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Determination of Crop Coefficient for Rice-2005

Dr M A Rashid
PSO
Irrigation and Water Management Division, BRRI, Gazipur-1701, Bangladesh

Abstract/ Executive Summary:

The study was conducted to determine the crop coefficient of different rice varieties in different seasons and their application in irrigation planning at BRRI farm, Gazipur during Aus, T. Aman and Boro seasons of 2004-05. The mean daily evapotranspiration (ET) rates was measured in rice field by closed bottom lysimeters. Meteorological daily data were collected from BMD. Crop evapotranspiration was calculated from climatic data. The Penman-Monteith method was used for the estimation of the standard reference crop to determine its evapotranspiration rate. In Aus season, the mean daily evapotranspiration (ET) rates were 4.25 mm/day, 4.21 mm/day and 5.33 mm/day during the month of May, June and July respectively giving a mean value of 4.60 mm/day for the season. In T. Aman season, the mean daily ET rates were 3.93 mm/day, 4.48 mm/day and 4.42 mm/day during the month of August, September and October respectively giving a mean value of 4.28 mm/day for the season. Similarly in Boro season, the mean daily ET rates were 3.55, 5.14 and 6.52 mm/day during the month of February, March and April, respectively averaging 5.07 mm/day for the whole growing season. In Aus season, the Kc values ranged from 1.10 to 1.14. The highest value was obtained from BRRI dhan39 and the lowest from BR 3. In T. Aman season, these values ranged from 1.03 to 1.07. Similarly in Boro season it varies from 1.13 to 1.16.The results of three seasonal field experiments showed that there were slight variations in Kc values from season to season but the difference among the varieties were negligible.

Keywords: Crop co-efficient, ET, Evaporation

Location: BRRI farm, Gazipur

Start Date: 01-07-2004

End Date: 30-06-2005

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

To determine the crop coefficient of different rice varieties in different seasons and their application in irrigation planning

Methodology:

The study was conducted at BRRI farm, Gazipur during Aus, T. Aman and Boro seasons of 2004-05. The mean daily evapotranspiration (ET) rates was measured in rice field by closed bottom lysimeters. Meteorological daily data of the following variables were collected from BMD: i) minimum temperature, ii) maximum temperature, iii) minimum relative humidity, iv) maximum relative humidity, v) sunshine hours vi) wind speed and vii) wind direction. Crop evapotranspiration was calculated from climatic data and by integrating directly the crop resistance, albedo and air resistance factors in the Penman-Monteith approach. The Penman-Monteith method was used for the estimation of the standard reference crop to determine its evapotranspiration rate, i.e., ETo Experimentally determined ratios of ETc/ETo, called crop coefficients (Kc), are used to relate ETc to ETo or ETc= Kc*ETo.

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Source of Information: Proceedings of the BRRI Annual Internal Review for 2005, BRRI, Gazipur-1701, Bangladesh

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In Aus season, the mean daily evapotranspiration (ET) rate was 4.60 mm/day for the season. In T. Aman season, the mean daily ET rate was 4.28 mm/day for the season. In Boro season, the mean daily ET rate was averaging 5.07 mm/day for the whole growing season. The ET rates showed a gradual increase as the crop growing season progressed. The ET rate in T. Aman season was slightly higher than that in Aus season and it was highest in Boro season. In Aus season, the Kc values ranged from 1.10 to 1.14. The highest value was obtained from BRRI dhan39 and the lowest from BR 3. In T. Aman season, these values ranged from 1.03 to 1.07. Similarly in Boro season it varies from 1.13 to 1.16.The results of three seasonal field experiments showed that there were slight variations in Kc values from season to season but the difference among the varieties were negligible.

Knowledge Management: Report/Proceedings