Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Water Use of Wheat: a Comparative Study by 'cropwat' Model

M. H. Ali
Agricultural Engineering Division, Bangladesh Institute of Nuclear Agricultural

Abstract/ Executive Summary:

This paper compares the ' CROPWAT' prediction result with the water use by wheat (grown in lysimeter) . Eleven years weather data (monthly average) and geo-graphical location were used as model input to obtain ETo value. The predicted ETo value along with soil, crop data and scheduling criteria were used to obtain crop water requirement and predicted yield reduction. The result shows that the model predicted ETo value (34.7 cm) agreed well with the crop water use (36.15 cm) under water supply at 75% depletion of available water. The model under-estimate the crop-water requirement (28.23 cm) a little bit compared to field water use (36.15 cm). The predicted yield reduction under various schedule (stress condition) does not agree well with the field yield data. It is revealed from the study that under the prevailing climatic condition, irrigation planning with the 'CROPWAT' model using the historical weather data may be reasonably done. But the yield prediction with CROPWAT under variable water supply may not be useful.

Keywords: CROPWAT, Wheat, Water use, Irrigation

Location: Mymensingh

Start Date: 12-11-1996

End Date: 23-03-1997

Program Area: Socio-economic and Policy

Commodity: Wheat

Objectives:

To compare the simulated ET₀ and crop water requirement by 'CROPWAT' with the water use by wheat

Methodology:

CROPW AT' is a computer program for irrigation planning and management. It includes a revised method for estimating reference crop evapo-transpiration (ET_o), adopting the approach of Penman-Monteith as recommended by the FAO Expert Consultation held in May 1990 in Rome. Details on the methodology can be found in the Irrigation and Drainage Paper No 56: "Crop Evapotranspiration". The model fits the monthly ET₀ values in a polynomial graph, and estimates daily ET₀ values from this graph. Also, the monthly rainfall is distributed using polynomial curve fitting..Eleven years weather data (1985 to 1996, except 1987 which was unavailable) collected from the nearby meteorological station was used as input for ' CROPWAT' model for calculating ET₀ value. Monthly average of the data were used. The characteristics of the weather variables (monthly average of 11 years) during the crop period . The calculated ET₀ value along with soil, crop data and scheduling criteria were used as input for simulating crop water requirement and yield reduction. The information required in weather, soil and crop data file

Source of Information: Bangladesh J. Agril. Sci. 28(1): 125-130, Januarv, 2001

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The ET₀ value obtained by the model 'CROPWAT' during the crop period is 34.7 cm. The amount of water applied in wheat (irrigating at 75% depletion of available soil moisture) during crop period was 40.95 cm, amongst which 4.8 cm water was left in the profile (compared to initial soil moisture). So the net irrigation water used was 36.15 cm, which was close to the value of ET₀ The crop water requirement obtained from 'CROPWAT' was 28.23 cm, which is lower than the field water use (36.15 cm) under available water supply (supplied at 75% depletion of ASMT. he simulation result of a model depends on many factors such as the principle of the model and the accuracy of the input data. The meteorological data collected and recorded by the Department of Meteorology, at the weather yard of Bangladesh Agricultural University campus, was used in this study. The variation of crop-time weather and historical average may influence on under estimation of crop water requirement. But the difference between field demand and predicted value is small (7.9 cm). One aspect in lysimeter study is that in lysimeter, there is no scope for capillary rise or upward flux (or moisture migration), but it may contribute in field situation a little bit. After all, the predicted result of ET₀ and crop water requirement can be used as a guide in irrigation planning, such as selecting command area of an existing supply or pump, or selecting a proper pump size for a command area. From the study it can be inferred that with the prevailing climatic condition and weather data input, the model predicted ET₀value and crop water requirement agreed reasonably with the crop water use at available moisture supply. So, irrigation planning with the 'CROPWAT' model based on the historical weather data may be reasonably done in this area. But the prediction of yield reduction under variable water supply may not be useful.

Knowledge Management: Journal