The needs of hydroponic plants change as the plant grows. The gardener monitors the plants and their needs, adjusting the system as needed to provide for the plants. Plants must have water, light, air and nutrients. Hydroponic systems attempt to deliver these under optimum conditions so that the plant is at its healthiest and produces the maximum. Once the system is set up and running, these procedures are vital to maintaining healthy plants.
Maintaining the nutrient at the proper strength and pH is crucial to the health of the plants. Hydroponic seedlings start on a dilute solution of approximately one-quarter strength. Gradually the strength increases until the plants are receiving full strength nutrients.
The nutrient solution needs to be topped off as it is used and completely replaced every two to three weeks. When the plant is ready for flowering, the nutrient formula changes to a formula that favors flowering.
Hydroponic systems approach the water-to-air ratio differently. The plant roots need both water and air. With the roots immersed in nutrient solution, an aerator provides oxygen to the plants. Systems that alternate water and air, such as misting systems and ebb-and-flow systems, require attention to the timing of watering. The roots must get water on time and the drains must flow properly.
pH and TDS
Maintaining the pH in at an acceptable level is important for the plant to be able to use the nutrients. The optimal pH varies from plant to plant, but for most plants, a pH between 5.5 and 6.0 is best. When the pH rises above 6.5, some of the nutrients will begin to fall out of solution and will not be available for plant use. Check the pH every day or two with a pH meter or pH test kit and adjusted with chemicals to maintain it in the optimum range.
Total Dissolved Solids (TDS) is a measure of the amount of nutrients available in the solution. As the plant takes up nutrients, the TDS drops in the nutrient solution indicating that the nutrients need to be replaced. The best TDS level depends on the plant and its life stage. The nutrient needs gradually increase as the plant grows. Very concentrated nutrients can burn the plant roots or kill the plant.
Hydroponic plants need about 18 hours of light a day. Unless the plants are receiving enough sunlight, artificial light provides the wavelengths that the plants need. To encourage flowering, light levels drop to 12 hours per day. Lights operate on a timer system, but care is required to make sure the plants receive enough light and that heat does not build up in the room. In most cases, an exhaust fan or air conditioning cools the room.