ORCID Profile
0000-0002-3101-5462
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Publisher: American Chemical Society (ACS)
Date: 31-03-2016
Abstract: Calcium phosphate (CaP) minerals may comprise the main phosphorus (P) reserve in alkaline soils, with solubility dependent on pH and the concentration of Ca and/or P in solution. Combining several techniques in a novel way, we studied these phenomena by progressively depleting P from suspensions of two soils (low P) using an anion-exchange membrane (AEM) and from a third soil (high P) with AEM together with a cation-exchange membrane. Depletions commenced on untreated soil, then continued as pH was manipulated and maintained at three constant pH levels: the initial pH (pHi) and pH 6.5 and 5.5. Bulk P K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the main forms of inorganic P in each soil were apatite, a second more soluble CaP mineral, and smectite-sorbed P. With moderate depletion of P at pHi or pH 6.5, CaP minerals became more prominent in the spectra compared to sorbed species. The more soluble CaP minerals were depleted at pH 6.5, and all CaP minerals were exhausted at pH 5.5, showing that the CaP species present in these alkaline soils are soluble with decreases of pH in the range achievable by rhizosphere acidification.
Publisher: MDPI AG
Date: 10-04-2019
DOI: 10.3390/RS11070872
Abstract: Knowledge of the aboveground biomass (AGB) of large pasture fields is invaluable as it assists graziers to set stocking rate. In this preliminary evaluation, we investigated the response of Sentinel-1 (S1) Synthetic Aperture Radar (SAR) data to biophysical variables (leaf area index, height and AGB) for native pasture grasses on a hilly, pastoral farm. The S1 polarimetric parameters such as backscattering coefficients, scattering entropy, scattering anisotropy, and mean scattering angle were regressed against the widely used morphological parameters of leaf area index (LAI) and height, as well as AGB of pasture grasses. We found S1 data to be more responsive to the pasture parameters when using a 1 m digital elevation model (DEM) to orthorectify the SAR image than when we employed the often-used Shuttle Radar Topography 30 m and 90 m Missions. With the 1m DEM analysis, a significant quadratic relationship was observed between AGB and VH cross-polarisation (R2 = 0.71), and significant exponential relationships between polarimetric entropy and LAI and AGB (R2 = 0.53 and 0.45, respectively). Similarly, the mean scattering angle showed a significant exponential relationship with LAI and AGB (R2 = 0.58 and R2 = 0.83, respectively). The study also found a significant quadratic relationship between the mean scattering angle and pasture height (R2 = 0.72). Despite a relatively small dataset and single season, the mean scattering angle in conjunction with a generalised additive model (GAM) explained 73% of variance in the AGB estimates. The GAM model estimated AGB with a root mean square error of 392 kg/ha over a range in pasture AGB of 443 kg/ha to 2642 kg/ha with pasture LAI ranging from 0.27 to 1.87 and height 3.25 cm to 13.75 cm. These performance metrics, while indicative at best owing to the limited datasets used, are nonetheless encouraging in terms of the application of S1 data to evaluating pasture parameters under conditions which may preclude use of traditional optical remote sensing systems.
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 02-2016
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/SR12358
Abstract: The potential to change agricultural land use to increase soil carbon stocks has been proposed as a mechanism to offset greenhouse gas emissions. To estimate the potential carbon storage in the soil from regional surveys it is important to understand the influence of environmental variables (climate, soil type, and landscape) before land management can be assessed. A survey was done of 354 sites to determine soil organic carbon stock (SOC stock Mg C/ha) across the Lachlan and Macquarie catchments of New South Wales, Australia. The influences of climate, soil physical and chemical properties, landscape position, and 10 years of land management information were assessed. The environmental variables described most of the regional variation compared with management. The strongest influence on SOC stock at 0–10 cm was from climatic variables, particularly 30-year average annual rainfall. At a soil depth of 20–30 cm, the proportion of silica (SiO2) determined by mid-infrared spectra (SiMIR) had a negative relationship with SOC stock, and sand and clay measured by particle size analysis also showed strong relationships at sites where measured. Of the difference in SOC stock explained by land use, cropping had lower soil carbon than pasture in rotation or permanent pasture at 0–10 cm. This relationship was consistent across a rainfall gradient, but once soil carbon was standardised per mm of average annual rainfall, there was a greater difference between cropping and permanent pasture with increasing SiMIR in soils. Land use is also regulated by climate, topography, and soil type, and the effect on SOC stock is better assessed in smaller land-management units to remove some variability due to climate and soil.
Publisher: American Chemical Society (ACS)
Date: 16-08-2019
Abstract: Acid-soluble soil phosphorus (P) is a potential resource in P-limited agricultural systems that may become critical as global P sources decrease in the future. The fate of P in three alkaline Vertisols, a major agricultural soil type, after acidic incubation was investigated using synchrotron-based K-edge X-ray absorption near-edge structure (XANES) spectroscopy, geochemical modeling, wet chemistry soil extraction, and a P sorption index. Increases in labile P generally coincided with decreased stability and dissolution of calcium phosphate (CaP) minerals. However, only a minor proportion of the CaP dissolved in each soil was labile. In two moderate-P soils (800 mg P kg
Publisher: Wiley
Date: 03-2019
DOI: 10.1111/SUM.12486
Abstract: Effective extension of soil research builds landholder capacity to manage soils productively and sustainably. Government‐funded extension programmes also aim to improve the state of the environment through efficient use of resources and mitigating or preventing further land degradation. To these ends, a soil extension programme aimed at farmers in south‐eastern Australia was conducted during 2005–2008. The programme was designed to equip landholders with the knowledge, skills and confidence to diagnose and address soil constraints, as well as compile spatial information on soil properties. The programme involved four workshops that covered agricultural productivity, soil management and potential off‐site impacts. Workshops were held on‐farm and involved discussion, theory supported with practical exercises, and field visits. More than 1,400 participants were provided with subsidized soil tests to encourage soil monitoring and underpin the workshop theory on land capability and soil constraints (e.g., soil acidity, sodicity, salinity, nutrient decline and toxicities). Prior to the course, most participants did not regularly soil test so training on monitoring protocols was provided. The soil data indicated considerable phosphorus deficiencies, low organic carbon levels, and acidity across both cropping and pasture systems. Participant knowledge and land management intentions were tracked throughout the workshop series using surveys. The surveys identified a positive shift in the knowledge, understanding and confidence of most participants. However, a follow‐up survey 10 years later indicated that these changes may not have been broadly sustained. Based on our study, we recommend continued engagement of landholders along a learning pathway to maximize investment in soil extension.
No related grants have been discovered for Karl Andersson.