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Duong T.T.T.,University of Adelaide | Duong T.T.T.,Rubber Research Institute of Vietnam | Verma S.L.,University of Adelaide | Penfold C.,University of Adelaide | Marschner P.,University of Adelaide
Geoderma | Year: 2013

Improved understanding of the effect of compost application on soil properties is critical for optimizing the desired effects of compost application. However there are no studies on the effect of composts on soil properties within the first centimetres of the compost layer. In this microcosm study three composts from different feedstocks, namely C1 (from animal manures) and C2 and C3 (from the organic fraction and municipal solid waste) were applied as a layer which was separated from the soil by a mesh. Microcosms without compost served as controls. Microbial and chemical properties of the soil were determined at 0-5 and 5-10. mm distance from the mesh after 30 and 63. days. During the 63 day incubation, the total C, N and P and available N concentrations in the composts decreased whereas the available P concentration increased. The composts induced higher microbial biomass and activity, total organic C and available N and P concentrations up to 10. mm into the surrounding soil with greater effects after 30 than after 63. days. The increase in nutrient concentrations was generally greater in soil adjacent to the two finer-textured composts with the higher nutrient concentration (C1 and C3) than in the coarser-textured compost (C2) which had lower nutrient concentrations, however the differences in nutrient concentrations in the soil were small compared to those among the composts. The 0-5 and 5-10. mm layers did not differ in most of the measured properties except for greater soil respiration and N and P availability in the 0-5. mm layer. It is concluded that composts release nutrients into the surrounding soil over a period of 2. months which increase nutrient availability and microbial activity, with the zone of influence extending at least 10. mm from the compost-soil interface. © 2012 Elsevier B.V. Source

Duong T.T.T.,University of Adelaide | Duong T.T.T.,Rubber Research Institute of Vietnam | Penfold C.,University of Adelaide | Marschner P.,University of Adelaide
Plant and Soil | Year: 2012

Background: Composts with different feedstocks may have differential effects on soil properties and plant growth which, may be further modulated by soil texture. Materials and methods: In a 77-day pot experiment in the glasshouse, we investigated the effect of a single application as mulch of six types of composts derived from different starting feedstocks in two soils (13% and 46% clay, referred to as S13 and S46) on soil physical, chemical and biological properties, plant growth and nutrient uptake. Composts were placed as 2.5 cm thick mulch layer on the soil surface and wheat plants were grown and harvested at 42 days and at 77 days (grain filling). Results: Composts differed in total and available N and P and particle size with C1, C3, C4 and C5 being fine-textured, whereas C2 and C6 were coarse-textured. Compost addition as mulch increased soil total organic C and EC, but had no effect on pH. In all treatments, cumulative soil respiration was higher in S13 than in S46 and was increased by compost addition with the greatest increase with C2 and C6. Compared to the unamended soil, most compost mulches (except C2) increased macroaggregate stability. Compost mulches significantly increased available P and N in both soils, except for C2. Compost mulches increased available N up to 6-fold in both soils with the strongest increase by C5. Most composts also increased wheat growth and shoot P and N concentrations with the greatest effect on plant N concentration by C5 and on plant P concentration by C4. However, C2 decreased shoot N and P concentrations compared to the unamended soil. Most compost mulches (except C2) increased mycorrhizal colonization by up to 50% compared to the unamended soil. Conclusions: Fine-textured compost mulches generally had a greater effect on soil properties and plant growth than coarse-textured composts. Despite distinct differences between the soils with respect to clay content, TOC and available P, the effect of the compost mulches on soil and plant properties was quite similar. © 2011 Springer Science+Business Media B.V. Source

Duong T.T.T.,University of Adelaide | Duong T.T.T.,Rubber Research Institute of Vietnam | Penfold C.,University of Adelaide | Marschner P.,University of Adelaide
Biology and Fertility of Soils | Year: 2012

Although the beneficial effects of compost on soil properties are well known, there are few systematic studies comparing the effects of composts on soils of different textures. The aim of this pot study was to assess the effects of a single application as mulch of two types of composts derived from different feedstocks, namely C1 (from garden waste) and C2 (from agricultural residues and manures) on three soils with different clay contents (46%, 22% and 13%, hereafter referred to as S46, S22 and S13) in terms of their physical, chemical and biological properties as well as on plant growth and nutrient uptake. The composts were placed as 2.5-cm-thick mulch layer on the soil surface, and wheat plants were grown for 35 days and to grain filling (70 days). The composts reduced the soil pH by 0.3-0.7 units, slightly increased total organic C, but increased soil electrical conductivity compared to unamended soil. Soil respiration was significantly higher in S13 than S46 in all treatments after 5 weeks. At grain filling, soil respiration was higher in S13 than in the other two soils and higher with C2 than with C1 and in the non-amended soil. The addition of compost significantly increased soil cation exchange capacity (CEC) in S22 and S46, but not in S13 which also had the lowest CEC among the soils. C2 increased the available P concentration and macro-aggregate stability in all soils compared to C1 and the unamended soil. Compost addition increased available N in S46 and S22 compared to the unamended soil with a stronger effect by C1. Both composts increased wheat growth and shoot P concentrations with the effect of C2 being greater than that of C1. It is concluded that the effect of composts varies with soil type as well as compost type and that this interaction needs to be taken into account when composts are applied to improve specific soil properties. © 2012 Springer-Verlag. Source

Nguyen B.T.,Cornell University | Nguyen B.T.,Rubber Research Institute of Vietnam | Lehmann J.,Cornell University | Hockaday W.C.,University of New South Wales | And 2 more authors.
Environmental Science and Technology | Year: 2010

Global warming accelerates decomposition of soil organic carbon (SOC) pools with varying rates and temperature sensitivities. Black carbon (BC) materials are among the slowest decomposing components of the SOC pool. Although BC is a large component of SOC in many systems, the influence of temperature on decomposition of BC bearing different chemical and physical structures remains poorly understood. Four BC materials, produced by carbonizing corn residue and oak wood at 350 and 600 °C (corn-350-BC, corn-600-BC, oak-350-BC, and oak-600-BC), were mixed with pure sand and incubated at 4, 10, 20, 30, 45, and 60 °C for 1 year. Corn-BC was more porous than oak-BC as determined by scanning electron microscopy (SEM). Increasing the charring temperature from 350 to 600 °C led to greater aromaticity with 5-15% more C in aromatic rings and a 39-57% increase in both nonprotonated aromatic C and aromatic bridgehead C quantified by nuclear magnetic resonance (NMR) spectroscopy and a greater degree of order and development of C layers as observed by transmission electron microscopy (TEM). With a temperature increase from 4 to 60 °C, C loss of corn-350-BC increased from 10 to 20%, corn-600-BC, from 4 to 20%, oak-350-BC, from 2.3 to 15%, and oak-600-BC from 1.5 to 14% of initial C content, respectively. Temperature sensitivity (Q10) decreased with increasing incubation temperature and was highest in oak-600-BC, followed by oak-350-BC, corn-600-BC, and corn-350-BC, indicating that decomposition of more stable BC was more sensitive to increased temperature than less stable materials. Carbon loss and potential cation exchange capacity (CECp) significantly (p < 0.05) correlated with O/C ratios and change in O/C ratios, suggesting that oxidative processes were the most important mechanism controlling BC decomposition in this study. © 2010 American Chemical Society. Source

Duy N.Q.,Universiti Sains Malaysia | Duy N.Q.,Rubber Research Institute of Vietnam | Rashid A.A.,Universiti Sains Malaysia | Ismail H.,Universiti Sains Malaysia
Polymer - Plastics Technology and Engineering | Year: 2012

Cassava starch-filled natural rubber (NR) composites were prepared by using direct blending and co-coagulation method. The effects of two different method and cassava starch loading on morphology, mechanical properties and thermal properties of cassava starch/NR composites were studied. X-ray diffraction results and scanning electron microscopy images proved that co-coagulation method promotes better dispersion of cassava starch than direct blending method. The composites prepared by co-coagulation method exhibited higher values of tensile strength, tear strength, hardness, and thermal stability. The optimum value of tensile strength and tear strength of cassava starch/NR composites were achieved at a 10 phr cassava starch loading. © 2012 Copyright Taylor and Francis Group, LLC. Source

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