Soil quality decline represents a significant constraint on the productivity and sustainability of agriculture in the tropics. In this study, the influence of biochar, compost and mixtures of the two ...on soil fertility, maize yield and greenhouse gas (GHG) emissions was investigated in a tropical Ferralsol. The treatments were: 1) control with business as usual fertilizer (F); 2) 10tha−1 biochar (B)+F; 3) 25tha−1 compost (Com)+F; 4) 2.5tha−1 B+25tha−1 Com mixed on site+F; and 5) 25tha−1 co-composted biochar–compost (COMBI)+F. Total aboveground biomass and maize yield were significantly improved relative to the control for all organic amendments, with increases in grain yield between 10 and 29%. Some plant parameters such as leaf chlorophyll were significantly increased by the organic treatments. Significant differences were observed among treatments for the δ15N and δ13C contents of kernels. Soil physicochemical properties including soil water content (SWC), total soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), nitrate-nitrogen (NO3−N), ammonium-nitrogen (NH4+-N), exchangeable cations and cation exchange capacity (CEC) were significantly increased by the organic amendments. Maize grain yield was correlated positively with total biomass, leaf chlorophyll, foliar N and P content, SOC and SWC. Emissions of CO2 and N2O were higher from the organic-amended soils than from the fertilizer-only control. However, N2O emissions generally decreased over time for all treatments and emission from the biochar was lower compared to other treatments. Our study concludes that the biochar and biochar–compost-based soil management approaches can improve SOC, soil nutrient status and SWC, and maize yield and may help mitigate greenhouse gas emissions in certain systems.
Grain yield, cation exchange capacity (CEC), soil organic carbon (SOC), soil water content (SWC) and N2O emission as influenced by fertilizer (F), biochar (B), compost (Com), Com+B and co-composted biochar–compost (COMBI). Display omitted
•Soil was amended with biochar, compost and their mixture at field level.•Maize grain yield was significantly increased by 10–29% by organic amendments.•Organic amendments significantly increased leaf chlorophyll and N and P content.•Organic amendments significantly improved soil water content, OC, N, P and CEC.•N2O emission from biochar was the lowest over time compared to other treatments.
•Biochar studies were assessed relating to experiment and crop types, biochar and soil condition.•Despite most studies in developed countries soils are less impaired than in developing ...countries.•Wood and municipal wastes were major biochar sources compared to crop residues and manures.•Averaged across many scientific studies, biochar increases crop yields ∼20% with about 10tha−1.•Strong collaboration is required globally to advance the research and adoption of biochar.
Multiple nutrient deficiencies related to severe soil fertility depletion have emerged as the major constraint to the sustainability of agriculture on a global scale. Use of biochar and biochar-compost mixtures from different alternative organic sources have been proposed as an option for improving soil fertility, restoring degraded land, and mitigating the emissions of greenhouse gasses associated with agriculture. We review the findings of 634 publications in the last decade on biochar and biochar-compost mixtures as soil amendments in order to identify the potential gaps in our understanding of the role of these amendments in agriculture. We found that: i) the majority of published studies have been carried out in developed countries where soils are less impaired in terms of food production capacity than in many developing countries; ii) studies on biochar produced in small kilns are more common than biochars produced at commercial scale in developed countries, whereas biochars produced using traditional techniques are more commonly used than biochars produced in modern pyrolysis units in developing countries; iii) laboratory and greenhouse studies are more common than field studies; and iv) wood and municipal wastes were the major feedstock for the preparation of biochar compared to crop residues and manures. Although, biochar-compost application proved to be more generally effective in improving soil properties and crop yields (field crops and horticulture crops) than biochar alone, along with desired soil properties, could be a feasible alternative to remediate the degraded soils and improve their productivity potential in the long-term. Overall, a lack of long-term, well-designed field studies on the efficacy of biochar and biochar-compost mixtures on different soil types and agro-climatic zones are limiting our current understanding of biochar's potential to enhance crop production and mitigate climate change. We further suggest that greater collaboration between researchers, biochar producers, and policy makers is required to advance the research and uptake of this important technology at a global scale.
The Pyrogenic Carbon Cycle Bird, Michael I; Wynn, Jonathan G; Saiz, Gustavo ...
Annual review of earth and planetary sciences,
05/2015, Letnik:
43, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Pyrogenic carbon (PyC; includes soot, char, black carbon, and biochar) is produced by the incomplete combustion of organic matter accompanying biomass burning and fossil fuel consumption. PyC is ...pervasive in the environment, distributed throughout the atmosphere as well as soils, sediments, and water in both the marine and terrestrial environment. The physicochemical characteristics of PyC are complex and highly variable, dependent on the organic precursor and the conditions of formation. A component of PyC is highly recalcitrant and persists in the environment for millennia. However, it is now clear that a significant proportion of PyC undergoes transformation, translocation, and remineralization by a range of biotic and abiotic processes on comparatively short timescales. Here we synthesize current knowledge of the production, stocks, and fluxes of PyC as well as the physical and chemical processes through which it interacts as a dynamic component of the global carbon cycle.
•Soil was amended with biochar, compost and their co-composted mixture at field scale.•Leaf chlorophyll, N, P and K were increased by organic amendments.•Peanut yield was increased by 18–24% and ...nodulation by 9–25% by organic amendments.•Soil OC, N, P, NO3−, NH4+, CEC and soil water content were significantly improved by organic amendments.•Greenhouse gas emissions were reduced by organic amendments.
This study investigated the effects of biochar and compost, applied individually or together, on soil fertility, peanut yield and greenhouse gas (GHG) emissions on a Ferralsol in north Queensland, Australia. The treatments were (1) inorganic fertilizer only (F) as a control; (2) 10tha−1 biochar+F (B+F); (3) 25t compost+F (Com+F)ha−1; (4) 2.5t Bha−1+25t Comha−1 mixed on site+F; and (5) 25tha−1 co-composted biochar-compost+F (COMBI+F). Application of B and COMBI increased seed yield by 23% and 24%, respectively. Biochar, compost and their mixtures significantly improved plant nutrient availability and use, which appeared critical in improving peanut performance. Soil organic carbon (SOC) increased from 0.93% (F only) to 1.25% (B amended), soil water content (SWC) from 18% (F only) to over 23% (B amended) and CEC from 8.9cmol(+)/kg (F only) to over 10.3cmol(+)/kg (organic amended). Peanut yield was significantly positively correlated with leaf chlorophyll content, nodulation number (NN), leaf nutrient concentration, SOC and SWC for the organic amendments. Fluxes of CO2 were highest for the F treatment and lowest for the COMBI treatment, whereas N2O flux was highest for the F treatment and all organic amended plots reduced N2O flux relative to the control. Principal component analysis indicates that 24 out of 30 characters in the first principal component (PRIN1) individually contributed substantial effects to the total variation between the treatments. Our study concludes that applications of B, Com, B+Com or COMBI have strong potential to, over time, improve SOC, SWC, soil nutrient status, peanut yield and abate GHG fluxes on tropical Ferralsols.
Organic amendments by N fertilizer interaction significantly increased grain yields at two sites (upper), and organic amendments significantly improved soil organic carbon and pH. Con: Control; B: ...Biochar; Com: Compost; COMBI: Composted biochar.
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•Nitisols were amended with biochar, compost and their mixture and N fertilizer at field level at two sites.•Barley grain yields were significantly increased by 30–49% at Holetta and 51–78% at Robgebeya by organic amendments.•Organic amendment by N fertilizer interaction had significantly additive effects on yields of barley at both locations.•Leaf chlorophyll and uptakes of N, P and K by plants were significantly increased by organic amendments.•Organic amendments significantly improved soil OC, N, P, soil pH, CEC and soil water content.
Sustaining soil fertility and enhancing food production on smallholder farms is a great challenge in sub-Saharan Africa. The effects of organic amendments and nitrogen fertilizer on soil physicochemical properties and barley yield were investigated in the central Ethiopian highlands. The treatments were factorial combinations of no organic amendment (control), 10tha−1 biochar only (B), 10tha−1 compost only (Com), 10t Com ha−1+2t B ha−1 and 10tha−1 co-composted biochar-compost (COMBI) as main plots, and five N fertilizer levels (0, 23, 46, 69 and 92kgha−1) as sub-plots, with three replicates at two sites (Holetta and Robgebeya) both on Nitisols in the 2014 cropping season. Application of organic amendments and N fertilizer all significantly improved soil fertility and barley yield. The highest yield, chlorophyll content, number of productive tillers and nutrient uptake were obtained from the Com+B soil amendment at Holetta and from Com at Robgebeya. Mean grain yield responses of barley to the organic amendments were 30–49% at Holetta and 51–78% at Robgebeya, compared to the control. Fertilizer N significantly increased grain yield, chlorophyll content and N uptake at both locations. The highest grain yield obtained was at 69kgNha−1 at Holetta and at 92kgha−1 at Robgebeya. The organic amendment by N fertilizer interaction significantly influenced grain yield at both sites. Com+B and 69kgNha−1 addition resulted in the highest grain yield (5381kgha−1) at Holetta, whereas Com and 92kgNha−1 resulted in the highest grain yield (4598kgha−1) at Robgebeya. Organic amendments significantly improved soil properties through increases in soil water content, soil organic carbon (SOC), cation exchange capacity (CEC) and pH (0–20cm depth). Addition of B, Com and B+Com increased SOC and CEC by 23–27% and 20–24% at Holetta and 26–34% and 19–23% at Robgebeya compared to their respective initial values. Soil pH increased from the initial value of 5.0 to 5.6 at Holetta and from 4.8 to 5.4at Robgebeya at harvest due to biochar soil amendment. Grain yield was significantly correlated with total biomass, number of productive tillers, SOC and CEC. We conclude that application of organic amendments optimizes soil physicochemical properties and will help sustain barley yields in the Ethiopian highlands. The use of B, Com or Com+B may substantially reduce the amount of mineral fertilizer required for the sustainable production of barley in the long term.
The effects of organic amendments and nitrogen (N) fertilizer on yield and N use efficiency of barley were investigated on a Nitisol of the central Ethiopian highlands in 2014. The treatments were ...factorial combinations of no organic amendment, biochar (B), compost (Com), Com+B and co-composted biochar (COMBI) as main plots and five N fertilizer levels as sub-plots, with three replicates. Application of organic amendment and N fertilizer significantly improved yield, with grain yield increases of 60% from Com+B+69kgNha−1 at Holetta and 54% from Com+92kgNha−1 at Robgebeya, compared to the yield from the maximum N rate. The highest total N uptake was obtained from Com+B+92kgNha−1 at Holetta (138kgha−1) and Com+92kgNha−1 at Robgebeya (101kgha−1). The agronomic efficiency (yield increase per unit of N applied, AE), apparent recovery efficiency (increase in N uptake per unit of N applied, ARE) and physiological efficiency (yield increase per unit of N uptake, PE) responded significantly to organic amendments and N fertilizer. Mean AE and ARE were highest at B+23kgNha−1 at Holetta and at B+23 and B+46kgNha−1 at Robgebeya. The PE ranged from 19 to 33kggrainkg−1 N uptake at Holetta and 29–48kggrainkg−1 N uptake at Robgebeya. The effects of organic amendments and N fertilizer on AE, ARE and PE were greater at Robgebeya than at Holetta. The enhancement of N use efficiency through application of organic amendments emphasizes the importance of balanced crop nutrition, ensuring that barley crops are adequately supplied with N and other nutrients. Overall, the integration of both organic and inorganic amendments may optimize N uptake efficiency and reduce the amount of N fertilizer required for the sustainable barley production in the long-term.
Agronomic efficiency (AE) and apparent nitrogen recovery efficiency (ARE) of barley under organic amendments (Con: control, B: biochar, Com: compost, Com+B and COMBI: co-composted biochar) and N fertilization at Holetta (upper half) and Robgebeya (lower half) sites of contrasting soil fertility levels. Display omitted
•The effects of Com, B and Com+B and N fertilizer on yield and N use efficiency of barley were investigated.•Com or Com+B with N fertilizer increased grain yield up to 60% compared to the yield with the highest N fertilizer alone.•Grain and straw N contents were significantly increased by organic amendments and N fertilizer at both sites.•B or Com+B with moderate rates of N (23–69kgNha−1) significantly improved the AE, ARE and PE at both sites.
The addition of organic amendments to agricultural soils has the potential to increase crop yields, reduce dependence on inorganic fertilizers and improve soil condition and resilience. We evaluated ...the effect of biochar (B), compost (C) and co-composted biochar (COMBI) on the soil properties, crop yield and greenhouse gas emissions from a banana and a papaya plantation in tropical Australia in the first harvest cycle. Biochar, compost and COMBI organic amendments improved soil properties, including significant increases in soil water content, CEC, K, Ca, NO3, NH4 and soil carbon content. However, increases in soil nutrient content and improvements in physical properties did not translate to improved fruit yield. Counter to our expectations, banana crop yield (weight per bunch) was reduced by 18%, 12% and 24% by B, C and COMBI additions respectively, and no significant effect was observed on the papaya crop yield. Soil efflux of CO2 was elevated by addition of C and COMBI amendments, likely due to an increase in labile carbon for microbial processing. Our data indicate a reduction in N2O flux in treatments containing biochar. The application of B, C and COMBI amendments had a generally positive effect on soil properties, but this did not translate into a crop productivity increase in this study. The benefits to soil nutrient content, soil carbon storage and N2O emission reduction need to be carefully weighed against potentially deleterious effects on crop yield, at least in the short-term.
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•Biochar and compost amendment has potential to improve tropical agriculture.•We monitored soil health, gas fluxes and crop yield under biochar and compost.•Biochar improved soil nutrient content, water retention and reduced N2O emissions.•Biochar significantly reduced banana yield performance and did not affect papaya yield.•Organic amendment is not an ‘always win’ scenario for tropical agriculture.
Stable carbon and nitrogen isotope analyses are widely used to infer diet and mobility in ancient and modern human populations, potentially providing a means to situate humans in global food webs. We ...collated 13,666 globally distributed analyses of ancient and modern human collagen and keratin samples. We converted all data to a common "Modern Diet Equivalent" reference frame to enable direct comparison among modern human diets, human diets prior to the advent of industrial agriculture, and the natural environment. This approach reveals a broad diet prior to industrialized agriculture and continued in modern subsistence populations, consistent with the human ability to consume opportunistically as extreme omnivores within complex natural food webs and across multiple trophic levels in every terrestrial and many marine ecosystems on the planet. In stark contrast, isotope dietary breadth across modern nonsubsistence populations has compressed by two-thirds as a result of the rise of industrialized agriculture and animal husbandry practices and the globalization of food distribution networks.
Rapid degradation of pyrogenic carbon Zimmermann, Michael; Bird, Michael I.; Wurster, Christopher ...
Global change biology,
November 2012, Letnik:
18, Številka:
11
Journal Article
Recenzirano
Pyrogenic carbon (PC‐ charcoal, biochar or black carbon) represents a poorly understood component of the global carbon (C) cycle, but one that has considerable potential to mitigate climate change ...through provision of long‐term soil C sequestration. Mass balance calculations suggest global PC production and stocks are not in balance, indicating a major gap in our understanding of the processes by which PC is re‐mineralized. We collected PC samples derived from the same wood material and exposed to natural environmental conditions for 1 and 11 years. We subjected these materials to repeated laboratory incubation studies at temperatures of up to 60 °C, as ground surface temperatures above 30 °C and up to 60 °C occur regularly over a significant area of the tropics and sub‐tropics. Mineralization rates were not different for the two samples and followed an exponential Arrhenius function that suggest an average turnover time of 67 years for conditions typical of a tropical savannah environment. Microbial biomass as measured by chloroform fumigation and DNA extractions was the same for the two samples, but abiotic CO2 production was lower for the fresh PC sample than that for the aged sample. Nuclear magnetic resonance spectroscopy, hydrogen pyrolysis and scanning electron microscopy demonstrate that the measured CO2 production originates dominantly from polycyclic aromatic compounds rather than any minor labile components. Therefore, rapid, sub‐centennial rates of re‐mineralization of PC on the soil surface in tropical and sub‐tropical environments may represent a major and hitherto unidentified mechanism for balancing the PC production at the global scale.
The isotope signatures registered in speleothems during tropical cyclones (TC) provides information about the frequency and intensity of past TCs but the precise relationship between isotopic ...composition and the meteorology of TCs remain uncertain. Here we present continuous δ18O and δ2H data in rainfall and water vapour, as well as in discrete rainfall samples, during the passage of TC Ita and relate the evolution in isotopic compositions to local and synoptic scale meteorological observations. High-resolution data revealed a close relationship between isotopic compositions and cyclonic features such as spiral rainbands, periods of stratiform rainfall and the arrival of subtropical and tropical air masses with changing oceanic and continental moisture sources. The isotopic compositions in discrete rainfall samples were remarkably constant along the ~450 km overland path of the cyclone when taking into account the direction and distance to the eye of the cyclone at each sampling time. Near simultaneous variations in δ18O and δ2H values in rainfall and vapour and a near-equilibrium rainfall-vapour isotope fractionation indicates strong isotopic exchange between rainfall and surface inflow of vapour during the approach of the cyclone. In contrast, after the passage of spiral rainbands close to the eye of the cyclone, different moisture sources for rainfall and vapour are reflected in diverging d-excess values. High-resolution isotope studies of modern TCs refine the interpretation of stable isotope signatures found in speleothems and other paleo archives and should aim to further investigate the influence of cyclone intensity and longevity on the isotopic composition of associated rainfall.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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