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Biochar for Sustainable Agricultural Systems and other Environmental Applications

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A special issue of Soil Systems (ISSN 2571-8789).

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 53871

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Prof. Balwant Singh

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Guest Editor

Sydney Institute of Agriculture, School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW 2006, Australia
Interests: soil chemistry; clay minerals; carbon cycling; biochar; trace elements; sorption-desorption; mineral-organic interactions; Fe oxides

Prof. Marta Camps Arbestain

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Guest Editor

Massey University, Private Bag 11 222, Palmerston North, 4442, New Zealand
Interests: environmental biogeochemistry; carbon sequestration in soil; organo-mineral interactions; biochar

Special Issue Information

Dear Colleagues,

The application of biochar for long-term carbon storage has now been established. The recent IPCC special report incorporates, for the first time, biochar technology and pyrogenic carbon capture and storage as a promising “negative emission technology”. However, biochar systems need to be more economically viable and better positioned so as to compete with other biomass uses. To achieve this, a better understanding of the impact of biochar and of functionalised biochar products on (i) soil fertility, (ii) N₂O emissions, (iii) indirect GHG emissions reduction resulting from reduced fertiliser needs by using biochar technology, and (iv) other environmental benefits of biochar, such as the rehabilitation of degraded land and filtering of waste waters, is needed.

We invite authors to submit their current work on the novel techniques of biochar characterisation for environmental applications; the production of functionalised biochars; sorption-desorption behaviour of biochars for emerging and other organic compounds, heavy metals, and nutrient elements; on the role of biochar in regulating GHG emissions and carbon storage using long-term field experiments; the application of biochar for the rehabilitation of degraded soils; and any other aspects in the environmental context.

Prof. Dr. Balwant Singh
Prof. Dr. Marta Camps Arbestain
Guest Editors

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Published Papers (11 papers)

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Research

16 pages, 970 KiB

Open AccessArticle

The 3R Principles for Applying Biochar to Improve Soil Health

by Mingxin Guo

Soil Syst. 2020, 4(1), 9; https://doi.org/10.3390/soilsystems4010009 - 4 Feb 2020

Cited by 47 | Viewed by 10169

Abstract

Amending soil with biochar is a promising approach to persistently improve soil health and promote crop growth. The efficacy of soil biochar amendment, however, is soil specific, biochar dependent, and influenced by the biochar application programs. To maximize the benefits of biochar application, this paper proposes the 3R principles for applying biochar to soils: right biochar source, right application rate, and right placement in soil. The quality of biochar as a soil amendment varies significantly with the feedstock and the production conditions. Biochar products capable of everlastingly sustaining soil health are those with high stable organic carbon (OC) content and high water- and nutrient-holding capacities that are manufactured from uncontaminated biomass materials. Acidic, coarse-textured, highly leached soils respond remarkably more to biochar amendment than other types of soils. Soil amendment with particular biochars at as low as 0.1 mass% (equivalent to 2 Mg ha⁻¹) may enhance the seasonal crop productivity. To achieve the evident, long-term soil health improvement effects, wood- and crop residue-derived biochars should be applied to soil at one time or cumulatively 2–5 mass% and manure-derived biochars at 1–3 mass% soil. Optimal amendment rates of particular biochar soil systems should be prescreened to ensure the pH of newly treated soils is less than 7.5 and the electrical conductivity (EC) below 2.7 dS m⁻¹ (in 1:1 soil/water slurry). To maximize the soil health benefits while minimizing the erosion risk, biochar amendment should be implemented through broadcasting granular biochar in moistened conditions or in compost mixtures to cropland under low-wind weather followed by thorough and uniform incorporation into the 0–15 cm soil layer. Biochars are generally low in plant macronutrients and cannot serve as a major nutrient source (especially N) to plants. Combined chemical fertilization is necessary to realize the synergic beneficial effects of biochar amendment. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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11 pages, 1893 KiB

Open AccessArticle

Evaluation of the Influence of Individual Clay Minerals on Biochar Carbon Mineralization in Soils

by Qingzhong Zhang, Claudia Keitel and Balwant Singh

Soil Syst. 2019, 3(4), 79; https://doi.org/10.3390/soilsystems3040079 - 3 Dec 2019

Cited by 4 | Viewed by 3668

Abstract

Although association between mineral and biochar carbon have been speculated in some studies, still there is no direct evidence for the influence of individual clay minerals on the mineralization of biochar carbon in soils. To address this, we conducted an incubation study using monomineralic soils constituted by separately mixing pure minerals, i.e., smectite, kaolinite, and goethite, with a sandy soil. Switch grass biochar (400 °C) was added to the artificial soils and samples were incubated for 90 days at 20 °C in the laboratory. The CO₂-C mineralized from the control, and biochar amended soil was captured in NaOH traps and the proportion of C mineralized from biochar was determined using δ¹³C isotopic analysis. The clay minerals significantly decreased the cumulative total carbon mineralized during the incubation period, whereas biochar had no effect on this. The least amount of total C was mineralized in the presence of goethite and biochar amended soil, where only 0.6% of the native soil organic carbon (SOC) (compared to 4.14% in control) and 2.9% of the biochar-C was mineralized during the 90 days incubation period. Native SOC mineralization was significantly reduced in the presence of biochar and the three minerals. Goethite was most effective in stabilizing both biochar and the native soil organic carbon. The short-term data from this study demonstrate that biochar application in Fe oxide rich soils may be an effective strategy to sequester biochar carbon, as well as to stabilize native soil carbon. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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15 pages, 1524 KiB

Open AccessArticle

Temporal Changes in the Efficiency of Biochar- and Compost-Based Amendments on Copper Immobilization in Vineyard Soils

by Christina Pump, Katharina M. Keiblinger, Elisabeth Scheiblauer, Simone Johnen, Niklas J. Lehto, Gerhard Soja and Franz Zehetner

Soil Syst. 2019, 3(4), 78; https://doi.org/10.3390/soilsystems3040078 - 27 Nov 2019

Cited by 3 | Viewed by 3410

Abstract

Copper (Cu)-based fungicides have been an important tool against disease in viticulture since the 19th century. However, their prolonged use can lead to Cu accumulation in the soil and negatively affect soil microbiology and plant growth. The application of biochar (BC)-based amendments is a promising mitigation strategy, due to BC’s longevity in the soil and its potential to complex Cu. This study investigated temporal changes in the efficiency of various compost- and BC-based amendments to immobilize Cu in a calcareous and a slightly acidic Austrian vineyard soil. The immobilization of both historically accumulated Cu and freshly spiked Cu (250 mg kg⁻¹) was studied. The soils were treated with six combinations of amendments containing compost and BC, with and without surface modification, as well as an additional lime treatment for the acidic soil. After treatment, the soils were incubated for 6 weeks and 3 years, after which the 0.01 M CaCl₂-extractable Cu was measured. The amendments were not effective in reducing the mobility of the historically accumulated Cu in the calcareous soil, with pure compost doubling the soluble Cu. Pure wood-chip BC was the only organic amendment that led to a reduction (by 20%) of soluble Cu after 6 weeks in the acidic soil; however, after 3 years, the same amendment reduced soluble Cu by 40% and all other tested amendments were also effective in reducing the mobility of the historically accumulated Cu. The lime treatment achieved the greatest reduction in Cu mobility (56%). Freshly spiked Cu was strongly immobilized in both unamended soils, with 0.06% and 0.39% extractable after 6 weeks in the calcareous and slightly acidic soil, respectively. The amendments did not effectuate additional Cu immobilization in the calcareous soil, but in the acidic soil, the soluble Cu was further reduced to between 25% and 50% of the unamended control by the tested organic amendments and to 6% by the lime treatment after 6 weeks of incubation. Overall, the acidic soil exhibited a stronger response to the amendments than did the calcareous soil, suggesting the amendments’ effect on the soil pH was an important factor for Cu immobilization in this study. These results show the importance of developing site-specific remediation strategies for Cu accumulation in agricultural soils. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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16 pages, 1521 KiB

Open AccessArticle

Nitrogen Dynamics in an Established Alfalfa Field under Low Biochar Application Rates

by Katherine S. Rocci, Steven J. Fonte, Joseph C. von Fischer and M. Francesca Cotrufo

Soil Syst. 2019, 3(4), 77; https://doi.org/10.3390/soilsystems3040077 - 26 Nov 2019

Cited by 6 | Viewed by 3879

Abstract

Sustainable nitrogen (N) management in agroecosystems is crucial for supporting crop production and reducing deleterious N losses. Biochar application with N-fixing legumes offers promise for increasing soil N retention and input. Strategic, low application rates (112 kg ha⁻¹) of pine and coconut feedstock biochars were tested in an established alfalfa (Medicago sativa) field. Soil inorganic N and plant growth, N concentrations, and δ¹⁵N were monitored over a growing season to follow mineral N availability, and plant N uptake and sourcing. Microbial and gene abundance and enzyme activity were measured to assess the potential for N cycling processes to occur. Biochar application had minimal effects on measured parameters. However, significant temporal dynamics in N cycling and correlations between alfalfa δ¹⁵N and soil N availability indicate differing plant N sourcing over time. Our findings indicate that low application rates of biochar in established alfalfa fields do not significantly affect N cycling, and that managing alfalfa to maximize N fixation, for example by intercropping, may be a better solution to increase N stocks and retention in this system. To determine when biochar can be beneficial for alfalfa N cycling, we need additional research to assess various economically-feasible biochar application rates at different alfalfa growth stages. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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16 pages, 8258 KiB

Open AccessArticle

Most Plant Nutrient Elements Are Retained by Biochar in Soil

by Tanawan Limwikran, Irb Kheoruenromne, Anchalee Suddhiprakarn, Nattaporn Prakongkep and Robert J. Gilkes

Soil Syst. 2019, 3(4), 75; https://doi.org/10.3390/soilsystems3040075 - 18 Nov 2019

Cited by 14 | Viewed by 3466

Abstract

Biochar may contain substantial amounts of plant nutrient elements, and at typical rates of application, may supply luxury levels of K, Ca, P, and other plant nutrients. However, little is known of the agronomic effectiveness of these nutrients because they exist in diverse compounds and are located in the microporous matrix of biochar particles. We have identified the compounds and location of nutrient elements in three biochars and observed their release from biochar particles in soil. Much K was quickly released from biochar but little or no Ca, Mg, S, and P were released over eight months, which represents a very different behavior from chemical fertilizers that are mostly water soluble. There is clearly a need to determine the availability to plant nutrients in biochar. Appropriate laboratory methods should be developed for measuring the availability of plant nutrients as standard methods of fertilizer analysis are ineffective. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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6 pages, 472 KiB

Open AccessCommunication

Biochar Enhances Nitrous Oxide Reduction in Acidic but Not in Near-Neutral pH Soil

by Engil Isadora Pujol Pereira, Jérôme Léchot, Rafaela Feola Conz, Abmael da Silva Cardoso and Johan Six

Soil Syst. 2019, 3(4), 69; https://doi.org/10.3390/soilsystems3040069 - 24 Oct 2019

Cited by 6 | Viewed by 3385

Abstract

We quantified nitrous oxide (N₂O) fluxes and total denitrification (N₂O + N₂) in an acidic (Ferralsol) and a near-neutral pH soil (Cambisol) to determine whether biochar’s alkalinization effect could be the mechanism inducing potential reductions in N₂O fluxes. In Ferralsol, decreases in N₂O emissions and in the N₂O to N₂O + N₂ ratio were observed in both biochar and lime treatments. In Cambisol, neither biochar nor lime decreased N₂O emissions, despite significantly increasing soil pH. The abundance and community structure of nosZ gene-bearing microorganisms indicated that gene abundances did not explain biochar effects, but a higher diversity of nosZ gene-bearing microorganisms correlated to lower total denitrification. Overall, our results suggest that biochar’s potential to decrease N₂O emissions, through soil alkalinization, may be more effective in acidic soils. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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15 pages, 2203 KiB

Open AccessArticle

Changes in Water Infiltration after Simulated Wetting and Drying Periods in two Biochar Amendments

by Karolina Villagra-Mendoza and Rainer Horn

Soil Syst. 2019, 3(4), 63; https://doi.org/10.3390/soilsystems3040063 - 25 Sep 2019

Cited by 7 | Viewed by 3363

Abstract

Biochar impacts soil-water related processes such as infiltration and contributes to the hydrological response of catchments. The aim of this work is to determine the impact of wetting and drying conditions on the infiltration behavior of two biochar amendments and to validate the performance of three infiltration models: Kostiakov, Horton, and Philips. Two materials, sand and a sandy loam, were mixed with 0%, 2.5%, and 5% (by dry wt.) mango wood biochar produced at a highest heating rate of 600 °C and with a particle size of <63 μm. A sequence of four wetting and drying cycles were simulated. In each cycle, infiltration was measured. We found that biochar addition decreased infiltration because the formation of narrower pores reduced infiltration capacity. The higher the biochar dosage, the more resilient the treatment became concerning the changes on the water infiltrated. Repetitive wetting and drying cycles resulted in a reconfiguration of structural pores affecting the transport of water and air. The infiltration models of Kostiakov and Horton could predict the infiltration dynamics in the amended materials, although they show some instabilities along the WD cycles. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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15 pages, 2224 KiB

Open AccessArticle

Effect of Biochar Application Rates on the Hydraulic Properties of an Agricultural-Use Boreal Podzol

by Daniel Altdorff, Lakshman Galagedara, Joinal Abedin and Adrian Unc

Soil Syst. 2019, 3(3), 53; https://doi.org/10.3390/soilsystems3030053 - 15 Aug 2019

Cited by 9 | Viewed by 3846

Abstract

Boreal agriculture struggles with soils of lower agronomic value, most of which are sandy with a low water holding capacity (WHC) and prone to nutrient leaching. Biochar amendments are associated with positive effects on soil hydraulic properties and enhanced nutrient retention. However, these effects are strongly related to feedstock type and pyrolysis parameters and depend on biochar application rates and soil types. While biochar could increase the productivity of boreal agriculture by improving water and nutrient use efficiency, little is known about its effects on hydraulic processes in podzol. In this study, we investigated the effects of biochar rates (10, 20, 40, 80 Mg carbon ha⁻¹) and maturity on soil hydrology for an agriculturally used Podzol in Labrador, Canada. The in-situ soil water content (SWC) and weather data over an entire growing season were analysed. Hydrus 1D simulations were used to estimate changes in water fluxes. SWC showed clear differentiation among storage parameters (i.e., initial, peak and final SWC) and kinetic parameters (i.e., rate of SWC change). Storage parameters and soil wetting and drying rates were significantly affected by biochar rates and its maturity. The magnitude of the changes in SWC after either wetting or drying events was statistically not affected by the biochar rate. This confirms that biochar mostly affected the WHC. Nevertheless, reductions in cumulative lower boundary fluxes were directly related to biochar incorporation rates. Overall, biochar had positive effects on hydrological properties. The biochar rate of 40 Mg C ha⁻¹ was the most beneficial to agriculturally relevant hydraulic conditions for the tested Podzol. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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14 pages, 4078 KiB

Open AccessArticle

Pyrolysis Temperature Effects on Biochar–Water Interactions and Application for Improved Water Holding Capacity in Vineyard Soils

by Jon Marshall, Richard Muhlack, Benjamin J. Morton, Lewis Dunnigan, David Chittleborough and Chi Wai Kwong

Soil Syst. 2019, 3(2), 27; https://doi.org/10.3390/soilsystems3020027 - 9 Apr 2019

Cited by 42 | Viewed by 7202

Abstract

Grapevine cane and stalks were considered for pyrolysis at 400 to 700 °C to produce biochar for increasing the water holding capacity of vineyard soil. Feedstocks were pyrolysed using a continuous feed reactor and the resulting biochars characterized in terms of physico-chemical properties, including water retention performance. Hydrophobicity was found in biochar from both feedstocks pyrolysed at 400 °C, but not at higher temperatures. At low soil matric potential, the pyrolysis temperature was the defining variable in determining water retention whereas at higher pressures, the feedstock was the more important variable. Available water content (AWC) of biochar increased with increasing pyrolysis temperatures, with optimal results obtained from grapevine cane at a pyrolysis temperature of 700 °C, which had an AWC 23% higher than a typical clay type soil. Principal component analysis showed variability in water retention of these biochars to be closely associated with the zeta potential, as well as the carbon and ionic content, suggesting that surface charge and hydrophobicity are key properties determining water holding capacity. Pure biochars were superior in water retention performance to typical sandy soils, and so biochar amendment of these soil types may improve water holding (particularly at field capacity). Further study with pot or field trials is recommended to confirm water retention behaviour and assess the feasibility of application under different viticultural scenarios. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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16 pages, 1739 KiB

Open AccessArticle

Variation in Feedstock Wood Chemistry Strongly Influences Biochar Liming Potential

by Sossina Gezahegn, Mohini Sain and Sean C. Thomas

Soil Syst. 2019, 3(2), 26; https://doi.org/10.3390/soilsystems3020026 - 3 Apr 2019

Cited by 52 | Viewed by 5648

Abstract

Chars intended for use as soil amendment (“biochars”) vary greatly in their chemical and physical properties. In the present study, 19 Canadian temperate wood feedstocks were charred across a range of pyrolysis temperatures from 300–700 °C. The resulting 95 biochars were tested for their physio-chemical properties and liming capacity. Data indicated increasing base cation concentrations including Ca, Mg, and K (elements that characteristically form liming compounds, i.e., carbonates) as pyrolysis temperature increased. Acidic surface functional groups were analyzed with modified Boehm titration: Carboxylic and lactonic functional group concentrations decreased and phenolic group concentration increased with pyrolysis temperature. Functional group composition also varied greatly with feedstock: In particular, conifer-derived biochars produced at pyrolysis temperatures <500 °C showed much higher carboxylic and lactonic functional group concentrations than did angiosperm-derived biochars. Liming capacity was assessed using soil incubation experiments and was positively related to biochar pH. Both acidic surface functional group concentration and nutrient element concentration influenced biochar pH: we developed a non-linear functional relationship that predicts biochar pH from the ratio of carboxylic to phenolic moieties, and concentrations of Ca and K. Biochar’s liming components that are inherited from feedstock and predictably modified by pyrolysis temperature provide a basis for optimizing the production of biochar with desired pH and liming characteristics. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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19 pages, 2045 KiB

Open AccessArticle

Chemical, Physical, and Hydraulic Properties as Affected by One Year of Miscanthus Biochar Interaction with Sandy and Loamy Tropical Soils

by Sara de Jesus Duarte, Bruno Glaser, Renato Paiva de Lima and Carlos Eduardo Pelegrino Cerri

Soil Syst. 2019, 3(2), 24; https://doi.org/10.3390/soilsystems3020024 - 29 Mar 2019

Cited by 15 | Viewed by 5017

Abstract

Biochar application has improved soil properties contributing to crop growth. This study evaluates the effect of biochar amount on soil physical, chemical and hydraulic properties in sandy (SD) and clay loam (CL) soils under tropical conditions. An incubation experiment was installed under laboratory conditions with eight treatments (control, two kinds of soils, SD and CL, and three biochar doses (6.25, 12.5, and 25 Mg ha⁻¹). Analyses of soil water retention, bulk density (BD), total porosity (TP), pores size, total carbon (TC), and N were performed after one year. The BD slightly decreased by 0.035 and 0.062 Mg m⁻³ and TP increased by 1.87 and 2.31% in CL and SD soil respectively, upon 6.25 to 25 Mg ha⁻¹ biochar application. TC increased in CL and SD by 6.5 and 4.2 kg kg⁻¹, respectively, compared to control. The total nitrogen content increased upon biochar addition in CL soil than in SD soil. We found a positive effect of biochar on water availability, microporosity, and a small effect on water retention, especially for CL soil at high biochar application, but this influence did not occur for SD, possibly due to the short time of interaction. Full article

(This article belongs to the Special Issue Biochar for Sustainable Agricultural Systems and other Environmental Applications)

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