When I worked in my Dad's greenhouses in Indiana in the '40s and '50s, we changed the soil every summer. Dug it out to the depth of a round point shovel, wheelbarrowed it to a flat bed truck parked outside, trucked it to one of the unplanted fields on the property, loaded up with fresh soil from the field, trucked the fresh soil back to the greenhouse, and wheelbarrowed it back into the beds . It took four or five of us high school/college sports about a month to do this. (Greenhouse work was too much fun; that's why I joined the Air Force and became a career pilot.)

I amend my soil twice a year...Spring and Fall...when I replant with season appropriate crops.
I add a good 4-5" of compost.

The sun was out today so the GH temp is 60 degrees although it was 18 degrees outside temp - good day to work in the GH! Thanks for your comments - I can relate to your story Billala! My dad didn't have a GH but I did my share of milking cows and associated chores! Your method is the concept I had in mind with the exception of adding amendments like Plantladyco after digging a shovel depth. I refreshed one of the beds today - right or wrong - this is how I did it.

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I removed current bed soil (shovel depth) in a wheelbarrow and dumped it in my outside garden area to spread with the tractor next spring. In a 70 sq ft area I added 4 cubic ft top soil, 4 cubic ft pearlite/vermiculite, 5.5 cubic ft compost, 3.5 cubic ft peat moss, 25 lbs Alpha Pellets, small amounts of colloidal Phosphate, Azomite, Green Sand, Potassium and Cotton Seed Meal. I just used my shovel to till the soil. I have a small weed-eater tiller but it makes a mess throwing soil every where in the raised beds. The soil was not froze in the raised beds as temperatures in the GH have been around 70 during the day for the past week - good time to refresh the soil in the beds! I am not suggesting you use the same method that I did to refresh your GH soil but just sharing ideas - this method as been working for us so far here in Wyoming!

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It's a great question Hudson, and one I have been pondering for a while.

It seems to me that one has the two opposing choices: Replace the soil, which has the issue of finding good quality replacement soil. Or amend the current soil which has issues with soil balance and possible disease/insect buildups.

In my location, my choices are somewhat limited. The local soil is quite poor (some might say non-existent), so any replacement soil will need to be purchased and trucked in. What I have been doing in my smaller GH is amending the soil every year, with occasional soil tests. The soil has actually gotten quite good, but 10 years of growing peppers and tomatoes in the same soil has led to some disease issues (for that family of plants anyway).

In my new GH, I plan on trucking in soil/compost to get it started, then amending as I can (and as the soil tests suggest). It will have considerably more space, so a decent crop rotation should be possible, which will hopefully control diseases. I am hoping to have a fairly decent planting medium there within a couple of years of amending. We will see how it goes.

Given the trouble/expense for me to get new replacement soil, I am leaning my approach to keeping the soil in place as much as possible. Although I suspect their may come a time when replacement will be necessary. However since purchased soils are generally OK at best, it is hard for me to toss away soil which I have been amending for any length of time.

I am curious how others will respond...

Its hard to believe that anyone would replace all of the topsoil in a greenhouse unless there was an imminent threat of a recurring disease and I'm not aware of any in the northern states that would warrant such action. I'd like to hear what types of disease problems would warrant such drastic action.
I've been planting the same crops (mainly tomatoes and cucumbers) for 14 years in a 20x96 greenhouse and 10 years in a 30x96' greenhouse with little disease pressure, much less than I notice in same field grown crops that are rotated. What I do to minimize diseases is to cover the entire soil surface with black plastic and only use that plastic for one season (after all plants are pulled, surface swept clean, and all debris hauled to a remote brush compost pile. I have been amending the soil prior to reworking each year in early spring; for the past 4 years I have split 30 bales of peat moss between the 2 structures and I've always needed to add lime also. I have relied on my own pH and basic nutrient testing to get me in the ballpark with fertilizer needs.
In my opinion this idea of crop rotation is grossly overated. I will admit that Nematodes might be a concern but I'd try to use a biofumigant crop to control that problem rather than remove tons and tons of soil. I'm just wandering what threats would merit such a drastic step.

Good topic. I don't know the answer either but DH has declared that he is replacing the soil in the GH this winter. Our production has declined over the years and this past summer was the first time ever that we had disease problems. Another route would be to get a good soil analysis and figure out the right way to amend it. That's probably what I would do if not for DH's proclamation (and implicit free labor). Our raised beds outdoors have declined too so for sure I will go the test/amend route for them.

BTW for bmoser, our GH is small so it's definitely not tons and tons of soil. If it were I would definitely not be replacing it!

Hudson, you did a beautiful job as usual. Thanks for the good thread!

Steve - I couldn't have said it better! One of the reasons I remove medium from the raised beds is because even after settling - by the time I amend the soil every year - something has to be removed to make room for the amendments. Actually, not much top soil is added proportionately with the amendments but we are fortunate to have reasonable priced great top soil available for purchase from a nearby excavation company. I always have a yard or two piled by the GH. This summer/fall I plan to mulch in the GH with grass clippings (not too deep) and leaves as well.

bmoser - black plastic may have a lot to do with your success! Do you use a drip irrigation system? I am also unable to rotate crops in the GH because Tomatoes, peppers and cucumbers take the majority of the GH space every year. It is good to hear that your soil is producing after 14 years of the same plants! In our outside garden I add at least a ton of alpha hay every year to the soil as well as a good dose of Azomite. It is too large an area to amend with the expensive GH amendments.

Hi Karin - I agree with your DH! Sometimes it is better to just get rid of the old and bring in some new! That's why I took out more of the top soil this year than usual - it just didn't look and feel like good rich soil - definitely needed compost badly - looks & feels good now - like bagged potting soil ! My outside raised beds need refreshing too - not sure how I will amend them though - I have five 5'x16' beds in addition to our outside garden - I may refresh them with Azomite and alpha hay with some manure from our steers we raise every year. It gets too expensive to amend them like we do our GH? You have a lot of outside raised beds - how do you refresh them?

HI Hudson,

Well, it's good that you agree with DH because he is resolute and won't change his mind! I'm glad you had good results, that is a nice motivator for us. We won't tackle the job until late Feb or March - which is when we start planting in there.

I'll have to think about what amendments to add. Usually I use peat moss, gypsum, and a low-dose organic pelleted fertilizer. I use those same things in the raised beds outside too. I upped the fertilizer amount last year and in some cases I did really lavish preparation. But overall I definitely have a lower yield. Maybe I need to do more re-mineralizing? Or switch to a different kind of fertilizer? Or get some organic manure? Plenty of time to ponder all that. For now I'm enjoying eating all the foods we put up last fall and thumbing through seed catalogs while dreaming of butter lettuce.

Hudson, I do use driptape under plastic. I would use hi-legume hay if "Rain hay" would be cheaply available- used it a few years ago and it required numerous trips over the hay with a 3-point mower followed by hours of cultivation to incorporate the material into the soil uniformly. In future I'd opt for a few inches at a time as I presently do with the peat.

Proper fertility is of utmost importance. One needs to start with a pH test and there is almost 100% chance that fertigation during the growing season will boost yields significantly. I'd be most concerned of where replacement soil is coming from and potential for herbicide residues, excess nutrients or even toxic minerals.