Effect Chitosan and Chitosan Nanoparticles on Marigold (Calendula officinalis L.) Plant Under Newly Reclaimed Soils Conditions

A field experiment was conducted during the 2019/2020 and 2020/2021 growing seasons at Qalabsho, Gamasa region, Dakahlia Governorate, Egypt, to evaluate the impact of foliar applications of chitosan (100, 200, 300 mg L⁻¹) and chitosan nanoparticles (20, 40, 60 mg L⁻¹) on Calendula officinalis L. cultivated under nutrient-deficient conditions in newly reclaimed soils. The results demonstrated that both chitosan and its nanoparticles significantly enhanced plant growth, floral yield, essential oil content, photosynthetic pigments, total flavonoids, and mineral uptake compared with untreated plants. Notably, chitosan nanoparticles at 40 mg L⁻¹ followed by chitosan at 300 mg L⁻¹. recorded the highest improvements across most traits compared to the lowest concentrations of chitosan or its nanoparticles under study. These treatments improved plant height, branch number, flower yield, essential oil percentage, chlorophyll, carotenoids, flavonoids, and macro- and micronutrient contents, thereby alleviating the negative effects of soil nutrient deficiency. Overall, the study highlights that foliar application of chitosan nanoparticles, particularly at 40 mg L⁻¹, is a promising eco-friendly strategy to improve growth, productivity, and biochemical attributes of Calendula officinalis L. under challenging soil conditions.