Remediating a too-rich garden bed

[Scott_R]

Earlier this year I built two deep (5' W x 10' L x ~2' H) raised beds for vegetables.

I had trouble getting good dirt delivered, the story too long and tangential for the question, so I ended up with bagged dirt from various retailers. Most of the bags were labeled as "raised bed garden soil."

Well after the fact (i.e., after doing my planting) I discovered, that, contrary to the name, it wasn't exactly soil but a soil amendment: small print on the bags said it wasn't for direct planting but to add it to existing soil. D'oh!

So, my results were mixed. I did my best to lower the (very) high organic content by getting basic top soil and mixing it in around the plant roots.

At this point, with the growing season winding down, what can I use to drop my organic content and very high K and P (though, oddly enough, not N) levels? I really should do another test now, but I'm doubt that the inorganic content is appreciably higher even with months of organic breakdown. Even the bagged topsoil I'd used to lower those levels has quite a bit of organic matter in it. What product is there that's basically the same as garden soil minus the organic content?

 

[Chuck]

I have never heard of anyone wanting to lower the organic content of their soil. One CANNOT HAVE TOO MUCH ORGANIC MATTER IN THE SOIL. If I could I would plant in pure compost. The only way you can have damaging amounts of P or K is to use chemical fertilizers or chemical amendments. You may have excess amounts of either but the only thing P will do is restrict uptake of nitrogen and perhaps lower it somewhat. If low on nitrogen just add a nitrogen additive such as bloodmeal or give the product time to adjust. Was this "raised bed soil" labeled organic? If not it had chemical fertilizers added to it and that is the problem you have. But not to worry. During this coming winter the chemicals will leach out and this coming spring all you have to do is fertilize with a good organic fertilizer.

 

[Scott_R]

Thanks for the reply. I'd sent the soil out to a lab recommended by the local university agricultural extension, and they came back with the report below. My organic matter was almost 32%; the analysis guide,

https://blogs.cornell.edu/gblblog/files/2016/07/Veggie-Info-Sheet-2016-1jsq90e.pdf

said that "Sandy soils with an organic matter content of 2-21⁄2% and clayey soils with 3-5% organic matter will perform fine. Organic matter levels twice this amount could lead to nutrient imbalances."

The bagged soil was labeled as organic.

 

[Verdun]

I think the soil will settle over a couple of years....the organic matter will break down.
If mine I would value it.
No way would I try to lower organic matter level. I can understand the recommendation to add nitrogen because the organic matter will be breaking down thus using nitrogen.
For me I would not overthink this.......I would be inclined to use a weak liquid feed in the growing season

 

[roadrunner]

I wouldn't worry about the soil's nutrient content, but if you were to fix it, the only way I see is to remove a portion and replace with native soil in your area to "dilute" it, but I wouldn't bother.

I'd just recommend growing some N2-fixing plants over the winter, to increase the nitrogen.

 

[headfullofbees]

That is ideal for onions, add a little (ureic) nitrogen for potatoes. Grow onions & potatoes first year, and it won't be far from ideal balance.