The Elements of Agriculture. George Edwin Waring

that the presence of certain ingredients is necessary to fertility. This may be better explained by the assistance of the following table:

      What can you say of the soils represented in the table of analyses?

      What proportion of the fertilizing ingredients is required?

      If the soil represented in the third column contained all the ingredients required except potash and soda, would it be fertile?

      What would be necessary to make it so?

      What is the reason for this?

      What are the offices performed by the inorganic part of soils?

      The soil represented in the first column might still be fertile with less organic matter, or with a larger proportion of clay (alumina), and less sand (silica). These affect its mechanical character; but, if we look down the column, we notice that there are small quantities of lime, magnesia, and the other constituents of the ashes of plants (except ox. of manganese). It is not necessary that they should be present in the soil in the exact quantity named above, but not one must be entirely absent, or greatly reduced in proportion. By referring to the third column, we see that these ingredients are not all present, and the soil is barren. Even if it were supplied with all but one or two, potash and soda for instance, it could not support a crop without the assistance of manures containing these alkalies. The reason for this must be readily seen, as we have learned that no plant can arrive at maturity without the necessary supply of materials required in the formation of the ash, and these materials can be obtained only from the soil; consequently, when they do not exist there, it must be barren.