Hint For Success

Use a garden fork to mix small areas. If the material is relatively fine, a small mechanical cultivator can handle it. For coar.-e, unfinished compost and unchopped hay or straw, use a larger rototiller.

Calculate how much material you will need (see °°9e 96). Unload the material in several equal-size piles spaced evenly over the entire bed. Rake out each pile to an even thickness, taking care to cover any gaps.

^on'» rake the soil smooth until just before planting. neven ^¡1 with large clods resists erosion better. If V'-u re working in fall, cover the soil with at least a thin ,J/s' at organic mulch to protect it until spring.

Mix the material lightly into the top 4 to 6 inches of soil, just enough to keep it from forming a separate layer that could mat down The idea is to put the amendment within reach of earthworms fungi. and bacteria.

Types of Soil Amendments

All of the softer or finer mulch materials also make good soil amendments. Hard materials take too long to break down. Any materials that contribute organic matter provide the following benefits: improved drainage, loosened clay and compacted soj^ improved nutrient and water retention in sandy soils, and supplies of micronutrients as well as traces of major nutrients.

A few materials that contribute organic matter aren't listed here because they're too concentrated. Poultry manure and bat guano should be treated as fertilizers rather than soil amendments, to prevent problems with excess nutrients. The last two materials listed here contribute no organic matter but condition the soil in other ways.

The amounts recommended here are for new gardens and soils low in organic matter. If your organic matter levels are about average, use half as much. Once your soil is really rich and fertile, you can use even less as a maintenance diet. In warm, humid climates, use a bit more than half this amount as a maintenance diet.

If your material is coarse and loose (such as unfinished compost), aim for the deeper end of the thickness range. If it's very fine (such as dehydrated manure), spread it more thinly. Depth isn't as critical for amendments as it is for mulches. (For metric equivalents. see "Useful Conversions" on page 208.)


Compost, homemade or commercial


Amount (or 100 Square Feet

50-100 lbs. (moist), 15 lbs. (dry); about 2-4 in. thick

Leaf mold

Chopped leaves

Fresh sawdust 15 lbs.; 2-3 in. thick

Hay or straw (as weed-free as possible)

Peat moss

Apple or grape 100 lbs.; 2-3 in. thick pomace




Excellent source of organic matter; finished compost can be used anytime; unfinished compost should be turned under in fall or several weeks before you wish to plant.

Excellent source of organic matter; supplies many nutrients so reduce fertilizer applications; well-aged or composted manures can be added anytime, but fresh and dried manures should be turned under in fall or several, weeks before planting; cow and steer manure can contribute to salt buildup, so they're not good for salty soils.

Excellent source of organic matter; can be used anytime.

Excellent source of organic matter; turn under in fall or several weeks before planting; good (low-level) source of many nutrients.

Good source of organic matter; very high in carbon, so compost first or add nitrogen (blood meal or fresh grass clippings) at same time: turn under in fall or a couple of months before planting.

Good source of organic matter; easier to turn under if chopped or after its been used as mulch; turn under in fall or several weeks before planting; high in carbon, so add a little nitrogen to help it break down quickly.

Supplies organic matter; acidifies soil, so use only for acid-loving plants or to help lower soil pH; mix well into soil, as peat moss repels water if left on soil surface; can soak up lots of moisture, so water soil after turning under.

Good (low-level) source of potassium and phosphorus; often free from I< producers; may contain pesticide residues; very moist unless composted first, so heavy and somewhat awkward to handle.

Supplies no organic matter; helps loosen clay soils; improves water and nutrient retention in sandy soils; rich, slow-release source of potassium and micronutrients, so don't add potassium for 3 years after applying; good source of growth-promoting silica.

Supplies no organic matter; corrects soil structure problems caused much magnesium or sodium; may help loosen clay soil; supplies! calcium (without changing pH), so don't use where calcium already high; not good for very acidic soils (those with pH

Using Topdressings

The simplest way to add organic matter is to spread it on top of the soil which is called topdressing. Any of the materials used as amendments ' «ill do. Topdressing works slowly — you have to depend on the soil ' organisms to do the mixing and get the material into the root zone You can speed up the process by using only well-decomposed materials such as fine compost and worm compost. Given time, earthworms and other organisms will do an excellent job of incorporating the material, saving you a lot of effort (yet another reason for maintaining an active community of organisms in your soil!).

Master Gardening Tip

Where to Use Topdressings

This method is particularly suited to established beds of perennial flowers and perennial crops such as asparagus and rhubarb. It also works well for plantings of blueberry bushes and ornamental shrubs whose shallow roots could be damaged by digging. If the plants are deep-rooted, you can scratch the surface soil to heip mix in the topdressing, which will speed its use by plants.

Topdressing is greot for giving annual crops and flowers on extra boost once they've started growing. Spread a well-decomposed form of organic matter in strips along rows, or in a circle around individual plants. (If you're using mulch, pull it out of the way first.) This method of topdressing is usually

1 * - — -1—.'Jr-i^ccinn referred to as sidedressing.

Homegrown Organic Matter

A green manure is a crop grown for the primary purpose of turning it under to supply the soil with organic matter. Some green manures offer additional benefits, such as weed control and disease reduction. Many farmers rely on them because they're cost-effective on a large scale, but backyard gardeners often don't realize how easy they are. You grow your own source of organic matter right where you need it.

Green manures improve soils in several ways. Their roots can reach much farther than any rototiller or plow — and also far enough into the subsoil to scavenge for nutrients. When the plants decompose, these nutrients are returned to the topsoil layer, where even shallow-rooted plants can reach them. As the roots decay, they leave organic matter and fine channels deep in the soil.

Save Money and Effort

If you don't like shoveling amendments or making compost, using green manures may be your method of choice, at least for vegetable and annual beds. They're cheap because you buy only the seeds. Don't look for them in fancy packets at the garden center; buy them by the pound and you'll save money. You don't need any special equipment, either. While a string trimmer is handy for cutting plants into smaller pieces and a rototiller is handy for turning under large areas, you can easily turn under smaller areas with a garden fork. All you need is to set aside some time for growing green manures, either before, after, or in between your other crops.

Why Grow Green Manurts

  • Enhances biologic*! activity in soil.
  • Adds lots of organic matter-«


  • Increases availability of existing nutrients.
  • Keeps nutrients from washing away.
  • Reduces need for nitrogen fertilizers (legume types).
  • Improves soil tilth.
  • Reduces weeds.
  • Reduces pests and diseases when used in crop rotations.

s>* Inexpensive.

Alfalfa roots can easily reach 9 feet deep in good soils, though most reach 5 feet down. Red clover and soybean roots can grow 5 or 6 feet deep, though most go down about 3 feet. Even grains and grasses can grow long roots in good soils, reaching from 2V2 to 5 feet down. The abundant, fine roots of grains and grasses make them good overall structure improvers.

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