yield from blood would be 700 pounds, from hoof meal 650 pounds and from leather 20 to 300 pounds."

These statements indicate how little an analysis of a fertilizer which gives only the per cent of nitrogen or ammonia tells of the real value as a supplier of nitrogen, and show very clearly that to arrive at any conclusion regarding the value of a nitrogenous fertilizer one should know the source or condition of the nitrogen as well as the per cent.

Two or three suggestions for the selection of nitro

Effect of top dressing grass land with nitrate of soda. The plot on the left received no nitrate, the center one half ration, and the one on the right a full ration of nitrate

gen fertilizers may be deduced from this discussion. For those crops which begin their growth early in the spring the best results will follow the use of Chili saltpeter, as the soil is likely to be poor in nitrates and the process of nitrification slow at that time. Such crops as have very short periods of growth will respond best to nitrogen in nitrates. Corn, on the other hand, and the other crops which make their growth after the season is well advanced can use the slower acting fertilizers, as can also those crops which occupy the ground permanently. Some agriculturalists prefer to use a fertilizer containing nitrogen in three forms

for the crops that grow during the greater part of the season, a little nitrate of soda for immediate use, sulphate of ammonia to supply nitrogen a little later and tankage to carry the plant to maturity, all these materials being mixed and applied at one time.

Nitrogen is Expensive.-Nitrogen is the most expensive element to supply in commercial fertilizers, costing as it does at least three times as much a pound as either phosphoric acid or potash. In ordinary or "extensive" farming it is seldom profitable to use nitrogenous fertilizers for the nitrogen of the soil can be readily maintained by means of the farm manure, and a proper use of leguminous crops in the rotation. Market gardening and other forms of intensive farming call for a liberal use of fertilizers containing nitrogen. A careful study of the materials used to supply nitrogen should be made by those engaged in this style of farming for as Wagner says, "The art of manuring is dependent upon a rational application of nitrogen."

CHAPTER XVIII

POTASH AND PHOSPHATE FERTILIZERS

Potash Sometimes Necessary in a Fertilizer.-It has been shown that most soils contain much more potash than nitrogen or phosphoric acid. The greater part of the potash in the soil is in very insoluble and unavailable forms, and although there are large quantities present the plant may be able to use so little of it that a good crop is impossible, as has been shown by the increased yield from the use of potash on clay soils that had a high content of this element of fertility. "It has been attested that potash is of relatively less importance than either nitrogen or phosphoric acid, inasmuch as good soils are naturally richer in this element, and because a less amount is removed in general farming than of either nitrogen or phosphoric acid, as the potash is located to a less extent in the grain than in the straw, which is retained on the farm. It is, however, a very necessary constituent of fertilizers, being absolutely essential for those intended for light, sandy soils and for peaty meadow lands, as well as for certain potash-consuming crops, as potatoes, tobacco and roots, since these soils are very deficient in this element, and the plants mentioned require it in larger proportion than do others. In fact it is believed by many careful observers, and the belief has been substantiated in large part by experiments already con

ducted, that the average commercial fertilizer does not contain a sufficient amount of this element. It is a particularly useful element in the building up of worn out soils, because contributing materially to the growth of the nitrogen-gathering legumes, an important crop for this particular purpose.”—Voorhees.

Wood Ashes at one time was the sole source of potash for fertilizing purposes, but at present ashes supply but a very small proportion of this element of plant food. The potash in wood ashes is one of the best forms for use as a fertilizer, but the supply is so limited and the price usually demanded so high that ashes can no longer be considered as an important source of potash. Wood ashes vary greatly in composition, the ash from soft woods containing less potash than that from the hard woods; the content of potash ranging from 2 to 8 per cent.

Potash as found in wood ashes is in a form that is very soluble in water so that ashes exposed to the weather may have practically all of the potash leached out of them. Leached ashes as a rule contain less than 2 per cent of potash. As it is not possible to distinguish between leached and unleached ashes by mere physical examination it is evident that this material should be purchased only from guaranteed analysis.

In addition to potash, ashes contain from 25 to 30 per cent of lime, and in many cases, doubtless, the beneficial results obtained from ashes were as much due to the lime in them as to the potash. All ashes produced on the farm should be carefully preserved and utilized, but they can seldom be purchased to advantage.

Stassfurt Salts.-At the present time practically all of the potash used in fertilizing comes from the Stassfurt mines in Germany. These mines contain immense deposits of potash salts, and are owned by a syndicate that controls the price and output of potash the world over. A number of different minerals containing varying percentages of potash are produced from the mines, and many of them are used in Germany. Only three or four of these products are in use in this country and they are the only ones that will be discussed here.

Kainite. This is one of the crude salts which has been ground to a powder. It looks somewhat like common salt but is darker in color and contains about 12.5 per cent of potash in the form of sulphate, mixed with the sulphate and chloride of magnesia. This substance has been used because it is cheaper than the next two substances to be mentioned, but even at the lower price a ton the actual potash costs more in kainite than in the concentrated form.

Muriate of Potash is manufactured from the crude minerals of the mines by concentration, and contains about 50 per cent of potash, all of which is combined. with chlorine in the form known by the chemists as potassium chloride. At the present price by the ton the muriate supplies potash at a cheaper price a pound than any of the other materials.

Sulphate of Potash is another concentrated product of the Stassfurt industry. What is known as high grade sulphate contains about 53 per cent of potash in the form of sulphate (i. e., combined with sulphuric acid). The actual potash in this compound costs a trifle more a pound than in the muriate. A lower grade