A simple empirical model for estimating actual evapotranspiration in mustard crop.

An accurate account of evapotraspiration is essential for water budgeting in irrigation project. It is also essential for irrigation management and crop production. Many methods are there to estimate evapotranspiration, but majority of them estimate potential evaporation from free water surface or from a reference surface with non limiting water condition.An empirical cum process based model as a function of potential evapotranspiration, relative water content and leaf area index was developed. Increasing soil moisture suction with decreasing moisture content and resistance to flow of soil moisture were used as restricting factor for evapotranspiration. Proposed model was calibrated and validated using an experimental datasets of two mustard (Brasica spp) cultivars (‘Pusa Jaikisan’ and ‘BIO-169-96’) grown at IARI research farm with two date of sowing (15th Oct and 30th Oct) for two consecutive years 2004–05 and 2005–06. In absence of runoff and deep percolation, weekly accumulated soil moisture loss from soil was used as observed value. The validation result of the pooled data of two varieties exhibited good prediction (R2 = 0.8686) of observed accumulated AET using the predictive equation proposed. The trend conformity is well represented with the calculated model efficiency of 0.861. Contrary to the calibration stage, the model validation shows that the model tends to slightly over-estimate its observed counterparts with CRM values pegged at −0.029.