Sap flow sensors are installed in some trees within the plantation for monitoring purposes. A portable meteorological station measures net Radiation (Rn), air Temperature (Ta) and Relative Humidity (RH) of air. Atmospheric vapour pressure Deficit (D) is calculated from temperature and relative humidity. Our modeling approach is different as it uses diurnal courses of variables instead of commonly used daily means (see dattached paper for details of the model). The farmers can monitor the field conditions from anywhere, especially the stomata closure due to drought stress which limits photosynthesis and therefore tree productivity. The innovation is precise farming and is highly efficient when compared with the conventional approach.