A Recipe for Soil Amending

One of the biggest issues with plant fertility in modern landscapes is soil quality. Houses are built on specific blends of soil fill materials that deliberately contain low concentrations of organic matter. This prevents structures from sinking due to soil decomposition and compression. What’s good for engineering, however, is terrible for plants and the ecosystems they support. Without carbon, this type of soil cannot hold onto plant nutrients or moisture, is unable to support soil-borne organisms and has issues with drainage and oxygen content. These conditions not only limit plant establishment and overall health; they also dramatically increase the rate of plant disease and mortality. The good news is that small additions of supplemental carbon can have big impacts on soil health and successive additions can eventually create a nearly self-sustaining soil ecosystem under appropriate management.

EQUIPMENT AND MATERIALS

Stiff garden rake or small garden tiller
Organic weed spray or propane weed torch (optional)
5-6 bags mushroom compost (5-6 cu ft) per 100 sq ft
5-6 bags pine fine mulch (10-12 cu ft) per 100 sq ft
Small sized mulch of choice to cover finished area

INSTRUCTIONS

Step 1
Remove all turf and weeds. This is ideally done by hand; however large areas can be cleared with organic weed sprays or propane torch. Materials like leaf litter, old mulch and other natural organic matter contain native microbes specific to the ecosystem and should be left in place.

Step 2
Using a stiff rake, loosen the top few inches of existing soil. For heavily compacted soils use a small tiller (I use a 4-inch tiller attachment on our trimmer motor head). Loosening this layer helps the amendments penetrate the soil spectrum without dramatically altering the existing layers.

Step 3
To add soil amendments, start by covering the area with about an inch-deep layer of organic mushroom compost or other high quality humic material. On top of this layer spread approximately two inches of pine fine mulch. Pine fine is the smallest grade of pine mulch and can be found at most independent garden centers. When combined with composts rich with both highly available carbon and macronutrients, the resulting mixture provides a long-lasting supply of available carbon.

Step 4
Lightly rake the area to mix the two layers with the existing soil and add your favorite plants followed by a layer of small sized mulch such as pine bark mini nuggets or pine straw. In successive seasons you can simply add a one-inch layer of organic compost over the existing mulch. Use a hose to wash the compost through the mulch layer and freshen with new mulch where needed. This layering helps support a diverse ecosystem of microbes and invertebrates.