Vol. 12, Issue 2 (2023)

Author(s):
S Vinitha and A Mani

Abstract:
In the study, the estimation of crop evapotranspiration was based on the Penman-Monteith model along with variable canopy resistance. The canopy resistance was calculated by using a modified climatological resistance weighed by a normalized soil water factor (F). Canopy resistance is considered as a variable parameter for each day. In the case, the daytime variation of canopy resistance was performed well with the standard FAO 56 Penman-Monteith method. During the crop season, The average surface canopy resistance ranged between 0 s m^-1 and 776 s m^-1 and the normalized soil water factor (F) ranged between 0.08 and 0.99. The largest values of rc were observed as 776 s m^-1 on 44 DAS, which signified the lowest values of VMC 64.35 mm (14.3%) in the experiment. The surface canopy resistance was more when it had the lowest moisture content. The above stated approaches were compared on the basis of RMSE and coefficient of determination (R2) values. Farias canopy resistance model was specified as best fitted with an RMSE and R2 values of 0.99 and 0.97. The results show that if the micrometeorological data such as temperature, relative humidity, vapour pressure deficit, wind speed, net radiation and soil moisture are available then the Farias canopy resistance model is the best one for computing ETC in semi-arid region. The yield obtained at all the harvest were the maximum and minimum yield of 24 kg and 3 kg respectively. The total yield gained was 9.8 t ha^-1. Water use efficiency obtained were under standard FAO-56 PM method and Farias canopy resistance model as 27.80 kg ha^-1 mm^-1 and 39.23 kg ha^-1 mm^-1 respectively. During the crop cycle, the Farias canopy resistance model was reasonably performed well. It indicated with the limiting amount of water used by the crop which could be improved the economic yield of the crop.