Traditional hempy medium is 70% perlite 30 vermiculite and has almost zero wicking power. People make all kinds of changes to the medium and style but the basic works just as good
i am going to engineer several mixes and actually measure the Overall airspace, water holding capacity and water wicking height. I will also do this for several container heights including 16, 24, 32 oz solo cups, 2 liter bottles and 5 gallon buckets because overall airspace percentage will go up as a container gets taller, also, overall drainage will better with an identical soiless mix in a taller container. If i get the funds i will buy some lab moisture meters and make all these measurements at various depths. For instance if i were using peat moss in a 5 gallon buckets at some particular depth the peatmoss will stay overly wet for a very long time. If the same container were filled with perlite, i might go another 4 to 6 inches deeper until i reach conditions as wet as a shallower depth of peatmoss. It is possible to engineer a soil mix that will wick water from a constant level reservoir to at least a height of 8 inches and possibly 12 or higher like in a 5 gallon bucket. I have a crop of clone mothers in 9 inch high fabric pots sitting in an inch tall saucer. they need to be transplanted up but for kicks and giggles i decided to stress them out and see how large i could grow in a 1 gallon pot and for how long. These mothers have been alive for over 10 months and are 3 1/2 by 3 feet. A grand daddy purple has a stem that is almost 1 1/2 inches in diameter. I can top water or bottom water as much as i want without ever overwatering. One of the plants actually drinks 3 cups of water every hour for 16 hours a day and i often water a few times in the dark period because it is still drinking. Any problems only arise if i have to wait 3 to 4 hours to top off the water again as the EC level will rapidly rise in the soil profile and cause some toxicity issues. I am taking apart my room and rebuilding it next week and it will all be automated. I found a timer that i can run up to 20 times a day in increments of a minute and i am going to dial it in so i keep the reservoir filled without wasting much to overflow. My current soiless mix is washed coco peat [to rinse out fines and rinse out salts then cal mag to load cation sites to avoid mag and calcium dificiencies] and washed perlite [to rinse out fines]. It is a layer cake mix bottom layer is 100 percent perlite 0 percent Coco, then 80/20 60/40 40/60 20/80 100 coco. Next time i will try 10 percent increments and i will also be looking at DE, Zeolite, various grades of pumice, etc. I soil cap my mix with a handful of non Calcined Diatomaceous Earth aka Blue Ribbon Kitty Litter from the local dollar store. DE is hated by fungus knats, even this coarse grade and acts as a surface mulch to block light and slow evaporation, plus it works like litmus paper. When i water only from the bottom saucer with a fresh dry layer of kitty litter, the kitty litter begin to darken with moisture thoroughly within 2o to 30 minutes which proves conclusively this layer cake mix is lifting or wicking water 8 full inches from the top of the water reservoir. I will test this same mix in a taller container soon to determine just how high the mix can lift. I would speculate that a 70/30 Perlite/Vermiculite would easily wick water at least 6 inches but i will have to test and share the results.
