Browsing by Author "Gunaratnam A"

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    A low-cost simple lysimeter soil retriever design for retrieving soil from small lysimeters
    (IOP Publishing, 2024-06-06) Gunaratnam A; McCurdy M; Grafton M; Jeyakumar P; Davies CE; Bishop P
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    Formulation and characterization of polyester-lignite composite coated slow-release fertilizers
    (Springer Nature Switzerland AG, 26/09/2022) Gunaratnam A; Bishop P; Jeyakumar P; Grafton M; Davies CE; McCurdy M
    Two polyester-lignite composite coated urea slow-release fertilizers (SRFs; Poly3 and Poly5) were developed and their physicochemical properties were studied. Both these SRFs significantly (p < 0.05) extended the urea release compared to uncoated urea; Poly3 and Poly5 by 117 and 172 h, respectively. The urea release characteristics of Poly5 were further enhanced by linseed oil application (Poly5-linseed). The SEM images demonstrated the coatings were in contact with the urea and encase urea particles completely with the average coating thickness of 167.2 ± 15 µm. The new interactions between polyester and lignite in the composite coating were confirmed by the FTIR analysis. Polyester-calcium carbonate (Polyester-CaCO3) coated SRFs (Calc3 and Calc5) were developed using CaCO3 as a filler in place of lignite and the urea dissolution rate was compared with Poly3 and Poly5. The urea release times for the polyester-CaCO3 formulations, 48 and 72 h, were significantly (P < 0.05) lower than the polyester-lignite formulation, showing that lignite imparted greater control over release time than CaCO3. Findings from this work showed that polyester-lignite composites can be used as a coating material for SRFs.
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    STUDY THE INFLUENCE OF SOIL MOISTURE AND PACKING INCREMENTAL LEVEL ON SOIL PHYSICAL AND HYDRAULIC PROPERTIES
    (14/07/2020) Gunaratnam A; Grafton M; Jeyakumar P; Bishop P; Davies C; McCurdy M; Christensen, C; Horne, D; Singh, R
    Reconstructed soil packing is an alternative for monolithic soil columns in lysimeter studies. The excavated soil is packed in uniform layers to represent the natural soil conditions. Reconstructed soil packing alters the physical properties, including bulk density and porosity, thus can distort the hydraulic properties of the soil, so consistency of the method used is critical. Therefore, the selection of a suitable packing method is imperative. This preliminary study comes under the broad research programme: “developing and testing new fertilizer formulations in lysimeters”. This work was aimed to study the effect of incremental packing methods on the hydraulic properties of soil to select the best combination for testing fertilizers. The selected soil matrix for this lysimeter study was composed of 10 cm topsoil and 30 cm washed builders’ sand. For this study, four different soil packs were trialled in lysimeters with the combination of two soil moisture conditions (dry/damp and wet) and two packing depth increments (5 and 10 cm). The flow rate and saturated hydraulic conductivity were measured. Subsequently, several pore volumes of water (around 5 – 6) was allowed to pass through the soil column and the soil subsidence level was measured for each packing method. Both soil moisture condition and packing increment level have influenced the flow rate and saturated hydraulic conductivity of the soil matrix. The saturated hydraulic conductivity of the dry-5 cm, dry-10 cm, wet-5 cm and wet-10 cm packing were 3.99, 6.70, 3.56 and 6.53 cm hr- 1 , respectively. Soil subsidence was also influenced by both the soil moisture condition and increment level. The highest soil subsidence was exhibited by dry-10 cm packing (13 mm) and lowest by wet-5 cm (2 mm) (p<0.05). This preliminary study showed that both moisture condition and increment level influence the soil hydraulic property and compaction level. Further study needs to be conducted to understand the influence of soil moisture and incremental level on other physical and hydraulic properties of soil packing.
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    The Nitrogen Dynamics of Newly Developed Lignite-Based Controlled-Release Fertilisers in the Soil-Plant Cycle
    (MDPI AG, 29/11/2022) Gunaratnam A; Grafton M; Jeyakumar P; Bishop P; Davies C; McCurdy M
    The effect of newly developed controlled-release fertilisers (CRFs); Epox5 and Ver-1 and two levels of Fe2+ applications (478 and 239 kg-FeSO4 ha−1) on controlling nitrogen (N) losses, were tested on ryegrass, in a climate-controlled lysimeter system. The Epox5 and Ver-1 effectively decreased the total N losses by 37 and 47%, respectively, compared to urea. Nitrous oxide (N2O) emissions by Ver-1 were comparable to urea. However, Epox5 showed significantly higher (p < 0.05) N2O emissions (0.5 kg-N ha−1), compared to other treatments, possibly due to the lock-off nitrogen in Epox5. The application of Fe2+ did not show a significant effect in controlling the N leaching loss and N2O emission. Therefore, a dissimilatory nitrate reduction and chemodenitrification pathways were not pronounced in this study. The total dry matter yield, N accumulation, N use efficiency and soil residual N were not significantly different among any N treatments. Nevertheless, the N accumulation of CRFs was lower in the first month, possibly due to the slow release of urea. The total root biomass was significantly (p < 0.05) lower for Epox5 (35%), compared to urea. The hierarchical clustering of all treatments revealed that Ver-1 outperformed other treatments, followed by Epox5. Further studies are merited to identify the potential of Fe2+ as a controlling agent for N losses.