SECTION LXVI. LIMING THE LAND
Occasionally, when a cook puts too much vinegar in a salad, the dish becomes so sour that it is unfit to eat. The vinegar which the cook uses belongs to a large group of compounds known as acids. The acids are common in nature. They have the power not only of making salads sour but also of making land sour. Frequently land becomes so sour from acids forming in it that it will not bear its usual crops. The acids must then be removed or the land will become useless.
The land may be soured in several ways. Whenever a large amount of vegetable matter decays in land, acids are formed, and at times sourness of the soil results. Often soils sour because they are not well drained or because, from lack of proper tillage, air cannot make its way into the soil. Sometimes all these causes may combine to produce sourness. Since most crops cannot thrive on very sour soil, the farmer must find some method of making his land sweet again.
So far as we now know, liming the land is the cheapest and surest way of overcoming the sourness. In addition to sweetening the soil by overcoming the acids, lime aids the land in other ways: it quickens the growth of helpful bacteria; it loosens stiff, heavy clay soils and thereby fits them for easier tillage; it indirectly sets free the potash and phosphoric acid so much needed by plants; and it increases the capillarity of soils.
However, too much must not be expected of lime. Often a farmer's yield is so increased after he has scattered lime over his fields that he thinks that lime alone will keep his land fertile. This belief explains the saying, "Lime enriches the father but beggars the son." The continued use of lime without other fertilization will indeed leave poor land for the son. Lime is just as necessary to plant growth as the potash and nitrogen and phosphoric acid about which we hear so much, but it cannot take the place of these plant foods. Its duty is to aid, not to displace them.
We can tell by the taste when salads are too sour; it is more difficult to find out whether land is sour. There are, however, some methods that will help to determine the sourness of the soil.
In the first place, if land is unusually sour, you can determine this fact by a simple test. Buy a pennyworth of blue litmus paper from a drug store. Mix some of the suspected soil with a little water and bury the litmus paper in the mixture. If the paper turns red the soil is sour.
In the second place, the leguminous crops are fond of lime. Clover and vetch remove so much lime from the soil that they are often called lime plants. If clover and vetch refuse to grow on land on which they formerly flourished, it is generally, though not always, a sign that the land needs lime.
In the third place, when water grasses and certain weeds spring up on land, that land is usually acid, and lime will be helpful. Moreover, fields adjoining land on which cranberries, raspberries, blackberries, or gallberries are growing wild, may always be suspected of more or less sourness.
Four forms of lime are used on land. These, each called by different names, are as follows:
First, quicklime, which is also called burnt lime, caustic lime, builders' lime, rock lime, and unslaked lime.
Second, air-slaked lime, which is also known as carbonate of lime, agricultural lime, marl, and limestone.
Third, water-slaked, or hydrated, lime.
Fourth, land plaster, or gypsum. This form of lime is known to the chemists as sulphate of lime. Do not forget that this last form is never to be used on sour lands. We shall therefore not consider it further.
Air-slaked lime is simply quicklime which has taken from the air a gas called carbon dioxide. This is the same gas that you breathe out from your lungs.
Water-slaked lime is quicklime to which water has been added. In other words, both of these are merely weakened forms of quicklime. One hundred pounds of quicklime is equal in richness to 132 pounds of water-slaked lime and to 178 pounds of air-slaked lime. These figures should be remembered by a farmer when he is buying lime. If he can buy a fair grade of quicklime delivered at his railway station for $5.00 a ton, he cannot afford to pay more than $3.75 a ton for water-slaked lime, nor more than $2.75 for air-slaked lime of equal grade. Quicklime should always be slaked before it is applied to the soil.
As a rule lime should be spread broadcast and then harrowed or disked thoroughly into the soil. This is best done after the ground has been plowed. For pastures or meadows air-slaked lime is used as a top-dressing. When air-slaked lime is used it may be spread broadcast in the spring; the other forms should be applied in the fall or in the early winter.