No soil incorporated? Just mushroom compost and nothing else? No active soil food web to convert the compost to usable nutrients. No fertilizer supplements?

Sounds like a good case of severe nutrient and mineral deficiency because your bed is essentially sterile.

Compost is only a source of nutrients IF there is an active soil micro herd in the bed to digest it and convert them. In a new bed that doesn't exist. And in a new bed with no incorporated soil it can't even begin to develop.

Compost is primarily a soil amendment, not a growing medium. It can be a source of supplemental nutrients with time to decompose over time but only dirt contains the needed minerals and micronutrients unless you provide them regularly.

So you need to mix in soil - dirt. Minimum of 1:1 soil to compost. And until the soil food web - the bacteria and soil residents - has time to develop over at least a couple of seasons you'll need to supplement with nutrients and micronutrients - fertilizers. The type you use is your choice but liquids are more fast acting than granular supplements.

Dave

If it is compost from cows that have ingested certain pesticides, then you can kiss your garden goodbye. Google toxic compost. Other than that, I mildly disagree with Dave. My dirt has no phosphorus for example. Some minerals are predominantly n the compost, which it is typically 1:0.5:1 by dry weight. In fact, too much manure, a component of compost, can create chlorosis conditions as excessive P displaces iron. I have planted in up to 3 inches pure compost with good results.

Check the pH. I heard that mushroom compost has a high ( alkaline) pH.

Also mushroom compost apparently can have high salt levels...and is recommended for use in moderation only.

I have noticed that fresh MC does tend to kill or stunt plants....after it's weathered a year, it's great stuff.

Sorry Dave, you seem taken aback. This is my first time planting in large beds and you can say I have no idea what I'm doing. What I don't understand is why I'd have to wait numerous seasons to use the beds. If I were to initially mix the compost with soul would they have been ready to plant right away?

While those raised beds do look great, as Dave strongly pointed out, you've created a very un-natural place for your plants to live.
I think the best option now is to carefully remove the plants from the beds, then remove half of the compost. Using a digging fork or shovel, dig deeply to mix the soil under the beds with the compost. Then after mixing, take a soil test and send it into a nearby lab (or try the link below). Adjust the soil ph with lime and add other necessary nutrients the test results suggest, then replant.
Not so easy, but unfortunately you missed some important steps the first time around. Don't worry though, everyone does!
-Mark

Here is a link that might be useful: soil test

No, sorry, not "taken aback" and any frustration that came across isn't directed at you. I just get so frustrated at the crazy sources out there that keep giving out such faulty info to new gardeners. Stuff like - "use straight mushroom compost for your garden and it will be great" - when they know it won't be without lots of other stuff/work.

They never bother to explain that compost has to be converted to nutrients usable by the plants and that conversion requires active, diverse soil bacteria and by soil-dwelling residents - worms, beneficial nematodes, grubs, pill bugs, etc.

They eat and digest the compost and poop out nutrients the plants can use and absorb with water. They are all lumped together under the label "soil food web". Unless you directly add them (which many do) and add dirt to the compost (which already contains them), it takes seasons of time for them to move into the beds.

Add to that the issues others have mentioned with mushroom compost (as opposed to manured compost) of low nutrient levels, high salts, and alkaline pH. All of those issues also require time to resolve themselves. The soil food web needs time to grow, the salts need time and rain to leach out, the compost needs time to decompose and neutralize the pH down to neutral, and the low nutrient levels need to be supplemented with additional sources.

You don't have to wait numerous seasons to use the beds. They can be used but you do have to supplement the nutrients and the soil web until the beds are well established and that takes seasons. You will also have to add fresh compost 2x a year as the beds shrink (decompose).

So mix in as much dirt as possible, research adding Mycorrhizae (bio-organics), look into nutritional supplements (both organic and synthetic), and accept very limited results this year. Over the winter the bed will be improving (any new beds need to be fall constructed) and salt leaching out so next year will be better if you keep up the supplements. By the 3rd year you'll see substantial improvement and by the 4th you'll have great beds that only need minimal side dressings with fresh compost to sustain good growth.

Hope this helps.

Dave