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Study on Bowen Ratio Components on Different Growth Stages of Rice

A K M Tajkir-Uz-Zaman
Department of Environmental Science Bangladesh Agricultural University Mymensingh - 2202, Bangladesh

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

M S Zannat
Soil Resource Development Institute, Farmgate, Dhaka-I2l5,

K Gosh
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh- 2202, Bangladesh

Abstract/ Executive Summary:

The experiment was conducted at the Environmental Science Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from August to December 2005 to study the Bowen ratio (β) components over rice field. The average value of major Bowen ratio component i.e .. latent heat flux density (IE) during study period was 11.72 MJm^-2 day^-1, which was 77% of the total Rn. Due to high evapo-transpiration from rice canopy IE was the dominant Bowen ratio as well as energy component, which approximately balanced the net radiation. In different growth stages of rice IE varied from 6.33 to 17.15 MJm^-2 day^-I and on an average the if was ranged from 63 to 92% of the whole Rn. Sensible heat flux (H) showed negligible values indicating absorption of the sensible heat by the wet soil from the upper air, which ultimately provided energy for LE. The average value of H obtained in this study was 1.07 MJm^-2 day^-1, which was only 10% of whole Rn. H represented the values which ranged from 0.05 to 2.93 MJm^-2 , day^-1 of total Rn. A minute portion of the energy balance components was soil heat flux (G). Thus the measured average value of Bowen ratio over rice field was 0.09.

Keywords: Bowen ratio,Latent heat, Sensible hea,Growth stage

Location: Field Laboratory of the Department of Environmental Science, Bangladesh Agricultural University, Mymensingh

Start Date: 00-08-2005

End Date: 00-12-2005

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To find out how micro meteorological processes lead to improve crop management system as well as food security in respect of production.

Methodology:

An experiment was conducted during the period from August to December 2005 at the Field Laboratory of the Department of Environmental Science, Bangladesh Agricultural University, Mymensingh, where the experimental plot was 50 m² in size. Transplant Aman (BR 11) was used in the experimental plot. Ground heat flow plate was positioned at an even and flat location under rice canopy following. Net radiation (Rn) over the rice canopy was measured with Net radiometer positioned at the center of the plot. Two Vaisala Sensors were placed at two different heights from the soil surface. First and second sensors were placed over rice field at a height of 60 and 230 cm, respectively from the soil surface for measuring the above canopy air temperature. Data from two heights were then averaged. Data from all the sensors were collected in the CRlOX Datalogger with the help of AM25T Multiplexer. To avoid solar radiation prevention from the sun the Data logger was placed in a small tin made house.

Source of Information: Bangladesh Journal Agric. and Environ. 3(2): 1-6, December 2007

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The study suggests that. if we can minimize Bowen ratio, we can achieve better yields along with better crop growth. Through controlling or manipulating the management practices like application of irrigation, drainage, mulching and so on, we can get the desired Bowen ratio and that should remain minimum as possible as we can. Thus the Bowen ratio components and their significant positive values can be used effectively for the estimation of canopy evaporation. Nowadays it is frequently used for the estimation of hourly averages of crop photosynthesis.

Knowledge Management: Journal