A field investigation was performed during the two successive growing seasons 2014/ 2015 and 2015/ 2016 at a private orchard, located at Brembal, Motobus district, Kafr EL- Sheikh Governorate, Egypt, on twenty years old Navel orange trees budded on Sour orange rootstock spaced at 6*6 metres apart to study the effect of irrigation scheduling at (0.0, 0.8, 1.0 and 1.2 of EP) under biostimulants foliar application on productivity, fruit quality, storability and some water relations for Navel orange trees.
The main results can be summarized as follows:
The highest values for WA (seasonal water applied), CU (seasonal crop water consumed) and Ecu (consumptive use efficiency) were recorded under irrigation treatment I0(control) combined with Azospirillum compared with Jisemar, while, the lowest values were recorded under irrigation treatment (I1). I1 and I2 treatments have recorded the highest values of PIW(productivity of irrigation water) and WP(water productivity).
Treatment I2 recorded the highest values of fruit set and the lowest rates of dropped, splitting and creasing fruits compared with the other treatments specially with Azospirillum while, the lowest irrigation level treatment (I1) showed the lowest rate of fruit set and the highest rate of fruit drop also, high irrigation levels (I0)gave the highest rates of splitting and creasing fruits compared with the lowest rates in I2. Results displayed a significant increasing of SSC% and SSC/acid ratio in fruits at the low irrigation level I1 when comparing with the low values in I0, as it was clear with Jisemar, whereas, acidity did not show any stable trend. Moderate irrigation level I2 recorded the high values of V.C and peel fruit firmness compared with the low values at I0 specially with-Azospirillum. Azospirillum application gave the high levels of chlorophyll with the high irrigation levels I0and I3compared with the lowest in I1,in contrast, I1 recorded the high rates of carotene than with I0, but Jisemar application was the most effective in that respect..
Treatment I2 combined with Azospirillum recorded the highest values of fruit number, yield(kg/tree) and ton/fed. during the two seasons, while I0 and I3 recorded the highest values for fruit weight than the others.
During storage, I2 treatment recorded the best results on reducing fruit weight loss, limiting of fruit decay and maintaining the high levels of fruit firmness till the end of storage period specially with (Azospirillum) with a high significant differences. I2 and I1treatments recorded the high levels of SSC% and VC juice contents at the end of storage during the two seasons.
Key words: Bio-stimulants, orange fruits, Azospirillum, irrigation, water relations and storability.