The Effect of Different Replacement Methods of Nutrient Solution on Growth, Physiological Characteristics and Concentration of Micronutrient of Three Varieties of Basil in NFT System

The concentration of elements in the nutrient solution used in soilless cultivation, especially in closed systems, is one of the most important factors for the successful vegetables production. With the aim of comparison of the effect of three nutrient solution replacement methods in NFT system in hydroponic greenhouse of Vali-E-Asr University of Rafsanjan, a factorial experiment based on completely randomized design with 4 replicates was conducted. Factors were nutrient solution replacement method (complete nutrient replacement, partial nutrient replacement according to EC, and partial nutrient replacement according to plant demand) and three basil cultivars (green, purple and; lettuce leaves). The results showed that the growth characteristics of lettuce under the influence of replacement method based on plant needs had the highest values, but in the methods of complete replacement of the nutrient solution and nourishment based on EC, due to the accumulation of nutrients, the growth characteristics, and absorption and transfer of nutrients by the roots decreased, and finally damage to photosynthetic pigments. Changing the nutrient solution after a certain period can cause irreparable damage to leafy plants such as basil, but by using new methods such as changing the nutrient solution based on the plant needs and even with accurate EC monitoring and optimizing the nutrient solution in the growth period can prevent damage to plants and provide the best conditions for increasing the biomass production of plants due to increasing the photosynthetic properties and increasing the absorption of elements. According to the results of this study, the replacement method of nutrient solution based on the plant needs is recommended for growing basil in closed systems; Because in this method, in addition to optimizing the nutrient solution for the desired plants, it is also possible to save water and nutrients and avoid damage caused by the use of nutrient solution with a high concentration of salts.