Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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Author: search.filters.author.Jeyakumar PSubject: search.filters.subject.04 Earth Sciences

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    Responses of rice (Oryza sativa L.) plant growth, grain yield and quality, and soil properties to the microplastic occurrence in paddy soil
    (Springer, 18/05/2022) Chen S; Feng Y; Han L; Li D; Feng Y; Jeyakumar P; Sun H; Shi W; Wang H
    Purpose: Agricultural soil has been recognized as a major sink of microplastic, an emerging pollutant to environmental biodiversity and ecosystem. However, the impacts of microplastic on soil–plant systems (e.g., crop growth, grain yield and amino acid content, nitrogen uptake capacity, and soil properties) remain largely unknown. Methods: Four typical microplastics, i.e., polythene (PE, 200 μm), polyacrylonitrile (PAN, 200 μm), and polyethylene terephthalate (PET) in diameter of 200 μm and 10 μm (PET200 and PET10), were tested to assess the consequent aforementioned responses under rice (Oryza sativa L.) paddy soil in a mesocosm experiment. Results: Microplastics multiply influenced the soil pH, NH4+-N and NO3−-N contents, which effects were depended on the rice growth stage and plastic type. Overall, microplastics significantly decreased the soil urease activity by 5.0–12.2% (P < 0.05). When exposed to PAN and PET (in both diameter of 200 μm and 10 μm), there were significantly 22.2–30.8% more grain yield produced, compared to the control (P < 0.05), which was attributing to the higher nitrogen uptake capacity of rice grain. Meanwhile, microplastics exhibited nominal influences on rice plant height, tillering number, leaf SPAD, and NDVI. The amino acids were affected by microplastic, depending on the types of plastics and amino acids. Conclusion: This study provides evidence that microplastic can affect the development and final grain yield, amino acid content, nitrogen uptake capacity of rice, and some major soil properties, while these effects vary as a function of plastic type. Our findings highlight the positive impacts that could occur when the presence of microplastics in paddy soil.
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    Copper induces nitrification by ammonia-oxidizing bacteria and archaea in pastoral soils
    (Wiley, 12/12/2022) Matse D; Jeyakumar P; Bishop P; Anderson C
    Copper (Cu) is the main co-factor in the functioning of the ammonia monooxygenase (AMO) enzyme, which is responsible for the first step of ammonia oxidation. We report a greenhouse-based pot experiment that examines the response of ammonia-oxidizing bacteria and archaea (AOB and AOA) to different bioavailable Cu concentrations in three pastoral soils (Recent, Pallic, and Pumice soils) planted with ryegrass (Lolium perenne L.). Five treatments were used: control (no urine and Cu), urine only at 300 mg N kg-1 soil (Cu0), urine + 1 mg Cu kg-1 soil (Cu1), urine + 10 mg Cu kg-1 soil (Cu10), and urine + 100 mg Cu kg-1 soil (Cu100). Pots were destructively sampled at Day 0, 1, 7, 15, and 25 after urine application. The AOB/AOA amoA gene abundance was analyzed by real-time quantitative polymerase chain reaction at Days 1 and 15. The AOB amoA gene abundance increased 10.0- and 22.6-fold in the Recent soil and 2.1- and 2.5-fold in the Pallic soil for the Cu10 compared with Cu0 on Days 1 and 15, respectively. In contrast, the Cu100 was associated with a reduction in AOB amoA gene abundance in the Recent and Pallic soils but not in the Pumice soil. This may be due to the influence of soil cation exchange capacity differences on the bioavailable Cu. Bioavailable Cu in the Recent and Pallic soils influenced nitrification and AOB amoA gene abundance, as evidenced by the strong positive correlation between bioavailable Cu, nitrification, and AOB amoA. However, bioavailable Cu did not influence the nitrification and AOA amoA gene abundance increase.