers across all ecoregions. The adjusted geospatial model with the 12 environmental controllers showed an R2 of 0.48 in testing dataset. Higher precipitation and lower temperatures were associated with higher levels of SOC stocks in majority of ecoregions. Changes in land cover types (vegetation properties) was important in drier ecosystem as North American deserts, whereas soil types and topography were more important in American prairies. Wetlands of the Everglades was highly sensitive to projected temperature changes. The SOC stocks did not change under SSP126 until 2100, however SOC stocks decreased up to 21% under SSP585. Our results, based on environmental controllers of SOC stocks, help to predict impacts of changing environmental conditions on SOC stocks more reliably and may reduce uncertainties found in both, geospatial and Earth System Models. In addition, the description of different environmental controllers for US ecoregions can help to describe the scope and importance of global and local models.

Conservation agriculture through no-till based on cropping systems with high biomass-C input, is a strategy to restoring the carbon (C) lost from natural capital by conversion to agricultural land. We hypothesize that cropping systems based on quantity, diversity and frequency of biomass-C input above soil C dynamic equilibrium level can recover the natural capital. The objectives of this study were to: i) assess the C-budget of land use change for two contrasting climatic environments, ii) estimate the C turnover time of the natural capital through no-till cropping systems, and iii) determine the C pathway since soil under native vegetation to no-till cropping systems. In a subtropical and tropical environment, three types of land use were used: a) undisturbed soil under native vegetation as the reference of pristine level; b) degraded soil through continuous tillage; and c) soil under continuous no-till cropping system with high biomass-C input. At the subtropical environment, the soil under continuous tillage caused loss of 25.4 Mg C ha

The conversion of native vegetation (NV) into agricultural land by clearing and tillage disrupts the soil structure, and depletes soil organic carbon (SOC) pool. Data on changes in SOC pools are needed to enhance scientific knowledge regarding the effects of land use and Conservation Agriculture (CA) on soil fertility, agronomic productivity, and soil C sink capacity. The objective of this study was to quantify changes in SOC fractions due to conversion of NV to agricultural land, and to assess the rate of recovery of SOC fractions and the resilience index of CA cropping systems under sub-tropical (Ponta Grossa/PR — PG) and tropical (Lucas do Rio Verde/MT — LRV) regions of Brazil.

The adoption of Conservation Agriculture (CA) and the maintenance of crop residues on the soil surface result in the long-term increase of carbon (C) in the system, promoting C sequestration and reducing C-CO2 emissions to the atmosphere. The present study conducted in subtropical and tropical regions in Brazil aimed to assess the impact of the continuous plow-based conventional tillage (CT) on soil organic carbon (SOC) stock vis-a-vis native vegetation (NV) as baseline, compare SOC balance among CT, CA cropping systems, and NV; and evaluate the redistribution of SOC stock in soil profile in relation to soil resilience.

In a climate change scenario, it is important to understand the factors that lead to changes in a soil carbon (C) sink. It is recognized that such process is highly dependent on climate, soil properties, topography, and vegetation. However, few studies demonstrate how these mechanisms operate in highly weathered Oxisols. Therefore, this study evaluated the driving factors for C recovery and accumulation and its relations with fertility attributes in the soil profile (0 to 1m depth) in no-till (NT) croplands of south Brazil. The adoption of NT in the studied fields started between 1978 (pioneer areas) and 1990 and represent a range of textural and mineralogical characteristics South Brazil main croplands. Soil samples were collected in paired fields of native vegetation and NT (NV vs. long-term NT) to a depth of 1m. The studied NT areas of Rio Grande do Sul State were managed according to the principles of conservation agriculture (minimum soil disturbance, permanent soil cover and diverse crop rotation). The processes that drove SOC recovery in the studied sites were soil fertility management allied with high C input through intense crop rotation. The C recovery was were for areas with the predominance of soybean in the cropping system, higher levels of Al3+ and lower levels of Mg2+ and P. Sites with medium/high cropping intensity, lower levels of Al3+ and higher levels of P, Ca2+, Mg2+, and K+ resulted in higher C recovery.

Soil organic carbon (SOC) pools, particularly labile pools, and soil enzymes are good indicators of short-term impacts of soil management. We hypothesized that labile SOC pools drives C accumulation and enzyme activity can be an efficient indicator for C build up in short-term conservation agriculture. The aims of this study were to quantify the impacts of tillage and crop rotations with diverse crop residue inputs on changes in SOC labile pools and enzymatic activities in rice-, soybean- and cassava-based cropping systems designated as RcCS, SbCS and CsCS, respectively. The four treatments in each cropping system consisted of: conventional tillage (CT), no-till in which main crops (rice, soybean and cassava) were grown in a one-year frequency pattern (NT1) and, no-till in which the main crops were grown in bi-annual rotations with maize (NT2 and NT3). After 5 years experiment period, greater hot-water extractable organic C (HWEO-C) stocks of 61%, 55% and 53%, and permanganate oxidizable C (POX-C) stocks of 23%, 21% and 32% were attributed to NT than those in CT soils under RcCS, SbCS and CsCS, respectively, at 0–5 cm soil layer. The pyrophosphate extractable organic C (PEO-C) and chemically stabilized organic C (CSO-C) stocks were almost constant in each depth among treatments, except 0–5 cm in CsCS. The β-glucosidase activity was 18%, 28% and 49% greater in NT than those in CT soils at 0–5 cm under RcCS, SbCS, CsCS, respectively. Arylsulfatase activity was 36% and 39% greater in NT than in CT under SbCS and CsCS, respectively but no significant differences in RcCS. A strong and positive correlation (P

Soil organic carbon (SOC) is a strong indicator of soil health. Development of efficient soil quality indicators is crucial to better understand the impact of land management strategies on the recovery of degraded ecosystems. We hypothesized that SOC fractions and biological attributes can compose strong soil quality indicators to assess an ecosystem recovery following disturbance. Thus, the objective of this study was to evaluate the use of soil biological activity and SOC fractions to study the impact of different land use systems and ecological successions in ecosystem recovery. We selected six land use systems: tobacco (Nicotiana tabacum) cultivation; pastureland; reforested land with Eucalyptus sp.; and natural ecological successions with 10, 20 and 35 years of vegetation regeneration, respectively. We collected disturbed and undisturbed soil samples in triplicate at 0–5, 5–10, 10–20 and 20–40 cm depth intervals. Several fractionation approaches were used to determine SOC pools: hot water extractable organic carbon, permanganate oxidized organic carbon, particulate organic carbon, mineral associated organic carbon and total SOC. The activity of the enzyme arylsulfatase was used to represent soil biological attributes. We calculated three indices to represent the soil quality: carbon management index, soil resilience index and biological activity index. Our results suggest that the SOC fractions and the enzyme activity followed the increase of vegetation complexity of the ecological succession stages. The labile SOC pool, in addition to enzyme activity, was the most sensitive variable to assess land use changes. The biomass-C input was considered to be the main reason of SOC increase, and the gains of labile SOC fractions were directly related to the increase of SOC stocks. Both, biological and carbon management indices were efficient tools to characterize the impact of studied management systems. Also, we found that assessment of deeper soil layers (20–40 cm) was extremely important as incomplete inferences might be reached while evaluating only surface soil layers (0–20 cm). We conclude that the carbon management and biological indices captured the stage of soil degradation and the influence of vegetation diversity in the soil resilience restoration, providing an advance in monitoring strategies that can be reproducible in any environment.

Soil organic carbon (C) plays a fundamental role in tropical and subtropical soil fertility, agronomic productivity, and soil health. As a tool for understand ecosystems dynamics, mathematical models such as Century have been used to assess soil's capacity to store C in different environments. However, as Century was initially developed for temperate ecosystems, several authors have hypothesized that C storage may be underestimated by Century in Oxisols. We tested the hypothesis that Century model can be parameterized for tropical soils and used to reliably estimate soil organic carbon (SOC) storage. The aim of this study was to investigate SOC storage under two soil types and three textural classes and quantify the sources and magnitude of uncertainty using the Century model. The simulation for SOC storage was efficient and the mean residue was 10 Mg C ha− 1 (13%) for n = 91. However, a different simulation bias was observed for soil with 600 g kg− 1 of clay, was 4 Mg C ha− 1 (5%) for n = 50, respectively. The results suggest a non-linear effect of clay and silt contents on C storage in Oxisols. All types of soil contain nearly 70% of Fe and Al oxides in the clay fraction and a regression analysis showed an increase in model bias with increase in oxides content. Consequently, inclusion of mineralogical control of SOC stabilization by Fe and Al (hydro) oxides may improve results of Century model simulations in soils with high oxides contents.

Brazil is one of the major global poultry producers, and the organic waste generated by the chicken slaughterhouses can potentially be used as a biofertilizer in agriculture. This study was designed to test the hypothesis that continuous use of biofertilizer to the crops, substituting the use of mineral fertilizer promote C-offset for the soil and generate crop energy efficiency for the production system. Thus, the objectives of this study were to evaluate the effects of biofertilizer use alone or in combination with mineral fertilizer on soil organic carbon (SOC) stock, carbon dioxide (CO2) mitigation, C-offset, crop energy efficiency and productivity, and alleviation of environmental pollution. The experiment was established in southern Brazil on a soil under 15 years of continuous no-till (NT). Experimental treatments were as follows: i) Control with no fertilizer application, ii) 100% use of industrial mineral fertilizer (Min-F); iii) 100% use of organic waste originated from poultry slaughterhouses and hereinafter designated biofertilizer (Bio-F), and iv) Mixed fertilizer equivalent to the use of 50% mineral fertilizer + 50% of biofertilizer (Mix-F). Effects of experimental treatments were assessed for the crop sequence based on bean (Phaseolus vulgaris), soybean (Glycine max) and corn (Zea mays) in the summer and wheat (Triticum aestivum) and black oat ( Avena strigosa Schreb) in the winter composing two crops per year, as follow: bean/wheat-soybean/black oat-corn/wheat-soybean/black oat-corn/wheat-bean. The continuous use of Bio-F treatment significantly increased the index of crop energy efficiency. It was higher than that of control, and increased it by 25.4 Mg CO2eq ha−1 over that of Min-F treatment because of higher inputs of crop biomass-C into the system. Further, continuous use of Bio-F resulted in a significantly higher CO2eq stock and offset than those for Min-F treatment. A positive relationship between the C-offset and the crop energy efficiency (R2 = 0.71, p

The application of lime and gypsum has been recognized as an important strategy for correcting soil acidity and for improving soil fertility, soil aggregation, and agronomic productivity in highly weathered soils. We hypothesized that the combined application of lime and gypsum would create favorable conditions for biological activity and result in increased SOC storage and agronomic productivity. Thus, the aim of this study was to evaluate the long-term ( i.e. , 15 years) impact of lime and gypsum application on the biological activity, SOC stocks, and agronomic productivity of plots under no-till soil management. The experiment was established in 1998 at a site with clayey Oxisol in southern Brazil, and was designed with a split-plot arrangement, completely randomized blocks, and three replicates. The main plot was subject to three lime treatments: (i) control (no lime); (ii) incorporated lime (IL):incorporation of 4.5 Mg lime ha −1 to a depth of 0–20 cm by; and (iii) surface lime (SL): surface application of 4.5 Mg lime ha −1 , which was equally divided among three annual applications during the first three years of the experiment. The subplots were comprised by surface applications of gypsum at 0, 3, 6, or 9 Mg ha −1 . Soil samples were collected in 1998, before of the experiment, and in October 2013, in order to evaluate soil enzyme activities, SOC pool stocks, crop productivity, C-biomass input, and soil fertility attributes. Both forms of lime application significant improved the stocks of several SOC pools, crop productivity, biomass-C input rates, soil fertility attributes, and enzyme activity. The SOC stocks were positively correlated with Ca 2+ content and biomass-C input, demonstrating the potential of calcium to improve C accumulation. Enzyme activities were significantly affected by both soil fertility and SOC pools, with increases in hot water extractable organic C yielding the greatest increases in enzyme activity. In addition, we also found that gypsum application significantly increased the stocks of labile SOC pools and arylsulfatase activity. However, effects of gypsum application were less apparent than those of lime application and the combination of surface lime (4.5 Mg ha −1 ) and gypsum (9 Mg ha −1 ) application yielded the greatest long-term increase in the stock of total organic C stock. Thus, the results of the present study suggest that lime and gypsum application, along with no-till management and biomass-C input, constitutes an efficient strategy for improving the biological activity, C stocks, and productivity of agricultural soils.

Resumo O objetivo deste trabalho foi determinar a relação dos indicadores de qualidade da água com o regime de chuvas e os padrões de uso da terra. Foram avaliadas quatro bacias hidrográficas e suas respectivas áreas de preservação permanente (APPs), fontes do reservatório Alagados, no Estado do Paraná. O uso dos solos nas bacias e nas APPs foi mapeado em ambiente de sistema de informações geográficas, e os padrões resultantes foram avaliados quanto ao índice de qualidade das águas (IQA) e ao regime pluvial. A qualidade das águas foi menor nos períodos de verão, quando há maior precipitação e manejo mais intensivo dos solos, com presença de maiores superfícies cultivadas na paisagem. A área total cultivada nas APPs teve efeito negativo sobre a qualidade das águas. Diferenças topográficas, geomorfológicas e pedológicas, bem como sua influência nos padrões de uso dos solos, foram discutidas para possível explanação dos valores observados de IQA nas bacias. A variabilidade dos padrões de IQA entre as bacias, bem com os valores extremos observados de acordo com as estações do ano, evidencia a necessidade de gerenciamento do uso das terras, particularmente no âmbito das APPs, para que sejam mantidos padrões desejáveis de vazão e qualidade das águas do manancial. Abstract The objective of this work was to determine the relationship of water quality indicators with rainfall regime and land use patterns. Four watersheds and their respective permanent protected areas (APPs), sources of the Alagados reservoir, in the state of Paraná, Brazil were evaluated. Land use at basin level and in the APPs were mapped in a geographic information system environment, and the resulting patterns were evaluated as to their relation with the water quality index (IQA) and rainfall regime. Water quality decreased in the summer periods, when higher average rainfall and more intensive land management were present, with larger cultivated areas in the landscape. Total cultivated area in the APPs had negative effect on water quality. Differences in topography, geomorphology, and soil types, as well as their effect on land use patterns, were discussed as a potential explanation for the observed values of the IQA in each basin. The variability of the IQA patterns among watersheds, as well as the extreme values observed according to the season, highlights the demand for land use planning, particularly within the APPs, in order to ensure desirable patterns of water flow and quality in the wellspring.

Currently the land use and land use change (LULUC) emits 1.3 ± 0.5 Pg carbon (C) year−1, equivalent to 8% of the global annual emissions. The objectives of this study were to quantify (1) the impact of LULUC on greenhouse gas (GHG) emissions in a subtropical region and (2) the role of conservation agriculture to mitigate GHG emissions promoting ecosystem services. We developed a detailed IPCC Tier 2 GHG inventory for the Campos Gerais region of southern Brazil that has large cropland area under long-term conservation agriculture with high crop yields. The inventory accounted for historical and current emissions from fossil fuel combustion, LULUC and other minor sources. We used Century model to simulate the adoption of conservation best management practices, to all croplands in the region from 2017 to 2117. Our results showed historical (1930–2017) GHG emissions of 412 Tg C, in which LULUC contributes 91% (376 ± 130 Tg C), the uncertainties ranged between 13 and 36%. Between 1930 and 1985 LULUC was a major source of GHG emission, however from 1985 to 2015 fossil fuel combustion became the primary source of GHG emission. Forestry sequestered 52 ± 24 Tg C in 0.6 Mha in a period of 47 years (1.8 Tg C Mha−1 year−1) and no-till sequestered 30.4 ± 24 Tg C in 2 Mha in a period of 32 years (0.5 Tg C Mha−1 year−1) being the principal GHG mitigating activities in the study area. The model predictions showed that best management practices have the potential to mitigate 13 years of regional emissions (330 Tg C in 100 years) or 105 years of agriculture, forestry and livestock emissions (40 Tg C in 100 years) making the agriculture sector a net carbon (C) sink and promoting ecosystem services.

Research data on the mechanisms of C stabilization and saturation affected by soil management systems in highly weathered soils remain scarce. Past studies have revealed the fundamental role of aggregation promoted by soil conservation practices in the physical protection of C fractions. This study is based on the hypothesis that the increased physical C protection provides sufficient time to strengthen the interaction between C fractions and soil minerals, as being the pathway for C stabilization and accumulation in highly weathered soils. Thus, the objectives of this study were to: i) evaluate the C stocks including labile and mineral-associated C fractions in soil under conventional (CT), no-till (NT) and native vegetation (NV), and, ii) assess the C saturation level in different C fractions through the use of contrasting mathematical models of C accumulation. Soil samples were collected (0–100 cm depth) from agroecosystems established in tropical (Lucas do Rio Verde) and subtropical (Ponta Grossa and Londrina) regions of Brazil. The data show that all C fractions were affected by soil management systems. However, the impact was more pronounced with the labile C fractions than with the mineral-associated C fractions. The depletion of C stock of labile fractions in the 0–5 cm layer upon conversion of NV to CT accounted for 86, 89 and 72% of total C in soil of Ponta Grossa, Londrina and Lucas do Rio Verde, respectively. On the other hand, compared to CT, restoration of 89, 15 and 12% of these labile fractions was observed at these respective sites with adoption of NT. The mineral-associated C fraction was the best fit to a C saturation model at all sites. The estimated C saturation level for this fraction was 98.1, 60.2 and 39.1 g C kg− 1 silt + clay at the Ponta Grossa, Londrina and Lucas do Rio Verde sites, respectively, which is still far from the current C content. Thus, the long-term use of NT might be the pathway for physical protection of the labile C fractions as well as strong organo-mineral associations. Together, these processes contribute to C stabilization and accumulation in highly weathered soils.

Conclusions based on studies of the impacts of soil organic carbon (SOC) fractions and soil texture on macroaggregation and SOC stabilization in long-term (> 20 years) no-till (NT) fields remain debatable. This study was based on the hypothesis that the amount and frequency of biomass-C input associated with NT can be a pathway to formation of macroaggregates and to SOC buildup. The objectives were to: 1) assess the macroaggregate distribution (proportional mass, class mass) and the SOC and particulate organic carbon (POC) stocks of extra-large (8–19 mm), large (2–8 mm) and small (0.25–2 mm) macroaggregate size classes managed for two decades by NT, and 2) assess the recovery of SOC stocks in extra-large macroaggregates compared to adjacent native vegetation (Andropogon sp., Aristida sp., Paspalum sp., and Panicum sp.). The crop rotation systems were: soybean (Glycine max L.), maize (Zea mays L.) and beans (Phaseolus vulgaris L.) in summer; and black oat (Avena strigosa Schreb), white oat (Avena sativa), vetch (Vicia sativa L.), black oat. + vetch (Avena strigosa Schreb + vetch) and wheat (Triticum aestivum L.) in winter. The experimental was laid out as 2 × 2 randomized block factorial with 12 replicates of a NT experiment established in 1997 on two highly weathered Oxisols. The factors comprised of: (a) two soil textural types: clay loam and sandy clay, and (b) two sampling depths: 0–5 and 5–20 cm. The three classes of macroaggregates were obtained by wet sieving, and the SOC content was determined by the dry combustion method. The extra-large macroaggregate classes in 0–20 cm depth for sandy clay (SdC) and clay loam (CL) Oxisol represented 75.2 and 72.4% of proportional mass, respectively. The SOC and POC stocks among macroaggregate classes in 0–5 and 5–20 cm depths decreased in the order: 8–19 mm > 2–8 mm ≈ 0.25–2 mm. The SdC plots under soybean/maize at 3:1 ratio recovered 58.3%, while those at 1:1 ratio (high maize frequency) in CL recovered 73.1% of SOC stock in the extra-large macroaggregates compared with the same under native vegetation for 0–20 cm depth. Thus, partial restoration of the SOC stock in original extra-large macroaggregate confirms the hypothesis that NT through higher maize cultivation frequency can be a pathway to fomation of macroaggregates and SOC buildup.

Field experiments have been used to explain how soil organic carbon (SOC) dynamics is affected by lime and gypsum applications, however, how SOC storage occurs is still debatable. We hypothesized that although many studies conclude that Ca-based soil amendments such as lime and gypsum may lead to SOC depletion due to the enhancement of microbial activity, the same does not occur under conservation agriculture conditions. Thus, the objective of this study was to elucidate the effects of lime and gypsum applications on soil microbial activity and SOC stocks in a no-till field and in a laboratory incubation study simulating no-till conditions. The field experiment was established in 1998 in a clayey Oxisol in southern Brazil following a completely randomized blocks design with a split-plot arrangement and three replications. Lime and gypsum were surface applied in 1998 and reapplied in 2013. Undisturbed soil samples were collected before the treatments reapplications, and one year after. The incubation experiment was carried out during 16months using these samples adding crop residues on the soil surface to simulate no-till field conditions. Lime and gypsum applications significantly increased the labile SOC stocks, microbial activity and soil fertility attributes in both field and laboratory experiments. Although the microbial activity was increased, no depletion of SOC stocks was observed in both experiments. Positive correlations were observed between microbial activity increase and SOC gains. Labile SOC and Ca2+ content increase leads to forming complex with mineral soil fractions. Gypsum applications performed a higher influence on labile SOC pools in the field than in the laboratory experiment, which may be related to the presence of active root system in the soil profile. We conclude that incubation experiments using lime and gypsum in undisturbed samples confirm that soil microbial activity increase does not deplete SOC stocks under conservation agriculture.