For example, if 300 pounds of superphosphate or mixed fertilizer are recommended per acre, you will find by turning to table 1 that this means 7 pounds per thousand square feet, or 11 ounces (1 ¹/₂ cups) per hundred square feet. Then, turning to table 2, you will find that 1 ¹/₂ cups per hundred square feet means ¹/₂ cup for each 10-foot row if the rows are 3 feet apart, or 6 tablespoonfuls for each plant if the plants are spaced 5 x 5 feet. A large number of such conversions are given for various kinds of fertilizer material and to fit various needs.

Table 3 shows volume measures (in cups, tablespoons, etc.) of chemicals to be added to each bushel of plant material in making a compost pile, based on directions in weight per ton of plant material.

The rates to be selected for the various materials depend on the soil and its previous treatments and the requirements of the plants. Certain materials- ground limestone, where needed, and superphosphate- are used in relatively large quantity; borax and others, sparingly. For example, small-rate supplemental additions of ammonium nitrate can be given tomatoes with advantage, whereas very much would injure the plants.

The values tabulated are near enough for all practical purposes, though they are only approximate, since the weight of a given volume of a material will vary with its moisture content and texture. In making the calculations it was assumed that the materials will be scooped up into the container without any packing, and that they will be loose and not lumpy. The standard pint, cup, tablespoon (tbs.), and teaspoon (tsp.) are used for liquid measure. Other than for liquids, level-full measures are understood, with two exceptions: Slightly heaped (indicated by h); and a trifle less than full (by s).

For materials not included in the lists, one may weigh carefully a full pint and determine approximately the group to which it belongs.

It will be useful to remember (1) that a pint of water weighs just a little more than a pound (actually, 1.046 pounds); (2) that an acre is equivalent to 43,560 square feet (a plot about 209 feet square); and (3) that a pint is equivalent to 2 cups, or 32 tablespoons, or 96 teaspoons.       Table 1. Weights of various fertilizing materials per acre, per 1,000 square feet, and per 100 square feet and the approximate equivalent-volume measures for 100 square feet, grouped according to weight in comparison with that of water.  

In making compost heaps with oak leaves as the chief source of organic matter, together with some grass and other plant materials, chemical aids are needed to disintegrate the more durable parts. If, however, a considerable quantity of lawn clippings and other plant tissue is used, the weight or measure of the chemicals named in table 3 may be somewhat reduced. When manure constitutes half the organic matter, no nitrogen is required-only the phosphate and limestone are needed. No limestone should be used if materials are to be applied to blueberries, azaleas, or similar acid-loving plants.

The compost may be prepared in layers, a layer of garden soil or dark-colored surface soil out of the woods about ½ to 2 inches thick, alternating with each 6- or 12-inch layer of fresh organic matter. When finished, the whole should be covered with 2 to 4 inches of soil.       Table 3. Volume measures of chemicals to be added separately to each bushel of plant material in making a compost pile, at specified rates per ton of material.  

Issued by Washington State University Cooperative Extension, and the U.S. Department of Agriculture. Reprinted from USDA Leaflet No. 307. Published May 1982.