Soil is created from rock by nature's weathering processes and by plant growth. At the bottom may be seen solid rock; just above are disintegrating rock fragments, and at the top, the soil.] Every type of real soil contains all the elements of plant growth. This plant food results from a breaking down of soil particles and the setting free of chemical elements which, either singly or in combination, serve as food for plants. Whatever the type of soil may be, it will be found that certain crops will make better growth in it than others. As a general rule, it may be said that the only way to determine which plants will grow best on a given soil is by the trial-and-error method. However, by observation of the growth on similar types of soil we can learn something of a soil's crop adaptability. There are some crops that will grow in almost any soil and there are others that need an exactness of texture, moisture and plant food which makes them highly specialized products. The operator must learn how to work in harmony with the peculiarities of his own soil before he can hope to get the best results. In acquiring a tract for the growing of plants of any kind it is desirable to get a soil type that will meet the requirements of most plants. As a general rule, this type contains enough clay to be retentive of moisture, enough sand to be easily worked and is generally suitable for bacterial growth. In other words, what is commonly called a loam is the ideal type for general agricultural and horticultural purposes. This may be a heavy loam, in which clay predominates, or a so-called light loam, in which sand particles predominate. An examination of a handful of soil by a person experienced in farming will indicate its nature and its adaptability to ordinary crop production. _Essential Elements of Plant Food._--Countless scientific experiments in plant growth show that potassium, lime, phosphorus, magnesium, iron, sulphur, nitrogen, carbon, oxygen and hydrogen are essential to normal development. The carbon, hydrogen and oxygen elements make up nearly 99 per cent of the entire composition of the plant and are derived from the atmosphere. All of the other elements are derived from the soil except in the case of peas, beans, clovers and other legumes which secure most of their nitrogen from the air. The mineral elements are not needed in large amounts but well-balanced plant growth is strictly dependent upon their presence in available form. Of these elements, those most likely to be deficient either in total amount or in availability are nitrogen, phosphorus, potassium and calcium. It is entirely feasible and economical to apply concentrated chemical fertilizers containing the first three elements so that their lack will not constitute a limit to size of crops harvested. In many cases it is necessary to apply chemical fertilizers to get satisfactory yields, even where natural manures are available and can be applied as well.