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Grow Media Guide
Guide Volume 2
Plants like beneficial bacteria and fungi . by Jason Mispagel , contributing writer
Jason Mispagel is the co-owner and operator of Year-Round Garden , a grower ’ s supply center serving both home and commercial customers since 2016 . His extensive growing experience in hydroponics and soil dates to the early days of legalization in Colorado , where he served as one of the state ’ s early caregivers . Year-Round Garden . 1225 W 103rd St , Kansas City , MO . 816.216.6917 – FB : yrroundgarden ● IG : @ yrroundgarden
Last month , in volume one , we explored neutral grow media typically used in hydroponics . They ’ re referred to as “ neutral ” because they lack the nutrition necessary to support plant growth without adding fertilizer . On their own , they ’ re simply a means to provide support to plant root systems . Hydroponic systems must then utilize liquid or water-soluble fertilizers to deliver nutrition to each plant , but that ’ s not the only way this type of media can be deployed . When neutral media are mixed with nutrient-rich amendments , organic matter , and micro-organisms , they become more than just neutral media — they become soil .
The Foundation
At its base , soil isn ’ t necessarily a heaping load of nutrition-packed compost . Most soil is actually only 5 % organic matter , 45 % minerals , 25 % water , and 25 % air — yeah , that ’ s right — air . Because all soil is made up of varying-sized particles with pores and gaps between them , it allows space for water and air to flow . If it didn ’ t , and the soil was a completely rigid , compacted block , plant roots wouldn ’ t be able to survive . From largest to smallest , those particles are sand , silt , and clay . Most soil contains a combination of these particles , the proportions of which determine its capacity for holding nutrients and water and allowing for drainage and airflow . For example , the more sandy the soil , the less capacity it has to retain water , the faster it drains , and the greater the ability for oxygen to reach the roots . The more clay in the soil , the greater the capacity to retain water , the
slower it drains and the lower the ability of oxygen to reach the roots . Gardeners typically desire a “ loam ” soil of around 40 % sand , 40 % silt , and 20 % clay , allowing for a nice blend of water retention , drainage , organic matter , and oxygen flow to plant roots . You won ’ t see this type of description on bagged soil from your local grow shop , but it ’ s important to understand , nonetheless .
Cation Exchange Capacity
( CEC )
I dread writing about this because I know I can ’ t possibly do the scientific concept justice in this short article . I ’ d be remiss for not bringing it up , though . CEC is a measure of soil ’ s ability to retain nutrients . It ’ s a measure that you can easily determine by sending a soil sample off to a lab . I ’ ve always had a great experience with Logan Labs out of Ohio , but they certainly aren ’ t the only soil testing service out there . So why is CEC important ? Well , it tells you the degree to which your soil can retain nutrients . The lower the CEC , the quicker nutrients run off through the grow media , which generally equates to a sandier soil . The higher the CEC , the longer nutrients remain available in the soil for your plant to access . An extremely high CEC isn ’ t necessarily good . It means your soil has a lot of clay , equating to reduced oxygen reaching your plant ’ s roots . There ’ s a happy medium with loam soil that ’ s ideal for cannabis . ( P . S . – For all you soil nerds , Google Bill McKibben ’ s interview on the KIS Organics podcast . and you won ’ t be disappointed .)