Effects of Foliar Amino Acid and Vitamin Applications on Heat Stress, Production, and Quality of Lettuce Head Improvements

Abstract

This study was conducted to investigate the effect of amino acid and vitamin foliar applications on improving iceberg lettuce (Lactuca sativa L.) production and quality during the summer. First, two hybrids (Patagonia and Bruma) were grown hydroponically in June 2018 and 2019. Then, for five consecutive weeks, plants were sprayed once a week with Stress Free (a commercial product comprising 0.5% vitamins [vitamin B complex/ascorbic acid] and 0.5% selenomethionine) at concentrations of 1.0, 2.0, and 3.0 g/L and Aminomad (20% free amino acids) at concentrations of 2.0, 3.0, and 4.0 cm3 /L. Investigations revealed that all plant growth aspects were positively improved with all foliar spray treatments than with the control. Furthermore, while mineral contents (nitrogen, phosphorus, potassium, calcium, and magnesium) showed positive responses to the applied treatments, the highest dose of amino acids showed the highest marketable and total yield effects among all foliar spray treatments with the Patagonia hybrid. However, the marketable and total yield of lettuce heads was lowest with the control treatment without spraying.