**19. Analysis of solution, tissue, and media**

Knowledge of the nutritional status of all components (nutrient solution, substrate/media, and plant tissues) of a soilless cultivation system is very much required to judge the success of fertilizer schedules with respect to plant nutrients availability and the plant tissue nutrient content and it also helps to identify the reasons of any deficiency and toxicity symptoms that may appear in plants. The costs of the information with respect to the nutritional status of all components are a form of assurance towards success. The nutrient solution in a recirculated hydroponics system of cultivation may be utilized for a few days (short use) to a few weeks (extended use). To extend the life of nutrient solution to a few weeks in recirculated soilless culture/hydroponics system, it is always better to analyse the solution periodically for pH, EC, and individual nutrient concentration. Based on the nutrient analysis, periodic replenishment or adjustment in nutrient solutions can be made using nutrient stock solutions. By doing so, the longevity of nutrient solutions can be extended and the cost required for buying nutrient solutions or

soluble salts can be reduced. Total salt content estimation on daily basis will also give the status of the nutrient content in the solution even though this cannot substitute for comprehensive analysis [2].

To avoid toxicity and deficiencies of nutrients in recirculated solutions due to continuous variation in nutrient status, it is necessary to do solution analysis for complete control over nutrient management in liquid soilless culture. The frequent requirement of solution analysis in water-based soilless culture gives a reason for switching over to solid substrate-based soilless culture. In solid substrate-based soilless culture systems, the evenly balanced nutrient solution is given to plants at the time of irrigation. In this way, the problem of nutrient solution management in solid substrate-based soilless cultivation systems can be minimized. Also, by accurately weighing the soluble salts at the time of nutrient solution preparation, it is possible to make a very properly working solution.

Like nutrient solution and substrate analysis, tissue analysis (leaf petioles or blades and whole leaves) is also warranted for successful nutrient management in plants. Tissue analysis during the crop growth period provides the current status of nutrient content in plants. Based on the nutrient content in plants, the fertilizer program may be adjusted or modified for better plant growth and productivity in soilless cultivation. Nutrient data obtained through tissue analysis may also help in interpreting nutrient deficiency or toxicity symptoms. Depending on plant parts sampled, location of sampling, and method used for analysis, the critical nutrient levels may vary. Critical nutrient concentrations for tomatoes, cucumbers, and different vegetables have been reported by various researchers [2, 35–37].

#### **20. Water management in soilless vegetable cultivation**

Substrate texture, porosity, and surface area to be wetted are vital considerations in making the right choice of irrigation in soilless vegetable cultivation [15]. While selecting an irrigation system for container or bag culture, one should keep in mind that the main purpose of irrigation is to apply nutrient solution homogeneously by making wet of entire growing media. A dry substrate or medium will make it very difficult for the plant root system to function properly [38]. Therefore, proper water management in soilless culture is very much important not only for meeting the water requirement of the plants but also for distributing the nutrients uniformly in the media. During summer, plants need extra water and hence the plants should preferably be irrigated twice a day. For soilless media, watering needs to be done only when the surface/subsurface of the media/substrate is dried and excess watering may be avoided.
