SOIL AMENDMENTS FOR CUMBERLAND COUNTY

• Peat Moss: If it dries, it repels water; if wet, it retains water. Clay already retains water for us. An added reason for not using peat moss is that peat is not a readily renewable resource. Bogs can be revegetated but it takes nature almost 5000 years to return the bog to its original state. Peat moss is acceptable for sandy soils and for house plants.

• Sand: You need at least 70% sand to 30% clay, and it is still not a good idea. The tiny clay particles fill in the spaces between the larger sand particles, making a readily compactable material. Add a bit of water and make your own parking lot.

• Anything freshly shredded: Until thoroughly decomposed, everything will deplete the nitrogen supply, to the detriment of plants.

Recommended materials:

• Pine Bark is probably the most practical material that is readily available for homeowners. Pine bark is a native material. An ideal size grind of pine bark (@ 1/4" to 1/2") is now available at most garden supply places as "Pine Bark Soil Conditioner." There are other products on the market called "soil conditioner" but many are too fine to provide the needed pore space. The most desirable size is about that of a flattened pea. Truckloads are available also; look in yellow pages under "Soils."

• Leaf Mold, aged vs composted leaf mold: The city's leaf pile is simply "aged" whereas compost has oxygen and nitrogen added. The Carbon/Nitrogen ratio of dry leaves is 90:1 (vs the desirable ratio for compost of 30:1), which means the nitrogen will come from the soil unless you add supplementary nitrogen. Freshly ground leaves are not a good soil amendment/conditioner if you want to plant immediately but they are fine if turned into the soil and overwintered with supplementary nitrogen.

• Compost: The perfect soil amendment, non-nitrogen-depleting, nutrient-providing, soil structure-improving, but few homeowners have it in quantities needed to amend a heavy clay soil.

• Humus: Humus is partly- to thoroughly-decomposed vegetable matter. A superb soil amendment but it is usually not available in quantities needed except by truckload.

• Pea Gravel: #78, 3/8" diameter gravel is esthetically horrendous but it does work. It is a permanent soil addition, doesn't break down. Your grandchildren will continue to profit from it, though your tiller won't.

• "Topsoil": "Topsoil" is often an unknown quantity and is offered in many formulations. Often it contains too much sand, and it may contain many weed seeds. Putting down a layer of a different soil on top of clay will encourage root growth in that top layer only. Roots will not penetrate the clay layer, decreasing survival chances of plants when under stress conditions. Use of "topsoil" depends on what is being planted in the area. It is fine for raised beds but for most other uses it should be incorporated into existing soil down to the level of the anticipated root area.

"Maybe" Group: Organic Senior Citizens only

• Sawdust: If very old and supplemented with nitrogen, sawdust is a good soil amendment. It has a 400:1 CARBON/NITROGEN ratio and will harm plants without supplementary nitrogen.

• Hardwood chips: May raise soil pH undesirably, depending on type and amount used. Requires nitrogen supplement and regular pH checks if used. They break down faster than pine chips. Must be aged before use.

• Wood chips from tree-cutting crews: Must be aged one to several years, depending on content of load. View them as having fairly distant future use only: composition is usually unknown, they often have 1-3' shreds or pieces of logs, and the CARBON/NITROGEN ratio can be 800:1, meaning a very high nitrogen supplement is essential.

• Manure well aged manure is an excellent soil amendment material that provides some minor nutrients as well, but its fertilizing capacity is often over-estimated. Most analyze at about 1-1-1. Some examples:

  	N	P	K
  Cow manure, dried	1.3	0.9	0.8
  Chicken manure, fresh	1.1	0.9	0.5
  Horse manure, fresh	0.6	0.3	0.5

RULE OF THUMB

The optimum CARBON/NITROGEN ratio is 30:1 but few of us can achieve this state of perfection. A very rough rule of thumb is: 1-2 cups Nitrogen per bushel of organic matter. Remember that organic matter requires oxygen to decompose (the reason compost piles need to be turned often) so breakdown time will depend on nitrogen supplementation + oxygen availability + temperature.