Planning on-site composting for spring planting

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Q. After filling newly created garden beds with fresh soil mix, we’ve been left with a large heap of the old, removed soil. It’s like dust. Moving the old soil off the property is impossible for us. Is there any way of using it to create another new bed?

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A. First, assess the site where the old soil has been placed. Most plants, including vegetables, need full or close to full sun.

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If the soil has been placed in a suitable location for your purposes, you could create a raised “lasagna” type bed using it as the base. Adding layers of organic materials to the old soil will create an on-site composting mass for planting on in the spring.

Early autumn, while the weather remains moderate, is the ideal time to begin the project. First, shape the mass into the size and shape you want. Next, begin adding layers of materials. This need not be an exact process, but aim for roughly twice as much “brown” matter as green materials. The more chopped-up and smaller the pieces, the faster will be decomposition.

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Among high-carbon (brown) materials to use are shredded dry leaves, strips of newspaper, straw, coconut fibre, and aged sawdust. Commonly used high-nitrogen (green) materials are grass clippings, compost, aged manure, young weeds and soft garden trimmings.

While the weather remains fair, the layered mass will shrink down with the composting process. Until the fall rains begin, make sure to keep the mass just modestly moist, to assist decomposition. With the rains, as long as the materials are appropriately moist, arrange a loose cover over the area to keep it from becoming sodden and leaching nutrients.

In the spring, cover the surface with 10 to 15 cm of finished compost, good top soil or a planting mix before planting. I use the same spring covering to transform two or three of my compost heaps into planting sites for squash.

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