I’ve grown chilis and cannabis without really knowing what I am doing, now I wanted to learn to grow any veggies, but finally learn about soil and prepare it well myself.
I naively tried to use coco substrate with tap water and killed off my tomato seedlings pretty fast. Then I’ve did some research into soil and learned about more organic approaches, and also that pure coco is a bit like dry hydroponics and needs a lot of understanding, and that I probably both over-fertilized and starved them at the same time.
I’m going to start from seeds in Mel’s mix with 1/3 coco 1/3 perlite/vernaculite 1/3 compost. Is this kind of substrate to be treated as organic or as mineral approach? The compost probably adds the typical soil properties including the buffering of pH and EC and taking care of fertilization.
But I do not want to re-pot all the time, it is messy and inconvenient. I don’t really like working with soil. Instead I want to use mineral fertilizers. Once the compost is depleted, can I consider it to be like a non-soil grow? I got a pH/EC sensor to check my water and the drain coming out, diluted a pH- down based on diluted citric acid to normalize my water to 6,5pH, which seems like a good starting point for any situation.
Does it make sense to follow some generic approach (like keeping pH/EC in certain ranges in certain growth stages)? I do not want to use commercial fertilization formula schemes. I want to work with standard off the shelf mineral fertilizers. Is it possible to get decent results with that?
And where can I find that kind of information for general vegetables, like tomatoes or cucumbers etc.?
The whole soil business is pretty overwhelming, but I want to learn enough (without getting a degree in agriculture) so that I can do this not blindly but improvise with available substrates and fertilizer. How to get this knowledge?
The most “outdoor” I have is the balcony, so it will be a pot- and box-based little garden (some that will be permanently outside and some more movable).
Thanks for the tips! Good point, I also maybe should not overthink or over-engineer it. I’m a software engineer so maybe I approach this way too analytical :D
In plant science and agriculture there is a shit ton of variables. The majority of them are unknown and/or constantly changing You can only create general approximations to cover the plants basic needs and hope for the best.
Water storage. Coir does a good job at this as long as it has been treated with the proper surfactant (wetting agent). Untreated coir is hydrophobic and a complete clusterfuck.
Gas exchange with the roots: Coir alone tends to hold too much water and blocks adequate air motion. I always blend in 40% sand with it to improve drainage and gas exchange. It also adds in some weight and keeps the pots from falling over in the wind.
Cation Exchange Capacity - this is the storage battery in soil for positively charged nutrients. Mineral Clay, Compost, Peat etc are all very high in these. Around 5% compost by weight is usually enough.
I usually blend in some 6 month slow release (polymer coated) fertilizer in my pots at the beginning of the season. I almost never have to add in more during the growing season. This needs to have a NPK ratio of around 3-1-2 plus a micronutrient blend.
I reuse the soil in the pots every year. Add 2-3% more compost to replace the lost organic matter and blend in some more fertilizer.
Good to know about reusing soil, I always thought it’s wasteful and inconvenient to throw it away and in an actual garden nobody would do that. So I am also definitely going to try reusing soil I use in the pots, just bought a sieve to simplify the process of removing roots etc. from used soil.
Only 5% compost ? I don’t know how dense compost is, but typical suggested DIY mixes use more like 1/4-1/2 compost, by volume.
I was planning to do 1/3 coir for the loose structure, 1/3 of some perlite or similar, to hold water better, and 1/3 compost for initial nutrients, and then see how it behaves and adjust.
Would you recommend to use other proportions? I was going to experiment with the perlite percentage and see how it behaves with respect to watering etc. But with compost I really don’t know how I would even estimate how much I need to add so that a plant has enough “food” from seedling up to the first weeks of growth.
Would adding more compost to the mix simply extend the “nutrient store” for longer? I’ve read that you cannot so easily over-fertilize with compost / organic fertilizers, so I guess it’s then more about price/availability?
Is it cheaper or simpler to have less compost and more of that (I guess solid) slow release fertilizer, is that why 5% is enough?
That does sound very convenient. If I could mix some soil with slow release fertilizer and it would last the whole season, that sounds pretty awesome. I guess it’s released due to repeated watering? Or is it decomposing and releasing at its own pace? Like, do I have to worry about releasing too much if I water too much?
The online guides assume that you want enough nutrients from the compost alone to feed the plant through the entire growing cycle. The actual nutrient analysis of compost varies radically based upon the source of the composted material. So they all assume the lowest testing stuff and overdo it.
If you are adding in compost as an organic matter “battery” to recharge with conventional fertilizer, 5% is plenty.
Go ahead and use vermiculite or perlite but you have to send me pictures after you water so I can laugh. It floats and makes a mess everywhere. It also makes the mix lighter and a little breeze will knock over the plants. If you want to reuse the soil, blend in a bit of sand. It stays put, adds weight, and does a better job. Commercial potting soil mixes use the lighter perlite/vermiculite to save on shipping costs.
Slow release fertilizers are coated with polymers that degrade at a steady rate based upon temperature and moisture. Leaching out nutrients with the water will occur but having a bit of organic matter to catch the positively charge ones helps immensely.
