• Authors:
    • Singh, B.
    • Smider, B.
  • Source: Agriculture Ecosystems and Enviroment
  • Volume: 191
  • Issue: SI
  • Year: 2014
  • Summary: Intensive greenhouse industry wastes large amounts of nutrient-rich green waste through improper disposal practices. Converting this greenhouse waste into biochar for soil application offers a viable option to recycle nutrients and long-term C storage. This study was carried out to evaluate the agronomic potential of a biochar produced from tomato green waste in two contrasting soils. We also estimated the amount of waste generated from intensive greenhouse tomato production in Australia. From weekly measurements of leaf picking over a 13-week period, we estimate approximately 133 Mg ha -1 year -1 of green waste on fresh weight basis. Biochar, produced by slowly pyrolysing the green waste at 550°C, had very high-pH (12.1), electrical conductivity (EC, 54.2 dS m -1), ash content (560 g kg -1) and CaCO 3 equivalence (330 g kg -1). Agronomic performance of the biochar was evaluated by growing Hybrid sweet corn ( Zea mays var. rugosa cv - Sentinel) in the greenhouse for 7 weeks. We used three levels of biochar (0, 5 and 15 g kg -1 soil) in a factorial combination with three fertiliser rates (0, 50 and 100% of the recommended rate) applied to two contrasting soils (an Orthic Tenosol and a Red Ferrosol). Biochar application to the Ferrosol significantly increased the shoot dry matter of corn and contrastingly decreased the yield in case of the Tenosol. The positive effect of the biochar in the Ferrosol was attributed to release of nutrients from the biochar and biochar's liming effect and associated increased availability of nutrients. However, in poorly buffered Tenosol the application of biochar produced phytotoxic effects due to excessive soluble salts and high pH. The uptake of most nutrient elements increased in the corn shoot in the Ferrosol and decreased in the Tenosol. Although the biochar produced from green waste was highly alkaline and contained excessive soluble salts, given the right soil properties it can be a good soil ameliorant. The true agronomic potential of the biochar should be further evaluated in different soil types under field conditions.
  • Authors:
    • Flower, K.
    • Riethmuller, G.
    • Manalil, S.
  • Source: Soil & Tillage Research
  • Volume: 143
  • Year: 2014
  • Summary: Field trials were conducted to study the emission of nitrous oxide during the summers of 2012 and 2013 from fields with harvested field pea, harvested wheat and winter fallow at Merredin and Cunderdin respectively, two wheat growing regions of Western Australia. The nitrous oxide emission fluxes from these treatments were regularly monitored during the postharvest summer period using a closed chamber technique, before and after wetting the soil. Very low nitrous oxide flux occurred in the dry soil conditions prior to wetting. However, significantly increased nitrous oxide flux was observed at both the sites after wetting, with emissions from a harvested field pea plots being 55-86 fold higher than prior to wetting at the two sites. After wetting, the field pea plots also had significantly higher emissions (3.47-3.87 g N2O-N ha(-1) h(-1)) than those following winter fallow (1.17-1.95 g N2O-N ha(-1) h(-1)), although no nitrogen fertiliser was applied to either during the crop growing period. The harvested wheat plots had emissions that were similar (1.18-3.15 g N2O-N ha(-1) h(-1)) or higher than the winter fallow treatment. The sudden increase in nitrous oxide was observed 3 h after wetting, with a significant reduction in nitrous oxide flux occurring approximately 20 h after wetting. This indicates the need for regular monitoring of nitrous oxide flux to capture the emission pulses that occur under favourable conditions. Nitrous oxide flux was positively correlated with soil nitrate-N, water filled pore space and soil temperature at both the sites. The study shows that the use of winter fallow does not result in high soil nitrous oxide emissions over the following summer, compared with harvested wheat or field peas. The studies are important because more frequent summer rains are predicted in the region, and as shown in this study, high summer temperature together with rainfall could lead to nitrous oxide emission peaks. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Bui, E. N.
    • Webster, R.
    • Rossel, R. A. V.
    • Baldock, J. A.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 9
  • Year: 2014
  • Summary: 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 areas of the Earth. Here, we derive spatially explicit estimates, and their uncertainty, of the distribution and stock of organic C in the soil of Australia. We assembled and harmonized data from several sources to produce the most comprehensive set of data on the current stock of organic C in soil of the continent. Using them, we have produced a fine spatial resolution baseline map of organic C at the continental scale. We describe how we made it by combining the bootstrap, a decision tree with piecewise regression on environmental variables and geostatistical modelling of residuals. Values of stock were predicted at the nodes of a 3-arc-sec (approximately 90 m) grid and mapped together with their uncertainties. We then calculated baselines of soil organic C storage over the whole of Australia, its states and territories, and regions that define bioclimatic zones, vegetation classes and land use. The average amount of organic C in Australian topsoil is estimated to be 29.7 t ha -1 with 95% confidence limits of 22.6 and 37.9 t ha -1. The total stock of organic C in the 0-30 cm layer of soil for the continent is 24.97 Gt with 95% confidence limits of 19.04 and 31.83 Gt. This represents approximately 3.5% of the total stock in the upper 30 cm of soil worldwide. Australia occupies 5.2% of the global land area, so the total organic C stock of Australian soil makes an important contribution to the global carbon cycle, and it provides a significant potential for sequestration. As the most reliable approximation of the stock of organic C in Australian soil in 2010, our estimates have important applications. They could support Australia's National Carbon Accounting System, help guide the formulation of policy around carbon offset schemes, improve Australia's carbon balances, serve to direct future sampling for inventory, guide the design of monitoring networks and provide a benchmark against which to assess the impact of changes in land cover, land management and climate on the stock of C in Australia. In this way, these estimates would help us to develop strategies to adapt and mitigate the effects of climate change.
  • Authors:
    • Smith, C.
    • Dargusch, P.
    • Visser, F.
    • Grace, P. R.
  • Source: Agroecology and Sustainable Food Systems
  • Volume: 38
  • Issue: 8
  • Year: 2014
  • Summary: An increasing concern over the sustainability credentials of food and fiber crops require that farmers and their supply chain partners have access to appropriate and industry-friendly tools to be able to measure and improve the outcomes. This article focuses on one of the sustainability indicators, namely, greenhouse gas (GHG) emissions, and nine internationally accredited carbon footprint calculators were identified and compared on an outcomes basis against the same cropping data from a case study cotton farm. The purpose of this article is to identify the most "appropriate" methodology to be applied by cotton suppliers in this regard. From the analysis of the results, we subsequently propose a new integrated model as the basis for an internationally accredited carbon footprint tool for cotton and show how the model can be applied to evaluate the emission outcomes of different farming practices. © Taylor & Francis Group, LLC.
  • Authors:
    • Andersson, K. O.
    • Rawson, A.
    • Murphy, B. W.
    • Simmons, A. T.
    • Badgery, W. B.
    • Lonergan, V. E.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 196
  • Year: 2014
  • Summary: Changes in land use and management have been proposed as a way to increase soil organic carbon (SOC) in crop and pasture systems. Some of the proposed activities to improve SOC are the introduction of pasture phases in cropping systems, stubble retention, no-till cropping, improved fertilisation, introduction of more productive pasture species and grazing management. There is also growing interest in novel farming systems, such as pasture cropping (intercropping cereal crops with established perennial pastures), which may improve SOC. However, there have been few broad scale surveys to determine whether these land management changes have an impact on commercial farms. In this study, comparisons of land use were established for mixed farming and pasture cropping systems in the slopes region (average annual rainfall: 500-650 mm) and for cropping and pasture in the plains region (average annual rainfall: 300-500 mm) of Central West NSW, Australia. The survey aimed to determine the difference in SOC stocks (MgCha -1) and the composition of three soil organic carbon fractions (particulate - POC, humus - HUM and resistant - ROC). The influences of management actions and pasture composition were also assessed across pasture and cropping land uses. Cropping systems had lower SOC stocks in the soil than pasture systems in each region, but pasture cropping was not different from perennial pasture. Generally, there were larger differences in the POC due to land use and management than the other SOC fractions. Management practices in cropping systems explained greater variability in SOC than in pastures. For cropping systems, higher amounts of P fertiliser were associated with higher SOC, POC and ROC while higher amounts of N fertiliser were associated with lower SOC, POC and ROC. For pastures, the proportion of bare ground was associated with lower SOC and POC. These associations indicate there is an opportunity to increase SOC by converting cropping land to permanent pasture, increasing the frequency of pasture phases, changing crop fertiliser regimes and reducing bare ground in pastures, but further work is needed to verify the causality behind these associations.
  • Authors:
    • Reardon-Smith, K.
    • Mushtaq, S.
    • Maraseni, T. N.
  • Source: JOURNAL OF WATER AND CLIMATE CHANGE
  • Volume: 5
  • Issue: 3
  • Year: 2014
  • Summary: While the prevailing rationale for new irrigation technology adoption is improved water use efficiency, this study evaluated trade-offs between water savings, greenhouse gas (GHG) emissions and economic gain associated with the conversion of a furrow irrigation system to a sprinkler irrigation (lateral-move) system on a cotton farm in eastern Australia. Trade-offs were evident when conversion to the pressurised sprinkler irrigation system was evaluated in terms of fuel and energy-related emission; the adoption of the new system saved water but increased GHG emissions. However, when we considered changes in farm machinery and input uses as a result of the conversion, we found an overall reduction in GHG emissions. Overall, the GHG modelling indicated that higher total quantities of GHGs were emitted from the furrow irrigation (4,453 kg CO 2e/ha) than from the sprinkler irrigation (3,347 kg CO 2e/ha) farming system. Water efficiency modelling indicated that, on average, water savings of 18% are possible, while economic modelling indicated that the conversion of irrigation technology is a viable option. Even at a carbon price of AUD$30/tCO 2e, investment in the sprinkler technology was an economically feasible option due to significant water savings and increased yield.
  • Authors:
    • Mcleod, M.
    • Schwenke, G.
    • Wilson, B. R.
    • Cowie, A.
    • Tighe, M.
    • Rabbi, S. M. F.
    • Badgery, W.
    • Baldock, J.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 197
  • Year: 2014
  • Summary: This project aimed to identify land uses and soil management practices that have significant associations with soil organic carbon (SOC) stocks (0-0.3 m) in New South Wales (NSW), Australia. The work presented in this paper is based on a one-off survey targeting key land uses and management practices of eastern NSW. Because of the nature of the work, the land uses and management combinations surveyed in different soils and climatic conditions were significantly unbalanced, and separately analyzing associations after breaking the dataset into different land uses may lead to significant increases in Type errors. Therefore, redundancy analysis (RDA) was undertaken to explore the association between explanatory variables (i.e., land uses, soil management, soil properties and environmental variables) and the variation in stocks (mass per unit area) of particulate organic carbon (POC), humic organic carbon (HOC) and resistant organic carbon (ROC) across 780 sites in eastern NSW, south eastern Australia. Results indicated that soil properties, land uses, soil management and environmental variables together could explain 52% of total variation in stocks of the SOC fractions. Specifically soil properties and environmental variables explained 42.8%, whereas land uses and management practices together explained 9.2% of the total variation in SOC fractions. A forward selection RDA was also undertaken considering soil properties and environmental variables as covariates to assess the statistical significance of land uses and management practices on stocks of POC, HOC and ROC. We found that pasture had significant positive associations on stocks of carbon fractions. Among the soil properties and environmental variables rainfall, longitude and elevation had a significant positive influence while pH and bulk density had a significantly negative influence on the HOC, POC and ROC stocks. Using a novel multivariate technique, the current work identified the land uses and soil management that had significant impact on carbon stocks in soil after accounting for influences soil properties and environmental variables.
  • Authors:
    • Mahanta, S. K.
    • Ghosh, P. K.
  • Source: Invited Article
  • Volume: 35
  • Issue: 2
  • Year: 2014
  • Summary: Globally soils contain around twice the amount of carbon in the atmosphere and thrice in vegetation. Therefore, soil is both 'a source and a sink' for greenhouse gases and balance between the functions is very delicate. The gases move continuously from one pool to another maintaining balance in different pools of the ecosystem. Appropriate management of soil offers to the potential to provide solutions for each of the challenges related to food security and climate change. The estimated carbon sequestration potential of world soils lies between 0.4 to 1.2 Gt per year which includes 0.01-0.30 Gt per year from grasslands. Carbon sequestration can be enhanced in grasslands through grazing management, sowing favorable forage species, fertilizer application and irrigation, restoration of degraded grasslands etc. However, there are certain limitations that hinder in adopting the practices for enhancing carbon sequestration in grasslands. The limitations include continuous degradation of grasslands, changing climate, paucity of information on carbon stock of grasslands from developing countries, disagreement on systems for documenting carbon stock changes over a period of time, hindrance in policy implementations etc.
  • Authors:
    • McMahon, T. A.
    • Peel, M. C.
  • Source: Research Article
  • Volume: 38
  • Issue: 2
  • Year: 2014
  • Summary: Estimating evaporation from standard meteorological data continues to be an active area of research and practical application. Here we report on recent progress in using standard meteorology data to estimate potential, reference and actual evaporation from terrestrial landscapes as well as evaporation from lakes and reservoirs. We also address recent enhancements to standard methodologies through use of remote sensing and data-driven procedures. From our report we observe that remote sensing offers significant potential for mapping spatial variations in evaporation. There has been limited progress in estimating actual evaporation via the complementary relationship, whereas applications of the Penman-Monteith and related equations incorporating actual surface resistance term(s) have dominated the recent literature.
  • Authors:
    • Peel, M.
    • Western, A.
    • Wei, Y.
    • Tesemma, Z.
  • Source: Journal
  • Volume: 15
  • Issue: 4
  • Year: 2014
  • Summary: Previous studies have reported relationships between mean annual climatic variables and mean annual leaf area index (LAI), but the seasonal and spatial variability of this relationship for different vegetation cover types in different climate zones have rarely been explored in Australia. The authors developed simple models using remotely sensed LAI data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and gridded climatic data from the Australian Water Availability Project. They were able to relate seasonal and annual LAI of three different land cover types (tree, pasture, and crop) with climatic variables for the period 2000-09 in the Goulburn-Broken catchment, Australia. Strong relationships were obtained between annual LAI of crop, pasture, and tree with annual precipitation (R-2 = 0.70, 0.65, and 0.82, respectively). Monthly LAI of each land cover type also showed a strong relationship (R-2 = 0.92, 0.95, and 0.95) with the difference between precipitation P and reference crop evapotranspiration (PET; P PET) for crop, pasture, and tree. Independent model calibration and validation showed good agreement with remotely sensed MODIS LAI. The results from the application of the developed model on the future impact of climate change suggest that under all climate scenarios crop, pasture, and tree showed consistent decreases in mean annual LAI. For the future climate change scenarios considered, crop showed a decline of 7%-38%, pasture showed a decline of 5 %-24%, and tree showed a decline of 2%-11% from the historical mean annual. These results can be used to assess the impacts of future climatic and land cover changes on water resources by coupling them with hydrological models.