Enhancing Productivity, Fruit Quality and Nutritional Status of ‘Washington’ Navel Orange Trees by Foliar Applications with GA and Amino Acids
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 (GA ) at (0, 25 or 50 ppm) as well as 3 individual foliar applications of a commercial compound Bioflow containing 27.3% amino acids at (0, 1 cm /L, TM 3 2 cm /L or 3 cm /L) on enhancing leaf nutritional status and increasing yield in terms of quantity and quality. 3 3 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 GA and amino acid treatments. The highest values for the different 3 parameters were recorded when the highest level of GA was combined with the highest rate of amino acids. 3 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 GA and amino acids. On the other hand, juice acidity % showed a steady decrease with 3 the increase of applications rates of the two tested substances. Total Chlorophyll content of fresh leaves was significantly increased in response to the different GA and amino acid treatments. Furthermore, the recorded 3 values increased steadily with increasing the application rates of the two applied substances. The highest Chlorophyll content was obtained when the highest GA was applied in combination with the highest amino 3 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 GA and/or amino acids resulted in steady significant 3 increases in the recorded values.