Regional Assessment of Soil Change in the Southwest Pacific

The Southwest Pacific region includes the 22 island nations of the Pacific1, New Zealand and Australia (Figure 15.1). The landscapes of the region are very diverse ranging from a large continental land mass through to tens of thousands of small islands across the enormous expanse of the southwest Pacific Ocean. There are extensive ancient flat lands through to some of the youngest and most tectonically active landscapes on the planet. Temperature and rainfall ranges are large because of the breadth of latitudes and elevations. As a consequence, the soils of the region are also diverse. The strongly weathered soils in humid tropical areas and the vast expanses of old soils across the Australian continent are particularly susceptible to disturbance and this is where some of the more intractable problems of soil management occur today

Molecular characteristics of permanganate- and dichromate-oxidation-resistant soil organic matter from a black-C-rich colluvial soil

16 páginas.-- 3 figuras.-- 3 tablas.-- 85 referenciasSamples from a colluvial soil rich in pyrogenic material (black C, BC) in north-west Spain were subjected to K2Cr2O7 and KMnO4 oxidation and the residual soil organic matter (SOM) was NaOH-extracted and analysed using analytical pyrolysis-gas chromatography-mass spectroscopy (Py-GC/MS) and solid-state 13C cross-polarisation magic angle spinning-nuclear magnetic resonance (13C CP MAS-NMR) in order to study the susceptibility of different SOM fractions (fresh, degraded/microbial, BC and aliphatic) towards these oxidising agents. Untreated samples that were NaOH-extracted were also analysed. The Py-GC/MS and 13C NMR indicated that KMnO4 promotes the oxidation of carbohydrate products, mostly from degraded/microbial SOM and lignocellulose, causing a relative enrichment of aliphatic and aromatic structures. Residual SOM after K2Cr2O7 oxidation contained BC, N-containing BC and aliphatic structures. This was corroborated by a relatively intense resonance of aromatic C and some signal of alkyl C in 13C NMR spectra. These results confirm that dichromate oxidation residues contain a non-pyrogenic fraction mainly consisting of aliphatic structures.The contribution of M. Camps-Arbestain to this research was funded by MAF and NZAGRC.Peer reviewe

Assessment of Mercury-Polluted Soils Adjacent to an Old Mercury-Fulminate Production Plant

Mercury contamination of soils and vegetation close to an abandoned Hg-fulminate production plant was investigated. Maximum concentrations of Hg (>6.5 g kg−1 soil) were found in the soils located in the area where the wastewater produced during the washing procedures carried out at the production plant used to be discharged. A few meters away from the discharge area, Hg concentrations decreased to levels ranging between 1 and 5 g kg−1, whereas about 0.5 ha of the surrounding soil to the NE (following the dominant surface flow direction) contained between 0.1 and 1 g kg−1. Mercury contamination of soils was attributed (in addition to spills from Hg containers) to (i) Hg volatilization with subsequent condensation in cooler areas of the production plant and in the surrounding forest stands, and (ii) movement of water either by lateral subsurface flow through the contaminated soils or by heavy runoff to surface waters

Research and application of biochar in New Zealand

Readers will appreciate the comprehensive review of the latest biochar research and applications and gain critical guidance in best biochar generation and use

Biochar determination in soils by applying pyrolysis GC-MS analysis and Black Carbon (BC) concentration trough dichromate and permanganate oxidation

Resumen de la Comunicación presentada en el Goldschmidt2013 Conference Abstracts. Biochar Interactions with Soil, Plant and Water – Processes and Fate, Florencia (Italia) 2013Distinguishing pyrogenic and non-pyrogenic SOM components is a difficult task as non-selective pyrolysis products such as MAHs, PAHs and phenols can derive from multiple sources. However, black carbon (BC) may contribute significantly to the MAHs and PAHs in a given pyrolysate, especially if BC is more abundant than alternative sources. In this study, samples from a soil rich in pyrogenic material in NW Spain were subjected to K2Cr2O7 and KMnO4 oxidation and the residual SOM was NaOH-extracted and analyzed using analytical Py-GC-MS in order to study the susceptibility of different SOM fractions (fresh, degraded/microbial, aliphatic and specially BC) towards this oxidation agent. Besides solid-state 13C CP MAS-NMR was also performed to support theses results. Non-oxidized samples following the same NaOH-extraction procedure were also analyzed. From Py-GC-MS, residual SOM after K2Cr2O7 oxidation contained BC, N-containing BC (BN) and aliphatic structures whilst carbohydrate products and lignocellulose were completely oxidized. This was corroborated by a relatively intense resonance of aromatic C and some signal of alkyl C (supporting the presence of a non-pyrogenic fraction mainly consisting of aliphatic structures) in 13C NMR spectra. Thus K2Cr2O7 effectively concentrates MAHs, PAHs and BN derived from BC. For KMnO4, both techniques indicated that this reagent promotes the oxidation of carbohydrate products, mostly from degraded/microbial SOM but slightly oxidized lignocellulose and aromatic structures (pyrogenic and nonpyrogenic) not providing a good assessment of the BC signal.Peer Reviewe

Fate of biochar in chemically- and physically-defined soil organic carbon pools

The objective was to elucidate the fate of biochar in physically- and chemically-defined fractions of organic carbon (OC) in soil after 510days of laboratory incubation. Fresh corn stover (CS) and biochar produced from corn stover at 350°C (CS-350) and 550°C (CS-550) were added to an Alfisol and an Andisol at a dose equivalent to 7.18tC/ha. After 295days, two undisturbed subsamples from each pot were taken: (i) in one, lucerne (Medicago sativa L.) was seeded and (ii) in the other, the incubation was continued without the plants. On days, 0, 295 and 510, soil samples were fractionated into coarse free particulate organic matter (fPOM), fine fPOM, silt+clay and heavy fractions, and analysed for δ13C value and OC content. The fractions were fractionated into dichromate-oxidisable and HCl-hydrolysable OC. After 295days, δ13C analysis revealed that >64% of the biochar C was recovered in the coarse fPOM fraction and 13-30% in the fine fPOM fraction. The same pattern was observed after 510days, although a significant increase (P<0.05) in the recovery of biochar C in the silt+clay fraction was observed. Treatments, including the presence of both biochar and plants, induced a significant additional accumulation of OC (P<0.05) in the Alfisol and Andisol amended with CS-350 biochar and CS-550 biochar, respectively, compared with the corresponding treatments with plants but no biochar. We argue the need for a modified physicochemical fractionation method for soils amended with biochar. The use of long term incubations in studies of soil OM turnover (including biochar), where no input of fresh detritus is made, is discouraged. © 2014 Elsevier Ltd.The authors acknowledge all the assistance of AgResearch, Grasslands Research Centre, Palmerston North, New Zealand. The valuable suggestions of R. Gentile as well as the technical assistance of B. Toes, T. Maruyama, M. Vazquez and A. Singh are also appreciated. H.M.S.K.H. was funded by the New Zealand Biochar Research Centre, under the Massey University Doctoral Scholarship Programme. Financial support was covered by the Ministry of Agriculture and Forestry, New Zealand and the New Zealand Agricultural Greenhouse gas Research Centre.Peer Reviewe

NaOH-extractable organic matter of andic soils from Galicia (NW Spain) under different land use regimes: a pyrolysis GC/MS study

The objective of this study was to determine to what extent the attenuation or loss of andic soil properties caused by land use change ¿ from forest (FOR, average C content 118.2 ± 23.7 g kg¿1) to agricultural land (AGR, average C content 55.7 ± 16.7 g kg¿1) use ¿ is reflected in soil organic matter (SOM) at the molecular level. For this, NaOH-extractable SOM of A horizons from 17 soils developed on amphibolitic parent material in NW Spain was studied by pyrolysis gas chromatography spectrometry (Py-GC/MS). We also included two buried andic A horizons (PAL, 2200 cal yr BP in age) on the same parent material, as a reference for the molecular composition of SOM from soils without recent litter additions. Organic matter of PAL soils had a composition largely different from that of superficial soils (FOR and AGR), with an important relative contribution of microbial polysaccharides and N-compounds, and an absence of compounds that characterize fresh plant litter (e.g. lignins). In the superficial soils, the relative contribution of lignin-derived compounds was greater in AGR than in FOR soils. Differences were also observed in the relative contribution of aliphatic compounds, FOR soils being enriched in this type of components compared with AGR soils. The results indicated that land use change from FOR to AGR, which was accompanied by a decrease in total SOM, resulted in an enrichment in primary SOM. The smaller relative abundance of primary SOM derivatives in andic FOR soils indicates that these compounds were quickly degraded in Andisol

DISTRIBUTION OF CARBON IN SIZE-FRACTIONS OF A PASTURE SOIL 26 MONTHS AFTER ADDING BIOCHAR

Fractionating soils according to size and/or density of particles improves our understanding of the importance of interactions between organic and inorganic soil components on the turnover of soil organic carbon (SOC). Conventional soil physical fractionation methodologies misrepresent the contribution of pyrogenic C (e.g., biochar-derived C) to the total SOC because of the relative long turnover time of this fraction, regardless the physical SOC physical fraction in which this is found. In this study, a combination of particle size fractionation and wet sieving, as well as chemical analysis (dichromate oxidation) was tested to isolate meaningful SOC fractions in a set of 34 soils with C content ranging from 19.1–43.0 g SOC/kg soil. Topsoil and subsoil samples were obtained after 26 months of simulating cultivation at pasture renewal including pine biochar (10 t/ha) as amendment (below 10 cm depth) and growth of contrasted plant species (ryegrass vs a mixture of red clover and cocksfoot) in a lysimeter experiment using a silt loam soil (Tokomaru soil, a Pallic soil with limited drainage at depth). Across all the soils considered, the allocation of SOC in size-fractions (i.e., 2000-200, 250-53 and <53 m) was obtained by conventional wet sieving. Additionally, the total content of resistant forms of SOC (i.e.both alkyl C forms and pyrogenic C from biochar) was calculated as the sum of the dichromate-resistant C obtained in the different size-fractions. This sum of all dichromate-resistant C pools can be used as a proxy to estimate contribution of pyrogenic C to the total SOC in the soils studied. The different C fractions isolated by the appropriate combination of methodologies (particle size fractionation, wet chemistry) is proposed as an alternative to obtain the particulate, humus and resistant organic carbon fractions (POC, HOC and ROC, respectively) used in models (e.g. RothC). The developed methodology will help to improve the prediction of SOC dynamics and any impact of climate change on SOC stocks when these contain pyrogenic C.falsePalmerston North, New Zealan

Experimental evidence for sequestering C with biochar by avoidance of CO2 emissions from original feedstock and protection of native soil organic matter

There is a need for further studies to compare the decomposition of biochar to that of the original feedstock and determine how these amendments affect the cycling of native organic matter (NOM) of different soils to improve our understanding of the resulting net C sequestration potential. A 510-days incubation experiment was conducted (i) to investigate the evolution of CO2 from soils amended with either fresh corn stover (CS) or with biochars produced from fresh CS at either 350 (CS-350) or 550 degrees C (CS-550), and (ii) to evaluate the priming effect of these amendments on NOM decomposition. Two soil types were studied: an Alfisol and an Andisol, with organic C contents of 4% and 10%, respectively. Except for the controls (with no C addition), all treatments received 7.18t Cha(-1). We measured C efflux in short-term intervals and its isotopic signature to distinguish between C evolved from C-4 amendments and C-3-dominated NOM. Emission rates were then integrated for the whole time period to cover total emissions. Total CO2-C evolved from the original C in fresh CS, CS-350 and CS-550 was greater in the Andisol (78%, 13% and 14%) than in the Alfisol (66%, 8% and 7%). For both soils, (i) no significant differences (P>0.05) were observed in the rate of CO2 evolution between controls and biochar treatments; and (ii) total accumulated CO2 evolved from the uncharred amendment was significantly higher (P0.05) net priming effect was observed. A C balance indicated that the C lost from both biochar production and decomposition broke even' with that lost from fresh residue decomposition after <35weeks. The break-even' point was reached earlier in the Andisol, in which the fresh CS mineralizes faster. These results provided experimental evidence for the potential of biochar to sequester C and avoid CO2 emissions from original feedstock while protecting native soil organic matter