Blaney-Criddle method for determining consumptive use of water by crop

The Blaney-Criddle method is a widely used empirical method to estimate the consumptive use of water by crops. This method is particularly useful in areas where meteorological data such as temperature, humidity, and wind speed are available. The method is based on the assumption that the crop requires a certain amount of water to maintain its growth and development, which can be estimated from the meteorological data.

Steps involved in the Blaney-Criddle method:

1. Obtain meteorological data: The Blaney-Criddle method requires meteorological data such as daily temperature, relative humidity, and wind speed. These data can be obtained from a local weather station or from online sources.

2. Determine the monthly mean temperature: The monthly mean temperature is calculated by adding the daily maximum and minimum temperatures for each month and dividing by two.

3. Calculate the temperature index: The temperature index is calculated by subtracting the base temperature (usually taken as 10°C) from the monthly mean temperature.

4. Calculate the monthly heat index: The monthly heat index is calculated by multiplying the temperature index by the number of days in the month.

5. Calculate the monthly water requirement factor: The monthly water requirement factor is calculated by dividing the monthly heat index by the product of the mean temperature and the number of days in the month.

6. Calculate the crop coefficient: The crop coefficient is a factor that takes into account the specific requirements of the crop being grown. It is usually obtained from published tables or by consulting experts.

7. Calculate the monthly consumptive use: The monthly consumptive use is calculated by multiplying the monthly water requirement factor by the crop coefficient.

8. Calculate the total consumptive use: The total consumptive use is the sum of the monthly consumptive use values.

Thus, the Blaney-Criddle method is a useful tool for estimating the consumptive use of water by crops, which is an important parameter for efficient irrigation management.