Effect of Organic Fertilization on the Physiological Status of Tomatoes under Abiotic Stress

During the vegetation period of the years 2020 and 2021 in the experimental field at Agricultural University - Plovdiv it was conducted a physiological study of tomato cultivar (Rugby) with determined growth under the treatment with chemical and organic fertilizers. The aims of the study were to determine the changes in physiological behaviour and productivity of field tomatoes depending on the fertilization and dates of planting. The physiological assessment included the measuring of some parameters of chlorophyll fluorescence and chlorophyll content index. Chlorophyll fluorescence has proved to have the potential to detect abiotic stress effects on photosynthetic efficiency. This technique was used to assess growth intensity in tomato plants (Solanum lycopersicum), grown in different types of fertilizer treatment and planted in three additional dates – 30.04, 07.05 and 14.05 in conditions of ambient heat stress. Results have shown the slight effect of the applied organic fertilizer upon fluorescence parameters but significantly improved chlorophyll content index compared to no treatment variant. Additionally, it was measured higher chlorophyll content index for the second and third planting dates. The highest average yield was calculated for the NPK variant, as the statistically significant differences of the yield between control and fertilization variants were calculated in 2021. It possessed the highest average yield for second planting compared to the third date of planting.