Jeffrey A. Baldock

The Commonwealth Scientific and Industrial Research Organisation | CSIRO · Agriculture

The analysis of stable carbon isotopes is commonly used in Quaternary science to reconstruct the environmental conditions and vegetation contributions to sedimentary sequences. However, the measured d 13 C signature of the total organic matter (OM) pool can also reflect other complexities within depositional environments. The peats of the Thirlmere...

The stock of organic carbon contained within a soil represents the balance between inputs and losses. Inputs are defined by the ability of vegetation to capture and retain carbon dioxide, effects that management practices have on the proportion of captured carbon that is added to soil and the application organic amendments. The proportion of organi...

Conversion of soils supporting native vegetation to agricultural production has led to a loss of soil carbon stocks. Replacing a portion of the lost stocks will sequester atmospheric carbon with the concurrent benefit of enhancing soil sustainability. The ability of the fine fraction of soils (≤50-µm fraction) to adsorb organic carbon (OC) is consi...

There is ample evidence to suggest that liming can regulate soil organic carbon (SOC) pools either directly through influencing the solubility of SOC or indirectly by altering total organic C input as crop residue and SOC loss via change in microbial activity. The aim of this study was to determine the long-term impact of lime application on the qu...

Soil organic carbon (SOC) cycling schemes used in land surface models (LSMs) typically account only for the effects of net primary production and heterotrophic respiration. To demonstrate the significance of omitting soil redistribution in SOC accounting, sequestration and emissions, we modified the SOC cycling scheme RothC (ref.) to include soil e...

In this paper, we present a framework for a space–time observation system for soil organic carbon (STOS-SOC). We propose that the RothC model be embedded within the STOS-SOC, which is driven by satellite-derived inputs and readily available geospatial inputs, such as digital soil maps. In particular, advances in remote sensing have enabled the deve...

Irrigated agriculture may contribute as much as two-thirds to future global food demand because of the high intensity of production that it offers. However, it also has relatively high fertilizer and water inputs and therefore, N 2 O emissions. This study examined how varying the volume of individual irrigation events could mitigate N 2 O emissions...

The oxidative ratio (OR) of the biosphere is the stoichiometric ratio (O2/CO2) of gas exchange by photosynthesis and respiration—a key parameter in budgeting calculations of the land and ocean carbon sinks. Carbon cycle-climate feedbacks could alter the OR of the biosphere by affecting the quantity and quality of organic matter in plant biomass and...

Soil carbon models are important tool to understand soil carbon balance and project carbon stocks in terrestrial ecosystems, particularly under global change. The initialization and/or parameterization of soil carbon models can vary among studies even when the same model and dataset are used, causing potential uncertainties in projections. Although...

The aims of this study was to characterise soil Corg quality and to examine its possible relationship with their site productivity classes, as a preliminary effort to explaining the possible mechanisms in soils studied that may support the site productivity in humid tropics. Previously, the productivity of G. arborea plantations were shown to be de...

Soil carbon (C) models are important tools for understanding soil C balance and projecting C stocks in terrestrial ecosystems, particularly under global change. The initialization and/or parameterization of soil C models can vary among studies even when the same model and data set are used, causing potential uncertainties in projections. Although a...

Nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for characterising the complex chemistry of soil organic carbon (SOC), but is prohibitively expensive, time-consuming and technically-demanding. Diffuse reflectance mid-infrared (MIR) spectroscopy is an attractive alternative because it is a high-throughput, cost-effective and ea...

Sorption of organic carbon (OC) to phyllosilicate clays and hydrous iron oxides retards its mineralization, thus contributing to stabilization of organic carbon in soils. The degree of protection varies with the nature of the minerals present. In a previous study, we reported that when the amount of OC exceeds the sorption capacity of minerals, the...

Ecosystem-, biome-, and global-level oxidative ratio (OR) estimates are used to understand ecosystem gas exchange processes, and assess the sizes of the terrestrial biosphere and ocean carbon sinks, and the mechanisms controlling them. We have developed analytical methods to measure the OR of terrestrial carbon stocks from biomass chemistry that gi...

Adsorption of dissolved organic compounds onto mineral surfaces is increasingly recognized as a significant, if not dominant, carbon stabilisation mechanism in many soils. By utilising carbon-13 enriched dissolved organic carbon (DOC) source materials in a repeated leaching-sorption-incubation study, we show here that the biochemical composition of...

An accurate measurement of soil pH buffer capacity (pHBC) is essential for estimating lime requirement and predicting soil acidification in farming systems. The soil pHBC is commonly determined by acid-base titration (1:5 soil : solution); however, no standardized equilibration time, type of acid and alkali or concentration of electrolyte has been...

Diffuse reflectance spectroscopy combined with chemometric analysis techniques has enabled the rapid and cost effective prediction of soil organic carbon. In this research, an attempt was made to predict soil organic carbon in archived legacy soil data. For this work the mid-infrared region of the spectra was utilized and statistical models were de...

The benefits of sequestering carbon are many, including improved crop productivity, reductions in greenhouse gases, and financial gains through the sale of carbon credits. Achieving better understanding of the sequestration process has motivated many deterministic models of soil carbon dynamics, but none of these models address uncertainty in a com...

This study aims to map the measurable fractions of soil organic carbon related to the RothC carbon model at the catchment scale and to assess the model and prediction quality. It also discusses how the outputs can be used to provide initial pool estimates for process modelling of soil carbon in a spatial context. The study was carried out in Cox's...

The importance of soil organic carbon (SOC) in maintaining soil health is well understood. However, there is growing interest in studying SOC with an emphasis on quantifying its changes in space and time. This is because of the potential for soil to be used to sequester atmospheric C. There are many issues which make this difficult, for example sho...

In this paper we present a framework for an observation system for soil organic carbon (OS-SOC). The aim of the OS-SOC is to predict soil organic carbon in space and time. Thus, we propose that the RothC model be embedded within the OS-SOC driven by satellite-derived inputs, such as evapotranspiration and biomass additions to soil which characteriz...

We can effectively monitor soil condition|and develop sound policies to offset the emissions of greenhouse gases|only with accurate data from which to define baselines. Currently, estimates of soil organic C for countries or continents are either unavailable or largely uncertain because they are derived from sparse data, with large gaps over many a...

Purpose This study aimed to investigate the effect of initial soil pH and organic anion-to-acid ratio on changes in soil pH. Materials and methods Two soils (Podosol and Tenosol) along with two carboxylic acids (malic and citric acid) and their anions (sodium malate and citrate), commonly found in plant residues, were used in this study. Stock sol...

The diversity of cropping systems and its variation could lead to great uncertainty in the estimation of soil organic carbon (SOC) stock across time and space. Using the pre-validated Agricultural Production Systems Simulator, we simulated the long-term (1022 years) SOC dynamics in the top 0.3 m of soil at 613 reference sites under 59 representativ...

Baseline map of Australian soil organic carbon stocks and their uncertainty. This is a fine spatial resolution (90 x 90 m pixels) baseline map of organic Carbon stocks at the continental scale. The uncertainty is described by the 95% confidence intervals and the standardised confidence intervals (range(95% CIs)/mean). The data on the soil's organic...

Soil organic carbon (OC) exists as a diverse mixture of organic materials with different susceptibilities to biological decomposition. Computer simulation models constructed to predict the dynamics of soil OC have dealt with this diversity using a series of conceptual pools differentiated from one another by the magnitude of their respective decomp...

Quantifying the content and composition of soil carbon in the laboratory is time-consuming, requires specialised equipment and is therefore expensive. Rapid, simple and low-cost accurate methods of analysis are required to support current interests in carbon accounting. This study was completed to develop national and state-based models capable of...

Perennial grass pastures are being increasingly adopted, but little is known about the flows of carbon (C) from photosynthesis into soil organic matter (SOM) that could be used for calculations in carbon accounting. Repeat-pulse labelling of perennial grass pastures (kikuyu and Rhodes grass) with 14C in the field in Western Australia was used to tr...

Identifying drivers of variation in soil organic carbon (OC) at a regional scale is often hampered by a lack of historical management information. Focusing on red-brown-earth soils (Chromosol) under dryland agriculture in the Mid-North and Eyre Peninsula of South Australia, our aims were 2-fold: (i) to provide a baseline of soil OC stocks (0.3 m) a...

Here we take advantage of the stable carbon isotope shift that occurs when a C4 plant is sown into a soil previously dominated by C3 vegetation, to explore the movement and fate of newly sequestered soil organic carbon (SOC) following establishment of subtropical perennial pastures in temperate regions of Australia. In kikuyu-based pastures up to 3...

Background and Aims Crop residues are important for the redistribution of alkalinity within soils. A net increase in pH following residue addition to soil is typically reported. However, effects are inconsistent in the field due to confounding soil processes and agronomic practises. Methods A column experiment investigated the effects of canola, ch...

Soil organic matter (SOM) is a complex mixture containing a variety of organic molecular structures. As a consequence, interpretation of the infrared (IR) spectra of SOM is difficult and ambiguous and there is a necessity to establish more reliable IR spectral band assignments. We investigated a novel approach to identify IR spectral bands based on...

Hydrology is central to the formation, growth and utilisation of peat soils. However, peat presents a difficult medium in which to measure hydrologic properties, due to its soft structure and high water content. The von Post scale is a widely used measure of the extent of decomposition of peat, which can be applied in the field or the laboratory wi...

Soil contains approximately 2344 Gt (1 gigaton = 1 billion tonnes) of organic carbon globally and is the largest terrestrial pool of organic carbon. Small changes in the soil organic carbon stock could result in significant impacts on the atmospheric carbon concentration. The fluxes of soil organic carbon vary in response to a host of potential env...

The use of subtropical perennial grasses in temperate grazing systems is increasingly being promoted for production and environmental benefits. This study employed a combination of elemental and stable isotope analyses to explore whether pastures sown to either kikuyu (Pennisetum clandestinum) or a combination of panic (Panicum maximum) and Rhodes...

The use of subtropical perennial grasses in temperate grazing systems is increasingly being promoted for production and environmental benefits. This study employed a combination of elemental and stable isotope analyses to explore whether pastures sown to either kikuyu (Pennisetum clandestinum) or a combination of panic (Panicum maximum) and Rhodes...

The mechanisms of soil pH change by agricultural residues were investigated under field conditions. Residues of three important crop species, canola, chickpea and wheat, differing in alkalinity content and C to N ratio were incorporated into columns containing either Podosol (initial pH 4.5) or Tenosol (initial pH 6.2) soil. Net alkalinity producti...

The aim of this study is to test the prediction quality of RothC model when it is run spatially across a catchment using readily available spatial data. The study area is the Cox's Creek catchment in northern New South Wales. Soil carbon data was available for the 2000-2002 time period. Initial carbon pools were determined after running the RothC i...

Saline soils cover 3.1% (397 million hectare) of the total land area of the world. The stock of soil organic carbon (SOC) reflects the balance between carbon (C) inputs from plants, and losses through decomposition, leaching and erosion. Soil salinity decreases plant productivity and hence C inputs to the soil, but also microbial activity and there...

We examine some variations of standard probability designs that preferentially sample sites based on how easy they are to access. Preferential sampling designs deliver unbiased estimates of mean and sampling variance and will ease the burden of data collection but at what cost to our design efficiency? Preferential sampling has the potential to eit...

The carbon chemistry of 10 profiles of peat soil has been described in detail using 13C nuclear magnetic resonance (NMR) spectroscopy. The changes with depth in the allocation of signal to different carbon functional groups were consistent with an increase in the extent of decomposition (EOD) of the organic material with depth. This increase in EOD...

Export Date: 2 January 2013, Source: Scopus, Article in Press

Organic carbon and nitrogen found in soils are subject to a range of biological processes capable of generating or consuming greenhouse gases (CO2, N2O and CH4). In response to the strong impact that agricultural management can have on the amount of organic carbon and nitrogen stored in soil and their rates of biological cycling, soils have the pot...

The objective of this study was to map the temporal change of soil carbon at the catchment scale using legacy soil data as the baseline. The study area was the Cox's Creek catchment in northern NSW, Australia. The legacy data were collected in 2000-2002 (referred to as 2000) and re-sampling was carried out in 2010. A linear model of co-regionalizat...

Soil organic carbon (SOC) models are used to predict changes in SOC stocks and carbon dioxide (CO(2)) emissions from soils, and have been successfully validated for non-saline soils. However, SOC models have not been developed to simulate SOC turnover in saline soils. Due to the large extent of salt-affected areas in the world, it is important to c...

Australia is currently embarking upon an unparalleled program to mitigate greenhouse gas emissions by engaging farmers and landholders to reduce emissions and store carbon in the soil. Currently, the magnitude of a potential soil carbon sink in Australian agricultural soils is largely unknown. The oft repeated rubric that adoption of recommended ma...

The vulnerability of soil organic carbon (SOC) to biological decomposition and mineralisation to CO2 is defined at least partially by its chemical composition. Highly aromatic charcoal-like SOC components are more stable to biological decomposition than other forms of carbon including cellulose. Solid-state 13C NMR has gained wide acceptance as a m...

Aims An incubation study was conducted to investigate how changes in soil water content affect labile phosphorus and carbon pools, mineralisation patterns and microbial community composition. Methods Two soils from different climatic histories were subjected to four long-term (15 weeks) soil water regimes (constant field capacity (m); 3 dry-rewet (...

The retention of agricultural residues in cropping systems to maintain soil fertility is also important for the redistribution of alkalinity. In systems that adopt minimum or no-tillage practices residue incorporation into the soil may occur slowly and the contribution of soluble and insoluble residue fractions to pH change may vary temporally and...

There is limited understanding of the relationship between carbon (C) chemistry and microbial community structure during decomposition of shoot and root residues and how plant age affects this. In this study, residues of young wheat shoots and roots, mature wheat shoots and roots or a 1:1 mix of mature shoot + root (MSR) were added to sand inoculat...

Symbiotic dinitrogen (N2) fixation of crop and pasture legumes is a critical component of agricultural systems, but its measurement is expensive and labour intensive. Simple models which can provide approximations based on crop or pasture dry matter production would be useful for agrononomists and those interested in regional nitrogen (N) cycle flu...

Northern, high latitude soils have stored vast amounts of organic carbon (OC) in permafrost and peats for many millennia, however, climate change may mobilize and release this particulate OC (POC) to arctic rivers. Deltaic and floodplain lakes that receive fluvial sediments, primarily during the spring freshet, may provide records of such changes i...

In salt-affected soils, soil organic carbon (SOC) levels are usually low as a result of poor plant growth; additionally, decomposition of soil organic matter (SOM) may be negatively affected. Soil organic carbon models, such as the Rothamsted Carbon Model (RothC), that are used to estimate carbon dioxide (CO2) emission and SOC stocks at various spa...

Figure 3 depicted the correlation between shoot dry matter and N 2 fixed but the plotted Y axis data actually depicted total shoot N rather than amounts of shoot N fixed. The correct Figure is presented below, the figure caption remains the same.

Background/Question/Methods A third of the terrestrial biosphere is made up of agricultural ecosystems, making understanding their ecology crucial to our understanding of the global carbon cycle. One key, poorly constrained gas exchange parameter is the terrestrial biosphere’s oxidative ratio (OR). OR is a property of gas exchange fluxes between...

Background/Question/Methods Global soil carbon (C) stocks (2 × 1018 g C) are large enough that a minor change in soil C dynamics would constitute a major climate feedback. The responses of soil C stocks to experimental manipulations of atmospheric carbon dioxide concentration ([CO2]) and temperature vary widely in direction and magnitude across d...

Soil organic carbon (SOC) models such as the Rothamsted Carbon Model (RothC) have been used to estimate SOC dynamics in soils over different time scales but, until recently, their ability to accurately predict SOC stocks/carbon dioxide (CO(2)) emissions from salt-affected soils has not been assessed. Given the large extent of salt-affected soils (1...

As soil organic carbon is central to the functioning of all soils, we require a more fundamental understanding of the climatic and management factors which influence its storage and persistence. The interest in carbon storage and sequestration has focused attention on changes in soil organic carbon across different regions, climates and management...

Net carbon dioxide (CO2) emission from soils is controlled by the input rate of organic material and the rate of decomposition which in turn are affected by temperature, moisture and soil factors. While the relationships between CO2 emission and soil factors are well-studied in non-salt-affected soils, little is known about soil properties controll...

Concerns about energy security and climate change have increased biofuel demand, particularly ethanol produced from cellulosic feedstocks (e.g., food crop residues). A central challenge to cropping for cellulosic ethanol is the potential environmental damage from increased fertilizer use. Previous analyses have assumed that cropping for carbohydrat...

Drying–rewetting (DRW) cycles are important for soil organic matter turnover; however, few studies have considered the short-term effects on nutrient availability. The pulses in soil respiration, extractable C, P and N pools were quantified after a single DRW cycle (ten sampling times over 49h). Soil was pre-incubated with or without glucose (2.5gk...