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In a no-till system (NTS) on naturally acidic soils, surface liming is essential to neutralize soil acidity and increases crop productivity. As a result, the soil organic matter (SOM) pools of the soil surface layers may change, reflecting increased C inputs by crop residues. The objective of this study was to quantify changes in SOM pools and the rate of C sequestration that occur in response to surface liming in a long-term NTS experiment. The experiment was conducted in an Oxisol in southern Brazil. The treatments consisted of the application of 0 or 6 Mg ha-1 of dolomitic lime on the soil surface in 1993 and a reapplication of 0 or 3 Mg ha-1 of dolomitic lime in 2000 to plots with or without the previous lime application. Liming caused total organic C (TOC) accumulation, especially in the 0- to 2.5-cm layer. The amount of TOC stored in the 20-cm layer was 49.9, 52.9, 52.7, and 57.5 Mg ha-1 in the control, 6 + 0, 0 + 3, and 6 + 3 Mg ha-1 treatments, respectively. The levels of particulate organic C (POC) and mineral-associated organic C (MAOC) in the SOM were also enhanced by liming. The increase in POC was directly related (R² = 0.99, P = 0.002) to the accumulation of C from crop residues, which was greater in the plots receiving lime treatment. There were positive correlations between TOC and C extractable with hot water, total polysaccharides, and labile polysaccharides. The correlation analysis also demonstrated that TOC was more tightly correlated with POC than with MAOC, indicating a greater influence of the labile fraction on the increase in TOC with surface liming. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanical chiseling decreased soil and plant quality in an 18 years no-till system. • The use of Raphanus Sativus L. was a good replacement for mechanical chiseling. • Effects on SOC stocks were observed only 42 months after chiseling. • Positive correlations between root development and SOC stocks were found. Soils under no-till (NT) in Brazil have been aimlessly chiseled mainly due to compaction symptoms. The impacts on soil organic carbon (SOC) of these operations as well as the effects of more sustainable alternatives are still highly unknown. We hypothesized that the use of plants with deep root systems in the crop rotation could be a suitable alternative to mechanical chiseling for no-till fields. Thus, our objective in this study was to evaluate changes in SOC stocks, root development, and crop yield over time caused by mechanical and biological chiseling in a long-term no-till system (i.e., 18 years). The experiment was laid out as randomized blocks with four replicates and the treatments were as follows: 1) No-till system without any mechanical disturbance, cultivated with black oats + vetch in winter, here called "No-till cover crop (NT-CC)". 2) No-till system with one mechanical disturbance through chiseling, also cultivated with black oats + vetch in winter, here called "No-till Mechanical Chiseling (NT-MC)". 3) No-till without any mechanical disturbance cultivated with black oats + forage radish (Raphanus Sativus L.) instead of vetch, here called "No-till Biological Chiseling". Compared to NT-CC, the use of NT-MC depleted the SOC stocks by -0.41 Mg ha−1 year−1. NT-MC also highly depleted proxies for microbial-related C pools such as hot-water and permanganate extractable C. It demonstrates the deleterious effects of the mechanical chiseling operations on the surface depths (0−30 cm depth) of our long-term no-till system and raises concerns about the use of these operations in highly weathered areas. On the other hand, the NT-BC promoted significantly higher sequestration rates of 1.29 Mg ha−1 year−1 (LSD test, p < 0.05). The NT-BC has also promoted significantly higher sequestration rates of proxies of microbial-related organic matter, and soybean and wheat root development (length and mass) than the other managements. For cumulative crop yield and biomass input, both NT-BC and NT-CC promoted significantly higher values than NT-MC during the four years of assessment. The root development of wheat and soybean significantly contributed to the increase of SOC stocks, observed by positive correlations (p < 0.01). The results demonstrated that the use of radish as an intercrop for alleviating soil compaction was a good alternative to replace mechanical chiseling in compacted NT fields due to its superior performance in increasing SOC stocks, promoting higher root development, and crop yield. [ABSTRACT FROM AUTHOR]

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 (CO 2) 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 CO 2 eq 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 CO 2 eq 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 < 0.001) indicated that the increase of C-offset was associated with the increase of energy balance and the amount of SOC sequestered. The higher energy efficiency and C-offset by application of Bio-F indicated that the practice of crop bio fertilization with poultry slaughterhouse waste is a viable alternative for recycling and minimizing the environmental impacts. Image 1 • The use of poultry slaughterhouse waste as biofertilizer promote higher soil C sequestration than those by mineral fertilizer. • The replacement of mineral fertilizer by poultry slaughterhouse waste promoted higher crop energy efficiency and productivity. • The increase in C-offset through biofertilizer can promote impact in CO 2 -Ceq mitigation minimizing environmental pollution. [ABSTRACT FROM AUTHOR]

Decaying plant material is the major source of soil organic carbon (SOC). Nevertheless, it still remains unclear how the biochemical composition of litter is affecting the formation of SOM. Thus, we aimed to disentangle the effect of plant litter composition on C transference into differently stabilized soil fractions. We did this by individually incubating 13C enriched Eucalyptus spp. organs (bark, leaves, twigs and roots) in topsoil (0–20 cm) of a sandy-clay loam (Haplic Ferralsol) from Paula Candido – Brazil (20º 52' S, 42º 58' E). Additionally, a soil sample without plant residue addition was incubated and used as a control. The samples were incubated at 80% of their water-holding capacity at 25 ºC. The molecular composition of the incubated plant organ material was characterized by solid-state 13C-CP/MAS-NMR spectroscopy. At the end of the incubation experiment (after 200 days), aliquots were taken and the SOM was physically fractionated using a combined density-particle size separation method. The total C content and the relative abundance of 13C (δ 13C) of each soil organic matter fraction were measured by IRMS, whereas the litter-C contribution for each SOM fraction was assessed using a two-end member isotope mixing model. No significant differences were observed for total SOC contents among the different treatments. Conversely, lower total SOC contents were observed for the control treatment without residue addition, indicating mineralization of inherited SOM along the incubation period. The partitioning of litter-derived C into SOM fractions and CO2 indicates that leaf had higher proportion of C transferred to the total SOC, followed by roots, bark and twigs. The amount of carbon transferred to the mineral associated organic matter (MAOM) was as follows: leaves > bark > twigs > roots. Contrastingly, for the particulate organic matter (POM) the order was as follows: roots > bark > twigs = leaves. Contrasting NMR spectra demonstrate the significant effect of the biochemical composition of each plant organ in the fate of C in soil. Carbon from leaves was preferentially allocated to the MAOM fraction, and was more enriched in carboxyl and alkyl groups. Twigs, bark and roots, which were more enriched in O-Alkyl group, were preferentially respired or allocated into the POM fraction. [ABSTRACT FROM AUTHOR]

The conversion of native vegetation (NV) to agricultural systems, especially with intensive tillage and low carbon (C) input, decreases soil organic carbon (SOC) stocks. However the adoption of conservation agriculture (CA) may partially restore SOC stocks. However, the magnitude of this restoration is dependent on the cropping system, quality and quantity of C input, soil, and climate. In this study, we assessed the redistribution and recovery of SOC stocks in six no-till (NT) fields (> 20 years) in the small grain production area of southern Brazil. The adoption of NT in the fields investigated started between 1978 and 1990 and represent a range of textural and mineralogical characteristics. Soil samples were collected in paired fields (NV vs. long-term NT) to a depth of 1 m. The pioneer NT areas of Rio Grande do Sul State investigated in this study were managed according to the principles of CA (minimum soil disturbance, permanent soil cover and diverse crop rotation). The sites had recovered to 92–100% of the original SOC stocks. The sites which represented medium cropping intensity recovered 79.5 and 85.4%, of NV SOC stocks. The sites representative of high cropping intensity had recovered 84.9–116.5% of NV SOC stocks. The lowest recovery of SOC stock (60.6%) had higher frequency of soybean ( Glycine max L. Merril) in the crop rotation. Therefore, NT following the principles of CA was an efficient system to restore SOC stock lost due to land-use change, performing a crucial role in the system productivity and soil quality. [ABSTRACT FROM AUTHOR]

Abstract: The stabilisation of soil organic matter (SOM) is the result of the simultaneous action of three mechanisms: chemical stabilisation, biochemical stabilisation and physical protection. The objectives of this study were (i) to evaluate carbon-protection mechanisms in different SOM pools in soil aggregates and (ii) to identify the association of Ca2+ with total organic carbon (TOC) under the influence of surface liming in a medium-textured Oxisol in a long-term experiment under no-till system (NTS) in southern Brazil (25° 10′ S, 50° 05′ W). The treatments consisted of application of zero or 6tons ha−1 of dolomitic lime on the soil surface in 1993 and a reapplication of zero or 3tons ha−1 of dolomitic lime in 2000 to plots with or without previous lime application. Soil samples collected at depths of 0–2.5, 2.5–5, 5–10 and 10–20cm were separated into seven aggregate classes. In each of these classes, TOC, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) were analysed. The 8–19mm sized aggregates from the 0–2.5cm layer were assessed by energy-dispersive X-ray spectroscopy (EDS) for the elemental analysis of carbon (C) and calcium (Ca). The liming caused an accumulation of TOC in the aggregates, mainly at a depth of 0–2.5cm. The aggregates from soils treated with lime had a higher mean weight diameter (MWD) that resulted in the accumulation of TOC, especially in the 8–19mm aggregate class, that was linear and closely related with C input (R2 =0.99). The proportion of large aggregates in the treatments with lime was closely correlated with the TOC content of the whole sample. The largest dose of lime (9tons ha−1) resulted in higher TOC, POC and MAOC values, mainly in the 8–19mm aggregate class. The elemental analyses for C and Ca revealed similar spectra between them for the surface-liming treatments in the clay fraction found in the centres of the 8–19mm aggregates. The surface application of lime to NT fields provided greater stability and protection of the intra-aggregate C, presumably due to Ca2+ acting as a cationic bridge between OC and the kaolinite in the clay fraction. [Copyright &y& Elsevier]

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., (Copyright © 2018 Elsevier Ltd. All rights reserved.)