Talks on Manures Part 55

"Dr. Vlcker says: 'The ash-a.n.a.lyses of plants do not afford a sufficiently trustworthy guide to the practical farmer in selecting the kind of manure which is best applied to each crop.'"

"Never mind the authorities," said the Deacon; "what we want are facts."

"Well," replied the Doctor, "take the wheat and turnip crop as an ill.u.s.tration.

"We will suppose that there is twice the weight of wheat-straw as of grain; and that to 10 tons of bulbs there is 3 tons of turnip-tops. Now, 100 lbs. each of the ash of these two crops contain:

_Wheat crop._ _Turnip crop._ Phosphoric acid 11.44 7.33 Potash 15.44 32.75 Sulphuric acid 2.44 11.25 Lime 5.09 19.28 Magnesia 3.33 1.56

"There are other ingredients," continued the Doctor, "but these are the most important.

"Now, if you were going to compound a manure for wheat, say 100 lbs., consisting of potash and phosphoric acid, what would be the proportions?"

The Deacon figured for a few moments, and then produced the following table:

100 Lbs. Special Manure for Wheat and Turnips.

_Wheat manure._ _Turnip manure._ Phosphoric acid 42 lbs. 18? lbs.

Potash 57 " 81? "

------------ ------------ 100 lbs. 100 lbs.

"Exactly," said the Doctor, "and yet the experiments of Lawes and Gilbert clearly prove that a soil needs to be richer in available phosphoric acid, to produce even a fair crop of turnips, than to produce a large crop of wheat. And the experience of farmers everywhere tends in the same direction. England is the greatest turnip-growing country in the world, and you will find that where one farmer applies potash to turnips, or superphosphate to wheat, a hundred farmers use superphosphate as a special manure for the turnip crop."

"And we are certainly warranted in saying," continued the Doctor, "_that the composition of a plant affords_, in practical agriculture, and on ordinary cultivated soils, _no sort of indication as to the composition of the manure it is best to apply to the crop_."

"Again," continued the Doctor, "if the theory was a correct one, it would follow that those crops which contained the most nitrogen, would require the most nitrogen in the manure. Beans, peas, and clover would require a soil or a manure richer in available nitrogen than wheat, barley, or oats. We know that the _very reverse_ is true--know it from actual, and repeated, and long-continued experiments like those of Lawes and Gilbert, and from the common experience of farmers everywhere."

"You need not get excited," said the Deacon, "the theory is a very plausible one, and while I cannot dispute your facts, I must confess I cannot see _why_ it is not reasonable to suppose that a plant which contains a large amount of nitrogen should not want a manure specially rich in nitrogen; or why turnips which contain so much potash should not want a soil or manure specially rich in potash."

"Do you recollect," said I, "that crop of turnips I raised on a poor blowing-sand?"

"Yes," said the Deacon, "it was the best crop of turnips I ever saw grow."

"That crop of turnips," said I, "was due to a dressing of superphosphate of lime, with little or no potash in it."

"I know all that," said the Deacon. "I admit the fact that superphosphate is a good manure for turnips. What I want to know is the reason why superphosphate is better for turnips than for wheat?"

"Many reasons might be given," said the Doctor; "Prof. Vlcker attributes it to the limited feeding range of the roots of turnips, as compared to wheat. 'The roots of wheat,' says Prof. Vlcker, 'as is well known, penetrate the soil to a much greater depth than the more delicate feeding fibres of the roots of turnips. Wheat, remaining on the ground two or three months longer than turnips, can avail itself for a longer period of the resources of the soil; therefore in most cases the phosphoric acid disseminated through the soil is amply sufficient to meet the requirements of the wheat crop; whilst turnips, depending on a thinner depth of soil during their shorter period of growth, cannot a.s.similate sufficient phosphoric acid, to come to perfection.' This is, I believe, the main reason why the direct supply of readily available phosphates is so beneficial to root-crops, and not to wheat."

"This reason," said I, "has never been entirely satisfactory to me. If the roots of the turnip have such a limited range, how are they able to get such a large amount of potash?

"It is probable that the turnip, containing such a large relative amount of potash and so little phosphoric acid, has roots capable of absorbing potash from a very weak solution, but not so in regard to phosphoric acid."

"There is another way of looking at this matter," said the Doctor. "You must recollect that, if turnips and wheat were growing in the same field, both plants get their food from the same solution. And instead of supposing that the wheat-plant has the power of taking up more phosphoric acid than the turnip-plant, we may suppose that the turnip has the power of rejecting or excluding a portion of phosphoric acid. It takes up no more potash than the wheat-plant, but it takes _less_ phosphoric acid."

But it is not necessary to speculate on this matter. For the present we may accept the fact, that the proportion of potash, phosphoric acid, and nitrogen in the crop is no indication of the proper proportion in which these ingredients should be applied to the soil for these crops in manure.

It may well be that we should use special manures for special crops; but we must ascertain what these manures should be, not from a.n.a.lyses of the crops to be grown, but from experiment and experience.

So far as present facts throw light on this subject, we should conclude that those crops which contain the _least_ nitrogen are the most likely to be benefited by its artificial application; and the crops containing the most phosphoric acid, are the crops to which, in ordinary practical agriculture, it will be unprofitable to apply superphosphate of lime.

"That," said the Doctor, "may be stating the case a little too strong."

"Perhaps so," said I, "but you must recollect I am now speaking of practical agriculture. If I wanted to raise a good crop of cabbage, I should not think of consulting a chemical a.n.a.lysis of the cabbage. If I set out cabbage on an acre of land, which, without manure, would produce 16 tons of cabbage, does any one mean to tell me that if I put the amount of nitrogen, phosphoric acid and potash which 10 tons of cabbage contain, on an adjoining acre, that it would produce an extra growth of 10 tons of cabbage. I can not believe it. The facts are all the other way. Plant growth is not such a simple matter as the advocates of this theory, if there be any at this late day, would have us believe."

CHAPTER x.x.xIX.

VALUE OF FERTILIZERS.

In 1857, Prof. S. W. Johnson, in his Report to the Connecticut Agricultural Society, adopted the following valuation:

Potash 4 cents per lb.

Phosphoric acid, insoluble in water 4 " " "

" " soluble " " 12 " " "

Nitrogen 17 " " "

a.n.a.lyses of many of the leading commercial fertilizers at that time showed that, when judged by this standard, the price charged was far above their actual value. In some cases, manures selling for $60 per ton, contained nitrogen, phosphoric acid, and potash worth only from $20 to $25 per ton. And one well-known manure, which sold for $28 per ton, was found to be worth only $2.33 per ton. A Bone Fertilizer selling at $50 per ton, was worth less than $14 per ton.

"In 1852," said the Doctor, "superphosphate of lime was manufactured by the New Jersey Zinc Co., and sold in New York at $50 per ton of 2,000 lbs. At the same time, superphosphate of lime made from Coprolites, was selling in England for $24 per ton of 2,240 lbs. The late Prof. Mapes commenced making "Improved Superphosphate of Lime," at Newark, N.J., in 1852, and Mr. De Burg, the same year, made a plain superphosphate of lime in Brooklyn, N.Y. The price, in proportion to value, was high, and, in fact, the same may be said of many of our superphosphate manures, until within the last few years."

Notwithstanding the comparatively high price, and the uncertain quality of these commercial manures, the demand has been steadily on the increase. We have now many honorable and intelligent men engaged in the manufacture and sale of these artificial manures, and owing to more definite knowledge on the part of the manufacturers and of the purchasers, it is not a difficult matter to find manures well worth the money asked for them.

"A correct a.n.a.lysis," said I, "furnishes the only sure test of value.

'Testimonials' from farmers and others are pre-eminently unreliable.

With over thirty years' experience in the use of these fertilizers, I would place far more confidence on a good and reliable a.n.a.lysis than on any actual trial I could make in the field. Testimonials to a patent fertilizer are about as reliable as testimonials to a patent-medicine.

In buying a manure, we want to know what it contains, and the condition of the const.i.tuents."

In 1877, Prof. S. W. Johnson gives the following figures, showing "the trade-values, or cost in market, per pound, of the ordinary occurring forms of nitrogen, phosphoric acid, and potash, as recently found in the New York and New England markets: _Cents per pound._ Nitrogen in ammonia and nitrates 24 " in Peruvian Guano, fine steamed bone, dried and fine ground blood, meat, and fish 20 " in fine ground bone, horn, and wool-dust 18 " in coa.r.s.e bone, horn-shavings, and fish-sc.r.a.p 15 Phosphoric acid soluble in water 12 " " "reverted," and in Peruvian Guano 9 " " insoluble, in fine bone and fish guano 7 " " " in coa.r.s.e bone, bone-ash, and bone-black 5 " " " in fine ground rock phosphate 3 Potash in high-grade sulphate 9 " in kainit, as sulphate 7 " in muriate, or pota.s.sium chloride 6

"These 'estimated values,'" says Prof. Johnson, "are not fixed, but vary with the state of the market, and are from time to time subject to revision. They are not exact to the cent or its fractions, because the same article sells cheaper at commercial or manufacturing centers than in country towns, cheaper in large lots than in small, cheaper for cash than on time. These values are high enough to do no injustice to the dealer, and accurate enough to serve the object of the consumer.

"By multiplying the per cent of Nitrogen, etc., by the trade-value per pound, and then by 20, we get the value per ton of the several ingredients, and adding the latter together, we obtain the total estimated value per ton.

"The uses of the 'Valuation' are, 1st, to show whether a given lot or brand of fertilizer is worth as a commodity of trade what it costs. If the selling price is no higher than the estimated value, the purchaser may he quite sure that the price is reasonable. If the selling price is but $2 to $3 per ton more than the estimated value, it may still be a fair price, but if the cost per ton is $5 or more over the estimated value, it would be well to look further. 2d, Comparisons of the estimated values, and selling prices of a number of fertilizers will generally indicate fairly which is the best for the money. But the 'estimated value' is not to be too literally construed, for a.n.a.lysis cannot always decide accurately what is the _form_ of nitrogen, etc., while the mechanical condition of a fertilizer is an item whose influence cannot always be rightly expressed or appreciated.

"The _Agricultural value_ of a fertilizer is measured by the benefit received from its use, and depends upon its fertilizing effect, or crop-producing power. As a broad general rule it is true that Peruvian guano, superphosphates, fish-sc.r.a.ps, dried blood, potash salts, plaster, etc., have a high agricultural value which is related to their trade-value, and to a degree determines the latter value. But the rule has many exceptions, and in particular instances the trade-value cannot always be expected to fix or even to indicate the agricultural value.

Fertilizing effect depends largely upon soil, crop, and weather, and as these vary from place to place, and from year to year, it cannot be foretold or estimated except by the results of past experience, and then only in a general and probable manner."

"It will be seen," said the Doctor, "that Prof. Johnson places a higher value on potash now than he did 20 years ago. He retains the same figures for soluble phosphoric acid, and makes a very just and proper discrimination between the different values of different forms of nitrogen and phosphoric acid."

"The prices," said I, "are full as high as farmers can afford to pay.

But there is not much probability that we shall see them permanently reduced. The tendency is in the other direction. In a public address Mr. J. B. Lawes has recently remarked: 'A future generation of British farmers will doubtless hear with some surprise that, at the close of the manure season of 1876, there were 40,000 tons of nitrate of soda in our docks, which could not find purchasers, although the price did not exceed 12 or 13 per ton.'"

"He evidently thinks," said the Doctor, "that available nitrogen is cheaper now than it will be in years to come."