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liquid sulphate of ammonia is freely separated into compounds available for plant food. It is one of the quickest ammoniates in its effects and is highly prized for its great forcing power. It is especially valuable for hastening the crop if for any reason it becomes retarded.
Owing to its very soluble condition, sulphate of ammonia should be applied just before setting the plants, at the time of the last harrowing. If applied earlier there is a possibility of loss through leaching, especially on light soils. Two hundred and fifty pounds per acre takes the place of 1,000 pounds of cottonseed meal or of 600 pounds of dry fish scrap. The better way to use it is to apply in conjunction with manure, although on any but very light soils it will produce favorable results alone, until the soil becomes depleted of organic matter through continuous cultivation. The best results are obtained by using a small quantity of sulphate of ammonia with manure and organic ammoniates, for the ammonia salt gives a quick start to the young plants, while the nitrogen from the other materials comes in for the later development of the crop. Sulphate of ammonia contains a large quantity of sulphuric acid, which is a decided objection, and the results of its use in Connecticut are such as to make it unpopular with the best growers. Care is necessary that the rootlets do not come into too close contact with it.
Nitrate of Soda.—Much that has been said of sulphate of ammonia applies with equal force to this salt, which is preferred to the sulphate because free of sulphuric acid. It is perfectly soluble and should be applied in the manner indicated for ammonia, and treated in all respects the same. It is a crystalline salt of somewhat pinkish cast, slightly deliquescent (capable of absorbing moisture), and is imported in enormous quantities for manurial purposes, as well as for other industrial uses. It exists in large beds in certain provinces of Chili, and is often called Chili saltpeter. It is clarified before shipment, and is very uniform in composition, containing about sixteen per cent of nitrogen. It is a combination of nitric acid with soda.
The use of nitrate of soda upon tobacco has not become general as yet, and possibly its large percentage of soda may have some qualifying influence on the crop; more extended experiments are necessary to determine this point. A small quantity of it, however, can be used with safety, and, like sulphate of ammonia, it has great value in giving the young plants a vigorous growth. It has been customary to apply half the nitrate at time of planting, or at first cultivating, and the balance at second cultivating. At Poquonock the application all at once, between rows, at first cultivating, gave best results.
The Necessity of Potash cannot be too strongly reiterated. We have shown in Chapter V that tobacco draws more heavily upon the soil's potash than upon any other single element. It also requires a larger amount of potash than does any other crop. Tobacco is a potash feeder to a remarkable extent. It is equally important to note that analyses of soils and practical experience unite in proving that in many localities where tobacco is grown, the land is deficient in potash. This is quite generally true of all tobacco lands that have not been well manured. It is also true of many other soils. Every farmer can readily test his own soil for potash, by planting tobacco or potatoes in plots without any potash, and with potash in varying quantities, moderate amounts of nitrogen and phosphoric acid being furnished in all the plots. If it appears that the absence of potash reduces the crop, and that its presence increases the yield, the imperative necessity of potash is proved.
The table of manurial analyses in Appendix shows how deficient ordinary stable manure is in potash, and how few substances furnish it in liberal proportion. Thus the deficiency of potash, both in the soil and in ordinary manurial substances, must be made good. But while potash is of paramount importance to the tobacco plant, great care must be exercised to exclude all contamination with chlorine. Potash combines freely with chlorine, and in the muriate of potash is wholly present; common salt (chloride of soda) is also frequently found in many potash salts. But the demand for a potash salt free from this defect has caused the introduction of high grade sulphates that are practically free from chlorine.
Potash Salts are obtained from the potash mines at Stassfurt, Germany, and are largely used for manurial purposes, both in Europe and this country. The native salt is a mixture of sulphate and muriate of potash with common salt, and is clarified after mining. Kainit, the lowest grade sulphate, contains 25 per cent of sulphate of potash (equal to 12 per cent actual potash), and 60 per cent of common salt, and should never be used for tobacco because of this last defect. Muriate of potash, 80 per cent purity, contains 50 per cent actual potash, and about 15 per cent common salt, and for this last reason is eschewed by tobacco growers. The first salt satisfactory for tobacco culture was the double sulphate of potash and magnesia, or doublc-manure-salt, and it is still used with good results. As its name implies, the sulphuric acid is combined with potash and magnesia, and also with soda to some extent; its analysis is given in Table IV, Page 112. But it contains so much chlorine that it is not now approved for fine wrappers, and the Poquonock results are against it. Whether its magnesia is of much use is also a question. Double manure salt is usually sold on a guarantee of 48 to 50 per cent sulpha'e of potash (equal to about 25 per cent actual potash), and lately the further guarantee "less than two and one-half per cent chlorine" is also given.
The high grade sulphate now imported is more desirable, since it contains no chlorine at all, is more concentrated and, moreover, comes in a fine, mealy condition. It is guaranteed to contain from 96 to 98 per cent sulphate of potash. This is equivalent to 50 or 51 per cent actual potash, or just about the same as is found in muriate of potash of 80 per cent muriate. The two to four per cent of other matter in this high grade sulphate is mainly composed of water. This is an admirable salt for the tobacco crop and should be used extensively.
How to Apply Potash Salts.—In Germany the usual custom is to apply potash salts in the fall upon all but very light land. In this country, spring applications are exclusively followed, and as no great additional benefit can be expected from fall applications, the present custom will probably continue. To raise a first-class crop of tobacco there should be at least 300 pounds of actual potash in the soil available for plant use. To furnish this it is necessary to apply 500 pounds of high grade sulphate, or 1000 pounds of double sulphate, per acre. In addition to this is the potash obtained from cottonseed meal, manure, stems or other articles. The same rule advanced in applying nitrogen,—the necessity of a much larger supply than the plant actually requires,— holds good in furnishing potash, though in a less degree. Potash does not leach, and what is applied remains permanently in the soil, but the trouble is that it is often too permanent. It has a tendency to form insoluble compounds, and when these are formed a certain per cent of potash becomes locked up and lost to the plant. Potash, however, has no forcing effect, and the only reason for an excess is to avoid the possibility of a deficiency, either from uneven distribution or from the formation of insoluble compounds. The salts should be applied broadcast, in the spring, at the time of the first harrowing.
Cottonhull Ash is extremely popular as a fertilizer, especially with scientific growers of prime tobacco for cigar wrappers. This is mainly due to the large quantity of potash the ash contains, and also to the fact that this potash is soluble. It also contains a goodly amount of magnesia, as well as lime and phosphoric acid; the two former elements being as essential for this crop as is the potash or the phosphoric acid. It is quite probable, too, that the soluble carbolic acid in cottonhull ash adds to its excellent effect on the soil. The following are complete analyses of a fair average sample of cottonhull ash, made by Jenkins at Connecticut station, and by Goessman at Massachusetts station:
Cottonhull ash varies widely in composition. Different samples contain from 10 to 40 per cent potash, average 23 per cent; phosphoric acid 3 to 14 per cent, average 8 per cent. Hence, this ash should only be bought on a guaranteed analysis, and at a price that will make the actual potash cost only four to six cents per pound. The wide variation is due to the carelessness with which the hulls are burned in Southern mills,