Living SoilDo you feed your plants every couple of weeks and still see a garden that never quite takes off? Have you ever wondered whether you are feeding the wrong thing?
Most feeding advice is about the plant: a bottle, a schedule, a number on a label. Living soil works the other way round. You feed the soil from the top, and the life in the soil does the delivering.
Why feeding the soil comes first
The nutrients in compost and other organic matter are not sitting there ready to use. Soil life slowly breaks organic matter down, and that decomposition is what makes the nutrients available to plants. The same organisms need a steady supply of their own: soil microbes must have a constant supply of organic matter, or their numbers decline.
Earthworms are part of the delivery system. They pull organic matter down below the surface, where other decomposers can reach it, and bring deeper soil up toward the top.
The big idea: put the food on top and let the soil life carry it down. The worms do the digging for you, without breaking up the soil.
What top dressing is
Top dressing means spreading compost on the soil surface instead of digging it in. Extension research calls it the simplest way to add compost to the garden. It is also the method that suits living soil best, because it leaves the structure of the soil alone.
The same guidance says there is no need to dig to mix compost in deeper. The bacteria, earthworms, fungi and other organisms in your soil bring nutrients and organic matter down through the layers and improve the soil structure as they go, rather than damaging it the way double digging or tilling does.
How to top dress with compost
First, rake away any mulch over the root zone, so the compost sits in direct contact with the soil. Then spread the compost over the root zone.
Keep compost away from stalks and stems. Piling it up around the base of a plant holds in moisture, and that invites pests and diseases.
For depth, one extension guide for existing beds says to apply a layer a quarter inch to 1 inch deep to the bed surface each year. It puts a ceiling on it for vegetables: a 1 cubic foot bag covers 12 square feet to a depth of 1 inch, and that is the most to add each year for existing vegetable areas.
Top dressing works on lawns too. There it means adding compost over the top of an existing lawn, which has its own guide: lawn topdressing.
Here is where the sources differ
Not every extension guide agrees that surface compost should stay on the surface. One says plainly that there is no need to dig compost in. Another, written for existing beds, says to incorporate the materials into the top 8 to 12 inches with a digging fork, spade or rototiller.
Both are published advice. No extension page found compares top dressing with digging in by measured yield in a home garden, so the research has no proven winner. If you are building living soil, the reasoning above is why the surface method fits: it feeds the soil life without breaking up the structure that life has built.
What side dressing is, and which crops want it
Side dressing means feeding alongside a row of crops or around the base of a single plant. Some crops are heavy feeders: tomatoes, peppers, corn, squash, melons and cucumbers are the usual examples.
Compost can be used as a side dressing too. One extension source says a handful per plant is generally enough, and suggests placing it before a rain so the nutrients make their way to the roots. Manure is not recommended unless it is completely composted.
For a nitrogen side dressing, blood meal and cottonseed meal are named among the organic slow release choices. Organic fertilizers such as blood meal and alfalfa pellets work well, though they take longer to show results.
Never use weed and feed products on vegetables. They contain weed killers that will kill vegetable plants.
When and where to side dress
Timing matters. A burst of nitrogen can push a plant into leaves rather than the vegetables you want. One extension source says to wait until tomatoes, peppers and squash are flowering, and to make another application about four weeks later. Broccoli, cabbage and their relatives can be fed from about four weeks after planting, then every two to three weeks. Another source says side dressing with nitrogen usually helps many garden crops about four to six weeks after planting.
Placement is about keeping fertilizer off the stem. If the bed is mulched, pull the mulch back where needed. One source says to apply fertilizer four to six inches from the base of the plant. Another says at least six inches from the main stem, to avoid burning. Six inches away satisfies both.
Why organic feeding is slow, and why that is fine
Organic slow release fertilizers release their nutrients by bacterial action. Even materials with a rapid release need at least a few days or weeks under ideal conditions before plants can take them up, and release is faster when the soil is warm. Slow materials can provide nutrients over several years from one application, but they will not fix a problem in the short term.
Two more findings explain why a well composted bed can still look hungry in spring. Organic matter usually holds little available nitrogen early in the season, and the microorganisms breaking organic matter down need nitrogen themselves, which can leave less for your plants. Compost is not considered an effective substitute for fertilizer, because its nutrient levels are low and its release is slow. Compost builds the soil. A hungry crop may still need a side dressing.
Where to start
This season, rake back the mulch on one bed, top dress with a thin layer of compost, and keep it off the stems. When your tomatoes or peppers flower, side dress beside the row and keep it away from the stems. For the bigger picture, read how to make living soil and how to use compost in beds and pots, or look up the guide for tomatoes.