Chapter 16

Fertilizers for Greenhouse Crops

(draft book excerpts)

Maintaining adequate nutrition is among the most critical aspects of producing greenhouse crops. Fertilizers are primarily valued for their ability to supply nutrients. Fertilizers typically provide three major nutrients for plants: nitrogen, phosphorus and potassium. These three are called macronutrients, usually found in most packaged fertilizers. Fertilizers also provide secondary nutrients: sulfur, calcium and magnesium. Sometimes trace elements are found, too, such as: boron, cobalt, manganese, iron, zinc, copper, molybdenum and selenium. These elements are also known as micronutrients. Of all those compounds, the most important ones as needed in largest quantity by plants are nitrogen, phosphorus, and potassium. Many different types of fertilizers are available for use in greenhouses and vary according to their source materials, nutrient quantities, and mechanisms of nutrient release. In general, fertilizers fall within two major categories: commercial fertilizer sources and organic sources. While it is difficult to make direct comparisons between these two sources, a few loose comparisons can be made. First, commercial sources are typically high analysis fertilizers, while organic sources are low analysis. This means that commercial fertilizers contain a larger percentage of a given nutrient than organic sources. As a result, commercial fertilizers are applied in lesser amounts than organic sources, since it take less commercial fertilizers to achieve a given rate. Secondly, composition of organic fertilizer is generally much more varied than commercial fertilizers. This lack of consistency can make it difficult to predict how much organic fertilizers should be applied in order to obtain a desired rate. Thirdly, commercial fertilizer production is fossil fuel intensive. As a result, the price of commercial fertilizer can be relatively expensive.

Click on the following topics for more information on fertilizers for greenhouse crops.

Topics Within This Chapter:

  • Introduction to Fertilizers for Greenhouse Crops
  • Inorganic Fertilizers
  • Advantages and Disadvantages
  • Advantages
  • Disadvantages
  • Fertilizer Grade
  • Other Nutrients
  • Regulatory Standards
  • Complete versus Incomplete Fertilizers
  • Fertilizer Forms
  • Solid Fertilizers
  • Liquid Fertilizers
  • Gaseous Fertilizers
  • Water-Soluble Fertilizers
  • Solubility of Fertilizers
  • Fertilizer Acidity/Basicity
  • Fertilizer Salt Index
  • Slow- and Controlled-Release Fertilizers
  • Advantages of Slow- and Controlled-Release Fertilizers
  • Disadvantages of Slow- and Controlled-Release Fertilizers
  • Slow-Release Fertilizers
  • Controlled-Release Fertilizers
  • Combining Controlled-Release and Water-Soluble Fertilizers
  • Application Methods of Slow- and Controlled-Release Fertilizers
  • Inorganic Fertilizer Materials
  • Nitrogen Fertilizers
  • Phosphorous Fertilizers
  • Potassium Fertilizers
  • Sulfur, Calcium, and Magnesium Fertilizers
  • Micronutrient Fertilizers
  • Chelates
  • Organic Fertilizers
  • Advantages and Disadvantages
  • Advantages
  • Disadvantages
  • U.S. Department of Agriculture’s National Organic Program Rule
  • Fertilizers Labeled as “Organic”
  • Animal-Derived Fertilizers and Amendments
  • Livestock Manure
  • Bat Guano
  • Blood Meal
  • Bone Meal
  • Compost
  • Feather Meal
  • Fish Meal and Emulsion
  • Plant-Derived Fertilizers and Amendments
  • Alfalfa Meal
  • Cottonseed Meal
  • Fruit Pomace
  • Soybean Meal
  • Seaweed Fertilizers and Amendments
  • Kelp Meal
  • Raw Seaweed Products
  • Seaweed Extracts
  • Mined Mineral Fertilizers
  • Sodium Nitrate
  • Colloidal Phosphate
  • Rock Phosphate
  • Potassium Sulfate
  • Langbeinite
  • Granite Dust
  • Glauconite
  • Feldspar
  • Wood Ash
  • Gypsum and Limestone
  • Micronutrients
  • Synthetic
  • Basalt Dust
  • Chelating Agents
  • Methods of Fertilizer Application
  • Adding Dry Fertilizers to Growing Media
  • Fertigation
  • Foliar Sprays
  • Advantages and Disadvantages in Foliar Fertilization
  • Proper Timing of Foliar Applications
  • Foliar Fertilizer Formulations
  • Adjuvants
  • Foliar Fertilization Equipment
  • References