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the spring, it is apt to promote a coarse-fibered leaf, deficient in elasticity and texture.
The Amount of Plant Food to Apply depends upon soil fertility, variety to be grown and quality and quantity of leaf desired. The amounts specified in this chapter are those used by the best growers in the Connecticut valley, on land of fairly good fertility. These men want at least a ton of cured leaf per acre, of the finest quality, and then have the soil left rich enough to yield two to four tons of hay per acre when seeded to grass. Such high cultivation is not yet practiced on old soils in other tobacco-growing districts of America, while on newer lands, it is not necessary. As a rule, however, the average
FIG. 16. MOVABLE FRAME FOR PLANT BED, WITH CLOSE FITTING CLOTH COVER PARTLY REMOVED.
planter stands more in danger of applying too little plant food than too much. On the other hand, the Poquonock experiments confirm much experience to the effect that, under the intense cultivation referred to, more plant food is put into the soil than is really profitable.
Their Necessity.—It has been shown by analyses of the plant, and by experience in the field, that tobacco requires a large quantity of nitrogen. It does not seem to possess the ability to get its nitrogen from the air, as do clover and certain leguminous plants. However, tobacco must get its nitrogen from the soil. This element must, therefore, be present in sufficient quantity, and also in a thoroughly available form, and intimately diffused throughout the soil, owing to the short period in which the plant development can be effected. Nitrogen is obtained from a number of waste products and chemicals, prominent among which are cottonseed meal, castor pomace, linseed meal, tankage, dried fish scrap, dried blood, dried animal matter, sulphate of ammonia, and nitrate of soda. Many growers use these and other chemicals, while others prefer the prepared fertilizers of
no. 17. PERMANENT BED, WITH BOTH GLASS AND CLOTH FRAMES
commerce that are rich in available nitrogen, and are prepared expressly for this crop.
Availability.—Tests have been made at the Connecticut experiment station to find out the crop-producing power of nitrogen, supplied in various forms. This was determined, not by chemical analysis, which practically fails to throw much light on the subject, but by the quantity of nitrogen which the crop took from the fertilizer. The crops were grown on artificial soil that contained only traces of available nitrogen, but all the other elements of plant food were present in excess of the crop needs. Of course, a single crop cannot take all the nitrogen from the soil, even when it is supplied in nitrate of soda, which is the most soluble form, because, for one reason, the plant roots do not reach every particle of the soil. Still less can one crop take all the nitrogen from animal, or vegetable, matters, that decompose but slowly in the soil. In any case, therefore, more or less of the nitrogen contained in the fertilizer fails to enter the crop. The tests were made with oats and corn in 147 pots, and resulted for the two years, as follows (Johnson, Britton and Jenkins):
AVAILABILITY OF DIFFERENT NITROGENOUS MANURES.
Column A shows the per cent of the total nitrogen furnished the crops of 'NO that was available—that is, was actually taken up by these crops, the balance of the nitrogen being left in the soil. In Column B, the amount of available nitrogen in nitrate of soda represents 100, and the figures beneath show the proportionate availability of
It will be seen that the nitrogen of castor pomace No. 4545 has shown the highest availability of any form of organic nitrogen. The other sample of pomace contained more oil, and its nitrogen was not quite as available. Cottonseed meal, linseed meal and dried blood were about equally available, thus scientifically confirming the experience of some of our most careful tobacco growers, who have found linseed meal fully as quick acting and effective as a fertilizer as either cottonseed meal or dried blood. Dried fish comes next in order, but it will be surprising to many that tankage, a popular nitrogenous fertilizer, gave up only forty per cent of its nitrogen to crops in two years, thus standing in availability at fifty-nine, compared to nitrate of soda as one hundred.
Ammonia should not be confused with nitrogen. Seventeen parts of ammonia contain fourteen parts of nitrogen. Oftentimes manufacturers give the equivalent proportion of ammonia, instead of the actual amount of nitrogen, for the same reason that the term phosphate of lime is used—because it looks bigger. Expressed in decimals, one part of ammonia contains 0.8235 of nitrogen. Thus, if a fertilizer contains five per cent (or one hundred pounds per ton) of ammonia, the nitrogen is only 4.12 per cent, or eighty-two and onethird pounds. For quick calculation, ammonia can be reckoned to contain four-fifths of nitrogen, and by deducting one-fifth from the quantity of ammonia, the amount of nitrogen actually present will be reached quite closely.
Cottonseed Meal.—Of all the sources of nitrogen, the most popular is cottonseed meal. As a concentrated food for cattle its value is highly appreciated, and it is one of the leading meals for milch cattle. But, apart from the tobacco crop, it is not much used as a fertilizer at the North. In the southern States cottonseed, fermented, to destroy the germ, has long been a favorite dressing for cotton fields, especially when mixed with plain superphosphate and kainit. Of recent years the practice of selling the seed to oil mills, and buying back the dry meal, has gradually spread, and in sections adjacent to railroads in these States, large quantities of meal are annually consumed for fertilizing purposes.
In the preparation of the meal, the cottonseed, which is about the size of a coffee bean, is taken as it comes from the gin, covered with a short fuzz of cotton fiber. In this shape the seed resembles the small cocoons in which the larvae of many insects are encased. This downy fuzz is removed by machinery, the lint finding a sale for certain industrial purposes. The seed is then almost bare. It is next decorticated; that is, the hard flinty shell is split open and then sifted from the pulp. The pulp is rich in oil, and the shell contains enough fat to make it readily combustible. The shell, or hull, is burned for fuel under the engine boilers, sometimes being the only fuel, but more often used with wood, and occasionally with coal. The resulting ash is called cottonhull ash, described under potash fertilizers. The pulp of the seed is subjected to heavy pressure, which expresses the oil, and the dry cake is then ground. Its final condition is that of a fine dry powder of an olive or yellowish green cast. Occasionally, the hulling process is omitted, and the entire seed is crushed and ground, the result being undecorticated meal. This product is darker than the usual brand, from containing fragments of the black hulls. Such meal is inferior to the normal, both as a fertilizer and as a fodder. The shells, or hulls, are much used in the South for feeding cattle, and though it may appear incredible, cattle fed on them are kept in good condition.
Cottonseed meal is admirably suited to fertilizing purposes; it is a fine dry powder, of excellent mechanical condition, free from odor, and very easily applied. It can be distributed very evenly, which insures a thorough distribution through the soil, and owing to its fine mechanical condition, it is easily disintegrated, and the fertilizing elements soon become available. It is not so rapid in its effects as the nitrate and ammonia salts, but it compares favorably with any animal matter. Chemically it is quite uniform, as appears from the analyses in Table IV, Page 112. A clearer idea of its constituents is obtained from the following more complete analysis: