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Bio-monitoring Study on Tropospheric Ozone Using White Clover at Bangladesh Agricultural University Farming Area

M. T. Islam
Department of Environmental Science, Bangladesh Agricultural University Mymensingh-2202, Bangladesh

M. A. Ashraf
Department of Farm Structure, Bangladesh Agricultural University, Mymensingh–2202, Bangladesh

M. A. Sattar
Department of Environmental Science, Bangladesh Agricultural University Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

A pot experiment was conducted at the field laboratory of the Department of Environmental Science, Bangladesh Agricultural University, Mymensingh to asses the visual ozone injury in white clover crops (Trifolium repens cv. Regal) started from May 13, 2007. Two genotypes of white clover were used of which one was ozone susceptible (NC-S) and the other was ozone resistant (NC-R). Each genotype was replicated into 20. The data on total plant dry matter harvested thrice at 28 days interval resulted in increasing biomass gradually in later harvests. The Monthly mean ozone values collected from passive ozone sampler during April to August’07 was recorded as 29, 35, 49, 28, and 61 ppb respectively, which seemed that ozone concentrations in the troposphere is increasing gradually in Bangladesh. The susceptible NC-S showed visual ozone injury symptom from very slightly (0-1%) to slight (1-5%) where as the resistant cultivar showed no visual injury symptom. The ozone susceptible cultivar generally produced comparatively less biomass than the resistant one at every harvest. The temperature and relative humidity was measured using Tinytag. The Tinytag hangs in the lower part of a tube, with the upper part of the tube being black and the lower part being either white or protected by a reflective cover (e.g. aluminium foil). The air will warm in the upper black part of the tube and rise, which will enable new air coming in from below. Alternatively, use a Stevenson screen if available or a simple arrangement with a shield made of aluminium foil through which air can pass, but within which the Tinytag is protected against direct sunlight. Data on total sunshine hour was collected from the weather station of Bangladesh Agriculture University, Mymensingh. Injury scoring system: 0 : No injury, 1 : Very slight injury, occurrence of the first symptoms, 2 : Slight injury, 1-5 % of the leaves with slight injury, 3 : Moderate injury, 5-25 % of the leaves with injury, 4 : Heavy injury, 25-50 % of the leaves injured, 5 : Very heavy injury, 50-90 % of the leaves injured, 6 : Total injury, 90 –100 % of the leaves are injured. The plant biomass (forage : leaves, flowers and stolon) at the height of 7 cm above the soil surface were harvested at first on June 6, 2007. The 2nd, 3rd and 4th harvests were done on July 8, August 5, and September 2, 2007 respectively at 28 days interval. The fresh plant materials were oven dried at 70oC for 72 hours and then their dry weights were taken. After collecting the data, it was correlated with ozone concentrations to know the yield losses in white clover by tropospheric ozone.

Keywords: Bio-monitoring, Tropospheric ozone, Plant biomass, White clover, Visual injury

Location: Bangladesh Agricultural University, Mymensingh, Bangladesh

Start Date: 15-04-2007

End Date: 13-05-2007

Program Area: Risk Management in Agriculture

Commodity: Weather/Climate

Objectives:

1. To know the ozone concentrations in the troposphere at Bangladesh environment,
2. To show the effects of tropospheric ozone on plant biomass, and
3. To show the temporal trends of tropospheric ozone in Bangladesh.

Methodology:

Two white clover (Trifolium repens cv. Regel, genotypes NC-S and NC-R) cuttings were collected from ICP Vegetation Coordination Centre, UK. They were at first established in small pots (1 litre) grown in glass house condition in Bangladesh Institute of Nuclear Agriculture, Mymensingh on April 15, 2007 and then transferred to main field experiment in the Field Laboratory of Dept. of Environmental Science, Bangladesh Agricultural University, Mymensingh on May 13, 2007 in 15 litre plastic pots and they were grown in well. The recommended dose of fertilizers and intercultural operations were practiced as prescribed as in the standard protocol. Each cultivar was replicated in to twenty. Measurement of tropospheric ozone Ozone was measured by passive sampler at 28 days interval. Passive sampling is an inexpensive, reliable and simple ozone measurement technique. The passive ozone samplers were hanged in the field 3 m above from ground to measure the ozone concentration in the elevated level. During measurement the gas molecules diffuse into the sampler through the grey net.

Source of Information: Progress. Agric. 18(2) : 215-222, 2007 ISSN 1017-8139

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The visual injury symptom appeared in the ozone sensitive genotype (NC-S) as very slightly (up to 1% injured leaves) to slightly (15 % injured leaves) with 50%, 55%, 45% and 55% ozone injured plant from 1St, 2nd, 3rd 4th harvesting respectively. The resistant cultivar showed no visual injury symptom. The ozone concentrations in troposphere increased gradually with time. So, routine research is essential to protect Bangladesh against the bad impact of global warming. The study was conducted on only white clover, which is very recognized ozone sensitive but not our native plant. Hence more study on local plant will be needed to conduct.

Knowledge Management: Journal