Fertilizers and Humus

Plant foods or prepared chemical fertilizer come in salt form, readily available, easily soluble in water. They are balanced in various percentages to contain the elements necessary for the plant. For instance, on a bag of commercial plant food with the marking 10-6-4, the first number (10) denotes the percentage of nitrogen; the second (6) is the percentage of available phosphorus; and the third (4) is the percentage of water-soluble potassium (also known as potash). The remaining 80% of the fertilizer mixture may contain trace elements and filler material to keep the plant food in good working condition.

There are different fertilizers offered for various types of plants. For instance, a lawn fertilizer high in nitrogen is not as suitable for dahlias and other bulbs or plants with a lot of mass in the root system, since roots are formed from phosphates and potassium.

Use chemical fertilizers sparingly. Over-stimulation is weakening to any plant. Young plants, especially, must be fertilized with care as the material is likely to be wasted if more is given than can be taken up by plants.

Chemical elements are held in solution for a longer time when water-holding, and soil-conditioning humus has been added to the soil. Also the humus itself, having a quantity of slowly available chemical elements, helps to provide a balanced ration for the plant.

Humus From the Garden Center

First, let's define humus (not to be confused with hummus, the creamy dip made from chick peas, tahini, and lemon juice). In a very general sense it's the partially decomposed organic material in soil. Think of what happens to fallen leaves through the winter and spring. Microorganisms continually break down the material of the leaves into smaller and smaller bits. Humus in the soil can have a significant impact on water and nutrient retention, so it's an important element to consider in managing soils.

A good, almost universally available source of humus for small gardens is peat moss, which is slightly decomposed sphagnum moss. It is usually sold in bales and is low in nitrogen and highly acid. In appearance, it is brown, fibrous, crumbly, and light. It is especially suitable for acid-loving plants such as rhododendron and azaleas, but is good for other plants as well. Now days peat moss should be a last choice to enrich a garden as peat bogs grow back at a very slow rate.

Sedge peat is a marsh peat, made by the laying down of thousands of generations of grasses, sedges, and reeds under water. The product known as "Michigan peat" is a sedge peat and is usually very dark in color.

Other sources of humus are leaf mold (decomposed leaves) such as accumulates on the floor of a forest or wood lot; seaweeds, spent hops, decomposed sawdust, decomposed wood ships, ground sugar cane residue (bagasse), ground corn cobs, decomposed animal manures, and compost. The compost heap should be a feature of every garden. It is made of layers of vegetable refuse from garden and kitchen, alternating with layers of soil, old sods and manure, if obtainable.

Compost piles do not have to be complicated, nor must they be built in bins. In fact, it is better for decomposition if the pile is started at ground level and gradually raised as debris is collected. It should be kept flat, or slightly hollow on top, rather than rounded, so that moisture can collect in the center. Keeping the pile moist enough is essential to proper decomposition.

Animal manures make fine humus and fertilizers when properly decayed. Before they can be safely incorporated in the soil around a plant, they should be rotted, usually for a year, by composting.

In the last few years (since approximately 2008) Mother Earth News has been reporting on "killer compost" - mostly composted cow manure that contains residues of the persistent herbicide Milestone(tm). This herbicide is mostly sprayed in pastures to keep down broad-leaf "weeds". The cows ingest this herbicide on the plants they graze, it passes through them, and ends up in the composted manure for several years. If this compost is applied to gardens it will severely inhibit the growth of just about everything in your garden. Make sure the compost you apply to your garden is free of this herbicide or you're garden will be a dead zone for several years until the chemical breaks down. The active ingredient in Milestone is aminopyralid. It's also sold under the names listed at right.

Cow manure is rich in plant-food elements. Being wet and heavy, it is therefore a first-class manure for light to medium loams. Horse manure is a dry manure which warms up the land and is excellent for heavy, cold, clay-like soils; there is, as a rule, a fairly large percentage of litter in it, and this also adds to its warming effects. It is best from stables where straw or peat is used for bedding. If wood shavings have been used, the manure is of less value in the garden, for the shavings, when incorporated with the soil, rot very slowly. Such manure is, however, good for liquid manure or surface mulching.

Pig manure is not unlike cow manure generally - a rich, strong manure, smelly to work with unless well rotted. It is most useful on light land. Sheep, poultry, and pigeon manures, when free of litter, are more like a bulky guano than manure. They should be stored under cover and kept dry, and, if to be stored for any length of time, they will benefit considerably if each day's accumulation is very slightly dusted with rock phosphate. Use 1/2 to 3/4 pound per square yard, and hoe it in lightly, applying at cropping time or as a top-dressing to plants. When mixed with an equal quantity of fine soil it forms a good top-dressing.

Decayed farmyard manure should be dug into the ground in the spring. Fresh manure should only go on in the autumn. Spread it in 2" to 3" layers.

Other Soil Additives

Green manures, or cover crops, are quick growing plants that are sown for the sole purpose of turning into the soil while they're lush and at the peak of green growth. Italian rye grass, buckwheat, vetch, rye, soybeans, rape, and turnips make excellent green manure. Instead of cutting and composting this plant material in a compost pile it's tilled directly into the soil. This could be considered a kind of "direct composting".

The various bone meals are fertilizers for general use and have more lasting effect than many; the finer they are ground, the more quickly they act. They are high in phosphate and contain some nitrogen. Bone meal is called the "safe" fertilizer because it does not burn and can be applied to almost any plant without injuring it. Use it with bulbs, dahlias, roses.

Wood ashes, the ashes left after vegetable matter of any kind is burned, help to loosen and "sweeten" soil (bring the pH to the alkaline side), and the fine dust has a percentage of potassium in a most useful form. Use at cropping time or later, as a top-dressing around established plantings and on lawns.

Dried blood or blood meal, when available, is fine, especially for rhododendrons and water plants. It contains nitrogen. Use at the rate of 2 to 3 ounces per square yard. It is also a rabbit repellant.

Cottonseed meal is slow to decompose and is excellent for acid-loving plants.

Milorganite is a good all-purpose fertilizer made from sewage sludge.

Soil Preparation

Careful tilling of the soil is one of the first essentials in making a flower bed or, in fact, in any kind of gardening.

Turning the ground, or ordinary digging, is done with a spade, garden fork or mechanical tiller. Ground is turned one spit deep (a spit means the depth of soil that can be conveniently moved in one spadeful). In this operation, any soil conditioner such as humus or fertilizer should be first spread over the ground and then worked through the soil. If the ground is to lie through cold weather, the clods should not be broken up but left rough. All roots, woody weeds and large stones should be gathered and removed.

Double digging is a lot more trouble, but is well worth the effort for long-term results. A line is stretched 2 feet from the end across the plot to be dug. A trench one spit deep and 2 feet wide is then dug, the soil being wheeled to the opposite end of the area and piled near the last strip to be dug. On the bottom of the open trench may be thrown a quantity of sand, stones or similar rubbish, together with leaves, straw, manure, or other conditioning material. This is spaded into the second spit of ground or subsoil. If the subsoil is sandy, use more humus, leaf mold or peat moss. The garden line is then moved 2 feet more, and the topsoil from this strip, mixed with suitable conditioning materials as in simple digging, is used to fill the first trench. The process is then repeated until the soil first removed is used to fill the last trench.

Mulching is also an essential aspect of soil management for the home gardener. Most mulching materials not only help prevent weed growth and retain moisture, but also gradually decompose and end by contributing humus to the soil.

Resources

Info on aminopyralid at Wikipedia.

Pictures of what aminopyralid does to plants from Washington State.

Mother Earth News' report on Killer Compost.