Fertilizers

• Fertilizer dosage has to be dependent on growing media.
• Soilless mixes have lower nutrient holding capacityand therefore require more frequent fertilizer application.
• Essential elements are at their maximum availability in the pH range of 5.5 to 6.5.l In general Micro elements are more readily available at lower pH ranges, while macro elements are more readily available at pH 6 and higher.

Forms of inorganic fertilizers: Dry fertilizers, slow release fertilizer and liquid fertilizers are commonly used in greenhouses.

a. Slow-release fertilizer

• They release the nutrient into the medium over a period of several months.
• These fertilizer granules are coated with porous plastic. When the granules become moistened the fertilizer inside is released slowly into the root medium.
• An important thing to be kept in mind regarding these fertilizers is that, they should never be added to the soil media before steaming or heating of media.
• Heating melts the plastic coating and releases all the fertilizer into the root medium at once.
• The high acidity would burn the root zone.
• Example: Bone meal, Fish meal, Neem cake, Compost manure, etc.

b. Dry fertilizer

• Solid, granular, or powdered forms of fertilizers applied directly to soil or growing media.
• Can be broadcast, banded, side-dressed, or incorporated before planting.
• Often used as a base fertilizer to provide long-term nutrient availability.
• Examples: Urea, Ammonium Sulfate, SSP, MOP, Calcium ammonium nitrate, etc.

c. Liquid Fertilizers

• Fertilizers dissolved in water and applied through irrigation (fertigation) or foliar sprays.
• Provides nutrients directly in available form to plant roots or leaves.
• Widely adopted in soilless culture, hydroponics, and precision greenhouse farming.
• Examples: Liquid Urea Ammonium Nitrate (UAN solution), Liquid Potassium Nitrate (KNO₃ solution), etc.