In the past, as I was working in the vegetable garden, I incorporated into the soil some of the organic amendments discussed previously. After many years of cultivation, the soil is of very good quality, but benefits from fresh amendments to replace what has decomposed during the past year. Every year, quantity and quality of amendments is determined by the condition of the soil. Initially, amendments were added very generously to the soil to compensate for many years of being used as a parking lot by cars which leaked automotive fluids profusely. Now, the soil is so rich, it would likely be very productive for many years without additional amendments.

Although organic soil amendments are used in large quantities, there are not specific directions for proper application. Each situation has specific requirements. Some horticulturists would recommend adding as much as an equal volume of amendments for each equal volume of soil if the soil is of poor quality. In my garden, however, I don’t think I have ever added more than one part amendments to three parts soil, even when the soil was of very poor quality.

If too much amendments are added at one time, the soil slowly collapses (sinks) as the amendments decompose. Of course, more amendments may be added over the years to compensate for decomposition. Lawn areas are usually not amended as deeply, so soil collapse may not be noticed. If it becomes a problem, shallow depressions in lawns are easily filled.

Addition of smaller but still generous quantities of amendments may not perfect the soil in one year. However, similar quantities may be added for several years until only minor amounts are required. Annual soil conditioning is very practical in areas of the garden which are cultivated regularly; such as beds of annual flowers or vegetable gardens.

Amendments should be incorporated into the soil very thoroughly and clumps or clods of dense soil should be crushed. The depth of incorporation is determined by what is to be grown. For example, petunias grow well in soil which has only been amended in the top few inches. However, larger types of dahlias prefer a deeper volume of amended soil. Amendment to about eighteen inches is ideal for most annual and herbaceous plants.

Areas which are permanently landscaped can not be conditioned as easily. Woody trees, shrubs and vines may be damaged by soil disturbances. For such application, soil amendments are used only once during installation to help roots of new plants become established. Because most roots are dispersed in the top eighteen inches of soil, amendments need not be added below newly installed plants. Such superfluous amendments will only cause problems as they decompose, causing the maturing plant to sink into the soil.

Although generous quantities of amendments are recommended for new installation, backfill soil (existing soil after it is mixed with amendment) should not be so different from surrounding soil that root dispersion is inhibited. If backfill soil is too rich but surrounding soil is too dense, most root growth will be limited to the volume of soil which was amended; as if growing in rich soil contained in a “clay” pot.