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.
In addition to supplying essential plant food, nitrogen, phosphorus and potassium perform specific functions in plant growth. The application of nitrogen in one of its readily available forms (e.g., nitrate of soda and sulphate of ammonia) will stimulate vegetative growth. If too much of this one element is applied, leaf and branch development may occur at the expense of the crop. Good results follow the use of nitrogen on grass sods and on leafy vegetables like spinach. On the other hand, corn, peas, beans and other seed-forming crops need to have the nitrogen balanced with phosphorus. Potatoes, in common with other tuber and root crops, will utilize plenty of potassium in the development of starch.