Chemical Changes In The Soil

The chemical changes that are constantly taking place in every farm soil are no less numerous and no less important than the changes resulting from the work of bacteria. The elements of which the soil is composed are always shifting and changing. The compounds, which are merely combinations of several elements, are continually dissolving partnership and the elements join themselves together in new bonds, according to affinity. The nitrogen released from a nitrate by the nitrogen wasting germs may be instantly seized by some near-by hydrogen to make ammonia. The ammonia may then be attacked by the nitrogen-saving germs and made into nitrous acid; which, in turn, may soon become a nitrate, or it may escape into the air and be lost to the soil, until brought down by rain. The phosphoric acid that the farmer applies in superphosphate or bone meal is at once seized by hungry elements and enters into several partnerships.

Some of it is readily soluble in water and might leach away were there not some lime or sodium handy to catch it. That part of it which is not used by plants the first year or two may get locked up so strongly in partnerships with other elements that it becomes valueless to plants. When a potash fertiliser, as ashes, is applied to the soil, the plant food it contains would mostly dissolve in the soil water and wash away were it not that it unites with some of the "bases" of the soil and becomes "fixed." In fact, the plant food in most fertilisers applied to soils would be quickly leached or washed away, if these chemical changes did not occur and hold it until the roots of plants can use it. Plants feed, not upon the materials that we apply to the soil — ashes, bones, phosphates, guano, and the like — but upon the chemical compounds formed in the soil by them. These and other chemical changes that all fertilisers pass through before they are absorbed by the roots of the plants illustrate what takes place with each and every constituent of the soil, whether it is essential to the growth of the plant or not.

The soil is a great chemical laboratory. Numberless reactions, or new adjustments of the partnerships between the elements, occur every hour. No chemist holds the beaker or fires the great retort; the changes take place in obedience to natural laws, quietly and methodically, yet with results so far reaching that we can hardly grasp their significance. It is the business of the chemist and the bacteriologist to explore this laboratory and report how its chemical changes are effected by the different methods of handling the soil. It is the business of the farmer to keep the soil laboratory in excellent working order, by a wise and varied husbandry ; and especially by giving careful attention to those principles of good farming that we already know make it run smoothly — thorough tillage, excellent drainage, and a rotation of crops.