Greenhouse Management Growing Media 1 Greenhouse Management

Four Functions of a Growing Medium (Root Medium) Provide a source of nutrients Provide a source of water Provide aeration and drainage Support the plant in the container

Types of Media Soil-based: contains soil Soil-less: contains no soil

Soil-based Media Require pasteurization.

Soil-less Media Contain no soil. Generally do not require pasteurization. Available to purchase bagged or in bulk. May be mixed on site.

Bulk bags

Soil-based Medium Recipe A typical recipe used by the greenhouse industry consists of: 1 part soil 1 part sphagnum peat moss 1 part perlite or coarse sand

Soil-less Media Ingredients Various components are mixed together to create a soil-less growing medium.

Sphagnum Peat Moss Origin Organic or Inorganic? Role in the Medium Decomposed sphagnum moss. Organic -Water holding capacity. -Acidic.

Composted Bark Origin Organic or Inorganic? Role in the Medium -Composted hardwood and softwood barks. -minus ¼ inch diameter. Organic -improves aeration and drainage. -CEC.

Composted Yard Waste Origin Organic or Inorganic? Role in the Medium Composted leaves, grass clippings and brush. Organic -Water holding capacity. -CEC.

Coir Origin Organic or Inorganic? Role in the Medium Waste product from coconut hulls after the fibers have been extracted. Organic -Water holding capacity. -Used like sphagnum peat moss in the medium. -Can be high in salt; leach before using.

Perlite Origin Organic or Inorganic? Role in the Medium Volcanic rock that has been crushed and heated to high temperatures. Inorganic -Improves aeration and drainage. -Available in different grades.

Vermiculite Origin Organic or Inorganic? Role in the Medium Mica-like mineral that is crushed and heated in a furnace to high temperatures. Inorganic -Water holding capacity. -CEC. -Available in grades. -Coarser grades improve aeration and drainage.

Calcined Clay Origin Organic or Inorganic? Role in the Medium Clay heated in a furnace to high temperature. Inorganic -Water holding capacity. -CEC.

Rockwool Origin Organic or Inorganic? Role in the Medium Synthetic fiber made from melted basalt, coke and limestone. Inorganic -Ground rockwool can improve water holding capacity.

Sand Origin Organic or Inorganic? Role in the Medium Coarse silica sand. Inorganic -Adds weight to the medium. -May improve aeration and drainage.

Pasteurization vs. Sterilization Kills harmful organisms such as weeds, weed seeds, insects, certain fungi, and nematodes without killing certain beneficial fungi and bacteria. Sterilization: kills all organisms.

Methods of Pasteurization Steam (aerated to lower temperature) Electric Chemical Treatment

Steam Pasteurization Steam Generator

Steam Pasteurization Aeration Blower

Cart - 2 cubic yard capacity Steam Pasteurization Cart - 2 cubic yard capacity

Electric Pasteurization 1 cubic foot capacity electric unit

Chemical Treatment Methyl Bromide Vapam Basamid

Disadvantages of Using Chemicals Chemicals are toxic. Worker Protection. Proper ventilation prior to use.

Preferred Method of Pasteurization Steam

Temperature/Time Parameters for Steam Pasteurization Text says between 140-160 degrees F. Time: minimum of 30 minutes after all the medium has reached 140-160 degrees F.

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