Complete Composition of Commercial Mixed Fertilizers

Although others—for example, McCandless (9)—have pub- lished fairly complete analyses of single samples of commer- cial fertilizers, and although ...
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FERTILIZER MIXINGUNIT

Courtesy, Davison Chemical Corporation

Complete Composition of Commercial Mixed Fertilizers FRANK 0. LUNDSTROM AND ARNON L. MEHRING Fertilizer Research Division, Bureau of Chemistry and Soils, Washington, D. C.

I

IY T H E sale of commercial fertilizers it is customary to

cent CaO, 0.75 per cent MgO, 3.78 per cent SO3,and 3.30 per cent C1. The insoluble part contained a large proportion of organic matter. Although others-for example, McCandless (Q)-have published fairly complete analyses of single samples of commercial fertilizers, and although the results of hundreds of thousands of miscellaneous chemical determinations on commercial fertilizers have also been published, no attempt has been made, as far as is known, to determine the complete composition of the average mixed fertilizer sold in this country. Fine crops may be grown on many unfertilized soils and on many other soils with applications of nitrogen, phosphorus, and potassium only. It is well known, however, that plants must also obtain certain other elements from the soil. If these other elements are not already present in the soil in

guarantee the presence of definite percentages of the primary fertilizer elements, expressed as nitrogen (X), phosphoric acid (P205),and potash (KzO). The sum of these three percentages is usually between 15 and 20 per cent and seldom exceeds 30 per cent. The portion that remains comprises from 70 to 85 per cent by weight of most fertilizers. Of what does this 70 to 85 per cent consist? One of the earliest attempts t o answer this question in part was made by Wheeler (15). He took 2-gram samples of fifty different commercial fertilizers and, after mixing them together thoroughly, extracted the composite mixture with boiling water and analyzed the solution. He found that his samples contained, on the average, in water-soluble form, 5.56 per cent PZOs,3.56 per cent K20,3.01 per cent KazO, 4.90 per 354

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both ordinary and high analysis grades. This study included available form and in adequate quantities, they must be added the chemical determination of the proportions of all elements to obtain normal plant growth. These secondary fertilizer ordinarily occurring in commercial fertilizers in more than elements are comprised in two classes. The first class is retraces and of those trace elements that have proved to be of quired in relatively large quantities and includes calcium, value in plant nutrition, and a statistical analysis of the remagnesium, and sulfur. The second class is required only in sults, using a selected group of samples believed to be repreminute traces and includes iron, copper, manganese, zinc, and sentative of conditions in recent years. boron. Compounds of the three elements in the first class, with those of phosphorus and potassium, make up the bulk of Selection of Samples the ash of plants, but traces of the elements in the second class Approximately 96 per cent of all commercial fertilizer mixare also always present. tures are complete mixtures; P-K mixtures account for the Large tonnages of more than fifty different commercial mamajor part of the remaining 4 per cent. All other kinds of terials are used in the manufacture of mixed fertilizers. They mixed goods constitute less than 0.5 per cent of the total. can be combined in many different ways to make the same Most of the samples, therefore, were chosen from ordinary grade of goods. For example, as an extreme case, a 4 - 8 4 complete grades, but enough P-K grades were included to be mixture can be made from marketed materials so that in representative. addition to the guaranteed quantities of the three primary Since the trend in fertilizer practice is towards higher conplant foods it will contain practically nothing but sand and centrations of N, PZOS, and KZO, and since this necessarily moisture. At the other extreme, a 4 - 8 4 mixture can also be involves changes in some of the other constituents, complete made from such ingredients that the remaining 84 per cent of mixtures representative of ordinary, double-strength, and the mixture consists almost entirely of the oxides of secondary concentrated grades were also included. plant food elements. Practically all commercial fertilizers Although, according to ft survey made by Mehring and occupy positions somewhere between these two extremes. Smalley (f 1 ) for the year ended June 30, 1934, a thousand or I n the past the quantities of secondary plant food elements more grades of fertilizer were sold in 1934, only twenty-seven present in fertilizers have been sufficient, except in very grades accounted for 74 per cent of the sales. The grades limited areas, to prevent noticeable symptoms of a deficiency selected in this investigation to represent the ordinary grades of these elements from appearing in crops. In recent years, of complete fertilizer were chosen from these twenty-seven. however, a trend towards smaller amounts of the secondary One of each of the five most important grades of P-K mixelements has been noted in the case of a number of fertilizers. tures given in t h a t This trend is due to the survey was also studied. fact that economic condiT h e a v e r a g e g r a d e of tions have made it profitcomplete mixture conable to raise the average Forty-four representative samples of comsumed in 1934 was 3.52grade of commercial fertimercial mixed fertilizers were collected 8.73-5.12 and of P-K mixlizers. There seems to be from manufacturers and state control ture was 0-11.36-7.55. little doubt that this trend Samples representative of will continue in the direcofficials in sixteen states in 1935. Ordinary these two classes were tion of grades containing complete mixtures were represented by selected in such a way that still higher proportions of twenty-seven samples with average nitrothe means would be as near N, P205, and KzO. An gen, phosphoric acid, and potash contents these values as possible. increase in the proporthe same as those of all commercial fertiTheaverage grade of the tions of primary fertilizer twenty-seven complete constituents necessarily lizers consumed in recent years. Doublemixtures used in this study results in a decrease of the strength and concentrated fertilizer mixwas 3.47-8.67-4.93, and remaining constituents. tures were also included in the study. This does no harm if it the average grade of the Chemical determinations were made for five P-K mixtures was causes the elimination of all constituents ordinarily occurring in 0-1 1.60-7.40. sand, usually present as The samples were colfiller, but if the secondary commercial fertilizers in more than traces lected from state control elements are removed parand also for those trace elements that tially or entirely, the efofficials and from fertilizer have proved to be of value in plant or animal manufacturers in sixteen ficiency of the fertilizer nutrition. may be decreased. It bestates, who were informed Nearly all fertilizers, including concenof the purpose for which comes increasingly importhey were to be used. tant, therefore, to investitrated grades, contain all of the secondary Samples were requested gate the composition of plant food elements as well as nitrogen, that had been taken in the fertilizers in order to dephosphorus, and potassium. The doubleofficial manner from goods termine what is present in strength mixtures contain about the same addition to the primary r e p r e s e n t a t i v e of t h e quantities of the various constituents fertilizer elements. Only grades specified. More in this way may a general than half of the forty-four found in ordinary grades except acid-indeficiency or excess of samples were of goods soluble matter. This indicates that the fertilizer elements be demade in 1935; most of the chief difference is in the amount of filler others were obtained from tected and well-balanced added. The concentrated mixtures conmixtures manufactured mixtures be obtained. tain less of most of the constituents other since 1929. The fertiT h e p u r p o s e of t h i s lizers from which these paper is to present the rethan those supplying nitrogen, phosphoric sults of a study of the comsamples were taken were acid, and potash. plete composition of commanufactured by twentymercial mixed fertilizers of nine different companies,

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0.

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Y *

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including all of the largest companies, several farmers’ cooperatives, and at least one representative of every other phase of the industry.

Methods of Analysis Since many of the nutrient elements known to be necessary to plant growth may occur in several forms, some of which are so insoluble as to be unavailable to plants, only the portions of these elements that were either water soluble or acid soluble were determined. In most cases, however, this portion is believed to be practically the same as the total. Because of the complexity of their composition, fertilizer mixtures present analytical difficulties that are not ordinarily encountered with simpler substances. This is especially true in the case of elements occurring only in traces which are often, even under the most favorable circumstances, difficult t o determine. The Official Methods of the Association of Agricultural Chemists (1) were used wherever possible. Otherwise the methods best suited for the determination in question were obtained from the literature or by private communication from workers familiar with them. Some alteration of methods and equipment was necessary since in many instances they had not previously been used for determinations on mixed fertilizers. Reagents were carefully examined for the elements sought in the analysis and for those which would cause interference in the determination, and wherever necessary the reagents were purified. Blanks on the reagents were determined and corrections made when necessary. PHOSPHORIC ACID. Official volumetric methods of the A. 0. A. C. were used to determine total water-soluble and citrateinsoluble phosphoric acid. Total P206 samples were previously ignited with magnesium nitrate and digested with hydrochloric acid. The citrate-soluble and available forms were calculated. NITROGEN.The various forms of nitrogen were determined by official methods of the. A. 0. A. C. MOISTURE was determined by the oven-drying method of the A. 0. A. C. This method gives not only free moisture but most of the water of crystallization as well. Loss ON IGNITION. The residue from the moisture determination was heated a t 550-90’ C. for one hour. ACID-INSOLUBLE RESIDUEAND ACID-SOLUBLESULFUR. A %gram sample was digested on the steam bath overnight with 40 cc. of aqua regia and then evaporated to dryness. Ten cubic centimeters of concentrated hydrochloric acid were added, and the solution was again evaporated to dryness to remove nitrates. Another 10 cc. of hydrochloric acid were added, and the solution was partially evaporated, diluted to 50 cc., and again digested. The solution was then filtered and the residue was washed with about 200 cc. of hot water. After being cooled, the filtrate was diluted to 250 cc. and reserved for the so3 determination while the residue was ignited to constant weight at 1,000” C. An aliquot of the filtrate was taken and the sulfur, ex ressed as SOo was determined gravimetrically by weighing as iarium sulfate after ignition at 900’ C. Modifications of methods outlined by Hillebrand and Lundell (6) were employed in the latter part of the sulfur determinations. ACID-SOLUBLE SODIUMAND POTASSIUM. One gram of the sample, 5 cc. of concentrated hydrochloric acid, and 10 cc. of water were placed in a 200-cc. volumetric flask and digested on the water bath overnight. Ammonium oxalate and ammonium hydroxide were added, and the solution was passed through a dry filter. An ali uot was evaporated with 1:l sulfuric acid, and the sodium an% potassium sulfates were weighed together. The potassium was later determined according to the official LindoQladding method, and the sodium was determined by difference. TOTALWATER-SOLUBLE MATERIALAND CHLORINE.A 2.5gram portion of the sample, on a 11-cm. No. 40 Whatman filter paper, waswashed to a volume of 250 cc. with boiling water. One 50-cc. aliquot was evaporated to dryness and heated a t 100105’ C. for 2 hours and designated as water-soluble material. Calcium nitrate and ammonia, barely to alkalinity, were added to the remaining solution in order to remove phosphates. After dilution to a definite volume and filtration, another aliquot was taken, the solution was rendered barely acid to litmus with 1 : l O nitric acid, and the determination was completed by the official method, using standard silver nitrate and potassium chromate indicator.

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CARBONDIOXIDE. This gas was expelled with hydrochloric acid, using Knorr’s apparatus. “Dehydrite” was used for drying purposes and “Ascarite” for absorption of carbon dioxide. ACIDITY. The tentative method of the A. 0. A. EQUIVALENT C. for acid-forming or nonacid-forming quality was used with the slight modification that a filter paper cone was employed to prevent spattering, and 0.5 N , instead of 1.0 N , sodium hydroxide was used. ACID-SOLUBLE CALCIUM, MAGNESIUM, ALUMISUM, IRON, AND MANGANESE.A 2.5-gram sample was ignited to 600’ C. for one hour and dissolved in 50 cc. of 1:I hydrochloric acid. Silica was then removed, the solution was diluted to 250 cc., and aliquots were taken for the various determinations. Calcium was determined volumetrically by titration with potassium permanganate after having been precipitated as the sulfate in alcoholic solution and reprecipitated as the oxalate. Magnesium was determined in the alcoholicfiltrate and washings from the calcium determination, gravimetrically as Mg2PZ0,,according to the method outlined by Hill, Marshall, and Jacob (4). hlanganese was determined colorimetrically by the periodate method (4, I?’). The iron and aluminum were precipitated and weighed together as phosphates (8). Iron was determined by titration with dichromate in the presence of diphenylamine ( 7 ) . The aluminum was then calculated by difference. ACID-SOLUBLE COPPERAND ZINC. Since copper compounds may volatilize at temperatures necessary to burn off organic matter without the assistance of other reagents, a 5-gram sample in a 250-cc. beaker was saturated with magnesium nitrate solution, evaporated to dryness, and ignited a t a low temperature by holding the beaker over a flame with tongs. The residue was taken up with 100 CC. of 1:l hydrochloric acid, digested, filtered, evaporated to dryness, taken up with concentrated hydrochloric acid, partially evaporated, and then diluted to 150 cc. with water. The copper was isolated by precipitation as the sulfide at a pH of 0.4 to 0.6, and estimated colorimetrically by the ferrocyanide method (4, 19). Zinc was also precipitated as the sulfide and then determined nephelometrically by the ferrocyanide method (4, 80). ACID-SOLUBLE FLUORINE. The method of Willard and Winter ( I @ , modified to some extent, was used in conjunction with a multiple-unit distillation apparatus (14). Several of the substances resent in fertilizer mixtures interfere in the determination of fuorine. The organic matter may cause an explosion if heated in contact with HClO4, and the resence of C1-, NOa-, SO4--, POr---, and other ions, usual& present in fertilizer mixtures, affects the titration of fluoride with thorium nitrate (6). There is danger of loss of fluorine by volatilization, even in the presence of lime, when ignition is resorted to in order to destroy organic matter (6). In order to overcome these difficulties, a 0.2-gram sample was first distilled a t 140-150O C. with Hap04 (2 volumes of 85 per cent acid and 1 volume of water); glass beads and about 0.25 gram of potassium permanganate crystals, as suggested by Reynolds (IS), were also added. Pod---, C1-, and NOs- ions may appear in the distillate; therefore the latter, after evaporation, was redistilled with 60 per cent HClOd a t 135-145’ C. Three or four drops of a saturated otassium permanganate solution were added previous to redistiiation. This second distillation frees the fluorine from Po4--- and converts Cl*, a t least partially, to chlorine. With’a sample of the size used, the volatilized substances that are objectionable do not reach a concentration that will exert an appreciable effect, as shown by Hoskins and Ferris (6). Sodium alizarin sulfonate was used as indicator, monochloroacetic acid as a buffer, and 0.02 N thorium nitrate for titration. BORONwas separated from the sample by distilling it with methanol after standing overnight or longer in the presence of 50 cc. of 85 per cent phosphoric acid. The usual apparatus (16) was modified by introduction of a second condenser in series, which materially improved the recovery of boron. The recovered boron was determined by titration with alkali according to the principle of Foote (9) as applied by Rader and Hill ( I d ) . The reagents and apparatus were practically boron-free. CRUDEPROTEIN.The A. 0. A. C. method for feeds was used. WATER-SOLUBLE NITROGENOUS ORGANICMATTERwas estimated by doubling the percentage of water-soluble organic nitrogen. This is not strictly correct but does not involve serious error because of the small percentages of this form of nitrogen. Urea and the CN2 radical are the principal constituents in this group, but various other compounds derived from the organic ammoniates are also involved. Urea contains 47 per cent, and the CNz radical, 70 per cent N. Most of the other compounds present in this fraction of a mixed fertilizer contain less than 50 per cent N.

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Courtesy, Davison Chemical Corporation

BAGGIXGAND SEWINGEQUIPMENT FOR FERTILIZER MIXTURES OXYGENEQUIVALENT OF HALOGENS.This Calculation was made in the usual manner from the percentages of the halogens found. In some cases calcium cyanamide was probably present in small quantities, but it was not. determined separately. In those instances where it was present, the deduction for oxygen is too small by a maximum of a few tenths per cent. WATEROF CONSTITUTION. For every mole of NH3 present in any compound likely to be found in fertilizers, 0.5 mole of water must be present also. For example, ammonium sulfate is essen1 mole of water, and 1 mole of SOa. Simitially 2 moles of "3, larly, phosphorus is present in fertilizers in the form of monoand dibasic orthophosphates rather than as PZO5.Therefore, water of constitution must be included in the analysis in order that the sum of the constituents as ordinarily reported will add , deup to approximately 100 per cent. Water-soluble P z O ~as termined in fertilizers, is almost always derived from monocalcium or monoammonium phosphates, whereas citrate-soluble PZO5is largely present as dicalcium phosphate. Water of constitution was therefore calculated from the percentages of NH,, water-soluble PzOj, and citrate-soluble P~OS, because no other constituents normally present in fertilizers in appreciable amount involve water of constitution. The above calculation gives correct results when no diammonium phosphate is present. Since diammonium phosphate is water soluble but includes less water of constitution per mole of PzOj than the monobasic phosphates, its presence would introduce an error. Calculation of the percentages of the various acids and bases to those of the corresponding compounds, however, indicated the presence of noticeable quantities of diammonium phosphate only in three of the most concentrated mixtures. Two of these further was actually present as tests showed that a large part of the PZO5 diammonium phosphate. The calculation of water of constitution for these three samples was made, therefore, on that basis. NONNITROGENOUS ORGAKIC MATTER. No convenient way is known to determine either the total organic matter or this fraction of it in mixed fertilizers. Loss on ignition gives the total organic matter in many substances but not in mixed fertilizers because they contain a variety of other constituents that are more or less volatile over the range of temperature required for this determination. A total carbon determination on mixed fertilizers is of no value in this connection because so many kinds of organic compounds are present, and little can be learned about the kinds or proportions in any given sample without a prohibitive amount of work. Nonnitrogenous organic matter is known to be an important constituent of most fertilizers. About half of the organic matter 359

in high-grade vegetable organic ammoniates; such as cottonseed meal and castor pomace, and the bulk of such materials as garbage tankage and peat consists of nonnitrogenous organic matter. From the materials used in making mixed ferti!izers in 1935 it is estimated that about 6 per cent of the total weight of fertilizers sold in that year must have been nonnitrogenous organic matter. The other constituents that were not determined or calculated, such as titanium dioxide, chromic oxide, lead monoxide, barium oxide, arsenious oxide, etc., occur only in traces, and all of them together probably constitute a few tenths per cent or less of the weight of commercial fertilizers. It seems reasonable to assume, then, that the difference between 100 per cent and the sum of the constituents already accounted for is approximately the content of nonnitrogenous organic matter. The result is not very reliable, however, for it also includes a n accumulation of all the errors involved in the determination of the other constituents. These errors are not additive, since the individual determinations are just as likely to be high as low, and therefore to some extent the errors are compensating.

Results The results of the chemical analyses are assembled in Table I. I n considering these results it should be remembered that a given grade of fertilizer can usually be made economically in a variety of ways. Another somple of any of the grades listed in this table, therefore, would probably have a somewhat different composition. The manner of selecting the samples in this work is thought t o ensure that the average composition of all those in one class is a close approximation t o the actual composition of that class of fertilizers in general. An idea of how close may be gained from a statistical analysis. A statistical analysis based on data of the kind here considered, derived from random sampling, is considered to be accurate only when fifteen or more samples are used. The complete mixtures of ordinary grade comprised twenty-seven samples, and this is the only class included in this study that

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contained enough samples to warrant further analysis. The results of a statistical analysis of this group are given in Table 11.

Averages of the samples falling into each class of commercial mixed goods are given in Table 111. The results for the ordinary complete mixtures are also subdivided further into those of goods manufactured in the years centering around 1930 and those made in 1935.

TABLE11. STATISTICAL ANALYSISOF THE PERCENTAGE COMPOSITIONS OF TWENTY-SEVEN REPRESENTATIVE SAMPLESOF COMPLETE COMMERCIAL FERTILIZERS OF ORDINARY GRADE

Discussion

Constituent NHa Kz0 Na2O CaO MgO Fez08 AlzOs CUO MnO ZnO PzOa NZOS

so8 c1 F

B208

COa Acid-insol. Protein HzO-sol. nitrogenous organic matter Moisture H10 of constitution Nbnnitrogenous organic matter, etc. Ammoniacal N Nitrate N Insol. N Sol. organic N Total N HrO-sol. PZOS Citrate-sol. Pa06 Available PzOa . Insol. PaOa Loss on i nition Total Hz%-sol.

Mean 2.76 5.36 4.08 16.38 0.78 0.80 0.58 0.006 0.024 0.022 9.87 1.62 20.04 5.86 0.70 0.012 1.05 12.95 3.94

Standrqrd Probable Deviation Error of from MiniMean Mean mum ~ 0 . 1 7 A1.29 0.22 2.54 0.21 1.59 1.38 0.23 1.81 5.96 0.41 3.13 0.11 0.86 0.12 0.06 0.43 0.34 0.23 0.15 0.03 0,004 0.001 0.0005 0,027 0.005 0.0035 0.0025 0.020 0.000 2.18 4.91 0.28 0.25 1.96 0.00 0.43 3.38 11.97 0.36 2.74 0.25 0.03 0.19 0.27 0.004 0,001 0.008 0.07 0.24 1.83 2.33 7.91 1.03 0.31 0.42 3.25

Maximum 5.96 9.76 7.38 23.52 3.39 2.43 1.07 0.017 0.114 0.075 14.10 7.79 27.65 11.39 1.00 0.043 7.65 30.50 14.38

0.68 4.90 3.58

0.06 0.23 0.25

0.54 1.78 1.89

0.04 1.66 1.82

2.06 9.40 12.50

5.58

0.61

3.95

0.00

15.20

2.27 0.42 0.63 0.34 3.66 5.14 4.10 9.24 0.64 25.60 45.31

0.14 0.07 0.07 0.03 0.18 0.25 0.23 0.25 0.06 0.94 0.95

1.06 0.51 0.52 0.27 1.35 1.95 1.74 1.93 0.45 7.22 7.32

0.18 0.00 0.05 0.02 1.08 1.81 1.39 4.81 0.15 14.22 30.34

3.90 2.02’ 2.30 1.03 7.04 9.43 8.28 13.27 2.08 47.02 59.06

According to the theories of statistics the chances are even that, if another series of samples were collected and analyzed, the mean values would fall within the limits set by the means plus or minus the probable errors given in Table 11. The chances are also even that the means might fall outside of these limits. If the samples were purely random but fairly representative and the methods of analysis gave correct results, it would be extremely unlikely that the means would fall outside of limits three times the probable errors of the present means. In other words, if the work were repeated with new samples, the average ammonia content, for example, would probably be between 2.59 and 2.93 and almost certainly would lie between 2.25 and 3.27. The samples, however, were not chosen merely a t random. They were selected with care to cover the entire range of normal conditions found in the industry but so that all together they would represent average conditions. Good reason, therefore, exists for believing that the real errors are less than those that would normally occur from random sampling and that in most cases the probable errors given in Table I1 really set the limits of error. When a large number of determinations are considered, the mean plus or minus the standard deviations sets the limits within which two thirds of the values fall. With a set of twenty-seven samples this relation will be only approximately true. The minimum and maximum values found for each constituent are also given in Table 11. If large numbers of random samples were analyzed, extreme values beyond these limits would undoubtedly be obtained. Since, however, the samples were selected to cover the normal range of conditions, the minima and maxima as given are probably the normal limits between which such determinations on nearly all complete fertilieers of the usual grade will fall.

Comparison of the figures for the 1930 fertilizers with those for 1935 shows that they are similar in composition. All the differences observed may be explained by the known trends in the industry. For example, in 1935 relatively much more muriate of potash and less kainite and 20 per cent manure salts were used in making commercial fertilizers than in 1930. This change should result in the 1935 fertilizers containing less XazO and C1 and more of something else, probably filler. In 1935 proportionately more free ammonia and less ammonium sulfate were used in preparing fertilizers. This change decreased the SO3 content and the relative solubility of the PzO6. Much more dolomite was used in compounding fertilizers in 1935 and this increased the CaO, MgO, and COZ contents and also decreased the relative solubility of the PzO,. All of these changes together resulted in a lower proportion of watersoluble salts in 1935. The observed changes in composition are therefore in the direction expected. These facts lend further support to the belief that the samples are, in fact, representative of actual conditions in the industry. If the proportion of nitrogen in the average sample of an ordinary complete mixture is taken as 1.0, other plant food elements are present in the following proportions: P 1.1, K 1.2, Ca 3.2, Mg 0.13, and S 2.2. From what is known of the needs of the most important crops and of the availability of FERTILIZERS TABLE 111. AVERAGEANALYSESOF COMMERCIAL BY CLASSES -Complete Mixtu;es-Constituent No. of Samiples NHa K2O Nap0 CaO MgO FezOa A1208

CUO MnO ZnO P2Oa

NzOs

808

c1 F BzO8 c02 Acid-insol. (sand) Protein HzO-sol. nitrogenous organic matter= Moisture Total detd. Less 0 equivalent t o C1 & F Cor. total ~

~~

~

Hz0 of constitutionb

Nonnitrogenous organic matter, etc.c

-14-21% Made around 1930 13 2.70 5.47 4.69 16.02 0.42 0.70 0.49 0.008 0.018 0.032 9.64 1.39 21.12 6.26 0.71 0.014 0.41 11.49 3.69

gradesMade in 1935 14 2.82 5.25 3.51 16.71 1.11 0.90 0.67 0.004 0.029 0.012 10.09 1.81 19.05 5.50 0.69

2440% grades 8 5.87 10.76 3.78 10.88 1.05 0.66 0.69 0.012 0.020 0.053 18.72 1.50 17.26 7.88 0.67 0.023 0.010 1.65 1.06 3.61 14.31 2.06 4.13

45-68% P-K grades Mixtures 4 5 0.01 10.83 7.15 11.73 2.46 6.08 20.54 5.74 1.13 0.27 1.02 0.69 0.96 0.84 0.004 0.013 0.038 0.010 0.017 0.035 12.82 30.13 0.00 7.32 18.23 11.02 6.75 3.18 0.97 1.28 0.011 0.008 1.75 0.46 19.64 0.61 0.31 1.25

0.86 0.56 0.48 0.76 4.28 5.47 5.00 2.87 90,412 94.285 92.038 95.126

0.06 4.27 98.13

1.72 1.52 2.06 1.26 1.93 ----88.692 92.765 89.978 93.866 96.20 3.91

3.28

7.38

10.27

2.40

7.40

3.96

2.64

0.00

1.30

8.91 0.01 4.83 2.22 2.32 Ammoniacal N 1.90 0.00 0.39 0.36 0.47 Nitrate N 0.06 0.33 0.20 0.59 0.66 Insol. N 0.03 0.24 0.38 0.43 0.28 Sol. organic N 11.39 0.09 5.79 3.61 3.72 Total N 6.60 14.47 27.24 5.60 4.71 H~O-SOl.PZOk 5.39 8.79 2.52 3.49 4.66 Citrate-sol. PZOS 11.99 9.09 9.37 18.26 29.76 Available PzOs 0.37 0.82 0.47 0.55 0.72 Insol. PI05 10.16 27.15 24.16 35.26 40.89 Loss on ignition 38.05 48.72 42.14 68.73 84.44 Total HzO-sol. a Estimated from soluble organic N. b Calculated from the percentages of “3, HaO-sol. PzOS, and citrate-sol PaOa. c By difference.

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INDUSTRIAL AND ENGINEERING CHEMISTRY

these elements in the ordinary soil, the proportions of Ca and S seem to be more than ample. The 24 to 40 per cent grade complete mixtures (doublestrength mixtures) contain all the constituents found in the ordinary grade and in most cases in about the same general proportions. The most noticeable difference is that the double-strength mixtures on the average contain about 10 per cent less sand. The ratios of the principal plant food elements in these mixtures is: N 1.0, P 1.4, K 1.5, Ca 1.3, Mg 0.11, and S 1.2. These mixtures, therefore, contain about the same proportion of Mg to N, P, and K as the lower analysis mixtures but relatively less Ca and S. All four samples containing 45 per cent or more of the three primary plant food constituents also contained all the elements found in the ordinary grade mixtures. They contained very little sand or organic matter. Although they contained as much of certain other elements as the ordinary grade mixtures, only one half to one third as much of such fertilizers would be applied to a given area of soil, and they would therefore supply relatively less of these elements to crops. The average ratios of the more important elements in these samples is: IT 1.0, P 1.1, K 0.9, Ca 0.4, Mg 0.02, and 8 0.4. The average sulfur found in these four samples is higher and the chlorine lower than is usual in this class of fertilizers. From published analyses (IO) of a much larger number of samples of such fertilizers, the following ‘averages were obtained: CaO 4.63 per cent, MgO 0.26, SO3 3.49, and C111.30, corresponding to Ca 0 29, Mg 0.01, and S 0.12 when the ratio of N is taken as 1. The P-K samples contained excessive quantities of sand with an average of nearly 20 per cent. The more important plant food elements were present in the following proportions : P 1.0, K 1.1, Ca 2.6, Mg 0.12, and S 1.3. Except for the fact that these mixtures contain no added nitrogenous materials, they are prepared from the same ingredients as the complete mixtures, and the results of this investigation show that the P-K mixtures contain essentially everything that is present in the complete mixtures with the exception of the nitrogenous constituents. Boron was present in measurable quantities in all samples of every class. The double-strength mixtures on the average contained twice as much boron as those of ordinary grade. The ratio of boron to the primary fertilizer elements is therefore the same in both classes. On the average, similar ratios of other elements, except copper and zinc, were lower in the double-strength mixtures than in those of ordinary grade. Determinable quantities of copper, manganese, and zinc were found in all but a few samples. Some of the highanalysis mixtures contain relatively large amounts of copper and zinc. This is probably due to the greater use in these mixtures of those products that in the course of manufacture come into contact with copper and galvanized equipment. The manganese content of Tennessee phosphate rock is comparatively high, and this fact is reflected in the manganese content of the mixed fertilizers prepared in states where Tennessec rock is used as the source of Pzo6. This fact accounts for the high average manganese content for the P-K mixtures (Table 111) because this class of mixtures is most important in the very states where Tennessee phosphate is generally used. At least two of the P-K samples undoubtedly contain superphosphate prepared from Tennessee phosphate rock. Young (21) gives the manganese, copper, boron, titanium, selenium, and barium contents of three standard commercial mixtures and of a wide variety of fertilizer materials. He also gives the chromium and vanadium contents of a few materials which normally contain these elements. Gaddum and Rogers (3) also give the barium, strontium, nickel, cobalt, manganese, vanadium, titanium, silver, copper, tin, zinc,

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lead, chromium, and boron contents of a considerable number of samples of various kinds of fertilizer materials. The results by these investigators for manganese, copper, zinc, and boron are not inconsistent with the results published here. The average moisture contents are approximately the same for each group except the concentrated fertilizers. The latter fertilizers contain much less moisture than the others. In the ordinary grade mixtures, ammoniacal nitrogen constitutes 62 per cent and in the higher analysis grades, approximately 80 per cent of the total nitrogen. The proportion of insoluble nitrogen decreases from 17 per cent for the average ordinary grade to 6 per cent for the double-strength and to less than 2 per cent for the concentrated mixtures. The proportion of the total water-soluble PzOs increases from 52 per cent in the ordinary grade to 90 per cent in the highest analysis grade, and conversely the ratios of both the citrate-soluble and -insoluble Pzo5decrease. Forty-five per cent by weight of the ordinary grade, 68 per cent of the double-strength, and 84 per cent of the concentrated mixtures consist of water-soluble material. Thus the water-soluble material does not increase nearly so rapidly as the percentages of primary plant food elements. It appears, therefore, that as the concentration of the fertilizer increases, the danger of delayed germination or crop injury from applications of equal amounts of plant food decreases.

Acknowledgment The authors wish to express their appreciation to the control officials and to the fertilizer companies that furnished the samples for this investigation. They are also indebted to W. L. Hill, L. F. Rader, Jr., and D. S. Reynolds for advice concerning methods used and the loan of equipment. Thanks are due also to Mrs. E. K. Rist for the nitrogen determinations and to L. M. White for the pH determinations.

Literature Cited (1) Assoc. Official Agr. Chem., Official and Tentative Methods of Analysis, 4th ed., 1935. (2) Foote, F. J., IND.ENQ.CHEM.,Anal. Ed., 4,39-42 (1932). n . Expt. (3) Gaddum, L. W.,and Rogers, L. H., Univ. Fla. A. Sta., Bull. 290, 1-15 (1936); (4) Hill, W. L.,Marshall, H. L., and Jacob, K. D., IND.ENQ. CHEM.,24, 1306 (1932). (5) Hillebrand, W. F., and Lundell, G. E. F., “Applied Inorganic Analysis,” New York, John Wiley & Sons, 1929. ENQ.CHEM.,Anal. Ed., 8, 6 (1936). (6) Hoskins and Ferris, IND. (7) Knop, J., J. Am. Chem. Soc., 46,263 (1924). (8) Lundell, G. E. F., and Hoffman, J. I., J. Assoc. Oficial Agr. Cham., 8, 184-206 (1924). (9) McCandless, J. M.,Ga. Dept. Agr., Bull. 41, 1-200 (1904). (10) Mehring, A. L., and Lundstrom, F. O., Am. Fertilizer, 88, No.2, 5 (1938). (11) Mehring, A. L., and Smalley, H. R. (introduction by Brand, C. J.), Proc. Natl. Fertilizer Assoc., 11, 139-203 (1935). (12) Rader, L. S., Jr., and Hill, W. L., J. Agr. Research, 57,90116 (1938). (13) Reynolds, D. S.,private communication. (14) Reynolds, D.S.,Kershaw, J. B., and Jacob, K. D., J. Assoc. Oficial Agr. Chem., 19, 156 (1936). (15) Wheeler, H. J.. Am. Fertilizer. 1, 162-5 (1894). (16) Wherry,’E. T.,and Chapin, W. H.,J. Am. Chem. SOC.,30,16871701 (1908). (17) Willard, H. H., and Greathouse, L. H., Ibid., 39, 2366-77 (1917). (18) Willard, H. H., and Winter, 0. B., IND.ENQ.CKEM.,Anal. Ed., 5,7 (1933)‘; (19) Yoe, J. H., Photometric Chemical Analysis,” Vol. 1, p. 182, New York, John Wiley & Sons, 1928. (20) Ibid., p. 397. (21) Young, R. S.,Cornel1 Univ. Agr. Expt. Sta., Memoir, 174,1-70 (1935). RECEIVED October 28, 1938. Presented before the Division of Fertilizer Chemistry at the 96th Meeting of the American Chemioal Society, Milwaukee, M‘is., September 5 to 9, 1938.