Thanks for the question.

Quite frankly I can’t provide you a definitive answer to your question. It is puzzling. The best I can do is to make a reasonably educated guess. I think that the peat moss might be causing the hydrophobic nature of your soil. I’m going to assume that you used peat moss you had purchased in a bag. Such peat moss can absorb a tremendous amount of water. After you constructed the mixture you described, it should have been watered in small amounts over a long period of time before using it for planting purposes. This watering should have been over at least an hour period. I’m going to guess that when you started to use this mix for planting purposes, the peat moss had not been sufficiently saturated with water. This peat moss then began to soak up water from the compost, the topsoil, and the garden soil. This led to overall hardening of the soil. I also wonder how well mixed the planting mix was before you put it into your gardens. Hydrophobicity would have been increased if all components were insufficiently blended with one another.

See:

https://ucanr.edu/site/uc-master-gardeners-santa-clara-county/watering-hydrophobic-soil?utm

Please see this from an “Ask a Master Gardener” forum in Colorado:

https://ask.extension.org/kb/faq.php?id=722976&utm

Here’s another site from an “Ask a Master Gardener” forum in Oregon:

https://ask.extension.org/kb/faq.php?id=145504&utm

Assuming I’m correct, here are my suggestions for going forward:

1). In your planted gardens, lightly cultivate the soil surface with a trowel or hoe to break the crusty surface. Hopefully you can do this without greatly disturbing the plants that are there. Try to get down as far as possible into the soil.

2). Then start to water very slowly over all the soil surfaces. Use either a soaker hose or a spray nozzle on your hose. Use a gentle shower setting, not a strong stream. A direct stream of water impacting the soil will only compact things more.

3). Water all garden surfaces, wait ten to fifteen minutes, and then water again. Repeat this three-step process for at least an hour.

4). After completing this watering procedure, wait for about an hour. Then push a trowel down to a depth of two to four inches and examine the soil at this depth. If the soil is damp to the touch the soil should be good to go.

5). If the soil at this depth is dry to the touch, you will need to repeat steps #2, #3, and #4 over and over until water is getting down into the soil for a depth of at least four inches.

Thinking into the future, avoid making a planting mix containing a large amount of peat moss unless it is thoroughly pre-moistened before mixing. Next time first wet the peat moss separately until it feels like a wrung-out sponge. Then mix it with compost and soil.

Good luck. If after a couple of weeks you are still having soil issues, please get back to us and we’ll be glass to reassess the situation.

Thanks for using our forum.

Thanks for the response.  I rather expected what happened.  

1).  Please take a couple of pics of the soil surface and send to me.  That will give me a better sense of what's going on.

2).  When you made up this soil mix, what were the relative amounts of each of the components?  I need to get a sense of how much peat moss we're dealing with.

3).  Where did you get the "city compost"?  If there was a label on the compost bag, please take a pic of it as well and send to me.

4).  When you said "garden soil, was this soil that you took from one of your other gardens?

We'll get to the bottom of this!  I understand your concern.  We'll work together!! 

Thanks for update on your and the soil pictures. It looks like after you wetted the soil, heavy clumping occurred. Sometimes this is seen in soils that have a relatively large amount of organic material. You indicated that you got the compost from a large pile in a parking lot. I wonder if this compost was fully decomposed. Good garden compost is the result of fungal and bacterial decomposition of things such as leaves, plant debris, etc. If the compost that you used had only recently been put onto this lot prior to your picking it up, I rather think that its components might not have been fully degraded. If so, Then instead of creating a crumbly soil, the soil can get dense, muddy, and low in oxygen.

Moving ahead, I suggest:

1). Stop watering. The soil needs to dry out. Rain is forecast for the Metro for the next couple days (5/17-5/19). Let the soil dry for a few days after that is done.

2). Do not add any more compost to the gardens. Likewise, do not add any more Miracle-Gro garden soil. It typically contains organic material as well.

3). When you mention “topsoil”, it is not clear to me where you got this and what it consists of. If you buy a bag with the designation of “topsoil”, look on the product label for words such as “screened topsoil”, “screened loam”, “sandy loam topsoil”, or “mineral topsoil”. This is what you now need to add to your soil to improve its base.

4). Keeping my comments about “topsoil” in mind, obtain some fresh mineral-based topsoil and work into the upper eight inches of so of the existing soil after it has had a chance to dry. Attempt to break up any clumps that may be present.

Don't worry about the pieces of pine mulch.  Pick them out if you want but no harm will be done by their remaining in the woil

You must be getting frustrated by now. That is part and parcel of gardening. Feel free to ask me any additional questions. Good luck.