Ground bone, bone meal, bone dust, indicate the mechanical conditions of the bones.

The bones are sometimes ground "raw" just as they come from the slaughter-house or kitchen, or they are sometimes first "steamed" to extract the fat for soap, and the nitrogenous matter for glue.

_Raw Bone._ a.n.a.lysis: Nitrogen, 2.5 to 4.5 per cent. Available phosphoric acid, 5 to 8 per cent. Insoluble phosphoric acid 15 to 17 per cent.

_Steamed Bone_ contains 1.5 to 2.5 per cent. of nitrogen, 6 to 9 per cent. of available phosphoric acid and 16 to 20 per cent. of insoluble phosphoric acid.

Steamed bone pulverizes much finer than raw bone and decays more rapidly in the soil because the fat has been extracted from it.

_Dissolved Bone._ Ground bone is sometimes treated with sulphuric acid to render the phosphoric acid in it more available. It is then called dissolved bone and contains thirteen to fifteen per cent. of available phosphoric acid and two to three per cent. of nitrogen.

_Dissolved Bone Black._ Bone charcoal is used for refining sugar. It is then turned over to the fertilizer manufacturers who sell it as "Bone Black" or treat it with sulphuric acid and then put it on the market as dissolved bone black.

The bone black contains thirty to thirty-six per cent. of insoluble phosphoric acid.

The dissolved bone black contains 15 to 17 per cent. of available phosphoric acid and 1 to 2 per cent. insoluble.

"_Thomas Slag_," "_Phosphate Slag_," "_Odorless Phosphate_."

Phosphorous is an impurity in certain iron ores. In the manufacture of Bessemer steel this is extracted by the use of lime which melts in the furnace, unites with the phosphorous and brings it away in the slag.

This slag is ground to a fine powder and used as a fertilizer. It contains 11 to 23 per cent. of phosphoric acid, most of which is available.

_Superphosphate._ The term superphosphate is applied to the phosphates that have been treated with sulphuric acid to make the phosphoric acid available. Dissolved bone, dissolved bone black, and the dissolved phosphate rocks are superphosphates.

_Fish Sc.r.a.p_, mentioned as a source of nitrogen, is also a valuable source of phosphoric acid, containing 6 to 8 per cent., which is quite readily available owing to the rapid decay of the sc.r.a.p.

SOURCES OF POTASH

The chief sources of potash used for fertilizers are the potash salts from the potash mines at Sta.s.sfurt, Germany, where there is an immense deposit of rock salt and potash salts.

The princ.i.p.al products of these mines used in this country are the crude salts:

_Kainite_, containing 12 per cent. of potash.

_Sylvinite_, containing 16 to 20 per cent. of potash, and the higher grade salts manufactured from the crude salts:

_Muriate of Potash_, containing 50 per cent. potash.

_High grade Sulphate of Potash_, containing 50 per cent. potash.

_Low grade Sulphate of Potash_, containing 25 per cent. potash.

_Wood Ashes_, if well kept and not allowed to get wet and leach, contain 4 to 9 per cent. of potash.

_Cotton Hull Ashes_ contain 20 to 30 per cent, of potash and 7 to 9 per cent. of phosphoric acid.

The potash in all these forms is soluble in water and equally available to plants. The crude salts, kainite and sylvinite, and the muriate contain chlorine and are not considered good for potatoes and tobacco as the chlorine lowers the quality of these products.

In tobacco regions tobacco refuse is a valuable source of potash, the stems are about five per cent. potash.

LIME

_Lime_ is generally supplied to the soil in the form of quicklime made by burning lime stone or sh.e.l.ls. Other forms are gypsum or land plaster, gas lime (a refuse from gas works) and marl. Most soils contain sufficient lime for the food requirements of most plants. Some soils, however, are deficient in lime and some crops, particularly the legumes, are benefitted by direct feeding with lime.

Lime is valuable for its effect on the soil properties which const.i.tute fertility.

Physically lime acts on the texture of the soil making clay soils mealy and crumbly, and causing the lighter soils to adhere or stick together more closely.

Chemically, lime decomposes minerals containing potash and other plant foods, thus rendering them available for the use of plants. It also aids the decay of organic matter and sweetens sour soils.

Biologically lime aids the process of nitrification.

The action of lime is greatest in its caustic or unslacked form.

Too much or too frequent liming may injure the soil. It should be carefully tried in a small way, and its action noted, before using it extensively.

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.