Effect of arginine, glutamine, humic acid, and fulvic acid spraying on olive cultivars in saline conditions

Olea europaea L. is a tree that is adapted to different soil conditions and can grow and produce fruits in relatively saline soils so that it has been mentioned as a plant species that is semi-resistant to salinity. Today, attention is increasingly drawn to the use of organic fertilizers to enhance yields with no environmentally destructive impacts. This study investigated the biochemical characteristics of three olive cultivars subjected to the foliar application of organic acids in a two-factor factorial experiment based on a randomized complete block design. The three cultivars included Zard, Arbequina, and Manzanilla, and the organic acids were applied at nine levels including control, arginine, glutamine, humic acid, fulvic acid, arginine + humic acid, arginine + fulvic acid, glutamine + humic acid, and glutamine + fulvic acid. The results showed that the highest fruit yield was obtained from Arbequina and Zard, the highest Brix value, membrane stability index, and Mg content from Zard, and the highest Ca content from Zard and Manzanilla. The plants treated with humic acid exhibited the highest electrolyte leakage and the lowest proline content. Based on the comparison of the means for the interaction of 'cultivar x organic acid', the highest yield was obtained from 'Zard x control', 'Arbequina x control', and 'Zard x glutamine + fulvic acid', the highest proline content from 'Arbequina x arginine', and the lowest electrolyte leakage and proline content from 'Zard x control'. Also, 'Zard x arginine + humic acid' exhibited the highest Ca content, 'Zard x control' exhibited the highest K content, and 'Arbequina x control' exhibited the highest N content.