raised beds — follow up

(Question)

Thank you for your reply to my earlier query on raised beds. It was very helpful. (Posted Oct 8)

I have one follow up question. I am going to try to order a dump of organic soil to fill the beds. What kind of soil should I be looking for?

And should it be ‘sterilized’? I read somewhere that if it isn’t it can bring with it a lot of weeds?

And do you have any suggestions about where I might buy such soil in Toronto?

Thanks

(Answer)

The soil provides a natural environment for efficient plant growth. It does this by providing a physical, porous medium that anchors and supports plants, protects the roots from light traffic, and allows gaseous exchange with roots.  Soil retains water that can be utilized by plants, it retains and supplies nutrients and provides a habitat for microorganisms that promote plant growth and decompose plant residues.

Soil consists of air spaces, organic matter, and mostly, mineral particles. Soil minerals come in three types: sand, silt, and clay. Sand is the largest particle in most garden soils. Silt particles are smaller than fine sand and larger than clay. Clay is the smallest particle. The relative proportions of these particles in the soil determine its texture.

Good soil is the backbone of a good garden. Well-prepared soil is fluffy and loose, so water, air, and nutrients can filter down easily, and roots have room to stretch. Soil is 45 percent mineral particles and 50 percent space between particles, space that’s filled with air and water.

Soil scientists consider the ideal garden soil to be 20 percent clay, 40 percent silt, and 40 percent sand. The sand encourages good drainage, while the clay and silt help to hold nutrients and some moisture for good root growth.

Generally, sterilized soil is used for indoor plants, starting plants from seed or when transplanting seedlings, it is not recommended for vegetable gardens. If weed and pests become a problem soil sterilization is a nonpesticidal method to control soil borne pests by placing plastic sheets on moist soil during high temperature days. Here is a link with more information on soil sterilization: https://vric.ucdavis.edu/pdf/soil_solarization.pdf

The soil will settle over time, so plan on regular additions of organic matter to maintain soil depth in the bed. Using organic mulch year round will also help feed and replenish the soil on an ongoing basis. Another option is to cover and protect the soil surface by growing a cover crop every winter, then turn that under each spring as a source of organic matter.

A reputable  nursery should be able to recommend a source.

Here is a link to our Gardening Guide: Improving your Soil orgainically for Succesful Gardening.