Abstract:
The study entitled “Crop water requirement and irrigation scheduling of selected crops
using CROPWAT: A case study of Pattambi region” was taken up to compute the crop water
requirement and irrigation schedule of major crops in Pattambi region. The study also focused on
analysing whether rain water could meet the evapotranspiration demand of crops. The CROPWAT
8.0 model developed by FAO was used for the determination of crop water requirement and
irrigation scheduling. Climatological data including temperature, sunshine hours, wind speed,
relative humidity and rainfall were collected from RARS Pattambi for the last 35 years (1983-
2017). The details of major crops of Pattambi region, viz, banana, pepper, pulses, rice (direct
sown), rice (transplant) and vegetables were also collected from RARS Pattambi. The required
soil, crop and climate data inputs were given to the model and the crop water demand and irrigation
schedule for each crop was obtained. The best criteria for scheduling irrigation was also
determined.
Water requirement for banana, pepper, rice, pepper, rice (transplant), rice (direct sown),
pulses and vegetables were found as 1546.2 mm, 327.7 mm, 550.4 mm, 543.3 mm, 351 mm and
564.3 mm respectively for the year 2017. The irrigation requirement for banana, pepper, rice
(transplant), rice (direct sown), pulses and vegetables were found as 807.2 mm, 0.0 mm, 309.7
mm, 300.1 mm, 311 mm and 473.2 mm respectively for the same year. The water requirement of
crops were found to be dependent on the ET o values while the IR was found to vary with rainfall.
The crops should be irrigated with that amount of water which is not provided by rainfall. For both
dry crops and wet crops, a lesser rainfall efficiency was found when irrigation was scheduled at
fixed interval per stage while a higher rainfall efficiency was found when irrigation was scheduled
at critical depletion for dry crops and up to a fixed water depth for rice.
The results of the study can be used as a guide for the farmers to plan their irrigation and
cropping pattern. Also the results can be extrapolated to the future to analyze the trends in future
crop water demands.
