Effect of Vermicompost and Foliar Spray with Potassium Nitrate on Vegetative Growth Characteristics and Yield of Lettuce Plants (Lactuca sativa L.) Var. Nader

Abstract

During the 2024/2025 agricultural season, the Vegetable Research Station of the Department of Horticulture and Landscape Engineering / College of Agriculture and Forestry - University of Mosul, Mosul City Center conducted the research. The hybrid lettuce variety (Nader F1) was used, and the experiment was carried out using three levels of vermicompost (0, 50, 100 tons ha⁻¹) and foliar spraying of potassium nitrate at four concentrations (0, 1000, 2000, 3000 mg L⁻¹ KNO3) at three times, starting after the formation of 3-4 true leaves, and the rest of the sprays with a time interval of 15 days between sprays. The research used a factorial experiment methodology and a three-replication Randomised Complete Block Design (RCBD). All attributes increased significantly with vermicompost soil treatment at both levels, with a slight difference between the two levels. The (50 t ha⁻¹) level had a noticeable influence on all traits. Foliar spraying with potassium nitrate resulted in substantial increases in most features, particularly at 3000 mg L⁻¹ concentration. However, only total chlorophyll content and plant dry weight did not achieve significance. The treatment of applying (50 t ha⁻¹) of vermicompost and spraying (3000 mg L⁻¹) of potassium nitrate is regarded the most effective for most features tested.