Refilling SFG

katjohn83 3/2/2021, 2:08 pm

A question for the experts. My SFG beds are 3-4" lower than when i planted last year so I need to refill them. As I understand I should just compost.

1. That's a lot of compost. I have (3) 4 x 8 (3) 4x4 and (1) 4 x 18. If 4 " is what I need then that is 71 cubic feet of compost or just over 2.5 yards.

2. This is supposed to be no till gardening, so If I just put compost on top and not mix it in with the rest, or tillling it in what is left, then I am planting in just compost with no peat and no vermiculite for water retention.

So with this information and my thoughts,

1. Do I just add 71 cubic feet of compost or 71 cubic feet of Mels mix?
2. Do I mix it with the rest?
3. Is this much reduction normal?

I have been doing SFG a few years but for some reason this much reduction has been extreme and it got me thinking.

OhioGardener 3/2/2021, 4:41 pm

My beds shrink 2" to 3" every year from the compost being digested by the microbes and consumed by the plants. Most years I just add enough home made compost to bring them back to the top, but every 4 or 5 years I will mix vermiculite and coir with the compost before adding it to the beds.

I never dig the new compost into the beds, but just leave it on top. The plants have always done well with that.

Mikesgardn 3/2/2021, 5:35 pm

Good questions.
My boxes are 9 years old now, and I just add compost. But I do mix it in a bit so that I have some vermiculite near the surface.
I usually add about 2 cubic feet of compost per 4x4 box (1.5" depth).
But I always add some compost when I re-plant a square. Maybe you have not been doing that?

katjohn83 3/3/2021, 11:03 am

Mikesgardn wrote:Good questions.
My boxes are 9 years old now, and I just add compost. But I do mix it in a bit so that I have some vermiculite near the surface.
I usually add about 2 cubic feet of compost per 4x4 box (1.5" depth).
But I always add some compost when I re-plant a square. Maybe you have not been doing that?

If you mean during the growing season, I don't do any succession planting, so I am getting ready to re-plant all of my squares at once. LOL It just seems like a lot of compost especially trying to find five different kinds (and expensive) And a lot of inches without any vermiculite or coir/peat.

**sanderson** 3/8/2021, 4:32 am

Katjohn, I think a 3" drop is unusual for a 6-7" bed of Mel's Mix. I think 2 things happen to the MM after a few years. One, the peat moss starts to decompose after a few years in the aerobic environment of Mel's Mix. Second, the coarse vermiculite gets broken into smaller pieces which makes it compact. Just my theory.

A couple years ago, I added another inch of coarse vermiculite to the beds when I amended the beds with compost. I mixed in the ingredients with a hand trowel and it made the MM lighter.

On the subject of mixing in or just applying compost to the top, it's a personal thing. OhioGardener justs tops off his beds. I crudely mix it in. With veggies, bacterial loads are more predominant than fungi, so mixing in won't hurt it. Trees and shrubs benefit from more fungi than bacterial loads.

**Scorpio Rising** 3/9/2021, 6:08 am

I lose a bit of volume every year. I attribute this to the harvest/actual removal of MM, also root balls grab some too.

Every couple years I refresh the vermiculite, and compost.

I do think that’s quite a bit of loss. I do crudely mix a scoop of compost in between crops.

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