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Growing Media For Horticultural Production. Scott Poague, Holtville High School. Properties Of Growing Media. Growing media consists of mixtures that provide water, air, nutrients, & support to plants. Growing media is not considered soil .
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Growing Media For Horticultural Production Scott Poague, Holtville High School
Properties Of Growing Media • Growing media consists of mixtures that provide water, air, nutrients, & support to plants. • Growing media is not considered soil. • 4 main factors affect air & water status in nursery containers • The media components & ratios • Height of the media in the containers • Media handling • Watering practices
Media Handling • The major concern is to avoid compaction. • Growing containers should never be stacked when filled with media. • Moisture content is also important. Adding water to peat-based mixes before filling trays causes the media to swell & helps create more aeration.
Media pH • Initial pH of growing media should be between 5.8 & 6.2. • Most media components are acidic, so dolomitic lime is added to start at an acceptable pH range. • Commercially blended media typically have limestone already incorporated. • If you mix your own, lime is added at a rate of 10-15lbs. per yard.
Media Components • Most greenhouse media contains 30-60% peat moss in combination with other materials. • Various materials are added for water drainage & aeration.
Peat • Main component of soil-less media mixes. • Produced by partial decomposition of plant material under low-oxygen conditions. • Peats from sphagnum mosses have a spongy, fibrous texture, high porosity & water holding capacity.
Bark • Byproduct of sawmills, & used extensively by nursery industry. • Must be aged or composted before use. • Low nutrient value
Coir • Originates from ground coconut husks. • Contains low levels of micronutrients, but higher levels of phosphorus & potassium.
Perlite • Volcanic rock that is crushed & heated rapidly to a high temperature. • White, light weight w/ high pore space. • Added to improve drainage.
Vermiculite • Silicate material that is processed much like perlite. • Available in a number of grades. • Particles are soft & easily compressed, so must be handled carefully.
Cow Manure • Heat treated & dried to kill bacteria & weed seed. • Adds various micronutrients to media mix.
Wood Shavings/Saw Dust • Used as a water holding agent. • Very little nutrient value.
Mixing Your Own Media • Purchasing commercial mixes is based primarily on production cost. • As a rule of thumb it is not economical to mix your own media with less than 100,000 square feet of growing space. • Mixing equipment can range from sophisticated, expensive equipment to a cheap cement mixer.
Commercial Formulations • Most common media used, are mixtures of peat, vermiculite, & perlite. • Designed to achieve high porosity & water retention with adequate aeration. • Formulations w/o wetting agents are available for growing sensitive plants like seedlings.
References • www.farmphoto.com • Growing Media for Greenhouse Production, University of Tennessee