Effect of Convection on the Exchange Coefficient of Oxygen and Estimation of Net Production Rate of Oxygen in Ponded Water of a Paddy Field

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概要

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• Dissolved oxygen (DO) in ponded water is essential to biological activities in paddy fields. DO concentrations results from the balance among photosynthesis, respiration, and exchange of oxygen between the atmosphere and water, all of which show daily changes. For the estimation of the net production rate of oxygen that is the overall response of photosynthesis and respiration, it is necessary to determine the exchange rate of oxygen between the atmosphere and water. The exchange of oxygen occurs in the form of reaeration and deaeration in the paddy fields. The exchange coefficients of reaeration and deaeration were determined in the laboratory considering field conditions. The coefficients of reaeration and deaeration were not identical. Both coefficients increased as the convective velocity in the water increased. It was considered that the convection in bulk water reduced the thickness of the water film at the air-water interface and increased the exchange coefficient. The reaeration and deaeration coefficients ranged from 2.1 to 2.4 and 5.7 to 6.3 d^-1, respectively. The rates of reaeration and deaeration were estimated using these exchange coefficients. The exchange rate was not constant in the paddy field throughout the day but varied with the convection, water temperature, and the degree of saturation in the ponded water. Taking these factors into consideration, the net production rate was estimated from the DO mass balance. The net production rate was positive from 5:30 to 15:30 and negative in the other part of the day. These results and analytical methods would contribute to the understanding of the physical, chemical, and biological processes in a paddy field.

• 社団法人日本土壌肥料学会の論文

著者

• Kasubuchi Tatsuaki

  Faculty of Agriculture, Yamagata University

• Kasubuchi Tatsuaki

  Faculty Of Agriculture Yamagata University

• Mowjood M

  Univ. Peradeniya Peradeniya Lka

• Mowjood M.I.

  The United Graduate School of Agricultural Sciences, Iwate University

• Mowjood M.I.Mohammed

  The United Graduate School of Agricultural Sciences, Iwate University:(Present adress)Department of Agricultural Enginnering, Faculty of Agriculture, University of Peradeniya

関連論文

• Absorption and Emission of CO_2 by Ponded Water of a Paddy Field (Soil Physics)
• Effect of vegetation on the convection of ponded water in a paddy field(Soil Physics)
• Effect of Convection on the Exchange Coefficient of Oxygen and Estimation of Net Production Rate of Oxygen in Ponded Water of a Paddy Field
• Effects of herbicide application on carbon dioxide, dissolved oxygen, pH, and RpH in paddy-field ponded water(Soil Physics)
• Convective velocity of ponded water in the vegetated paddy lysimeter

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