Reducing the harmful effect of salinity on lettuce productivity by foliar application of plant extracts under greenhouse conditions

Two greenhouse experiments were conducted during 2019/2020 and 2020/2021 at the Fayoum University of Egypt’s Agricultural Test Station, Faculty of Agriculture, to study effect of leaf Nitrogen, Phosphorus, Potassium, Calcium and Sodium contents, inorganic and organic osmotica substances contents, productivity and quality of lettuce plants (Lactuca sativa L) to elucidate their potential to reduce the harmful effect of soil salinity (ECe = 7.00 ± 0.20 dS m-¹). Treatments comprised with twelve of plant growth promoters; palm pollen grains (100 and 200 mg L-¹), corn grain extract (100 and 200 mg L-¹), soybean seed extract (100 and 200 mg L-¹), mannitol (1500 and 3000mgL-¹), sorbitol (1500 and 3000 mg L-1) and calcium phosphate (800 and 1000 Ca3(PO4)2 mg L-¹), as well as, tap water. Three times of the thirteen treatments were made as foliar applications to runoff; 25, 40 and 55 days after transplanting. A randomized complete blocks design with five replications comprised the experimental setup. All the foliar application of the twelve treatments (plant extracts, mannitol, sorbitol and calcium phosphate) were better and considerably greater mean values were obtained of leaf N, P, K, and Ca contents, inorganic and organic osmotica substances contents as well as decreased of leaf Na comparing to control. As a result, the physio-biochemical components of plants were improved, which reflected on improve productivity and quality of lettuce plants (cv. Big Bell) under the salinized soil stress of the Fayoum Governorate and other related regions. Generally, foliar application of soybean seed extract at a 200 mg L-1 concentration or palm pollen grains extract at at a 100 mg L-1 concentration were superior and substantially higher mean values were recorded of data recorded comparing to other treatments.