Impact of spraying asparagine and yeast extract on growth, yield and fruit quality of Medjool date palms

Abstract

The present investigation was designed to study the impact of foliar sprays with asparagine (an amino acid) and yeast extract on the yield and fruit quality traits of Medjool date palms. Seven treatments were tested, including asparagine (at 2.5 and 5 mL L⁻¹) and yeast extract (at 5 and 10 g L⁻¹), individually or in combined applications, compared with the control. The results demonstrated that both amino acid and yeast extract significantly improved fruit set, bunch weight, yield per palm, and fruit number per strand compared to the untreated palms. Amino acids act as powerful bio-stimulants, enhancing nutrient uptake, photosynthesis, and assimilate translocation, which leads to increased fruit size, flesh weight, and reduced seed weight. Yeast extract contributes natural growth regulators, vitamins, and enzymes that stimulate cell division and sugar accumulation, thereby improving fruit sweetness and consumer acceptability. The combined treatments produced the highest values across all measured parameters due to the synergistic effect of the amino acid and yeast extract on maximizing fruit set, yield, flesh-to-seed ratio, and sugar content. The superior performance observed with the combination of 5 mL L⁻¹ amino acid with 10 g L⁻¹ of yeast extract underscores the importance of integrated bio-stimulant use. Overall, foliar application of amino acid and yeast extract, particularly in combination, represents a sustainable strategy to improve productivity and marketability of Medjool date palm.