A common way of using lime is to place twenty to forty bushels on an acre in heaps of three to five bushels, covering them with soil until the lime slacks to a fine powder.  The lime is then spread and harrowed in.  Lime tends to hasten the decay of humus.  It should not be applied oftener than once in four or five years.

Gypsum, a sulphate of lime, is similar to lime in its action on the soil.  Its most important effect is the setting free of potash from its compounds.

Gas lime should be used with great care as it contains substances that are poisonous to plant roots.  It is best to let it lie exposed to the weather several months before using.

Marl is simply soil containing an amount of lime varying from five to fifty per cent.  It has value in the vicinity of marl beds but does not pay to haul very far.

CHAPTER XXII

COMMERCIAL FERTILIZERS—­CONTINUED

MIXED FERTILIZERS

What they are.

There are a large number of business concerns in the country which buy the raw materials described in Chapter XXI, mix them in various proportions, and sell the product as mixed or manufactured fertilizers.  If these mixtures contain the three important plant foods, nitrogen, phosphoric acid and potash, they are sometimes called “complete” manures or fertilizers.  In some parts of the country all commercial fertilizers are called “guano.”

Many brands.

These raw materials are mixed in many different proportions and many dealers have special brands for special crops.  There are consequently large numbers of brands of fertilizers which vary in the amounts, proportions and availability of the plant foods they contain.  For instance, in 1903, twenty-three fertilizer manufacturers offered for sale ninety-six different brands in the State of Rhode Island.  In Missouri one hundred and ten brands, made by sixteen different manufacturers, were offered for sale.  Eighty-three manufacturers placed six hundred and forty-four brands on the market in New York State during the same year.  Of one hundred and twenty brands registered for sale in Vermont in the spring of 1904, there were seventeen mixtures for corn and thirty-four for potatoes.

The result of this is more or less confusion on the part of the farmer in purchasing fertilizers, and with many a farmer it is a lottery as to whether or not he is buying what his crop or his soil needs.

Some of the manufacturers are not above using poor, low grade, raw materials in making these mixtures.

This means that the farmer should make himself familiar with the subject of fertilizers if he desires to use them intelligently and economically.

Safeguard for the farmer.

As a safeguard to the buyer of fertilizers the State laws require that every brand put on the market shall be registered and that every bag or package sold shall have stated on it an analysis showing the amounts of nitrogen, or its equivalent in ammonia, the soluble phosphoric acid, the reverted phosphoric acid, the insoluble phosphoric acid, and the potash.