Chapter 11

Growing Media for Greenhouse Crops

(book excerpts)

Successful greenhouse production of container-grown plants is largely dependent on the chemical and physical properties of the growing media or substrate as it is oftern referred to. The word media is the plural of medium. The media should be well drained and yet retain sufficient water to reduce the frequency of watering. In greenhouse production, it is important that the substrate has good structural characteristics, so it can hold up to frequent irrigation, root growth, and temperature change over the life of the crop. At the same time, it must serve as a reservoir for water and nutrients and be able to allow air exchange between the root system and the aerial environment. Other parameters to consider include cost availability, consistency between batches, and stability in the media over time. Media is used to grow a wide variety of plants including vegetables, fruits, floriculture ornamentals, and speciality plants. Selection of the proper media components is critical in the successful production of plants. Today, growers can select from various components, including peat moss, vermiculite, perlite, rockwool shredded coconut husks (coir), soil, or composted materials; and from various substrate additives to produce the substrates that best fit the needs of their crops. Because these individual components rarely have the optimal physical and chemical properties required when used alone, two or more components are often blended together to produce a composite material that will have the appropriate properties for the crop being grown and the specific cultural conditions under which the substrate will be used. Recipes are specially formulated for propagation, specific crops, or general use. Grow¬ers must be familiar with the positive and negative characteristics of the vari¬ous ingredients and how they will affect plant growth when creating a suitable growing medium, or even when purchasing a commercial mix.

Click on the following topics for more information on growing media for greenhouse crops.

Topics Within This Chapter:

  • Properties of Growing Media
  • Growing Media Physical Properties
  • Bulk Density
  • Water-Holding Capacity
  • Air-Filled Porosity
  • Media Stability
  • Growing Media Chemical Properties
  • Cation Exchange Capacity
  • pH
  • Electrical Conductivity
  • Carbon-to-Nitrogen Ratio
  • Ingredients Used in Formulating Media
  • Organic Media Components
  • Peat
  • Shredded Bark
  • Coir
  • Sawdust
  • Rice Hulls
  • Soil
  • Animal Manure Composts
  • Inorganic Media Components
  • Vermiculite
  • Perlite
  • Calcined Clay
  • Sand
  • Rockwool
  • Polystyrene Chips
  • Common Media Amendments
  • Limestone
  • Application Rates
  • Iron Sulfate, Aluminum Sulfate, and Elemental Sulfur
  • Wetting Agents
  • Formulations
  • Fertilizers
  • Biological Control Agents
  • Grower-Mixed Media versus Commercial Media
  • Commercial Media
  • Grower-Blended Media
  • Media Mixing Methods