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Growing Media (GM) for plants (2) Physical Properties (a) Water (Young…
Growing Media (GM)
for plants
1) Functions
support, air, water,
supply nutrients, space.
2) Physical
Properties
a) Water
Young plants use a lot of water
for photosynthesis
held in micropores - need
lots of organic matter
b) Air =
O2 for respiration to break down sugar for energy - drainage important so roots have enough O2 available
c) Bulk Density =
light to start off with then higher bulk density to support more weight
Weight per volume
3) Chemical Properties -
.
CEC
Cation Exchange Capacity = can the GM hold onto nutrients. Compost, peat moss and vermiculite have high CEC's
Cations = Mg+, K+, Ca2+, electrically charged atoms attach onto the negatively charged organic matter
Nutrient Level
Low Initially and then need to increase if potting on
pH
Optimum is 5.5 - 7 otherwise less
nutrients and microorganisms
4) Biological Properties
Ideally pathogen and weed free
Peat = common, good water retention, acidic, banned after 2020
Wood residues = may need to add extra N as micro-organism use a lot of N to break it down
Milled Tree bark = Good potential with natural fungicide propeerties
Sawdust = Species dependent + need etc N due to depletion during decomposition
Leaf mould = good for aeration / drainage + water holding capacity
Bagasse = waste from creating sugar - good for aeration / drainage. High sugar stimulates Microbes. N can be low
Rice Hulls = by product good for aeration and not as low in N as other organic matter
Coir = from waste coconut industry - good CEC, water holding capacity and some nutrients also
Elephant Grass = could be grown very quickly and composted
Cow manure = Caroline Robinson uses it for seed sowing
Compost Nutrient Tea = could put trays in tea filled barrel after sowing to give a boost