EyeDelight said: ...
This one planter was a very low spot that collected water, so being of small means I used what I had available. Which was a little sand, a little black dirt, twigs and leaves at the bottom ( to make a base of sorts ) then sawdust mixed with a large bag of miracle grow garden soil. There's a whole layer of sawdust between the twigs/leaves and the sawdust/garden soil mix on top. I needed volume :-\
...
Can I remedy this with raking in a bag of compost on the small bed ... and maybe sprinkle some blood meal ...? ... Should I use something quick release or slow release or both? I read fish meal is immediate and blood meal is slow release?
EyeDelight, I realize this has no value at all for you, a year later, but I just saw this. I've read that it's tough to overcome that kind of sawdust / nitrogen-deficit.
I added too much wood to a bed once and tilled it in. It's a slight exaggeration to say that "nothing would grow there for a year", but almost. And I tried to add lots of N after I, like you, read about what I had just done. Then I dug back to the woody layer and had the ugliest mess of white powdery nastiness I never expected to see in soil!
Force-feeding N for a year DID let the bed recover, but I was never able to get ahead of the decomposing sawdust.
I think the things growing in a sawdust-rich mix would have needed frequent, fairly heavy additions of soluble nitrogen to grow at all well. (Or a lot of other fast-release sources).
I guess you could use either soluble chemical fertilizers, perhaps even daily, or so much slower-release sources like compost that they release enough N every DAY that the root hairs get at least a little before the fungi get it all.
That sawdust and the fungus population explosion it caused will suck up every ion or molecule of nitrogen almost as fast as you add it. They're just that good and that omnipresent in soil.
Being single-celled or in very thin mycelia, fungi have much faster and closer access to nutrients than root hairs.
The fungi would be like 100,000 hungry rats packed shoulder to shoulder on a football field. The closest root hair would be like one hungry cow somewhere on that football field.
Now you scatter a handful of grain over that football field.
The rats get most it ALL in the first few seconds.
The cow is lucky to get ANY.
Similarly, any given nitrate ion is almost certain to encounter a fungal mycelium before meeting a root hair.