effects of soluble salts on insoluble · phosphates more soluble in water than they would otherwise...

EFFECTS OF SOLUBLE SALTS ON INSOLUBLE PHOSPHATES.’

BY J. E. GREAVES.

(Associate Chemist, the Utah Experiment Station.)

(Received for publication, January 14, 1910.)

INTRODUCTION.

This study has been taken up from two viewpoints. First, a study of field and pot experiments, with a view of determining, if possible, the indirect action of various salts when used as fertilizers; to ascertain if the increase in yield obtained from the use of a fertilizer is not due in part to the solvent action which it exerts on the comparatively insoluble phosphorus in the soil. Second, to study in the laboratory, the solvent action of the more common salts on phosphates, using distilled water as a standard.

That some fertilizers have an indirect effect has long been an acknowledged fact. It is no longer believed, that the increase in yield obtained from the use of one ton of barnyard manure, is alone due to the addition of the two or three pounds of phosphorus and the ten or twelve pounds each of nitrogen and potassium which it contains; but no small part of the increase is due to the liberation of more plant food. This (I) is brought about by the decaying of organic matter with the formation of various acids which in turn act as solvents on insoluble plant food already in the soil. The benefits obtained from the use of gypsum and lime are due not only to the neutralizing of acid and supplying of calcium, but it is acknowledged that they act indirectly by liberating potassium. From certain results obtained in various experiments, which will be considered later, it seems as if this may be due in part, to the liberation of phosphorus from its less soluble forms.

‘This investigation was suggested by Dr. C. G. Hopkins of the Univer- sity of Illinois, and many valuable suggestions were received from him.

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Effect of Salts on Phosphates

The theory of the liberation of phosphorus by the addition of various soluble salts to the soil is not a new one for some writers speak of it as an established fact. This was understood in a gen- eral way by Justus von Liebig, for in his article (2), “Some Points in Agricultural Chemistry,” he says: “ These salts (speaking of the ammonium salts) contain an acid which exerts an action on the constituents of the soil, an action which is not exerted by pure ammonia. The acids of the ammoniacal salts render the earthy phosphates more soluble in water than they would otherwise be.”

A. Stood (3), in a study of the effects of salt water on the soil, attributes part of the bad effects of salt water on land to the rendering soluble the phosphates which are subsequently washed beyond the plant roots.

For some time in England the agricultural investigators were divided into two schools. One of these claimed that a great increase in yield could be obtained by the use of an insoluble phosphate; while the other claimed that very little, if any increase in yield could be obtained by its use. Each supported his claim by actual field tests. This difference in results was explained by E. Waldt (4) as being due to the salt which in some cases had been used in connection with the phosphate. Some salts, he claims, when used in connection with a phosphate tend to render it more soluble. Especially does he attribute this property to the various nitrates.

Coming down to the present time we have the statements of Hilgard (5) that lower percentages of potassium,l phosphorus and nitrogen are adequate, when a large proportion of lime carbonate is present. He states further, that a high percentage of lime carbonate may offset a small percentage of phosphorus apparently by bringing about greater availability. Again, in summing up the chemical actions of carbonates he states that carbonates liberate phosphorus and potassium from insoluble forms.

Wagner (6) found that some of the benefits which result from the use of sodium nitrate are due to its rendering more soluble certain phosphates.

‘Throughout this article potassium and phosphorus have been stated as the elements in place of potash and phosphoric acid. When quoting from others this change has been made.


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J. E. Greaves 289

SALTS CONTAINING NITROGEN COMPARED WITH DRIED BLOOD AS A

SOURCE OF NITROGEN.

As a source of nitrogen, the nitrate of soda is usually considered to produce a much better yield than an equivalent amount in the form of dried blood. This is well illustrated in a series of pot experiments by Voorhees (7). The experiments were carried out in the year Igor and 1902. Sodium nitrate and dried blood were the sources of nitrogen; equivalent amounts of nitrogen being used in each case. As an average of two years and of three experiments each year, dried blood gave a yield of 106.8 grams while sodium nitrate yielded 110.4 grams of dry plant.

Patterson (8) obtained similar results with field tests as the following table will show. Each result is the average of two years’ work.

CBOP.

Corn.. . . . Corn.. . . Corn.....

Wheat.. . . Wheat.. . . Wheat. . . .

Hay.. . . . . Hay.. . . . Hay. .

. . . . , . . . . . . Sodium nitrate

. . . . . . . . . . . Ammonium sulphate

. . . . . . . f... Dried blood

. . . . . . .

.......

.......

. . . . . . .

. . .

. . . .

-- bus. 61.5 52.7 49.7

3Eo 2625 2812

Sodium nitrate 14.9 2030 Ammonium sulphate 14.3 1830 Dried blood 9.0 884

Sodium nitrate 4150 Ammonium sulphate 1900 Dried blood 2550

GRIIN.

The above shows that corn with sodium nitrate yielded I I. 8 bushels and with ammonium sulphate 3 bushels more than it did with an equivalent amount of nitrogen in the form of dried.blood. Wheat with sodium nitrate yielded 5.9 bushels and with ammonium sulphate 5.3 bushels more than with the dried blood. Hay produced 1600 pounds more with sodium nitrate and 650 pounds less with the ammonium sulphate than with the dried blood.

A. Muntz (9) also shows that sodium nitrate produced better yields than an equivalent amount of nitrogen in the form of dried blood.


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290 Effect of Salts on Phosphates

Therefore under ordinary conditions sodium nitrate is more effective than ammonium sulphate, which, however, is more effective than an equivalent amount of dried blood. This, however, in the case of sodium nitrate and ammonium sulphate is reversed under certain conditions as will be shown in the following discussion.

THE RELATIVE VALUE OF SODIUM NITRATE AND AMMONIUM SUL-

PHATE WHEN USED IN CONNECTION WITH AN INSOLUBLE PHOS-

PHATE.

It seems likely that this difference in value of the two fertilizers may be due in part to some indirect effect of the salt. This is at least indicated by the difference in action of ammonium salts and sodium nitrate when used in connection with insoluble phosphate. On ordinary soil sodium nitrate is usually conceded to give the better yield (IO). However, when an insoluble phosphate is used in connection with the nitrogenous manure the ammonium salt gives a larger yield than the sodium nitrate or nitrogen from organic sources. Besides, plants grown with the ammonium salts contain a larger percentage of phosphorus.

A great number of experiments have been carried out to ascertain the relative value of insoluble phosphates. A few of them are as follows: Jameson (II) conducted a series of experiments with turnips, in which a soluble and insoluble phosphate was used. In one series a soluble salt was used with the phosphates, in the other phosphates were used alone. As an average of forty experiments he obtained with the soluble phosphate 15,133 kilos per acre, while with the insoluble phosphate he obtained but 14,663 kilos. per acre. This is a difference of 470 kilos in favor of the soluble phosphate. When the same phosphates were used in connection with ammonium sulphate in a series of twelve experiments, the yield was as great with the insoluble as with the soluble phosphate. Now, when the same two phosphates were used in connection with sodium nitrate the soluble gave a yield of 22,240 kilos, while the insoluble gave but 20,525 kilos. It may be seen that there was I 7 I 5 kilos per acre in favor of the soluble phosphate. When the above facts are taken into consideration remembering that nitrates are usually the best form of nitrogen it would seem that


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J. E. Greaves 291

the ammonium sulphate had some effect on the insoluble phosphate.

Krocker and Grahl (13) obtained as large a yield with insoluble phosphate as with the soluble phosphates when ammonium sulphate was used in connection with the phosphate.

A number of experimenters have noted the above facts and carried out various experiments to ascertain the nature of this effect. One of the prominent workers in this field is H. G. Soderbaum (14) from whose work the following table was taken. The crop grown was oats.

Soluble phosphate. . _ _ . . . . . . . . . . . _ . . . _ . . _ _ . . _ . . _ _ . . . . . _ . . . . “ ‘I + sodium nitrate.. . . . . _ _ . . _ . _ _ . . _ _ . . .

Bone meal+sodium nitrate............................... 1‘ U + ammoniumnitrate............................. I‘ “ + ammyium suly)ate + sodium nitrate. . . . . . . ‘I “ ,....................... “

16.1 61.9 49.4 57.9 55.9 62.9

w + urea.......................................... 63.1 “ “ “ + albumin.. . . . . . . . . . . . . . . . . . . . . . 61.1

The yield with the bone meal and ammonium sulphate was as great as that with the soluble phosphate and sodium nitrate. While not so good as ammonium sulphate, ammonium nitrate gives a better yield than sodium nitrate or the organic manures. It may be seen that when used with slightly soluble phosphate sodium nitrate is no better than the organic manure.

This greater yield with the ammonium salts has been attributed to a physiological action of the ammonium sulphate on the plant, and not to a solvent action on the insoluble plant food. The experiment of Schulov (IS), however, seems to indicate that it is due to the latter cause. In these experiments there were two sets of pots, one set in which the ammonium salts and the phosphate were thoroughly mixed ; while in the other set the ammonium salts and phosphate were separate but both were accessible to the plant. Where the fertilizers were mixed there was a much larger yield obtained with the ammonium nitrate than with the sodium nitrate. However, where the nitrogen and phosphorus were separate the yield with each fertilizer was the same.

The work of Brooks (16), at the Hatch Experiment Station on the comparative value of potassium chloride and potassium sul-


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phate, is of interest in this connection. In a three years test on potatoes, there was an average of 22. I bushels more where the sulphate was used than where the chloride was used.

We must bear in mind that this beneficial effect of the sulphate may be due in part to the plant food which it supplies in the form of sulphur. That plants require the presence of sulphur to make a healthy growth is well known. Bogdanov (I 7), Haseloff and Goosel, Konig and others have found that part of the beneficial effects obtained from the use of a sulphate is due to the sulphur which acts as a plant food. With Brook’s experiment, however, there was an increase in the starch in the potato, and Seisl and Gross (59) found that leaves of potatoes which were rich in starch invariably contained more potassium and phosphorus than ones low in this constituent.

That the increase is not due entirely to the action of the sulphur as a plant food is further shown when we make a study of the phosphorus in the plants which have been grown with various fertilizers. A Swedish (18) investigator found that oats grown with an ammonium salt contained .397 per cent of phosphorus while those grown without the ammonium salt contained .375 per cent phosphorus. D. Praimschukow (22) found that buckwheat grown with insoluble phosphate and sodium nitrate contained .1o5 per cent of phosphorus; while that grown with the same phosphate, in connection with ammonium nitrate contained .253 per cent phosphorus. Barley grown with ammonium nitrate contained .IO per cent more phosphorus than that grown with sodium nitrate.

The experiment which illustrates this best is the mixed herbage of permant grass land by Lawes and Gilbert (23). As an average of eighteen years, the plot which received no manure had 2.288 per cent phosphorus in the ash of the grass, while that which received ammonium salts had 2.790 per cent. This is 502 per cent more phosphorus in the ash of the plants which had received ammonium salts. Besides, this increase there was a greater yield of hay on the manured than on the unmanured so that the total phosphorus taken up would be considerably more in the one case than in the other.

Again, take the plot in the Rothamsted (24), experiment with wheat, which received ammonium salts and compare it with tha


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J. E. Greaves 293

unmanured plot. The plot which received no manure produced as an average of 42 years 12% bushels of wheat per acre, while the one receiving ammonium salts averaged 193 bushels per acre. We find that I I .64 pounds of phosphorus were taken up by the crop on the unmanured land ; while the one receiving ammonium salts gave as an average 14.5 pounds per acre. From this we see that there was 2.93 pounds per acre more taken up where the ammonium salts had been used. However, in this case the percentage composition is no higher in the manure gram.

That the phosphorus is more soluble on the plots which have been manured with ammonium salts is further shown by a comparison of the drainage water (25) of the two plots. The unmanured plot had as an average .275 parts per million of phosphorus in the drainage water. The plot which received ammonium salts had as an average .62g parts per million of phosphorus, thus showing that the drainage water from the manured plot is richer in phosphorus than from the unmanured.

The above facts show that of the nitrogen compounds ammonium nitrate is the most effective in causing the assimilation of phosphorus from insoluble phosphates. The ammonium sulphate stands next, while sodium nitrate has little if any effect. This is well illustrated by the work or D. Priamschukow (12) who made some very thorough tests in which he used phosphorite with various nitrogenous salts. The following table gives the results he obtained with oats.

Yield in grams. 6.9 ’ 22.0 Per cent phos-

phorus. . . . .039 .131 Total phosphor-

us in plantmg. 2.707 30.815

20.5

.249

50.99 -__

--

!

1.6 18.9

.637 .244

9.21 46.02

iHzPO, I

--

i

19.8

,231

45.75

The yield was as great with the ammonium nitrate and phosphorite as it was with the soluble phosphate and sodium nitrate.


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The percentage of phosphorus in thetwo crops was also the same. Similar tests were made using barley, buckwheat, peas, flax, vitch and in every case where the ammonium nitrate was used with the phosphate the yield was practically as large as it was with the soluble phosphate. The percentage of phosphorus in the plant was also high with ammonium salts. Thinking this may be due to nitrification he carried on tests in sterile cultures where nitrification did not occur and found that even then the ammonium nitrate increased the assimilability of phosphorus of insoluble phosphates.

SODIUM CHLORIDE AS A FERTILIZER.

Sodium chloride, when used as a fertilizer, seems to vary cnder different conditions. Some experimenters obtain a good yield from its use, others obtain just as good a yield without it. It seems as if there must be some cause for this difference and it may be due to its indirect effects on other plant food through a physiological action on the plants.

F. Stoup (26), in an article on sodium chloride as a manure, attributes the benefit derived from its use as due to its decom- posing insoluble plant food. If this be the correct theory we can account for yields such as those obtained by Dr. Voeckler (27). As an average of five experiments, on land which had been manured with common salts, the yield of mangels was 36,060 pounds. On the adjoining unmanured ground there was but 26,035 pounds; a difference of a little over 10,000 pounds due to the use of common salt. Now if the land was rich in insoluble plant food and the chloride was able to liberate it we could expect a large yield. On the other hand, if the land had been poor in unavailable plant food no good result would have followed its use. Wheeler (18) seems to have established the fact that sodium chloride cannot to any great extent take the place of potassium salts. However, he does think that sodium chloride can liberate phosphorus from insoluble forms as the following will show : “It may, however, be stated here that sodium salts seem to liberate phosphorus and potassium so that under certain circumstances they may act as an indirect manure.” In a later report (29) he shows that the percentage of phosphorus


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J. E. Greaves 295

in a plant is increased by the use of a sodium salt. With rad- ish this was, in some cases, as much as .052 per cent more in the crop from land which had received a full ration of sodium over that which received but a part ration. In the case of turnips there was a difference of .I~I per cent; the beets .035 per cent; the carrots .074 per cent; while in the case of the chickory the results are practically the same in the crop from the manured and unmanured land. The report contains many more cases in which the sodium salt increased the phosphorus in the plant. However, the laboratory tests which have been made on phosphates show that sodium chloride depresses the solubility of a phosphate. If we understood the metabolism of a plant, and plants were grown on the soil containing a phosphate and the chloride, we may find that sodium chloride indirectly rendered the phosphate more assimilable as the above facts tend to show.

EFFECTS OF LIME ON PHOSPHORUS.

It seems to be a well established fact that lime will under certain conditions liberate phosphorus from the soil. The more recent work on this subject is that of the Rhode Island Experi- ment Station. B. L. Hartwell and J. W. Kellogg (30) in speaking of their turnip experiments, with and without lime, say: “The crop of turnip roots from the limed plot which had received finely ground bone was 62 per cent greater than from the cor- responding unlimed plot and the per cent of phosphorus in the dry matter of the roots was 0.378 from the limed plot and 0.351

from the umlimed one. Again, the increase in the crop of turnip roots from the limed plot to which slag meal had been added was 34 per cent as compared with the unlimed plot and phosphorus in the dry matter of the roots was 0.324 per cent from the lime plot and 0.309 percent from the unlimed one. These increases in the percentage of phosphorus in the turnip roots grown upon the limed plots furnish some evidence that more of the phosphorus in the plots was assimilable. ”

These same authors made a test of the phosphorus in the soil by extracting with and without lime. They found more phosphorus in the solution from the soil which had been treated with lime than that which had not.


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In this same line are the experiments of 0. Kellner (31) and his co-workers. They found in the field and laboratory test that phosphorus was liberated by the use of lime.

Again, the work of Sutherst (3 2) shows that insoluble phosphates of the soil become much more soluble when treated with lime. Especially was this true in the case of the ferric phosphate. The solvent action was not found to take place when calcium carbonate was used.

The work of H. J. Wheller and G. E. Adams, in “A Test of Nine Phosphates with Different plants,” is full of illustrations in which lime has been effectual in the liberation of phosphorus. They even claim that it may be of value when a soluble phosphate is used as may be seen from the following: “The results seem to indicate that in a soil deficient or devoid of carbonate of lime and well supplied with the oxides of iron and aluminum, liming may extend the period of efficiency of the soluble phosphates possibly by combining with such of the phosphorus at once, and thus holding it in more assimilable combinations than if it were possible for it all to unite immediately with the iron and aluminum oxides. ”

EFFECT OF IRON SULPHATE ON PHOSPHORUS.

Some writers have made great claims for iron sulphate as a fertilizer. A goodly number of these claims have been made by persons who would profit by its sale. Even when we ignore these cases, there are still cases in which it has produced good results.

The man who made the greatest claim for this, and backed his claim with actual field tests, was Griffiths. (33) Hemadetests with it as a manure on a number of crops. The yields which he obtained were much greater with than without it. Especially was this true with beans, turnips, mangels, potatoes, meadow hay, and grass. With wheat and other grains the yield did not appear to increase with the application of the iron sulphate. Griffiths attributed this increase in yield to the supplying of iron to the plant. For he found considerably more iron in the plants, which had been grown on land manured with the iron sulphate than those grown on the unmanured land. The increase may be due in part to this cause, but a study of the phosphorus of the crop would seem to indicate that there is also another cause.


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J. E. Greaves 297

As an average of three years the bean plants grown on land manured with iron sulphate contained 17.95 per cent (33) of phosphorus in the ash; while those grown on adjoining unmanured land contained but 16.47 per cent of phosphorus. In the ash of the pods alone, there was 15.78 per cent phosphoric acid in those from the manured land and ~5.~3 from the unmanured. The phosphorus in the seed from the manured and unmanured land was the same. With turnip leaves it stood 3.03 per cent in the ash of those grown with the manure and 1.84 per cent in those grown without it. In the roots there was 0.61 per cent more phosphorus in the ash of those grown with sulphate than in those grown without it. Meadow hay had 3.39 per cent phosphorus in the ash of that grown on land manured with the sulphate and 2.34 per cent in that grown without it. Practically the same relationship exists in grass grown under the two conditions. Mangels, 1.00 per cent, potatoes, 1.01 per cent, beet roots, I. I 8 per cent more in the ash of those grown on land manured with sulphate than those grown of land not thus manured. Wheat was about the same on manured and unmanured land.

Boetet and Paturel (35) obtained an increase in the crop due to the use of iron sulphate but differ from Griffiths in not find- ing a greater amount of iron in the plants grown on land manured with iron sulphate.

The Hill (36) experiments in England are of the same type. Wheat was grown in pot experiments with and without iron sulphate. The pot which received no sulphate yielded 35.38 grams of wheat and straw, while an average of the three manured pots was 36.48 grams. The yield was greatest on the pot which received at the rate of IOO pounds of iron sulphate per acre.

W. P. Brooks (55) obtained a larger yield of soy beans on land manured with iron sulphate than on unmanured land. However, he did not find a deeper green in the plants. on the manured land as did Griffiths.

Taking into account the above facts it would seem as if under some conditions iron sulphate can assist in the assimilation of phosphorus. Just how this is brought about is hard to say for extraction tests show that iron sulphate renders phosphates less soluble.


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CALCIUM SULPHATE.

Calcium sulphate is the most powerful land stimulant we have. This is mostly caused by its liberation of plant food, especially potassium. However, there are some experiments which tend to show that it affects the phosphorus of the soil.

The experiments carried on at Tokyo (37) show that rice yielded better and had a better color when grown on land manured with gypsum.

The analysis made by Baussingault and quoted by Storres (38) shows a greater amount of phosphorus in clover taken from land manured with gypsum. The phosphorus in the clover from the manured land was 10.57 kilos; that from the unmanured 4.80 kilos. The following year although no more manure was applied the phosphorus from the hay grown on the manured land was 6.93 kilos more than from the unmanured.

Pfeffer (56) states that Knop found that when seeds are in water containing calcium sulphate, the calcium of the salt is absorbed in a somewhat greater amount than the acid. If this be true it is easy to see how calcium sulphate can assist in the assimilation of phosphorus, even though the phosphates are found to be less soluble in a calcium sulphate solution.

EFFECT OF OTHER SULPHATES ON PHOSPHORUS.

The sulphates seem to act very strongly on the insoluble phosphorus of the soil. Where there is a lack of available phosphorus, the sulphates produce yields over and above the chlorides or nitrates with the exception of ammonium nitrate. The Roth- amsted experiments illustrate this in a very striking manner. The following table gives the yield of wheat from plots 3, I I, I 2,

13 and 14.


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J. E. Greaves 299

Table showbag the average yearly yield of wheat for 51 years on the Rothamsted Experimental Farm.

PLOT NO.

T

TREATMENT. ! OF48

YE*FlS 1852-92.

Unmanured continuously.. . . 12; 400 lb. amm. salts 350 lb. super-l

phosphates.. . . . . . . . . . 242 400 lb. ammonium salts, 350 lb. super-

phosphates, 3663 lb. Na,SO,. . . . . 30 400 lb. amm.-salts, 350 lb. superphos-

phates 200 lb. K,SO,. . . . . . . . . . 314 400 lb. amm.-salts 350 lb. superphos-

phates 280 lb. Mg. SO,. . . . . . . . 30;

1899. 1900.

--.-.-A--

12 i 12;

214 18;

282 242

' 26: 28i

282 ! 23t

18.0

18.9

30.5

39.4

26.0

It may be seen from the above table that the plot which received sodium sulphate gave as an average 30 bushels per acre, or 54~ bushels more than plot I I which with the exception of the sodium sulphate was treated the same. This yield is within 14

bushels of that of plot 13 which received the potassium sulphate. This beneficial effect produced by sodium sulphate is usually attributed to the liberation of potassium. While a considerable part of this beneficial effect is undoubtedly due to this cause, a study of the phosphorus yielded by each plot, will at least indicate that there is another factor entering. The average yield of phosphorus from plot II was 8.27 pounds (40) per acre; while the average on plot 12 was 9.82 pounds per acre. It may thus be seen that as an average of 20 years there were 1.55 pounds more of phosphorus taken from the sulphate plot than from the plot which received no sulphate. When one takes into consideration this excess of 31 pounds of phosphorus which had been re- moved it would seem that the sulphate had in some way made the phosphorus more available. As an average of 4p years the plot which received superphosphate alone had 16.46 per cent (41) phosphorus in the ash of the wheat. The plot whichreceived sodium, potassium, and magnesium salts in addition to the superphosphate had 16.7% per cent phosphorus in the ash of the wheat.

The above facts point very strongly to a liberation of phosphorus by various sulphates. This is well shown by the work of


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Dyer (42). He made a careful study of the soil from the Hoos Field, Rothamsted. The land had been in barley for 42 years. The plot which had received no manure was found to contain 22.27 pounds more per acre in the first nine inches than the one which had received ammonium salts. However, the amount soluble in a I per cent solution of citric acid was 5.24 pounds more in the latter than in the former. When the plots throughout the entire field were taken the same relationship was found to hold. There was more soluble phosphorus in every case in the plots which had received a sodium, potassium, magnesium, or ammonium salt. If we take Dyer’s averages of the plots which were treated nearly alike this fact is brought out even more forcibly than the above. The four plots which received nitrogen, but no mineral manure yielded, as an average of 38 years, 28+ bushels of barley per acre. The soluble phosphorus in these plots was 69 pounds per acre. Now taking the four plots which received nitrogen, sodium, potassium and magnesium but no phosphoric acid, yielded as an average for the same length of time 30+ bushels, and contained ro3.47 pounds per acre of soluble phosphorus. It may be seen that the latter in the course of 38 years yielded 72 bushels more barley than the former and at the end of this period had 32.61 pounds per acre more soluble phosphorus in the soil. Again, the four plots which received a complete fertilizer had an average yearly yield of 398 bushels per acre. The plots which received only nitrogen and phosphorus yielded 38% bushels. At the end of the period there were 549.7 pounds of soluble phosphoru; in the one which received complete fertilizer; while the plot which received nitrogen and phosphorus only, had in the first nine inches 477.6 pounds of soluble phosphorus per acre. This is 72. I pounds in favor of the plots which received sulphates.

Later Dyer (44) made a study of the Rothamsted wheat soil; determining the potassium and phosphorus present in a soluble and insoluble condition. The following is what he had to say concerning the effect of sodium, potassium, and magnesium salts on the solubility of phosphorus in the soil. The summary is quoted nearly in full on account of its direct bearing on the subject under consideration.


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J. E. Greaves

EFFECT OF ALKALINE SALTS ON THE SOLUBILITY OF PHOSPHORUS

IN THE SOIL.

“It will have been seen that two of the six phosphate manured plots differ notably from the others in the subsoil contents of citric-acid-soluble phosphorus. These are plots 5 and 7. These two plots alone, in addition to phosphorus have had persistently supplied to them potassium, sodium, and magnesium salts (400 pounds per annum in the aggregate). To three of the other four plots one or the other of these salts has been supplied, but only to these two have all three salts been given. One of the two (plot 7) has received ammonium salts also in the same quantities as plots I I to 14. The other (plot 5) has received the same full phosphatic and mineral saline dressing, but without ammonium salts.

Plot 5, getting no nitrogen, and yielding in consequence an annual average crop not very greatly exceeding that of the unmanured soil, has naturally accumulated a far larger quantity of phosphorus, nearly 218

pounds more per acre being found by analysis in the first 9 inches than in the average of the plots receiving both ammonium salts and mineral manures. As would be expected, there is also a much larger accumulation of citric-acid-soluble phosphorus and the proportion of citric-acid- soluble to total accumulation is greater than in the average of these other plots. Further, in both the second and third depths we find a tangible excess of citric-acid-soluble phosphorus beyond that in the unmanured plot, showing that the available phosphorus in the subsoil has been in excess of the demands of the crops. That this is not wholly due to the supply of a relatively large abundance of phosphorus without nitrogen, but also to another cause, appears on comparison with the results found in the case of plot 7, which in addition to a precisely similar liberal supply of phosphates and other saline minerals has received also ammonium salts.

Plot 7 has yielded in virtue of the full supply of potassium, sodium, and magnesium salts, in addition to phosphate and ammonium salts, a persistently larger yield of both wheat and straw than any of its companions. Consequently, its output of phosphorus has been greater and its accumulation less. Instead however, of being poorer in available phosphorus it is now richer to the extent of some hundreds of pounds per acre than its companions which received either less alkaline salts or none.

It seems that the full supply of potassium, sodium, and magnesium salts has either exerted a solvent action on natural store of otherwise unavailable phosphorus in the soil, or, which appears more probable, that the manurial phosphates have entered into combination with the saline bases, and been retained in a less insoluble condition then where these have been absent or less in quantity.

Plot I 1, which has received phosphates and ammonium salts only and has yielded smaller crops and accumulated more phosphorus than plots I 2, I 3, and I 4, shows less citric-acid-soluble phosphorus than any of them. Next comes plot 12 which has annually received 3666 pounds per annum of sodium sulphate. and which, though accumulating less phosphorus, is


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nevertheless appreciably richer in citric-acid-soluble. Next is plot 14, accumulating almost the same phosphorus as plot 12, but getting 280 pounds per annum of magnesium sulphate, and showing, in the surface soil, 32.75 pounds more of citric-acid-soluble phosphorus though less in the subsoil. Next come plots 13 and 14, getting respectively 200 pounds of potassium sulphate and 280 pounds of magnesium sulphate per annum, There have accumulated respectively 27.94 pounds less and 5.24 pounds more of phosphorus per acre than plot I 2, but are respectively 24 pounds and 32.75 pounds richer in citric-acid-soluble in the first 9 inches.

The following figures show the proportion borne by the excess of citric-acid-soluble phosphoric acid over plot 3 (both in the first 9 inches and in the whole 27 inches) to the calculated accumulated excess over plot 3.

1893 SAMPLES.

Ratio of excess of citric-acid-soluble phosphoric acid over unmanured plot to calculated excess of phosphoric acid supplied per acre over unmanured plot, the calculated excess in each case being taken as roe.

PLOT.

5

7

13

14

12

11

-

_- TRE.4TMENT.

PIRBT 9 INCHEB.

per cent. Phosphates, potassium, sodium and magne-

siumsalts................................. 48 Ammonium salts, phosphates, pot,assium,l

sodium and magnesium salts. . . . . . . . .’ 50 Ammonium salts, phosphates and potassium

salts..................................... 36 Ammonium salts, phosphates and magnesium

salts.. , . . . . . . . . . . . . . . . . . . . . . 35 Ammonium salts, phosphates and sodium

salts..................................... 33 Ammonium salts, and phosphates only.. . . i 31

27 INCHES.

per cent.

50

50

34

34

32 29

It appears that the action of sodium sulphate (366 pounds per annum) in maintaining the phosphate in an easy soluble condition has been somewhat less than that of magnesium sulphate (280 pounds per annum), and that this again has had less effect than potassium sulphate (200 pounds per annum). But the addition to the 200 pounds of potassium sulphate of IOO pounds magnesium sulphate and roe pounds sodium sulphate has greatly affected the condition of the phosphorus in the surface soil, and has appreciably affected it in the subsoil.”

The above facts tend to show that the solvent action of potas-

sium was greater than that of sodium or magnesium salts. How- ever, when we take into consideration the fact that sodium and magnesium sulphate carry considerable water of crystallization,


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J. E. Greaves

we find there was more of the dry potassium sulphate applied than either of the other salts. There would beof the dry salts 200

pounds of potassium sulphate, 162 pounds of sodium sulphate, and 137 pounds of magnesium sulphate. The relationship is brought out clearly in the following table which shows the ratio between the dry salt applied and the soluble phosphorus found in the soil.

FIRST PKJT. TRELTMENT. 9 INCHES.

12

13

14

Ammonium s&s, phosphates and sodium salts..................................... 10.6

Ammonium salts, phosphates and potassium salts.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . / 9.2

Ammonium salts, phosphates and magne-’ sium salts.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8

PIRBT 27 INCHE$.

10.4

8.7

13.2

From the above it may be seen that pound for pound the magnesium salts are the most effective in keeping the phosphorus soluble. The sodium sulphate comes next and the potassium salts have least effect.

All the above facts point to the conclusion that some soluble salts when applied to the soil either alone or in connection with a phosphate tend to made the phosphate more available to the plant. The salts which appear to have this effect are calcium, iron, sodium, ammonium, potassium, and magnesium sulphate and ammonium nitrate. This may be due to either of the following causes or both. First, to the feeding power of the plant, or in the case of the ammonium compounds to bacteria, which break down the salt applied and render the soil solution slightly acid. That this may in part account for the solvent action is indicated by the effect of ammonium sulphate on soil. When this compound is used for some time on a land poor in hme the land becomes acid. Now even though this acidity be ever so small, with most salts on ordinary soil, there would still be its action on soil particles which would tend to make the plant food more available. Second, this effect may be due to the direct solvent action of the salt as applied or indirectly by its reaction with salts already in the soil and their subsequent action on the


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phosphates. Considerable light will be thrown on this solvent action by means of the laboratory tests which have been carried on in connection with the above study.

EFFECT OF SALINE SOLUTIONS ON PHOSPHATES.

Historical.

A number of experimenters have done some work, in the laboratory, to determine the solvent action of various salts in solution on phosphates. This, in the main, has been fragmentary, one making a few tests on one compound under certain conditions, while others working with different compounds and maybe under different conditions made other tests. Again, many of these tests were made on chemically pure substances. While this may give us the action of the solvent on the phosphate, it will not, however, give us the indirect action if there be one. That is, there may be a reaction between certain compounds in a soil or impure phosphate, and then an interaction between this new compound and some element in the phosphate. Or it may be that the solution of the new compound formed will hold more of the phosphate in solution than the original solution would. Some of the experimenters have based their conclusions on single tests; another test may reverse the conclusion. Again, some of the work was done before the present delicate methods for determining phosphorus were known.

The following is a brief summary of the most important work done on this subject.

Schulov (45) found that a solution of ammonium sulphate extracted more phosphorus from a phosphorite than did the same volume of distilled water. This was found to be true with the nitrate also, but not to as great an extent as with the sulphate solution.

Cameron (46), working with chemically pure iron phosphate, aluminum phosphate, and calcium phosphate, found that the calcium phosphate was slightly more soluble in a solution of potassium chloride, and less soluble in calcium chloride and calcium nitrate than in distilled water. The iron phosphate was more solu-

ble in a potassium sulphate solution and less soluble in a potassium chloride and a sodium nitrate solution than in water. He


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J. E. Greaves 305

showed further that equilibrium was not established until at least ten days after the solution had been added to the phosphate.

Kalmann (47), extracted soil with a solution of calcium sulphate and with distilled water and obtained the same amount of phosphorus in each case.

Feedler (48), obtained less phosphorus by extracting the soil with sodium nitrate solution than with distilled water. Krouch (49)) however, obtained more with a sodium chloride solution than with water. Thompson (so), found the same to hold true when a superphosphate was used in the place of soil.

Both Kellner (5 I), and Sutherst (5 2), found that lime rendered the phosphorus of the soil more soluble. Later, Hartwell (53), and Kellogg at the Rhode Island Station found the same to be true.

Voelcker (54)) working with phosphate, bone meal, Cambridge and Suffolk caprolites, found that they were all more soluble in ammonium chloride and in ammonium carbonate solutions than in distilled water. Sodium nitrate solution extracted more of the phosphate than did water while the caprolites yielded the same to each solvent.

Sutherst (52), found that lime extracted more phosphorus from iron and aluminum phosphates than water but when calcium carbonate was used in place of the lime the same amount of phosphorus was obtained with each solvent. He also found that potassium chloride and sodium chloride solutions each extracted less from bone meal than did distilled water. However, when he used bone flour in place of bone meal each salt extracted considerable more than the distilled water. He explains this apparent contradiction by assuming that bone meal, when in the soil, under- goes fermentation by which the phosphorus is rendered more soluble but when quantities of inorganic salts are present this fermentation is prevented.

Liebig (57), showed that sodium nitrate increased the solubility of calcium phosphate, while Lachonicy (58), found that it decreased the solubility of iron phosphate.

It may be seen from the above summary that lime, the chloride, carbonate, sulphate, and nitrate of ammonia, were always found to increase the solubility of a phosphate. The nitrate, chloride, and carbonate of calcium were found to always decrease the solu-


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bility of phosphates while the sulphate had no effect. Potassium sulphate rendered the iron and aluminum phosphates less soluble but it increased the solubility of calcium phosphate. Sodium nitrate with two exceptions extracted less than water. And it is to be noticed that in these cases the compounds were bone meal, which is rich in calcium phosphate, and a chemically pure calcium phosphate. So it would seem as if the calcium phosphate is more soluble and the iron phosphate less soluble in sodium nitrate solu-

tions than in distilled water. The results obtained where sodium chloride was used as the solvent vary and with the data at hand it is not easy to explain this difference.

EXPERIMENTAL.

On account of the great importance of the phosphates in agriculture, and especially the insoluble ones, as they are the ones which would be found in largest quantities in the soil, it seems that time would not be badly spent in making a test of the solvent action of various salts on insoluble phosphates, to see if more definite information can be obtained on this subject.

In making this study six phosphates, three brown, two blue, one white, and a combination of brown phosphate and soil, have been extracted with solutions of the following compounds; sodium, potassium, calcium, magnesium, ammonium and ferrous sulphate, also the chlorides and nitrates of sodium, potassium, calcium, magnesium, and ammonium.

Methods of Investigation.

Two grams of the phosphate to be tested were treated in a IOOOCC.

glass stoppered bottle with 500 cc. of a1 I per cent solution of each of the above compounds. This was let stand with occasional shaking for from IO to 14 days. At the end of this time they were filtered through 18 cm. filter paper under which was a I I cm. filter. To 450 cc. of the solution thus obtained were added IO cc. of a I

per cent solution of iron chloride, the solution acidified and evaporated nearly to dryness. While still hot this was precipitated

9n the case of calcium sulphate a saturated solution of the salt was used.


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J. E. Greaves 307

with ammonium hydroxide, care being taken not to get an excess, and filtered, and washed with hot water. The precipitate was dissolved with nitric acid, evaporated to dryness, taken up with a few drops of hydrochloric acid, evaporated to dryness and heated in an air oven for 30 minutes at 105~ C. This residue was taken up with acidulated water, the silica filtered off and washed with hot water and the filtrate concentrated to IO or 20 cc. This was treated with ammonium hydroxide and barely enough nitric acid added to dissolve the precipitate which was formed. The solution was then heated to 56’ C. and IO cc. of molybdic acid solution of the same temperature added, and kept at this temperature for two hours. At the end of this time it was set in a cool place for about twelve hours. The solution was then filtered and washed with a . I per cent solution of ammonium nitrate until free of acid. the last two washings being with cold distilled water. The precipitate was dissolved in potassium hydroxide of such a strength that I cc. of the solution was equivalent to .2 mg. of phosphorus. The excess of alkali was titrated with a nitric acid solution I cc.

of which was equivalent to ICC. of the standard alkali, using phenolphthalein as an indicator.

Dark Brown Rock Phosphate.

The first sample tested was a dark brown phosphate containing IO. 6 per cent of the element phosphorus. This was a sample of the phosphate used by the Illinois Agricultural Experiment Sta- tion. It was taken just as used on the soil, i. e., without further grinding.


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TABLE 1

Phosphorus dissolved by 450 cc. of 1 per cent solution of each of the following

solvents from a graves of dark brown rock phosphate.

BOL.VENT UJBED. I- ! 1

Distilled water Ammonium nitrate : Iic Ammonium sulphate. 0.86 Sodiumsulphate.. . . 0.86 Ammonium chloride. 0.94 Potassium sulphate.. 0.68 Magnesium sulphate 0.74 Magnesium nitrate. . 0.52 Sodium nitrate . . . 0.58 Magnesium chloride. 0.62 Potassium chloride. . 0.58 Potassium nitrate. . . 0.50 Sodium chloride.. . . . . 0.54 Calcium nitrate.. . . . 0.24 Gypsum............. 0.22 Calcium’sulph. C. P. 0.20 Calcium chloride.. . . . 0.14 Iron sulphate. . . . . . . 0.20 Distilled water., . . . . 0.58

___-

2

0.59 0.90 0.82 0.90 0.98 0.72 0.80 0.48 0.59 0.57 0.63 0.64 0.52 0.24 0.20 0.26 0.16 0.22 0.59

3 4

D.36 0.61 0.54 0.78 0.56 0.74 0.60 0.42 0.28 0.48 0.30 0.49 0.50 0.36

0.36

5 1

_-

0.21

0.56 0.82 0.59 0.78 0.86 0.38 0.26 0.58 0.30 0.46 0.42 0.52

0.58 0.66 0.62 0.65 0.42

0.48 0.40

0.32

0.12 0.16 0.10 0.14 0.12 0.24 0.36 0.36 0.21

4verage.

0.42 0.79 0.67 0.80 0.74 0.71 0.68 0.45 0.43 0.55 0.44 0.52 0.46 0.34 0.21 0.23 0.13 0.18 0.42

%+m3nce from that extracted

by water.

0.37 0.25 0.38 0.32 0.29 0.26 0.03 0.01 0.13 0.02 0.10 0.04 0.08

-0.21 -0.19 -4.29 -0.24

P, ‘The first solution of calcium sulphate, marked C. P., used extracted from 2 to 5 mg. of

but on testing it was found to be slightly acid.

It may be seen from Table I that the duplicate tests in the main agree fairly well. Columns no. I and z do not fully agree with columns 3 and 4 but this difference is very likely due to a difference of temperature and the amount of shaking received during extraction. However, the same relationship exists throughout between the amount extracted by’ water and the various solvents. In every case the calcium and iron solutions extracted less phosphorus than the water. Sodium, magnesium, ammonium, and potassium sulphate, magnesium and ammonium chloride, and ammonium and potassium nitrate extracted considerably more phosphorus than distilled water. This is especially high in the case of sodium sulphate and the ammonium compounds. The amount extracted by sodium and potassium chlo-


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J. E. Greaves 309

ride and sodium and magnesium nitrate is about the same as that extracted by distilled water. The table shows very plainly that the sulphates in every case extracted more than the nitrates and they in turn extracted more than the chlorides.

Phosphate and Soil.

The same phosphate was tested with soil to see if it would change the solubility. In this case eight grams of a sandy loam soil was mixed with two grams of the phosphate and extracted as in the previous case.

TABLE 2

Phosphorus dissolved by&O cc. of a 1 per cent solution of each of the following solvents, from d grams of ph

Distilled water ......................... Ammoniumnitrate ..................... Ammonium sulphate ................... Sodium sulphate ....................... Ammonium chloride .................... Potassium sulphate. ................... Magnesium sulphate. .................. Magnesiumnitrate ..................... Sodium nitrate ........................ Magnesium chloride .................... Potassium chloride ..................... Potassiumnitrate ..................... Sodium chloride ........................ Calciumnitrate ........................ Calcium sulphate C. P .................. Calcium chloride ....................... Iron sulphate .......................... Distilled water ........................

081

--

1

I I I t ( ( ( (

shate and 8 grams of sbil. -

1 2 Average

-‘-

1

I

0.76 1.44 0.80 0.96 0.58 0.88 0.68 1.24 0.06 0.70 0.44 D.86 3.80 3.44 I.39 1.40 I.32 I.76

-- , ,

,

/ I I

j I

1 1

I’ I (

I( i ( i (

i

0.78 1.46 0.84 0.98 0.60 0.86 0.70 1.22 0.95 0.66 0.42 D.84 3.74 3.46 1.42 1.44 I.28 I.78

0.77 1.45 0.82 0.97 0.59 0.87 0.69 1.23 0.96 0.68 0.43 0.85 0.77 0.45 0.40 0.42 0.30 0.77

I ,.

--

xfference from that extracted

by water.

0.68 0.05 0.20

-0.18 0.10

-0.08 0.46 0.18

-0.09 -0.34

0.08 0.00

-0.32 -0.37 -0.35 -0140

Eight grams of the soil alone was extracted with each of the solvents. The calcium and iron compounds did not extract enough phosphorus from the soil to give qualitative tests while the rest of the solvents extracted barely traces. Therefore, practically all of the phosphorus reported in table 2 is from the phosphate.


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The noteworthy facts shown in table 2 are as follows. The amount of phosphorus extracted byeach solvent is much greater where soil is used with the phosphate than where either is used alone, being especially marked in the case of the nitrates. Where the soil is used with the phosphate the nitrates extract more phosphorus than the sulphates, but where the phosphate is extracted alone the reverse is true. When soil is mixed with the phosphate the calcium and iron compounds and all thechlorides extract less thandistilled water. Sodium and potassium sulphate, magnesium and ammonium nitrate extract more than water.

Light Brown Rock Phosphate.

A sample of light brown phosphate of loose texture containing I 2.6 per cent of phosphorus, was ground and extracted with each of the solvents. The grinding was done in a large steel mortar, and may not have been ground as fine as the preceding sample. This may account for the small amount of phosphorus extracted by each solvent.


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J. E. Greaves 311

TABLE 3

Phosphorus dissolved by .450 cc. of a I per cent solution of each of the following solvents, from two grams of light brown rock phosphate.

Distilled water.. . . . . . . . Ammonium nitrate.. . Ammonium sulphate. . . Sodium sulphate. . . . Ammonium chloride. . . Potassium sulphate . Magnesium sulphate . . . Magnesium nitrate. . . Sodium nitrate.. . . . Magnesium chloride.. . Potassium chloride. . . . Potassium nitrate.. Sodium chloride.. . . . . . Calcium nitrate. . . Gypsum............... Calcium sulphate C. P . Calcium chloride . . . . . . . Iron sulphate. . , . . . . . . . . Distilled water.. . . . . . . .

-- 0.30 1.70 0.38 0.27 0.33 0.34 0.34 0.50 0.32 0.30 0.20 0.29 0.18 0.36 0.20 0.18 0.20 0.15 0.30

0.23 0.78 0.36 0.20 0.26 0.38 0.34 0.32 0.20 0.28 0.22 0.23 0.36 0.38 0.22 0.14 0.18 0.11 0.23

0.36 1.56 0.48 0.36 0.56 0.36 0.46 1.18 0.34 0.22 0.18 0.26 0.26 0.14 0.37

0.42 1.66

0.36 0.58 0.36 0.34 0.62 0.36 0.26 0.30 0.36 0.14

0.18 0.12 0.18 0.20 0.36 0.42

Average.

0.33 1.43 0.41 0.30 0.43 0.36 0.37 0.66 0.31 0.26 0.23 0.28 0.21 0.37 0.21 0.16 0.17 0.16 0.33

.- lifference from ,hat extracted

by water.

1.10 0.08

- .03 0.10 0.03 0.04 0.33

-0.02 -0.07 -0.10 -0.05 -0.12

0.04 -0.12 -0.17 -0.16 -0.17

An examination of table 3 shows that to a certain extent there is the same regularity as observed before. The calcium and iron compounds with the exception of calcium nitrate have prevented the phosphorus from going into solution. The sodium, potassium, and magnesium chlorides seem to have exerted this influence also. The ammonium compounds and magnesium nitrate are the only ones which have, to any great extent, exerted a solvent action on the phosphate. The amount extracted by ammonium nitrate was very large being nearly five times as great as that extracted by water. Columns 3 and 4 were extracted for fourteen days, and they are almost invariably higher than columns I and 2 which were extracted but ten days. This would indicate that equilibrium was not established at the end of ten days.


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White Rock Phosphate.

The next phosphate tested contained 13.3 per cent of the element phosphorus. It was much harder than the phosphates pre- viously tested and was nearer a pure calcium phosphate contam- ing but little iron. The phosphate was ground in an agate mortar until free from grit then extracted with the various solvents.

TABLE 4

Phosphorus dissolved by 450 cc. of a 1 per cent solution of each of the following solvents, from B grams of white rock phosphate.

Distilled water ......................... Ammoniumnitrate ..................... Ammonium sulphate .................... Sodium sulphate ....................... Ammonium chloride .................... Potassium sulphate. ................... Magnesium sulphate. .................. Magnesium nitrate ...................... Sodiumnitrate ......................... Magnesium chloride .................... Potassium chloride ..................... Potassiumnitrate ...................... Sodium chloride ........................ Calciumnitrate ........................ Gypsum ............................... Calcium sulphate C. P .................. Calcium chloride ....................... Ironsulphate ..........................

Distilled water ..........................

1

0.34 1.14 0.90 0.86 0.74 0.68 0.66 0.82 0.82 0.60 0.62 0.66 0.34 0.14 0.18 0.22 0.14 0.12

0.34

2

0.40 1.18 0.96 0.78 0.96 0.78 0.72 0.68 0.74 0.64 0.50 0.64 0.44 0.16 0.26 0.23 0.24 0.16 0.36 0.40

Averape.

0.37 1.16 0.93 0.82 0.85 0.73 0.69 0.70 0.78 0.62 0.56 0.65 0.39 0.15 0.22 0.22 0.19 0.14

0.37

D t

--

ifferenoe from hat extracted

by water.

0.79 0.56 0.45 0.48 0.36 0.32 0.33 0.41 0.25 0.17 0.28 0.02

-0.22 -0.15 -0.15 -0.18 -0.23

The calcium and iron compounds extract less phosphorus than distilled water while the sodium extracts about the same as distilled water. All the remaining compounds render the phosphate more soluble. This is especially marked with the nitrates and sulphates of sodium and potassium, and all the ammonium compounds.


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J. E. Greaves 313

Blue Rock Phosphate.

The next sample tested was a blue phosphate, the outer edges of which had weathered and had become dark brown. The sample was separated into two parts, weathered and unweathered. The former contained 9.9 per cent phosphorus and was harder than the latter, which contained but 8.9 per cent of phosphorus. The samples were tested separately with the results reported in table 5.

TABLE 5

Distilled water.. . . . 0.20 Ammonium nitrate. . 0.54 Ammonium sulphate 0.26 Sodium sulphate. . . . 0.16 Ammonium chloride. 0.28 Potassiumsulphate. 0.22 Magnesium sulphate 0.28 Magnesium nitrate. 0.36 Sodium nitrate.. . . 0.16 Magnesium chloride. 0.29 Potassium chloride. 0.16 Potassium nitrate. . 0.15 Sodium chloride. . . 0.18 Calcium nitrate.. . . . 0.24 Gypsum.. . . . . . . . 0.16 Calcium sulphate C.

0.26 0.23 0.52 0.53 0.26 0.26 0.18 0.17 0.42 0.35 0.28 0.25 0.28 0.28 0.30 0.33 0.24 0.20 0.22 0.25 0.14 0.15 0.18 0.16 0.14 0.16 0.20 0.22 0.18 0.17

P . . . . . . . . . . . . . . . . . . 0.14 0.22 0.18 Calcium chloride. . . 0.08 0.12 0.10 Iron sulphate.. . . . 0.02 0.06 0.04 Distilled water . . . . 0.20 0.26 0.23

2

_-

0.30 0.03

-0.06 0.12 0.02 0.05 0.10

-0.03 0.02

-0.08 -0.07 -0.07 -0.01 -0.06

-0.05 -0.13 -0.19

1

0.39 0.41 0.40 0.54 0.78 0.66 0.72 0.74 0.73 0.56 0.52 0.54 0.40 0.48 0.44 0.51 0.49 0.50 0.49 0.46 0.48 0.32 0.28 0.30 0.36 0.36 0.36 0.36 0.22 0.29 0.36 0.42 0.39 0.27 0.33 0.30 0.32 0.28 0.30 0.20 0.15 0.17 0.14 0.16 0.15

0.18 0.20 0.19 0.04 0.16 0.10 0.06 0.08 0.07 0.39 0.41 0.40

--

2

-

_-

,-

-

0.26 0.33 0.14 0.04 0.10 0.08

-0.10 -0.04 -0.11 -0.01 -0.10 -0.10 -0.23 -0.25

-0.21 -0.30 -0.33

The weathered phosphate yielded its phosphorus to solvents much more readily than the unweathereed. With the exceptions of sodium sulphate, magnesium chloride and nitrate the same relationship is found in both phosphates. The calcium and iron


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compounds, sodium and potassium chloride and nitrate prevented the phosphorus from going into solution. The ammonium compounds, as usual, had the greatest solvent action.

Another sample of blue phosphate containing 8.5 per cent of phosphorus was tested. This yielded enough phosphorus to the magnesium and ammonium sulphate, ammonium chloride and ammonium and potassium nitrate solutions to give a qualitative test. None of the other solvents extracted sufficient for a test. So it may be seen that the solvents which extracted a comparatively large amount of the preceding phosphate gave a qualitative test with the second.

Summary of Solubility Tests.

The relationship existing between the various phosphates and solvents is brought out much clearer if the results with like phosphates are brought together. The light brown, dark brown, and weathered blue can very naturally be classed together as weathered phosphate. The white, while equally a weathered phosphate, seems to have been worked over and differs from the brown in being nearer pure calcium phosphate. The two samples of blue can be classed as unweathered.

The following table shows the relationship existing between the various weathered and unweathered phosphates stated as-mg. of phosphorus extracted from two grams of each phosphate by 450 cc. of the various solvents.


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J. E. Greaves 315

TABLE 6

Phosphorus dissolved by 450 cc. of a 1 per cent solution of each of the following solvents, from B grams of each of the phosphates. Average of all the

determinations.

-- _- Distilled water.. . . . . . 0.33 0.44 0.40 0.37 0.23 Ammonium nitrate.. . 1.43 0.79 0.66 0.96 0.53 Ammonium sulphate.. 0.41 0.67 0.73 0.60 0.26 Sodium sulphate. . . . 0.30 0.80 0.54 0.55 0.17 Ammonium chloride. 0.43 0.74 0.44 0.53 0.35 Potassium sulphate. . 0.36 0.66 0.50 0.51 0.25 Magnesium sulphate. 0.37 0.68 0.48 0.51 0.28 Magnesium nitrate. . . 0.66 0.45 0.30 0.47 0.33 Sodium nitrat,e.. 0.31 0.43 0.36 0.37 0.20 Magnesium chloride. 0.26 0.57 0.29 0.37 0.25 Potassium chloride.. . 0.23 0.44 0.39 0.35 0.15 Potassium nitrate.. 0.28 0.48 0.30 0.35 0.16 Sodium chloride.. . . . 0.21 0.46 0.30 0.33 0.16 Calcium nikate.. . 0.37 0.39 0.17 0.28 0.22 Gypsum.............. 0.21 0.21 0.18 0.20 0.20 Calcium sulphate C. P 0.16 0.23 0.16 0.18 0.15 Calcium chloride.. . . 0.17 0.13 0.10 0.13 0.10 Iron sulphate.. . . . . . 0.17 0.18 0.07 0.14 0.04 Distilled water.. . . . . 0.33 0.44 0.40 0.37 0.23

Light BU3WJ.

Dark BKJWIl.

‘eathere Blue. Iverage.

No. 1 Blue.

No. 2 BlW.

traces traces

traces

traces

traces

The above table shows that the sodium, potassium and magnesium sulphates and all the ammonium compounds extract more phosphorus from the weathered phosphate than is extracted by the same volume of distilled water. All the calcium and iron compounds and sodium nitrate depress the solubility of the phosphate. The remaining solvents have little effect or else the effect varies with the phosphate. The most phosphorus is extracted from the unweathered phosphate by the ammonium compounds, magnesium sulphate, and potassium nitrate.

Inasmuch as there is a similarityinall theweatheredphosphates we can take an average of them and compare this average with the average of the unweathered, white, and a mixture of soil and


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brown. In this way factors that are common to all are brought out. Furthermore, it shows the effect of soil on brown phosphate.

In studying table 7 we find that with all the phosphates the calcium compounds have depressed their solubility. This is what may have been expected for the phosphate and calcium salt would each form common ions (Ca) and if the two solutions, the calcium phosphate solution and the other calcium salt solution, were brought together the calcium ion from the calcium salt would force back, as it were, some of the calcium ions from the phosphate with the result that more of the phosphate would be precipitated; hence we would find less soluble phosphorus in the calcium salt solution than in water.

TABLE 7

Average of phosphorus dissolved by 460 cc. of a 1 per cent solution of each of the following solvents from B grams of each of the phosphates.

I-

Distilled water ................ Ammonium nitrate ............. Ammonium sulphate ........... Sodium sulphate ............... Ammonium chloride ............ Potassium sulphate. ........... Magnesium sulphate. .......... Magnesium nitrate ............. Sodiumnitrate ................. Magnesium chloride ............ Potassium chloride .............. Potassiumnitrate .............. Sodium chloride ................ Calcium nitrate ................ Gypsum. ...................... Calciumsulphate C. P ........... Calcium chloride ............... Iron sulphate ................... Dist.illed water .................

‘i

4

Weathered Phosphate

0.37 0.96 0.60 0.55 0.53 0.51 0.51 0.47 0.37 0.37 0.35 0.35 0.32 0.28 0.20 0.18 0.13 0.14 0.37

Y . --

-

-7

nweatherec Phosphate.

White Phosphate

0.23 0.37 0.53 1.16 0.26 0.93 0.17 0.82 0.35 0.85 0.25 0.73 0.28 0.69 0.33 0.70 0.20 0.78 0.25 0.62 0.15 0.56 0.16 0.65 0.16 0.39 0.22 0.15 0.20 0.25 9.15 0: 20 0.10 0.19 0.04 0.14 0.23 0.37

Soil and Phosphate. --

0.77 1.45 0.82 0.97 0.59 0.95 0.69 1.25 0.96 0.68 0.43 0.81 0.77 0.45

0.40 0.42 0.30 0.77

In every case the iron solution extracted less than the water. This would also appear reasonable, for if there be any change in the basic ions there would be formed iron phosphate which is still


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J. E. Greaves 3’7

less soluble in water than calcium phosphate. In every case the potassium sulphate, ammonium sulphate, magnesium and ammonium nitrate extracted more phosphorus than did water. Dis- regarding the result obtained with the soil and phosphate mixed, we find that magnesium sulphate and ammonium chloride rendered the phosphate more soluble. This, however, is reversed on addition of soil to the phosphate. Sodium sulphate, except with the unweathered phosphate, extracted more than water. Com- paring the results with sodium and potassium nitrate we find where the brown phosphate was used these solvents depressed the solubility, where the white phosphate (a phosphate containing more calcium and little iron) was used they rendered thephos- phate more soluble. This is in accord with the work of other experimenters who have found that these salts depress the solubility of iron phosphate and increase the solubility of calcium phosphate. Sodium, magnesium, and potassium chloride have little if any effect on the phosphate.

Throughout the work it has been noted that ammonium sulphate and especially ammonium nitrate rendered the phosphate more soluble. This was thought to be due to nitrification but on testing for nitrates by means of the Gill’s method there was found to be no more nitrates present at the end than at the beginning of extraction.

SUMMARY AND CONCLUSIONS.

A number of eminent writers have noted the fact that some salts render insoluble phosphates more soluble.

Sodium nitrate and ammonium nitrate give better yields than an equivalent amount of nitrogen in the form of dried blood.

Ammonium nitrate and sulphate are the best form of nitrogen to use in connection with insoluble phosphates.

Ammonium salts, especially ammonium nitrate increase the phosphorus of plants.

A number of experimenters have obtained good results from the use of common salt in connection with insoluble phosphates.

It seems to be well established that lime acts as a solvent on phosphates.

Some experimenters have found that iron sulphate increases the phosphorus of plants.


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The Rothamsted experiments point to the conclusion that potassium, sodium, magnesium and ammonium sulphate liberate phosphorus.

Dyer’s analysis of the Rothamsted soil showed that the phosphorus was more “available” in the soil which had been treated with sodium, potassium, magnesium and ammonium sulphate.

Various experimenters have shown that lime, ammonium nitrate, ammonium sulphate, ammonium carbonate and ammonium chloride increase the solubility of phosphates.

Sodium nitrate exerts a solvent action on calcium phosphate and depresses the solubility of iron phosphate.

Further investigation showed the following: Calcium and iron salts render phosphates less soluble. Sodium sulphate, calcium sulphate, ammonium sulphate,

ammonium chloride, ammonium nitrate, and magnesium nitrate render phosphates more soluble.

Sodium and potassium nitrate render calcium poshphate more soluble and iron phosphate less soluble.

The effect of magnesium sulphate, sodium chloride, magnesium chloride and potassium chloride is small or it varies with the different phosphates.

The presence of soil with the phosphate causes the solvent to act more vigorously; especially is this the case with ammonium nitrate.

(1) (2)

t:; (5) (6) (7) (8) (9)

(10) (11) (12) (‘3) (14)

(1s)

BIBLIOGRAPHY

Storer: Agriculture, i, 269, 270, 469.

Jour. Royal Agr. Sot., vii, 301. Landw. Versucks-stat., I 13-118, 1889 Bied. Centr., 460-462, 1882.

Hilgard’s Soil, 354, 355, 357. Bied. Centr., xxviii, 367-370~ 1899. Kew Jersey Sta. R@., 148-184, 1903.

Maryland Sta. Bul., no. 9 I. Jour. Ckem. SOG., 1184 abstract, 1890.

Storer: Agriculture, i, 329-335.

Bied. centr.. 652-656, 1879.

Ber. de&. bot. Gesell., 238-17, 1905.

Landw. Versucks-stat., xxvii, rg~-160. Landw. Versucks-stat., lxiii, 247-263, 1906. Experiment Station Record, xiv, 85 I, abstract.


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J. E. Greaves 319

(16) (‘7) (18) (20) (21) (2 2) (231 (24)

(2s) (26) (27) (28) (29)

ti (3:) (33)

::i;

(37) (38) (39) (40)

(41) (42)

(43)

(44)

(45)

(46)

(47)

(48)

(49)

(50) (51) (52) (53)

(54)

(55)

(56)

(57)

(58)

(59)

Hatch Experiment Station Rpt., 1896.

Experiment Station Record, xi, 7 2 3 abstract. Experiment Station Record, xvi, 952 abstract. Bed. centr., xxxii; 535-536, 1903. Experiment Station Record, xii, 570 abstract. Landw. Versucks-stat., :xv, 36. Philosophical Transactions of the Royal Society, cxcii, 174, 1900. Jour. Chem. Sot., xlv, 305-407.

Philosophical Transactions of the Royal Society, cxciv, series B, 267. Bied. CeMr., 76-87, 1884. Jour. Roy. Agr. Sot., iii, series 2, 87-91. Rhode Island Station Bulletins, 104 and 106. Nineteenth Annual Report R. I. Sta., 196-202. Eighteenth Annual Report R. I. Expt. Sta., 265. Imp. Univ. Coil. Agr. Tokyo, Bul. 9, r-25, 1891. Ckem. News, lxxxv, 157, 1902. Grifitk’s Treatise on Manures. Ann. Agron., xviii, 4r8-450. Jour. Roy. Agr. Sot., Ixvi, 205. Jour. Ckem. Sot., lxxxviii . Part, 2, 347 abstracts. Storer: Agriculture, i, 347. Memoranda of Rotkamstead Experiments, 1901 and 1905. Jour. Ckem. Sot., XIV, 307-407, 1884.

The Highland and Agr. Sot. of Scotland, 5th Series, 7, 254. Jour. Ckem. Sot., lxv, 146. Jour. Ckem. Sot., Ixv, 148.

Philosophical Transactions of tke Royal Society, xcxiv, series B. 235-2',0.

Experiment Station Record, xiv, 343 abstract. Jour. Amer. Ckem. Sot., xxv, 885-913.

Landw. Versuck’s-stat., xxi, 349-355. Landw. Versuck’s-stat., xxvi, 135-165.

Landw. Versck’s-stat., xxviii, 468-472.

Bied. Centr., xix, 585-588. Imp. Univ. Coil. Agr. Tokyo, Bul. 9 Ckem. News, lxxxv, 157. 92, 185 Rhode Island Agr. Expt. Sta. Rpt., 266, 1905. Jour. Roy. Agr. Sot. zd. series, xlii, 176.

Experiment Station Record, ix, 341 abstract. Pfeffer’s Physiology of Plants, i, 132.

Amer. Chem. Phar., cvi, 185, 1859. Quoted in Bulletin, 41, Bureazz of Soils, 49.

Experiment Station Record, xiv, I 19 abstract.


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J. E. GreavesINSOLUBLE PHOSPHATES

EFFECTS OF SOLUBLE SALTS ON

1910, 7:287-319.J. Biol. Chem.

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