soil improvement raised beds. - Ask Extension
Along the back of my apartment building there are several large raised beds against a retaining wall. Only about 1/2 day of sun, but plenty could gro...
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soil improvement raised beds. #570539
Asked June 15, 2019, 8:58 AM EDT
Along the back of my apartment building there are several large raised beds against a retaining wall. Only about 1/2 day of sun, but plenty could grow there. BUT soil in the beds is very poor with asphalt, rock, interspersed, and in some beds is 6-7 inches below the lip of the bed. Right now the beds are growing a very healthy crop of weeds, so there must be some nutrients. The landlord said he would pay for adding and improving soil, but after offering to organize this project, I realized that I don't actually know what to add to the beds. A lot of soil mixes say "mix with native soil" but this "native soil" is such poor quality that I am reluctant to do that. That much potting soil would be very expensive. The size of the beds varies, between about 11 and 14 sq. feet. Not sure how to proceed--feel like maybe I am in over my head here.
Hennepin County Minnesota
Expert Response
Eliminate grass or weeds that might be in the planned garden area. A raised bed does not have to be very deep. Eight to 12 inches is usually adequate. The soil mixes should be incorporated into the screened existing soil. Make a soil sifter to screen the rocks out of the existing soil. T
This is how to build a gravel sifter.
Place the soil sifter over a wheel barrel. Sift the existing soil into the wheel barrel. https://extension.umn.edu/planting-and-growing-guides/raised-bed-gardens
Some business sell soil mixes for raised beds. In general most soil mixes contain some sifted soil, compost, and peat moss. Most landscape companies have their own mixes and
percentages of products that they use. In general, common mixtures are
three-fourths topsoil and one-fourth compost, two-thirds topsoil and
one-third compost, or half topsoil and half compost. The higher the
organic material content the sooner you will need to add more
soil/compost to the bed, because the organic matter breaks down over
time.
