Soil bed design in solar greenhouse

Hi,

I am new to the forum and I'm looking for some advice on a greenhouse soil bed that I will be designing and mixing up in the near future. I see there are many different forums so let me know if this belongs in a different forum.  I attached a sketch of the greenhouse design. This is my first attempt at this so any advice or design suggestions are welcome. Basically I will be using two 275 gallon tote's which are buried under the greenhouse, used in an air-to-water heat exchange system.  I will have a layer of 2 inch rigid foam above the totes(sloped to drain) and 4 inch foam around the perimeter of the soil bed.  I plan to mix compost, rice hulls and additional ingredients to create a living soil.  50° is my target temperature stay above in the winter.   I'm looking for advice on:

1) what to mix together initially to get a good start and also whether it's realistic to be able to grow a variety of vegetables in the same bed. The main vegetables will be tomatoes, bell peppers, squash, leafy greens, and peas.  

2) Are the drainage rocks a good idea below the soil and above the foam?

1.) as far as soil is concerned, you want a soil that is as vibrant and nutritious as any garden. There are lots of ways to accomplish this.  The main thing that I would suggest is that whatever soil you are planting directly into (i.e. the "top" soil) be very active and alive  if you want the plants to do well.

Mixing rice hulls into the soil, and then planting into that soil before the rice hulls have decomposed,  with tend to starve the soil of macronutrients (NPK) as the bacteria work on breaking down the rice hulls. It would be better to compost everything well before planting into,  just like any garden.   You can look up "soil nutrient immobilization" for more details on that.

Also,  when working in a greenhouse,  it is important to keep the soil very alive and  full of nutrients  because there is on 18" of soil there in an box which is isolated from the outdoors.  The typical ecosystem services  of an outdoor garden are not present,  so you need to be ready to provide them if you want to maximize yields in a small space - which is usually what folks are after with greenhouses.

2.) I don't fully understand the designs, but I think that the rocks on top of the foam would likely cause damage to the foam which may not be desireable.  

The manner in which you are insulating and using an IBC and air-water heat exchanger is not something that I've ever seen done before, so I can provide no real answers.  

- the design seems to use a lot of materials and tech for a small space. I also have concerned about placing 300 gallons of water on top of closed cell insulation panels.  My sense is that it will crush the foam.   Also, having the water tanks down underground  may make it difficult to access and maintain.

If you are interested, the below image portrays a typical manner in which greenhouses, passive solar homes (and other structure looking to isolate a large thermal mass under the building to provide temperature regulation) insulate their foundation.



it uses a lot less material, and is quite effective.

Hi Andrew,

Thanks for the quick and detailed response. I apologize, I should have added more detail to the drawing.  Here is an update to the drawing showing the air-to-water heat exchanger detail.

The foam below and above the totes is extruded polystyrene, rated at 25 psi, and all of the components above the bottom foam are less than 2 psi so I wasn't concerned about the foam compressing.

I agree it has a number of components but I think it will be needed to try growing year-round where I am.  I am in Denver, Colorado where the nighttime winter temperatures are in the 20s and 30s so I wanted enough thermal mass to stay above 50° at night.

I am new to organics and the purpose of the rice hulls were to keep the soil aerated, I didn't think about their role in decomposition. Do you suggest something for aerating the soil/keeping it from compacting?

Hi Dan, welcome to Permies!  That is a neat greenhouse design.  You might want to create another post in the Greenhouse section that describes the function of the greenhouse with that great layout drawing.  Folks may want to ask more questions and provide more feedback (if you want that...) if it was a separate thread.  Then this thread can stay focused on the soil part of your design.

Great work!  I have feedback but I'll save it if you'll be doing another thread

Thanks Mike,

Good point.  I will make another post in greenhouse to get feedback on the greenhouse design as you suggest.  I'll make sure I provide as much detail as possible.

I added a post to the greenhouse forum here:
https://permies.com/t/62395/Greenhouse-build-thermal-mass-storage#532375

Dan, compost is pretty easy to make, it takes a bit to get it done so if you are in a hurry you might be able to locate a truckload of good organic compost nearby ?

Here at permies we advocate planting in a polyculture , if you are unfamiliar with that just do a search and settle in for some very interesting reading.

I will be looking forward to seeing how this works out, keep us updated.

Thanks Miles,

I've been making some compost but I'm not hundred percent confident with it so I may use it in other areas.  I found a good local source for 1/8" screened compost for $50 a yard.
I'm reading some books and learning about how different plants nearby interact with each other, it's pretty amazing.  I'll read up more on polyculture.  

Do you know a good ingredient for adding aeration to the soil and a good ratio? Maybe lava rock or biochar?

I added this thread to the greenhouse forum for you.

For aerating your soil, have you considered introducing composting worms directly to your greenhouse?

Otherwise, I've had good results in planters using high concentrations of vermiculite. Looking at the way you're isolating your soil it looks to me more like you will be growing in ground level planters rather than in the ground itself.

I think your idea of biochar also has good potential. Just remember if you're making it yourself that it needs to be 'charged' before you use it. Otherwise it's just charcoal. The benefit to knowing that is that buying large amounts of wood charcoal without additives and charging it yourself can make it much less expensive. There's a lot of different instructions of how to do this online, but most of them are fairly straightforward. You just want to saturate the charcoal with nutrients and introduce it to an active microbe community. I think soaking it in a bucket of compost tea can be enough.

I love growing in polycultures, but I don't know if you can benefit as much from one it such an enclosed space. You won't have access to the full community of beneficial insects and micro organisms that would usually be drawn to a diverse planting to fight off marauding insects and disease. In your situation I think I would be looking more into crop rotations. Polyculture might work, I can still think of benefits that would still work in an enclosed system. Legumes will still fix nitrogen. Mustard roots will still decay in a way that kills root not nematodes. Just research carefully. One of my favorite sayings about permaculture is "it depends" There are very few solutions that apply to every situation.

Casie Becker wrote:I added this thread to the greenhouse forum for you.

For aerating your soil, have you considered introducing composting worms directly to your greenhouse?

Otherwise, I've had good results in planters using high concentrations of vermiculite. Looking at the way you're isolating your soil it looks to me more like you will be growing in ground level planters rather than in the ground itself.

I think your idea of biochar also has good potential. Just remember if you're making it yourself that it needs to be 'charged' before you use it. Otherwise it's just charcoal. The benefit to knowing that is that buying large amounts of wood charcoal without additives and charging it yourself can make it much less expensive. There's a lot of different instructions of how to do this online, but most of them are fairly straightforward. You just want to saturate the charcoal with nutrients and introduce it to an active microbe community. I think soaking it in a bucket of compost tea can be enough.

I love growing in polycultures, but I don't know if you can benefit as much from one it such an enclosed space. You won't have access to the full community of beneficial insects and micro organisms that would usually be drawn to a diverse planting to fight off marauding insects and disease. In your situation I think I would be looking more into crop rotations. Polyculture might work, I can still think of benefits that would still work in an enclosed system. Legumes will still fix nitrogen. Mustard roots will still decay in a way that kills root not nematodes. Just research carefully. One of my favorite sayings about permaculture is "it depends" There are very few solutions that apply to every situation.

Thanks for the reply
I did not consider adding worms.  How many worms do you think I would need for 150 cubic feet of soil and are there any other critters I should add?
I guess I should ask "what's the best I can do in an enclosed space with 9' x 11' x 18" deep of soil?"  what would be the most beneficial plants to grow to help maintain a healthy soil.  It sounds like legumes and mustard roots should be in there.

http://crmpi.org/  I would recommend reading some at the Central Rocky Mountain Permaculture Institute's page.  Jerome Ostenkowski has been growing in greenhouses in the Colorado Rockies for twenty years or more.  His experiences and methods might be relevant for you in Denver.