In hydroponic cultivation, leaf fertilizers containing a low percentage of active ingredients can be used as a source of nutrition. According to Dr Ir Anas Dinurrohman Susila MS, an expert from the Department of Agronomy and Horticulture at Bogor Agricultural University (IPB), the percentage of active ingredients should not exceed 20%. If the percentage is higher, the presence of Urea, KCl, and TSP fertilizers can cause the plants to burn.

Hydroponic systems require low doses of fertilizer and a regularly given solution. When using foliar fertilizers, growers should be aware that they usually contain little calcium and may need to add more to prevent leaf burn in lettuce.

Additionally, it is important to consider the dissolved oxygen level when applying foliar fertilizer as a nutrient, as it is vital for photosynthesis and plant respiration. The dissolved oxygen level increases as the water temperature decreases. In nutrient tanks, the dissolved oxygen level is typically around 10 ppm at a temperature of 25°C in the top nutrient layer.

Meanwhile, the water layer below can have a temperature of 20°C with a dissolved oxygen level of 12 ppm. However, in the heat of the day, when the water temperature reaches 30°C, the dissolved oxygen level drops to only 5-6 ppm. To achieve this, the tank should be placed underground with the tank head at ground level. Therefore, it is crucial to stabilize the temperature of the nutrient tank to avoid interfering with the photosynthesis and respiration process of the plants.