After adding a large quantity of compost and fertilizer to establish a new garden, the living system you have created must be maintained by periodically feeding it more organic matter and minerals. Consider that every pound of spinach leaves, tomatoes, or zucchini is made mostly of material taken from the soil. In order for the soil to maintain its level of fertility that pound of material has to be replaced.
In order to continue building soil fertility, it is best to add at least a 3-inch depth of compost across the surface of your garden each growing season for the first several years. This can be done in one big application at the beginning of the season or you could split it into several applications. When growing in raised beds, simply keep the beds topped up by adding compost whenever there is room.
For a small garden, the best way to incorporate this compost is to turn over the top layer of your garden soil with a shovel and mix the compost and the soil together as much as you can. This is much the same process as making a new garden, but the soil will be much easier to work than it was the first time around. It is also not necessary to incorporate the compost so deeply into the soil. Once the garden has been established, organic matter and nutrients from the top layer will naturally work their way down into the soil. For a small garden, you can even do this light cultivating with a trowel or hori-hori.
Some growers, like Urban Farmer Curtis Stone, even operate very large market gardens using a “no till” method. This method still involves mixing compost, worm castings, or other amendments and fertilizers into the very top tow or three inches of soil, but nature takes over from there, allowing water, earth worms, and other natural mechanisms to carry nutrients down into the soil without disturbing the natural soil environment. This is a great option for a home gardener as well, especially if digging with a shovel or trowel isn’t your idea of a fun Saturday afternoon. We still recommend doing as much digging as you can to start a new garden, though.
To determine how much compost you need for a 3″ layer in your garden:
- Divide the total area (in square feet) by 4 to get the total amount of compost IN CUBIC FEET.
- Divide this number by 27 to get the same amount IN CUBIC YARDS.
Compost is usually sold in bags (2 or 3 cubic feet) or in cubic yards if you are buying in bulk.