This investigation was carried out on 12-years old ‘Washington’ navel orange trees budded on sour
orange rootstock during two successive seasons (2016 and 2017). The trees grew in a loamy sand soil under
surface irrigation system at a private orchard, Qalubia Governorate, Egypt. The objective of the study was to
examine the effect of individual foliar applications of gibberellic acid (GA3) at (0, 25 or 50 ppm) as well as
individual foliar applications of a commercial compound BioflowTM containing 27.3% amino acids at (0, 1 cm3/L,
2 cm3 /L or 3 cm3/L) on enhancing leaf nutritional status and increasing yield in terms of quantity and quality.
Foliar applications of combinations between the two materials at the different concentrations were also
examined. Applications were applied for five times at one-month intervals starting at full-bloom time during both
seasons. The results of the current investigation revealed that, in both seasons, recorded yield parameters
(fruit set %, fruit retention %, number of fruits/tree, yield (kg) /tree and average fruit weight (gm)/ tree) were all
favorably influenced by the different GA3 and amino acid treatments. The highest values for the different
parameters were recorded when the highest level of GA3 was combined with the highest rate of amino acids.
Fruit size and juice % content also followed the same trend. Most of the recorded Juice quality parameters
(TSS%, TSS/Acid ratio, Vitamin C content and Total sugars%) showed desirable responses to increasing
application rates of GA3 and amino acids. On the other hand, juice acidity % showed a steady decrease with
the increase of applications rates of the two tested substances. Total Chlorophyll content of fresh leaves was
significantly increased in response to the different GA3 and amino acid treatments. Furthermore, the recorded
values increased steadily with increasing the application rates of the two applied substances. The highest
Chlorophyll content was obtained when the highest GA3 was applied in combination with the highest amino
acids rate. The results also revealed that for most of the determined leaf nutrient contents (viz., N, P, K, Ca, Mg,
Fe, Mn and Zn), in general raising the application rates of GA3 and/or amino acids resulted in steady significant
increases in the recorded values. |
