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Medium additives

Medium additives. Video. Choosing a soil mix – a quick intro so a few of the ideas behind using a medium in a greenhouse. Review. There are many things to take into consideration when choosing a soil for your plants Aeration Bulk Density Pore Spaces Porosity Water Holding Ability CEC

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Medium additives

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  1. Medium additives

  2. Video • Choosing a soil mix – a quick intro so a few of the ideas behind using a medium in a greenhouse

  3. Review • There are many things to take into consideration when choosing a soil for your plants • Aeration • Bulk Density • Pore Spaces • Porosity • Water Holding Ability • CEC • Organic Mater • pH

  4. Peat and Peat-Like Materials • Peat moss is formed by the accumulation of plant materials in poorly drained areas • Sphagnum Moss is the most desirable from of organic matter for the preparation of growing media. • Drainage and aeration are improved in heavier soils while moisture and nutrient retention are increased in lighter soils.

  5. Wood Residues • These materials cause nitrogen depletion by soil microorganisms during the decomposition process. • Leaf Mold – can improve the aeration, drainage, and water holding properties of a growing media (also it is readily available at low costs). • Barks – a byproduct of the pulp, paper, and plywood industries, this product produces physical properties similar to those of sphagnum moss.

  6. Rice Hulls • A by product of the rice milling industry, they are extremely effective at improving drainage. Unlike other media additives N depletion is not a serious problem found with rice hulls.

  7. Perlite • A silicous mineral of volcanic origin. Its lightness and uniformity make perlite very useful for increasing aeration and drainage.

  8. Vermiculite • A mineral with plate like particles which have a very high water holding capacity and aid in aeration and drainage. It also has excellent exchange and buffering capacities as well as the ability to supply potassium and magnesium. • Because of these chemical and physical properties it is very desirable for container media.

  9. Calcined Clays • Have a relatively high CEC as well as water holing capacity. It is also a very durable additive which makes it a great amendment to growing medias.

  10. Preparing Soilless Growing Media • Although amendment combinations may vary, basic objectives in the preparation of a growing media are alike. An effective program should produce a growing media that is: (Continued on next slide)

  11. Preparing Soilless Growing Media • Porous and well drained, yet retentive of sufficient moisture to meet the water requirements of plants between irrigations; • Relatively low in soluble salts, but with an adequate exchange capacity to retain and supply the elements necessary for plant growth; • Standardized and uniform with each batch to permit the use of standardized fertilization and irrigation programs for each successive crop; • Free from harmful soil pests; pathogenic organisms, soil insects, nematodes and weed seeds • Biologically and chemically stable following pasteurization; primarily free from organic matter that releases ammonia when it is subjected to heat or chemical treatments.

  12. Commonly Used Soilless Mixtures

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