Effect of phosphorus fertilizers in combination with planting management on morphological and physiological traits, seed yield, and mucilage yield of isabgol (Plantago ovata Forsk.) under drought stress

Because of the growing population and the pharmaceutical industry's urgent need for medicinal plants as raw materials for drug production, as well as the importance of their active ingredients in the food, cosmetics, and health industries, there has been increased interest and research on these plants in terms of cultivation, production, and consumption. Drought, as the most important non-living factor limiting plant growth and yield, causes or worsens other stresses, particularly nutrient deficiency stress in plants. Primary metabolite production decreases and increases with secondary metabolite production under drought stress conditions. The purpose of this study was to determine the effect of drought stress, phosphorus fertilizers, and planting methods on some morphological and physiological traits, seed and mucilage yield of the medicinal plant isabgol.

This experiment was carried out as a split-factorial in the form of a randomized complete block design with three replications at Zabol University's research farm in Chah Nimeh. The experimental treatments included three drought stresses, irrigation after 60, 120 and 180 mm evaporation from a class A evaporator as the main-factor, and the combination of seed planting method (flat or ridge planting) and types of phosphorus fertilizer (100% chemical phosphorous fertilizer, Phosphate Barvar2, and 50% chemical phosphorous fertilizer + Phosphate Barvar2) as the sub-factor. Plant height, number of leaves per plant, number of fertile tillers, seed and biological yield, mucilage yield, SPAD index, ionic leakage percentage, and relative leaf water content were the traits studied.

The results showed that the most plant height, number of leaves per plant, number of fertile tillers, seed and biological yield, mucilage yield, SPAD index and relative leaf water content were obtained in the greatest quantity from irrigation treatment after 60 mm of evaporation from the evaporation pan, with the exception of ionic leakage, which was obtained in the greatest quantity from irrigation treatment after 180 mm of evaporation from the evaporation pan. With the exception of ionic leakage, the combined bio-chemical fertilizers of phosphorus increased the studied traits. Also, except for ionic leakage, which had the highest values from the ridge planting method, the flat planting method increased the evaluated traits. The highest biological yield (6201 kg ha-1) is associated with irrigation treatment after 60 mm evaporation from evaporation pan with combined application of phosphorus fertilizers in flat planting method, and the highest ionic leakage (48%) is associated with irrigation treatment after 180 mm evaporation from evaporation pan with no fertilizer application in ridge planting method.

According to the findings, using irrigation treatment after 60 mm of evaporation from the evaporation pan and a combination of chemical and biological phosphorus fertilizers in a flat planting method can result in increased production of the medicinal plant isabgol.