Amino Acids as Safe Biostimulants to Improve the Vegetative Growth, Yield, and Fruit Quality of Peach

The influence of exogenous application of the amino acids Glutamic acid (Glu), Methionine (Met), L-Tryptophan (L-Try), and Lysine (Lys) at concentrations of 250 and 500 ppm was studied relative to the growth of peach trees. The trees were sprayed three times; before flowering, during full bloom, and one month later by 250 ppm Glu + 250 ppm Met + 250 ppm L-Try + 250 ppm Lys (combination 1) and 500 ppm Glu + 500 ppm Met + 500 ppm L-Try + 500 ppm Lys (combination 2), in comparison to trees that were not sprayed (control). A randomized complete block design was used. The individual application of four amino acids positively improved the shoot diameter, leaf chlorophyll, leaf area, and productivity as opposed to not spraying the trees. Additionally, the applied amino acids increased the fruit weight, size, firmness, length, and diameter, and the fruit content from the percentages of total soluble solids (TSS), TSS-acid, and anthocyanin contents, in contrast to the control. They also improved the fruit content from total, reduced, and non-reduced sugars as well as vitamin C and the leaf nutritional content from NPK. The application of combination 2, over the two seasons, was more beneficial.