It is planned to provide irrigation in a crop field having field capacity and permanent wilting point of the soil as 0.21 cm³ cm^-3 and 0.09 cm³ cm^-3, respectively. The crop root zone depth is 0.90 m. The growing period of this crop is 1st January to 31st March, during which the observed reference evapotranspiration ET_r, effective rainfall P_e and crop coefficients K_c are listed below. Considering management allowable deficit MAD for this crop as 50%, the average irrigation interval during the growing period in days is _______.