ORCID Profile
0000-0002-0615-6407
Current Organisation
James Cook University Cairns Campus
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Ecological Impacts of Climate Change | Photogrammetry and Remote Sensing | Surfacewater Hydrology | Ecological Applications | Ecological Applications not elsewhere classified | Atmospheric Sciences | Global Change Biology | Soil Chemistry | Geomatic Engineering | Applied Hydrology (Drainage, Flooding, Irrigation, Quality, Etc.) | Geochronology And Isotope Geochemistry | Climate Change Processes | Isotope Geochemistry | Plant Physiology | Other Agricultural and Veterinary Sciences | Other Biological Sciences | Environmental Monitoring | Palaeoecology | Fertilisers And Agrochemicals (Application Etc.) | Technology not elsewhere classified |
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Climate Change Adaptation Measures | Physical and Chemical Conditions of Water not elsewhere classified | Land and water management | Integrated (ecosystem) assessment and management | Earth sciences | Land and Water Management of environments not elsewhere classified | Climate change | Forest and Woodlands Soils | Climate and Climate Change not elsewhere classified | Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and Industrial Use) | Physical and Chemical Conditions of Water in Coastal and Estuarine Environments | Other environmental aspects | Forest and Woodlands Flora, Fauna and Biodiversity
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Publications
Spatial analysis of melioidosis distribution in a suburban area
Publisher: Cambridge University Press (CUP)
Date: 22-01-2010
DOI: 10.1017/S0950268809991634
Abstract: Burkholderia pseudomallei , the causative agent of melioidosis is associated with soil. This study used a geographic information system (GIS) to determine the spatial distribution of clinical cases of melioidosis in the endemic suburban region of Townsville in Australia. A total of 65 cases over the period 1996–2008 were plotted using residential address. Two distinct groupings were found. One was around the base of a hill in the city centre and the other followed the old course of a major waterway in the region. Both groups (accounting for 43 of the 65 cases examined) are in areas expected to have particularly wet topsoils following intense rainfall, due to soil type or landscape position.
Pyrogenic carbon from tropical savanna burning: production and stable isotope composition
Publisher: Copernicus GmbH
Date: 20-03-2015
Abstract: Abstract. Widespread burning of mixed tree–grass ecosystems represents the major natural locus of pyrogenic carbon (PyC) production. PyC is a significant, pervasive and yet poorly understood "slow-cycling" form of carbon present in the atmosphere, hydrosphere, soils and sediments. We conducted 16 experimental burns on a rainfall transect through northern Australian savannas with C4 grasses ranging from 35 to 99% of total biomass. Residues from each fire were partitioned into PyC and further into recalcitrant (HyPyC) components, with each of these fluxes also partitioned into proximal components ( μm), likely to remain close to the site of burning, and distal components ( μm), likely to be transported from the site of burning. The median (range) PyC production across all burns was 16.0 (11.5) % of total carbon exposed (TCE), with HyPyC accounting for 2.5 (4.9) % of TCE. Both PyC and HyPyC were dominantly partitioned into the proximal flux. Production of HyPyC was strongly related to fire residence time, with shorter duration fires resulting in higher HyPyC yields. The carbon isotope (δ13C) compositions of PyC and HyPyC were generally lower by 1–3‰ relative to the original biomass, with marked depletion up to 7‰ for grasslands dominated by C4 biomass. δ13C values of CO2 produced by combustion were computed by mass balance and ranged from ~0.4 to 1.3‰. The depletion of 13C in PyC and HyPyC relative to the original biomass has significant implications for the interpretation of δ13C values of savanna soil organic carbon and of ancient PyC preserved in the geologic record, as well as for global 13C isotopic disequilibria calculations.
The effects of biochar, compost and their mixture and nitrogen fertilizer on yield and nitrogen use efficiency of barley grown on a Nitisol in the highlands of Ethiopia
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.SCITOTENV.2016.05.033
Abstract: 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.
Soil and crop responses to different tillage systems
Publisher: Elsevier BV
Date: 04-1994
Quantifying nitrogen losses in oil palm plantations: models and challenges
Publisher: Copernicus GmbH
Date: 30-09-2016
Abstract: Abstract. Oil palm is the most rapidly expanding tropical perennial crop. Its cultivation raises environmental concerns, notably related to the use of nitrogen (N) fertilisers and the associated pollution and greenhouse gas emissions. While numerous and erse models exist to estimate N losses from agriculture, very few are currently available for tropical perennial crops. Moreover, there is a lack of critical analysis of their performance in the specific context of tropical perennial cropping systems. We assessed the capacity of 11 models and 29 sub-models to estimate N losses in a typical oil palm plantation over a 25-year growth cycle, through leaching and runoff, and emissions of NH3, N2, N2O, and NOx. Estimates of total N losses were very variable, ranging from 21 to 139 kg N ha−1 yr−1. On average, 31 % of the losses occurred during the first 3 years of the cycle. Nitrate leaching accounted for about 80 % of the losses. A comprehensive Morris sensitivity analysis showed the most influential variables to be soil clay content, rooting depth, and oil palm N uptake. We also compared model estimates with published field measurements. Many challenges remain in modelling processes related to the peculiarities of perennial tropical crop systems such as oil palm more accurately.
Molecular composition of recycled organic wastes, as determined by solid-state 13C NMR and elemental analyses
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.WASMAN.2013.06.013
Abstract: Using solid state (13)C NMR data and elemental composition in a molecular mixing model, we estimated the molecular components of the organic matter in 16 recycled organic (RO) wastes representative of the major materials generated in the Sydney basin area. Close correspondence was found between the measured NMR signal intensities and those predicted by the model for all RO wastes except for poultry manure char. Molecular nature of the organic matter differed widely between the RO wastes. As a proportion of organic C, carbohydrate C ranged from 0.07 to 0.63, protein C from <0.01 to 0.66, lignin C from <0.01 to 0.31, aliphatic C from 0.09 to 0.73, carbonyl C from 0.02 to 0.23, and char C from 0 to 0.45. This method is considered preferable to techniques involving imprecise extraction methods for RO wastes. Molecular composition data has great potential as a predictor of RO waste soil carbon and nutrient outcomes.
Dynamics of the water extractable organic carbon pool during mineralisation in soils from a Douglas fir plantation and an oak-beech forest—an incubation experiment
Publisher: Springer Science and Business Media LLC
Date: 12-11-2009
Key unknowns in nitrogen budget for oil palm plantations. A review
Publisher: Springer Science and Business Media LLC
Date: 29-02-2016
Dispersed clay and organic matter in soil: their nature and associations
Publisher: CSIRO Publishing
Date: 1999
DOI: 10.1071/S98076
Abstract: Clay dispersion in soil results in structural instability and management problems. The aim of this study was to determine whether or not the easily dispersed colloidal materials differ in their properties from colloidal materials that do not disperse easily. Soil s les from the topsoil of sodic and non-sodic variants of an Alfisol under irrigated pasture (Kyabram, Victoria, Australia), and from the topsoil and subsoil of a sodic Alfisol under cultivation (Two Wells, South Australia) were fractionated into easily dispersed, moderately dispersed, and difficult to disperse clay, and silt, sand, and light fractions. As a proportion of total clay, easily dispersed clay content was greatest in the subsoil, and least in the Kyabram topsoils. In the topsoils, easily dispersed clay had larger particle size and lower cation exchange capacity than difficult to disperse clay, suggesting that high surface area and charge lead to increased inter-particle interactions and lower dispersibility. Easily dispersed clay had lower organic C contents than difficult to disperse clay. Organic matter was examined by 13C nuclear magnetic resonance, and the spectra were interpreted using major groups of biomolecules as model components. In all soils, organic matter in the easily dispersed clay fraction contained a high proportion of amino acids, suggesting that amino acids or proteins acted as dispersants. Difficult to disperse clay contained a high proportion of aliphatic materials in the topsoils, and carbohydrate in the subsoil, suggesting that these materials acted as water-stable glues. Selectivity for Na (KG) was negatively correlated with organic C content in the clay fractions. In the Kyabram soils, KG was greater in easily dispersed clay than in difficult to disperse clay. In Two Wells soil, clay with high KG appeared to have already moved out of the topsoil, into the subsoil. This work showed that variability in the nature of organic matter and clay particles has an important influence on clay dispersion in sodic and non-sodic soils.
Erratum to: Methods to account for tree-scale variability in soil and plant-related parameters in oil palm plantations
Publisher: Springer Science and Business Media LLC
Date: 06-03-2014
Charcoal re-combustion efficiency in tropical savannas
Publisher: Elsevier BV
Date: 05-2014
Supplementary material to "Quantifying nitrogen losses in oil palm plantations: models and challenges"
Publisher: Copernicus GmbH
Date: 17-05-2016
Farming with crops and rocks to address global climate, food and soil security
Publisher: Springer Science and Business Media LLC
Date: 19-02-2018
DOI: 10.1038/S41477-018-0108-Y
Abstract: The magnitude of future climate change could be moderated by immediately reducing the amount of CO
Accurate water‐table depth estimation using seismic refraction in areas of rapidly varying subsurface conditions
Publisher: Wiley
Date: 05-2015
Image-based quantification of Fusarium wilt severity in banana
Publisher: Springer Science and Business Media LLC
Date: 23-05-2019
Development of an oil palm cropping systems model: Lessons learned and future directions
Publisher: Elsevier BV
Date: 12-2014
Tropical dairy pasture yield and nitrogen cycling: effect of urea application rate and a nitrification inhibitor, DMPP
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/CP15400
Abstract: In tropical dairy production systems, where high rates of urea fertiliser are applied, little is known about nitrogen (N) fertiliser response, fertiliser-use efficiency and losses to the environment. This study aimed to determine the effects of N fertiliser (urea) application rate and a nitrification inhibitor (3, 4-dimethylpyrazole phosphate, DMPP) on pasture yield and N losses in a dairy production system in North Queensland, Australia. The experiment was a factorial design with two fertiliser rates (industry standard per application 57 kg N ha–1 or half that, applied ~3-weekly), two DMPP rates (0 or 4.86 g kg–1 urea) and four replicates, completed over 1 year. Urea applied at half the industry standard rate, together with DMPP, provided annual dry matter pasture yields (11 462 kg ha–1) not significantly different from those when urea was applied at the higher rate, with or without DMPP (10 691 and 11 156 kg ha–1, respectively). The low rate of urea without DMPP had the lowest annual dry matter yield (8386 kg ha–1). Most of the fertiliser N lost from the system appeared to be via leaching, with loss in surface runoff minimal. During the ryegrass phase, an experiment with 15N labelling showed that, 3 months after application, 27–39% of the applied N had been taken up by the pasture, 23–45% was recovered in the soil, and 18–40% had been lost. Emission of N2O peaked within a day of fertiliser application, and DMPP did not reduce emissions during that period. The findings indicate good potential for farmers to use DMPP-treated urea as a means of reducing N fertiliser rates without loss of productivity and with less loss of N to the environment.
Influence of soil clay content on dissolved organic matter in stream waters
Publisher: CSIRO Publishing
Date: 1990
DOI: 10.1071/MF9900761
Abstract: Dissolved organic carbon (DOC) is of major importance for freshwater ecology and water treatment, particularly in Australia. Work comparing two small catchments, one yielding water with high DOC concentrations (Lawless) and the other yielding water with low DOC concentrations (Retreat Valley), is described. Differences between stream DOC concentrations in the two catchments were related to differences between the properties of the catchment soils. The Retreat Valley soils had higher C contents than the Lawless soils, but the C was less soluble, resulting in lower DOC concentrations in soil core leachates. The lower solubility of C in the Retreat Valley soils was the result of a higher clay content and hence a higher surface area for adsorption reactions. The Retreat Valley soils had a higher adsorption capacity for organic matter than did the Lawless soils. The clay contents of soils was found to be an important factor influencing stream DOC concentrations throughout the Mt Lofty Ranges, and the prediction of DOC concentrations in streams on a broad scale is discussed.
Sodicity and Clay Type: Influence on Decomposition of Added Organic Matter
Publisher: Wiley
Date: 07-1997
Preferential Production and Transport of Grass-Derived Pyrogenic Carbon in NE-Australian Savanna Ecosystems
Publisher: Frontiers Media SA
Date: 12-01-2018
Temporal variation in abundance of leaf litter beetles and ants in an Australian lowland tropical rainforest is driven by climate and litter fall
Publisher: Springer Science and Business Media LLC
Date: 05-05-2018
Mineralisation of soil organic carbon in two Andisols under oil palm: an incubation study into controlling factors
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/SR16089
Abstract: Understanding the factors controlling stability against mineralisation of soil organic matter is important for predicting changes in carbon stocks under changed environment or management. Soil carbon dynamics in oil palm plantations are little studied and have some characteristics that are unusual compared with other agricultural soils, such as high management-induced spatial variability and warm moist conditions. The aim of this work was to determine the factors controlling the mineralisability of the intermediate-stability carbon fraction of volcanic ash surface soils (0–5 and 15–20 cm depth) from oil palm plantations in Papua New Guinea. Soils with carbon contents of 2.2–35.2%, from areas with low and high organic matter inputs, were incubated for up to 812 days and soil respiration was measured periodically. Mean carbon turnover rates were 0.18–1.58, 0.07–0.23 and 0.03–0.07 a–1 on Days 54, 379 and 812 respectively. Turnover rate was initially (Day 54) correlated with pre-incubation total carbon content (r = 0.88), the ratio of permanganate-oxidisable carbon to total carbon (r = 0.62) and the ratio of oxalate-extractable Al and Fe to total carbon (r = –0.51 and –0.54 respectively), but the correlations decreased with time, being insignificant on Day 812. In the soils that had changed from C4 grassland 25 years previously, turnover rate was negatively correlated with δ13C, which increased with depth, but δ13C did not change significantly over the course of the incubation. Temperature sensitivity of mineralisation varied little, despite large differences in soil properties and changes in mineralisation rate. This suggested that turnover rates were affected to similar extents by biochemical recalcitrance and physical protection, as these two factors influence temperature sensitivity in opposing directions. Physico-chemical protection of organic matter appeared largely related to interaction with poorly crystalline Al and Fe oxides.
Oil palm expansion transforms tropical landscapes and livelihoods
Publisher: Elsevier BV
Date: 12-2012
Buried lava flows crossing the Great Divide in north Queensland: discovery using magnetic methods, and implications for hydrology
Publisher: Informa UK Limited
Date: 04-2010
Concentration and composition of dissolved organic carbon in streams in relation to catchment soil properties
Publisher: Springer Science and Business Media LLC
Date: 1993
DOI: 10.1007/BF00000573
Decomposition of 14C-labelled plant material in a salt-affected soil
Publisher: Elsevier BV
Date: 04-1996
Changes in dispersible clay content, organic carbon content, and electrolyte composition following incubation of sodic soil
Publisher: CSIRO Publishing
Date: 1998
DOI: 10.1071/S98024
Abstract: Measurement of dispersible clay is important for the diagnosis of structural stability problems in soil. However, clay dispersibility is known to change with water content and time. The purpose of the present study was to determine how incubation of sodic soil under different water content regimes influences clay dispersibility. Two topsoils (depth 0-0·1 m), one sodic [exchangeable sodium percentage (ESP) 9 · 7] and the other non-sodic (ESP 3·8), were collected from an experimental pasture at Kyabram, Victoria, and 2 soils, a sodic topsoil (depth 0-0·1 m, ESP 6·9) and the corresponding subsoil (depth 0·2-0 m, ESP 25·7), were collected from a cropped field at Two Wells, South Australia. The soils were incubated for 264 days in a split-plot design. The main treatments were soil type and incubation water content: continuously air-dry, continuously wet (-50 kPa), or with wet/dry cycles. The subtreatment was water content at analysis: air dry or wet (-50 kPa). Clay dispersion was greater when measured on wet soils than dry soils, irrespective of water contents during the prior incubation. Electrical conductivity increased, and sodium adsorption ratio (SAR), pH, and organic carbon content decreased as a function of the time for which the soils were wet. In the Kyabram soils that were wet when analysed, easily dispersible clay content increased with SAR. Decreases in moderately dispersible clay under the wetting/drying regime were not related to electrolyte composition, and were attributed to particle rearrangement and cementation. The decreases in clay dispersibility with time occurred despite net losses of carbohydrate and aliphatic materials. An implication of the work is that the decomposition of soil organic matter, even in the absence of fresh additions, may reduce clay dispersion in sodic soils by altering electrolyte concentration and composition.
Shifts in prokaryotic communities under forest and grassland within a tropical mosaic landscape
Publisher: Elsevier BV
Date: 04-2018
IN‐Palm: An agri‐environmental indicator to assess nitrogen losses in oil palm plantations
Publisher: Wiley
Date: 26-02-2020
DOI: 10.1002/AGJ2.20109
Phosphorus Response and Fertilizer Recommendations for Wheat Grown on Nitisols in the Central Ethiopian Highlands
Publisher: Informa UK Limited
Date: 11-09-2015
Suppressiveness or conduciveness to Fusarium wilt of bananas differs between key Australian soils
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/SR18159
Abstract: Soils are known to differ in suppressiveness to soil-borne diseases, but the suppressiveness or otherwise to Fusarium wilt of Australian soils used to grow bananas is unknown. In this work we tested the relative suppressiveness of six key soil types. Banana (Musa (AAB group) ‘Pome’, cultivar ‘Lady Finger’) was grown in pots of the soils inoculated or not with Fusarium oxysporum f.sp. cubense (Foc) ‘Race 1’. Sixteen weeks after inoculation the plants were harvested and disease severity was assessed by measuring discoloration within the rhizome. In the inoculated pots, disease severity was greatest in the alluvial Liverpool and Virgil soils and least in the basaltic origin Tolga soil. No disease was detected in the non-inoculated pots. Soils with the lowest disease severity had the highest root mass, irrespective of inoculation, and the largest (negative) effect of inoculation on root dry mass. Disease severity in inoculated pots was negatively correlated with soil clay content and β-glucosidase activity. The results indicate that the risk of Fusarium wilt negatively impacting banana growth differs between soils of the main Australian banana-growing region.
Using Soil Water Depletion to Measure Spatial Distribution of Root Activity in Oil Palm (Elaeis guineensis Jacq.) Plantations
Publisher: Springer Science and Business Media LLC
Date: 15-07-2006
Sorption behaviour of per- and polyfluoroalkyl substances (PFASs) in tropical soils
Publisher: Elsevier BV
Date: 03-2020
Supplementary material to "Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China"
Publisher: Copernicus GmbH
Date: 17-08-2015
The ameliorating effects of biochar and compost on soil quality and plant growth on a Ferralsol
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/SR14118
Abstract: Deteriorating soil fertility and the concomitant decline in agricultural productivity are major concerns in many parts of the world. A pot experiment was conducted with a Ferralsol to test the hypothesis that application of biochar improves soil fertility, fertiliser-use efficiency, plant growth and productivity, particularly when combined with compost. Treatments comprised: untreated control mineral fertiliser at rates of 280 mg nitrogen, 70 mg phosphorus and 180 mg potassium pot–1 (F) 75% F + 40 g compost pot–1 (F + Com) 100% F + 20 g willow biochar pot–1 (F + WB) 75% F + 10 g willow biochar + 20 g compost pot–1 (F + WB + Com) 100% F + 20 g acacia biochar pot–1 (F + AB) and 75% F + 10 g acacia biochar + 20 g compost pot–1 (F + AB + Com). Application of compost with fertiliser significantly increased plant growth, soil nutrient status and plant nutrient content, with shoot biomass (as a ratio of control value) decreasing in the order F + Com (4.0) F + WB + Com (3.6) F + WB (3.3) F + AB + Com (3.1) F + AB (3.1) F (2.9) control (1.0). Maize shoot biomass was positively significantly correlated with chlorophyll content, root biomass, plant height, and specific leaf weight (r = 0.99, 0.98, 0.96 and 0.92, respectively). Shoot and root biomass had significant correlations with soil water content, plant nutrient concentration, and soil nutrient content after harvesting. Principal component analysis (PCA) showed that the first component provided a reasonable summary of the data, accounting for ~84% of the total variance. As the plants grew, compost and biochar additions significantly reduced leaching of nutrients. In summary, separate or combined application of compost and biochar together with fertiliser increased soil fertility and plant growth. Application of compost and biochar improved the retention of water and nutrients by the soil and thereby uptake of water and nutrients by the plants however, little or no synergistic effect was observed.
Emission of CO2 from tropical riparian forest soil is controlled by soil temperature, soil water content and depth to water table
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/SR15040
Abstract: Tropical forests play a key role in the global carbon cycle. However, little is known about carbon cycling in the substantial portion of tropical forests that are low-lying, with shallow and fluctuating water tables. This study aimed to determine what factors control emissions of CO2 from soil in a riparian rainforest in Queensland, Australia. Emissions were measured over the course of 1 year, using static chambers. Emission rates were significantly related to soil temperature (0–0.1 m depth), soil water content (0–0.12 m depth) and depth to water table. The most efficient linear model of emissions as a function of measured parameters, which also included soil pH (0–0.1 m depth), had r2 = 0.355. CO2 emissions were highest (5.2–7.5 μmol m–2 s–1) at moderate soil temperature (24−28°C), water table depth (0.2–1.5 m) and soil water-filled porosity (0.25–0.79). They were lowest ( .5 μmol m–2 s–1) at low soil temperature ( °C) or when the water table was within 0.15 m of the surface. An additional interaction between temperature and soil water was determined in the laboratory. Incubation of soil cores showed that temperature sensitivity of the heterotrophic component of respiration increased as the soil dried. It is clear that models of soil respiration in lowland tropical forests should take into account depth to water table, which is a key, but hitherto unreported, controller of CO2 emissions in tropical forests.
Oil Palm and Deforestation in Papua New Guinea
Publisher: Wiley
Date: 27-08-2013
DOI: 10.1111/CONL.12058
Nitrogen and carbon management in Australian mango orchards to improve productivity and reduce greenhouse gas emissions
Publisher: International Society for Horticultural Science (ISHS)
Date: 07-2019
A native arbuscular mycorrhizal fungus inoculant outcompetes an exotic commercial species under two contrasting yam field conditions
Publisher: Elsevier BV
Date: 12-2017
Extraction of metals from mildly acidic tropical soils: Interactions between chelating ligand, pH and soil type
Publisher: Elsevier BV
Date: 06-2020
Reply to discussion by J. Nott (2014) on ‘Displacement of the Great Divide in north Queensland associated with Neogene lava flows’
Publisher: Informa UK Limited
Date: 03-10-2014
Benefits of biochar, compost and biochar–compost for soil quality, maize yield and greenhouse gas emissions in a tropical agricultural soil
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.SCITOTENV.2015.11.054
Abstract: 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) 10 t ha(-1) biochar (B)+F 3) 25 t ha(-1) compost (Com)+F 4) 2.5 t ha(-1) B+25 t ha(-1) Com mixed on site+F and 5) 25 t ha(-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 δ(15)N and δ(13)C 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.
Publisher Correction: Farming with crops and rocks to address global climate, food and soil security
Publisher: Springer Science and Business Media LLC
Date: 25-05-2018
DOI: 10.1038/S41477-018-0162-5
Abstract: In the version of this Perspective originally published, 'acidification' was incorrectly spelt as 'adification' in Fig. 4. This has now been corrected.
Short-term effects of incubated legume and grass materials on soil acidity and C and N mineralisation in a soil of north-east Australia
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/SR01099
Abstract: Perennial grass growth forms the basis of beef production systems in northern Australia. To improve pasture productivity the woody legume Stylosanthes has been introduced into these native pastures. However, the growth of legumes has been recognised to be a major factor in soil acidification, thereby reducing soil fertility. In order to determine impacts of Stylosanthes scabra (stylo) or Urochloa mosambicensis (urochloa) residues on soil pH, acid neutralising capacity (ANC), and C and N mineralisation, their tops and roots were incubated at a rate equivalent to 10 t dry matter/ha at 25�C for 25 days in topsoil s les of a Mottled-Subnatric Yellow Sodosol from a long-term field experiment under urochloa or under stylo cover. The amount of CO2-C released during the first 2 days of incubation was correlated with the decrease in dissolved organic C. Plant material addition immediately raised the pH and ANC relative to the control. This was related to the amount of ash alkalinity of the plant residues added to the soil. Since the ash alkalinity is a measure for the organic anion content of plant material, it was concluded that the pH buffering was due to protonation of organic anions. During incubation, net N mineralisation was only observed in the urochloa soil amended with stylo leaves. In all other treatments, N added in the residues was immobilised by microorganisms due to the high availability of easily degradable C-sources. Consequently, there was no further change in pH or ANC during incubation, since no significant amounts of H+ were produced or consumed during N conversion processes.
Nitrogen leaching from the root zone of sugarcane and bananas in the humid tropics of Australia
Publisher: Elsevier BV
Date: 11-2013
Estimating the molecular composition of a diverse range of natural organic materials from solid-state 13C NMR and elemental analyses
Publisher: Springer Science and Business Media LLC
Date: 2005
The role of surface charge and pH changes in tropical soils on sorption behaviour of per- and polyfluoroalkyl substances (PFASs)
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.SCITOTENV.2019.04.055
Abstract: This study investigated the effect of surface charge on the sorption of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS) onto 7 tropical soils as a function of pH. The net surface charge became less negative with decreasing pH (from 7.5 to 3.5) in all soils. The rate of change in net surface charge varied from -0.6 to -2.8 (cmol/kg) H unit. The effect on sorption behaviour of PFASs was variable among soils. For two soils, the average sorption increased 54- and 45-fold for PFOS, 33- and 9-fold for PFOA, and 39- and 400-fold for PFHxS, across the pH range 7.5 to 3.5. Sorption in another sandier soil showed negligible change with decreasing pH. Sorption in the other soils did not change significantly until the pH decreased to approximately 5.5. The soils with high contents of sesquioxides (Fe and Al oxides) showed the most marked increase in sorption with decreasing pH. This study demonstrated that in addition to hydrophobic interactions with OC and other processes, electrostatic interactions are also important in the sorption process for these chemicals in soils. In acidic, variably charged tropical soils there is the possibility that any PFOS, PFOA or PFHxS sorbed to the soils may become desorbed if management practices (e.g. liming) raised soil pH.
Evaluation of methods for field diagnosis of sodicity in soiland irrigation water in the sugarcane growing districts of Queensland, Australia
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/SR02028
Abstract: Sodicity and related properties of soils and irrigation water restrict sugarcane yields and cause environmental problems such as turbid runoff. The aim of this work was to assess the usefulness of several field diagnostic tests for soils and waters of the Australian sugar industry. Tests were evaluated using over 500 soil s les collected from 0–0.75 m depth from the 6 main sugarcane growing districts. Exchangeable sodium percentage (ESP) in the topsoil (0–0.25 m) could be predicted by electromagnetic induction (Geonics EM38) in 2 districts (r2 = 0.64–0.82), and in the subsoil (0.25–0.5 m) in 3 districts (r2�=�0.63–0.86). Dispersion index (DI) was a function of ESP in all districts, with 54–67% of variation accounted for in four districts. Soil pH was a function of ESP in all districts (59–73% of variation accounted for) except Bundaberg. ESP could be predicted from pH, electrical conductivity (EC), and Na concentration (by portable Na-selective electrode) of 1 : 5 soil : water suspensions (r2 = 0.57 for Bundaberg and r2�=�0.66–0.84 in all other districts). In irrigation waters (141 s les), measurements of Na concentration, by portable Na-selective electrode, and EC could be used to estimate Na (r2 = 0.85) and Ca + Mg (r2 = 0.87) concentrations, allowing sodium adsorption ratio to be estimated. Depending on the circumstances, these tests can provide useful estimates of sodicity and related properties in the field.
Assessing the extent of decomposition of natural organic materials using solid-state 13C NMR spectroscopy
Publisher: CSIRO Publishing
Date: 1997
DOI: 10.1071/S97004
Abstract: Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy has become an important tool for examining the chemical structure of natural organic materials and the chemical changes associated with decomposition. In this paper, solid-state 13C NMR data pertaining to changes in the chemical composition of a erse range of natural organic materials, including wood, peat, composts, forest litter layers, and organic materials in surface layers of mineral soils, were reviewed with the objective of deriving an index of the extent of decomposition of such organic materials based on changes in chemical composition. Chemical changes associated with the decomposition of wood varied considerably and were dependent on a strong interaction between the species of wood examined and the species composition of the microbial decomposer community, making the derivation of a single general index applicable to wood decomposition unlikely. For the remaining forms of natural organic residues, decomposition was almost always associated with an increased content of alkyl C and a decreased content of O-alkyl C. The concomitant increase and decrease in alkyl and O-alkyl C contents, respectively, suggested that the ratio of alkyl to O-alkyl carbon (A/O-A ratio) may provide a sensitive index of the extent of decomposition. Contrary to the traditional view that humic substances with an aromatic core accumulate as decomposition proceeds, changes in the aromatic region were variable and suggested a relationship with the activity of lignin-degrading fungi. The A/O-A ratio did appear to provide a sensitive index of extent of decomposition provided that its use was restricted to situations where the organic materials were derived from a common starting material. In addition, the potential for adsorption of highly decomposable materials on mineral soil surfaces and the impacts which such an adsorption may have on bioavailability required consideration when the A/O-A ratio was used to assess the extent of decomposition of organic materials found in mineral soils.
Iron chelates have little to no effect on the severity of Fusarium wilt of bananas in soils of the humid tropics
Publisher: Springer Science and Business Media LLC
Date: 26-03-2021
Exploring the response of sugar cane to sodic and saline conditions through natural variation in the field
Publisher: Elsevier BV
Date: 06-2000
Tree-scale spatial variability of soil carbon cycling in a mature oil palm plantation
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/SR15211
Abstract: Soil carbon fluxes are highly variable in space and time under tree crops such as oil palm, and attempts to model such fluxes must incorporate an understanding of this variability. In this work, we measured soil CO2 emission, root biomass and pruned frond deposition rates and calculated carbon fluxes into and out of the soil in a mature (20-year-old, second planting cycle) oil palm plantation in Papua New Guinea. Tree-scale spatial variability in CO2 emission and root biomass was quantified by making measurements on a 35-point trapezoid grid covering the 38.5-m2 repeating unit of the plantation (n = 4 grids). In order to obtain an overall mean soil CO2 emission rate within 5% of the most accurate estimate, ≥24 measurement points were required. Soil CO2 emissions were spatially correlated with calculated carbon inputs (r2 = 0.605, slope 1 : 1), but not with soil water content or temperature. However, outputs were higher than inputs at all locations, with a mean overall output of 7.24 µmol m–2 s–1 and input of 3.02 µmol m–2 s–1. Inputs related to fronds, roots and groundcover constituted 60%, 36% and 4% of estimated inputs, respectively. The spatial correlation of carbon inputs and outputs indicates that mineralisation rate is controlled mostly by the amount rather than the nature or input depth of the additions. The spatially uniform net carbon emission from soil may be due to inaccuracies in calculated fluxes (especially root-related inputs) or to non-biological emissions.
Hydrology of a forested riparian zone in an agricultural landscape of the humid tropics
Publisher: Elsevier BV
Date: 11-2013
Estimating organic carbon content of soil in Papua New Guinea using infrared spectroscopy
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/SR16227
Abstract: Quantification of soil organic carbon (SOC) content is important for sustainable agricultural management and accurate carbon accounting. Infrared (IR) absorbance can be used to estimate SOC content, but the relationship differs between regions due to matrix effects. We developed an IR-based model specific for SOC in Papua New Guinean soils. A total of 437 s les from 0.0–0.3m depth were analysed for SOC using Dumas combustion. IR absorption spectra were collected from the same s les, and a predictive regression model was developed using the 6000–1030cm–1 spectral range. Using a validation set, predicted SOC values resulting from the IR-based model compared well with values from Dumas combustion (R2=0.905 ratio of performance-to-deviation=5.64). Constraining wavelengths to positively correlated regions of the spectra was also explored and showed improved model performance (R2=0.932). Overall, IR analysis provides a robust method for estimating SOC content for a range of Papua New Guinean soils.
Impacts of soil abiotic attributes on Fusarium wilt, focusing on bananas
Publisher: Elsevier BV
Date: 12-2018
The distributed-order fractional diffusion-wave equation of groundwater flow: Theory and application to pumping and slug tests
Publisher: Elsevier BV
Date: 10-2015
Risk mapping of soil acidification under Stylosanthes in northern Australian rangelands
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/SR01018
Abstract: The inclusion of Stylosanthes into pastures and cropping systems has proved to be a low cost method of improving product quality in Asia, Africa, South America, and northern Australia. However, there is recent evidence that accelerated soil acidification has occurred under these production systems, questioning their long-term sustainability. In an effort to assist producers and extension officers in identifying soils that are predisposed to accelerated acidification, an acidity risk map of the Dalrymple Shire in Queensland, Australia, was developed using information from a recently completed land resource survey. Validation of a previously derived pedotransfer function that predicts pH buffering capacity was undertaken using an independent set of soil s les collected from the Shire. Excellent agreement between measured and predicted pH buffering capacity was obtained. The pedotransfer function was used to estimate the pH buffering capacity of 44 soil associations in the Shire. These values were used to predict the number of years that it would take for soils to acidify from their current pH to 5.0 assuming a constant net acid addition rate of 2.1 kmol H& lus & sol ha.year. Approximately 62& ercnt of the total area of the Shire is predisposed to accelerated acidification and would take between 10–20 years to acidify to pH 5.0. In contrast, a relatively minor proportion of the total area of the Shire (17& ercnt ) had significant internal buffering capacity. However, the degree of uncertainty associated with these estimations on certain soil associations may be too high to be of relevance. In order to overcome this limitation a field test designed to assess the risk of accelerated acidification on a paddock basis is proposed and outlined in the paper. pH, buffer capacity, pedotransfer function.
Methods to account for tree-scale variability in soil- and plant-related parameters in oil palm plantations
Publisher: Springer Science and Business Media LLC
Date: 12-09-2013
Organic Matter, Sodicity, and Clay Type: Influence on Soil Aggregation
Publisher: Wiley
Date: 07-1997
Soil carbon balance following conversion of grassland to oil palm
Publisher: Wiley
Date: 25-03-2015
DOI: 10.1111/GCBB.12138
Soil fertility changes following conversion of grassland to oil palm
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/SR14049
Abstract: Impacts of palm oil industry expansion on bio ersity and greenhouse gas emissions might be mitigated if future plantings replace grassland rather than forest. However, the trajectory of soil fertility following planting of oil palm on grasslands is unknown. We assessed the changes in fertility of sandy volcanic ash soils (0–0.15 m depth) in the first 25 years following conversion of grassland to oil palm in smallholder blocks in Papua New Guinea, using a paired-site approach (nine sites). There were significant decreases in soil pH (from pH 6.1 to 5.7) and exchangeable magnesium (Mg) content following conversion to oil palm but no significant change in soil carbon (C) contents. Analyses to 1.5 m depth at three sites indicated little change in soil properties below 0.5 m. There was considerable variability between sites, despite them being in a similar landscape and having similar profile morphology. Soil Colwell phosphorus (P) and exchangeable potassium (K) contents decreased under oil palm at sites with initially high contents of C, nitrogen, Colwell P and exchangeable cations. We also assessed differences in soil fertility between soil under oil palm (established after clearing forest) and adjacent forest at two sites. At those sites, there was significantly lower soil bulk density, cation exchange capacity and exchangeable calcium, Mg and K under oil palm, but the differences may have been due to less clayey texture at the oil palm sites than the forest sites. Cultivation of oil palm maintained soil structure and fertility in the desirable range, indicating that it is a sustainable endeavour in this environment.
Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China
Publisher: Copernicus GmbH
Date: 07-12-2015
Abstract: Abstract. Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate-containing soils and 1700 km sub-transect with non-carbonate-containing soils) across northern China. Soil pHBC was greater in the carbonate-containing soils than in the non-carbonate-containing soils. Acid addition decreased soil pH in the non-carbonate-containing soils more markedly than in the carbonate-containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC), carbonate content and exchangeable sodium (Na) concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC) content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate-containing soils and CEC was the main determinant of buffering capacity in the non-carbonate-containing soils. Along the transect, soil pHBC was different in regions with different aridity index. Soil pHBC was positively related to aridity index and carbonate content across the carbonate-containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate- and non-carbonate-containing soils. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.
Nitrogen, Phosphorus, and Organic Carbon in Streams Draining Two Grazed Catchments
Publisher: Wiley
Date: 11-1996
Yield and nitrogen losses in oil palm plantations: Main drivers and management trade-offs determined using simulation
Publisher: Elsevier BV
Date: 08-2017
Nitrate in shallow fluctuating groundwater under sugarcane: Quantifying the lateral export quantities to surface waters
Publisher: Elsevier BV
Date: 11-2013
Availability of organic carbon in soluble and particle-size fractions from a soil profile
Publisher: Elsevier BV
Date: 11-1994
Pyrogenic carbon from tropical savanna burning: production and stable isotope composition
Publisher: Copernicus GmbH
Date: 28-10-2014
DOI: 10.5194/BGD-11-15149-2014
Abstract: Abstract. Widespread burning of mixed tree-grass ecosystems represents the major natural locus of pyrogenic carbon (PyC) production. PyC is a significant, pervasive, and yet poorly understood "slow-cycling" form of carbon present in the atmosphere, hydrosphere, soils and sediments. We conducted sixteen experimental burns on a rainfall transect in northern Australian savannas with C4 grasses ranging from 35 to 99% of total biomass. Residues from each fire were partitioned into PyC and further into recalcitrant (HyPyC) components, with each of these also partitioned into proximal ( 125 μm) and distal ( 125 μm) fluxes. The median [range] PyC production across all burns was 16.0 [11.5]% of total carbon exposed (TCE), with HyPyC accounting for 2.5 [4.9]% of TCE. Both PyC and HyPyC were dominantly partitioned into the proximal flux, likely to remain (initially) close to the site of production. Production of HyPyC was strongly related to fire residence time, with shorter duration fires resulting in higher HyPyC yields. The carbon isotope (δ13C) compositions of PyC and HyPyC were generally lower by 1–3‰ relative to the original biomass, with marked depletion up to 7 ‰ for grasslands dominated by C4 biomass. δ13C values of CO2 produced by combustion was computed by mass balance and ranged from ~0.4 to 1.3‰. The depletion of 13C in PyC and HyPyC relative to the original biomass has significant implications for the interpretation of δ13C values of savanna soil organic carbon and of ancient PyC preserved in the geologic record, and for global 13C isotopic disequilibria calculations.
Biochar and biochar-compost as soil amendments: Effects on peanut yield, soil properties and greenhouse gas emissions in tropical North Queensland, Australia
Publisher: Elsevier BV
Date: 12-2015
Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China
Publisher: Copernicus GmbH
Date: 17-08-2015
DOI: 10.5194/BGD-12-13215-2015
Abstract: Abstract. Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate containing soils and 1700 km sub-transect with non-carbonate containing soils) across northern China. Soil pHBC was greater in the carbonate containing soils than in the non-carbonate containing soils. Acid addition decreased soil pH in the non-carbonate containing soils more markedly than in the carbonate containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC), carbonate content and exchangeable sodium (Na) concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC) content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate containing soils and CEC was the main determinant of buffering capacity in the non-carbonate containing soils. Soil pHBC was positively related to aridity index and carbonate content across the carbonate containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate and non-carbonate containing soils, leading to different rates, risks, and impacts of acidification. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.
Eucalyptus cloeziana mulch suppresses Fusarium wilt of banana
Publisher: Elsevier BV
Date: 09-2021
Site‐specific fertilizer recommendations for oil palm smallholders using information from large plantations
Publisher: Wiley
Date: 04-03-2011
Crop yield, plant nutrient uptake and soil physicochemical properties under organic soil amendments and nitrogen fertilization on Nitisols
Publisher: Elsevier BV
Date: 07-2016
Displacement of the Great Divide in north Queensland associated with Neogene lava flows
Publisher: Informa UK Limited
Date: 04-07-2014
Cropping sequence and nitrogen fertilizer effects on the productivity and quality of malting barley and soil fertility in the Ethiopian highlands
Publisher: Informa UK Limited
Date: 27-01-2014
Soil sampling in oil palm plantations: a practical design that accounts for lateral variability at the tree scale
Publisher: Springer Science and Business Media LLC
Date: 30-04-2015
Fluvial dynamics of dissolved and particulate organic carbon during periodic discharge events in a steep tropical rainforest catchment
Publisher: Wiley
Date: 11-2011
Soil physicochemical properties impact more strongly on bacteria and fungi than conversion of grassland to oil palm
Publisher: Elsevier BV
Date: 05-2016
The molecular composition of soil organic matter as determined by 13C NMR and elemental analyses and correlation with pesticide sorption
Publisher: Wiley
Date: 21-11-2006
Losses of nitrogen fertiliser under oil palm in Papua New Guinea: 1. Water balance, and nitrogen in soil solution and runoff
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/SR07171
Abstract: Nitrogen (N) fertiliser is an important and expensive input to oil palm in Papua New Guinea. Of about 3000 mm/year of rainfall, about 1300 mm is lost as evaporation. This leaves an excess of mm/year lost as surface runoff and/or deep drainage, and with it the potential for N loss. Approximately 11% of rainfall reached the ground as stem flow. Throughfall was generally lowest near the trunk and highest where canopies overlapped, but random spatial variability was large. The difference between the measured rainfall and stem flow plus throughfall was 6%, indicating relatively little interception. Surface runoff from the volcanic ash soils was 6% of rainfall at one site, but only 1.4% at the other. Less than 2% of the applied N was lost in the surface runoff after an ammonium chloride application. Calculations of N leaching losses made using suction cup data and the water balance indicated that significant losses occur, but the estimates were not reliable due to the huge spatial variability in the suction cup and throughfall data. Therefore, another technique is needed to study N leaching in oil palm plantations.
Soil pH buffering capacity: a descriptive function and its application to some acidic tropical soils
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/SR09150
Abstract: Calculation of soil acidification rates requires knowledge of pH buffering capacity (pHBC), which is measured using titration methods. The pHBC is often quoted as a single value for a particular soil, implying a linear relationship between pH and the amount of acid or alkali added. However, over its whole range, the relationship is sigmoid rather than linear, and in many soils pH is low or high enough to be outside of the linear range. In this work we fitted a simple sigmoid function to pH buffer curves of 8 tropical Australian soils obtained using one titration method and 58 Papua New Guinean (PNG) soils obtained using another titration method. The function described the curves well for all soils (adjusted r2 0.93 for all s les and .99 for 90% of s les), irrespective of the titration method, allowing pHBC to be calculated as a function of pH across the range of pH values established. Using the function, the contribution of variable charge to pHBC was calculated for the PNG soils on average it was 93% at the pH buffer curves’ inflection point, which corresponds with the soil’s minimum pHBC. Factors other than variable charge became important at pH (1 : 5, 0.002 m CaCl2) values .8 or .0. The relationship between pHBC and soil organic matter content was closest at pH 6.0–6.5. Application of the sigmoid function could facilitate more accurate assessments of acidification risks, acidification rates, and potential management interventions, particularly as soils become increasingly acidic.
Impact of oil palm development on the integrity of riparian vegetation of a tropical coastal landscape
Publisher: Elsevier BV
Date: 07-2018
Coupled Polymer-Membrane Equilibration and Cavity Ring-down Spectrometry for the Highly Sensitive Determination of Dissolved Methane in Environmental Waters
Publisher: Informa UK Limited
Date: 20-05-2020
Understanding and managing groundwater and salinity in a tropical conjunctive water use irrigation district
Publisher: Elsevier BV
Date: 10-2008
Structural stability of sodic soils in sugarcane production as influenced by gypsum and molasses
Publisher: CSIRO Publishing
Date: 2002
DOI: 10.1071/EA00113
Abstract: The aim of this work was to determine whether molasses, a by-product of sugar manufacture, alone or combined with gypsum, could improve the structural stability of sodic soils used for sugarcane production. A Burdekin sandy clay loam with an exchangeable sodium percentage (ESP) of 7.9, and a Proserpine loamy sand with an ESP of 18.8 were incubated with molasses (0 and 10 t/ha) and gypsum (0 and 10 t/ha) for 12 weeks, during which time they were leached 5 times with water (0.5 pore volumes each time). In the Burdekin soil, molasses and gypsum, either alone or combined, decreased spontaneous clay dispersion from 2.6 to .2 g/kg soil. Mechanical dispersion was reduced from 21.2 to .2 g/kg soil by gypsum alone, and to 14.9 g/kg soil by molasses alone. Molasses and gypsum both increased wet aggregate stability, with the combined effect being greatest the proportion of aggregates μm was 31% in the control and 71% with molasses + gypsum. Electrical conductivity (EC 1:5) was 0.1 and 1.9 dS/m, pH1:5 in water was 7.7 and 7.1, and ESP was 4.1 and 0.2 in the control and molasses + gypsum treatments respectively. In the Proserpine soil, the amounts of dispersible clay were much less than in the Burdekin soil. The effects of molasses and gypsum in decreasing spontaneous and mechanical clay dispersion were similar to those in the Burdekin soil, but less pronounced. Molasses and gypsum, either alone or combined, improved the structural stability of both soils by decreasing dispersion and/or slaking. An implication of this work is that molasses may be a useful ameliorant for sodic soils, either alone or combined with gypsum.
Bacterial community structure and denitrifier (nir-gene) abundance in soil water and groundwater beneath agricultural land in tropical North Queensland, Australia
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/SR10055
Abstract: We explored the microbial ecology of water draining through the soil (lysimeter s les) and in the shallow aquifers (bore s les) underlying sugarcane and banana fields near the Great Barrier Reef (GBR), Australia. Lysimeter and bore water s les were collected and analysed chemically and with DNA fingerprinting methods (PCR-DGGE and clone library sequencing) to characterise the structure of the bacterial community. Bacterial communities in soil water and bore water were distinct (P 0.05), and a primary factor linked with bacterial community structure was water pH (P 0.05), particularly in water s led from lysimeters. Irrespective of treatment, % of all rRNA gene sequences originated from proteobacteria. However, groundwater communities differed from those in soil water by greater occurrence of Neisseriales and Comamonadaceae (P 0.01). qPCR was used to measure copy numbers of the nirK and nirS genes encoding NO-forming nitrite reductases. Copy numbers of both genes were greater in soil water s les than groundwater (P = 0.05), with the difference in nirK being greater under sugarcane than banana. These differences in nirK-gene abundance show that there is greater potential for denitrification in soil water under sugarcane, leading to low concentrations of nitrate in the underlying groundwater. This knowledge can be used towards development of soil and land-use management practices promoting bacterial denitrification in groundwater to lessen the undesirable ecological consequences where groundwater discharges lower in the GBR catchment zones.
Quantifying nitrogen losses in oil palm plantations: models and challenges
Publisher: Copernicus GmbH
Date: 17-05-2016
DOI: 10.5194/BG-2016-177
Abstract: Abstract. Oil palm is the most rapidly expanding tropical perennial crop. Its cultivation raises environmental concerns, notably related to the use of nitrogen (N) fertilisers and associated pollution and greenhouse gas emissions. While numerous and erse models exist to estimate N losses from agriculture, very few are available for tropical perennial crops. Moreover, there has been no critical analysis of the performances of existing models in the specific context of tropical perennial cropping systems. We assessed the capacity of 11 models and 29 sub-models to estimate N losses in a typical oil palm plantation over a 25-year-growth cycle, through leaching and runoff, and emissions of NH3, N2, N2O, and NOx. Estimates of total N losses were very variable, ranging from 21 to 139 kg N ha−1 yr−1. On average, 31 % of the losses occurred during the first three years of the cycle. Leaching comprised about 80 % of the losses. Based on a comprehensive Morris sensitivity analysis, the most influential variables were soil clay content, rooting depth and oil palm N uptake. We also compared model estimates with published field measurements. Many challenges remain to model more accurately processes related to the peculiarities of perennial tropical crop systems such as oil palm.
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