olddaddy
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Location: Davenport, FL

Another soil question

I'm new here and did look around at some of the soil threads before posting this one. My garden is made up of 55 gallon plastic drums cut in half and 5 gallon buckets. The soil I have is a mix of mostly three ingredients, mushroom compost which is hay and horse manure, black kow and a composted soil I buy in bags at the local bigbox store. I've had mixed results, some good and some not and wondered if my soil might need more attention? What might I add to improve what I have? I turn the soil in each container prior to planting anything new, so I have the opportunity to add any amendments that might help. Any advice greatly appreciated.

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rainbowgardener
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That sounds like a very moist, dense mixture which would likely compact in your containers. I think it needs ingredients to keep it better aerated and it needs more mineral components.

A basic potting mix recipe goes like: compost or something organic that supplies texture and nutrients, something to keep it fluffy and moisture holding, something mineral or gritty to promote drainage, more or less thirds of each. In my quest for eco-friendly sustainable potting mix, the recipe I have come up with is mushroom compost (left over from growing mushrooms), coconut coir (outside fuzzy stuff from coconuts) instead of the peat moss that people often use, rice hulls (left over from milling rice) instead of perlite or vermiculite. All of this is agricultural by-products and all but the coconut coir can be fairly locally sourced. None of it is mined, heated to high temperatures or otherwise environmentally destructive to produce.

Mostly you only have the first third of this. I would suggest adding peat or coconut coir, rice hulls or perlite, and some gravel, oyster shell, etc.

olddaddy
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Location: Davenport, FL

Thanks for your reply. You confirmed what I was suspecting, I have mud not soil.....sort of. As it happens I scaled back my garden eliminating most of the hydroponic stack pots and have some coir and lots of perlite. I'll start there and look for rice hulls and more coir as well. I'll report back!

imafan26
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Potting mixes are different from in ground soil mixes. They have to be lighter and well drained and to avoid compaction and shrinkage, it is better not to have dirt soil in a pot.

I add 3-4 inches of compost every time I replant. Compost sinks in the soil over time and it gets used up by the soil denizens. I try to switch to different types of compost instead of using the same brand. I am not completely organic, but I do test my soil every 3 years and I only add the nutrients I need which is only small amounts of nitrogen. In 2019, I had good base soil with a pH 6.0. I did lime it to keep it from getting any lower. I do have a ton of weeds so I decided to mulch with newspaper (C:N 171:1) and I tried two different brands of organic raised bed soil mix and miracle grow. I had each type of mix in a section of my garden. The organic sections did not perform as well as the miracle grow potting mix. They were harder to wet and one of the mixes dried out much faster than the rest of the garden. The mixes claimed to have enough nutrients for 3 months. I did not give the organic mixes any other supplements. I did not supplement miracle grow either. In hindsight, I did know how slowly organics release nutrients and that nutrient % in organic mixes are about 1/10 of what synthetic fertilizers deliver with one application, so I probably did need to supplement the organic mixes weekly. It did have fewer issues with weeds for at least the first 3 months with the newspaper mulch.
Potting mixes are different. I mix my own or buy potting mix. I make peatlite which works the best for me. I only started reusing some potting soil late in 2019. Previously, I had always dumped the remaining potting mix in the garden, washed the pots, and used new soil mix. Since the pots were fallow in the summer of 2019, the roots had time to decompose and not cause me issues so I reused part of the old potting soil to save some money and hauling more bags of 3.8 cu ft peat moss around. I never had good results before using old potting mix, but I finally figured out that it was because I under estimated the residual fertilizer and found out, my initial fertilizer recipe is just enough to get through the planting season, so I actually had poor results because I should have used the full amount of my initial starter fertilizer. (1 cup per 18 gallon pot of 6-4-6 + osmocote).

I use 50% perlite 50% peat moss = peatlite. I water daily, but this mix works well for me as a year round mix. I have to water daily in summer, but I can go a couple of days in the rainy season. If I used a wetter mix, the plants would drown when the rains come. Perlite is on the allowed NOP list and is a lot lighter than builder's sand. It is also hard to find sand that is not beach sand here. Beach sand would be too salty. The peat moss would have to be the one without wetting agents. This type of peat moss is very difficult to wet and much harder to keep from drying out. Peat moss is natural, but it is not sustain-ably harvested. People do substitute coir, but I have had mixed results. Coir is very wet when it is wet and really dry when it is dry. Coir is a man made substitute. Normally, I would only have used coconut husks for mounting orchids because they take years to break down. If you use coir it does not hold nutrients very well except for negligible amounts of calcium and some micros. You would not have to use as much perlite if using coir since it does drain well, but unlike perlite it still compacts. It is a very light product when it is dry and there are problems with tall potted plants falling over unless the pot is heavy. It is suitable for some plants especially ones that like to dry between watering. We did use it in an aquaponic biofilter for things like carrots which would not have nice roots if planted in cinder. (Ebb and flow system).

Below is an organic potting mix developed by Cornell.


Cornell Soilless Mix (adapted for organic growers*):
1/2 cubic yard peat moss or coconut coir.
1/2 cubic yard perlite.
10 lbs. bone meal.
5 lbs. ground limestone.
5 lbs. blood meal.

There is a soil calculator in two of the links. It is helpful for me when I use recipes, because I mix my potting soil in a 5 gallon bucket and my measuring cup is a coffee can, so it is easier for me to use parts instead of weights or volume. I really should get an outdoor scale for some things like fertilizer.

https://www.soiltest.uconn.edu/documents ... 2-5-15.pdf
https://www.soildirect.com/calculator/c ... alculator/
https://www.finegardening.com/article/p ... il-recipes
https://www.planetnatural.com/potting-mix-recipes/
https://www.mysquarefootgarden.net/mels-mix/

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TomatoNut95
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Personally I'm quit fond of coconut coir. You're right, when it's wet it's goopey and when it's dry it's crunchy, but it is very soft and makes an excellent seed starting medium.

It may not hurt to use a little sand. I was just given some sand and I plan to mix it with some store-bought Scotts Humus and Manure and a little MG to use in potted vegetables in grow bags.



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