UNIVERSITY OF CALIFORNIA PUBLICATIONS 
 
 IN 
 
 AGRICULTURAL SCIENCES 
 
 Vol. 1, No. 7, pp. 141-172 April 25, 1914 
 
 STUDIES ON AMMONIFICATION IN SOILS 
 BY PURE CULTURES 
 
 BY 
 
 C. B. LIPMAN and P. S. BURGESS 
 
 The study of the physiological efficiency of soil bacteria 
 rather than their number is admittedly the dominant method in 
 soil bacteriological investigations. In view of this fact it is 
 singularly striking to note how little work has been accomplished 
 in the study of some phases of the physiological efficiency of pure 
 cultures of certain groups of soil bacteria. This is especially so, 
 since the introduction of radical changes in our soil bacterio- 
 logical methods have made it necessary to repeat some, if not all, 
 of the work which had been carried out by the old methods. 
 However this may be, it remains a fact that, since the publication 
 of MarchalV splendid work on ammonification in solution 
 cultures, but scant information has been adduced from studies 
 of soil bacteria which relate to the physiology as well as the 
 physiological efficiency of even the more common ammonifying 
 bacteria. Certainly, the work carried out along this line in 
 direct soil cultures, which recent work has shown to be so far 
 superior to solution cultures, has been very meager indeed. 
 
 In order, therefore, to glean some useful information relative 
 to the physiological efficiency of pure cultures of a number of 
 ammonia-producing bacteria, the writers deemed it wise to select 
 a number of organisms and to compare their power to produce 
 ammonia not only from one form of organic matter, but from 
 several forms, most of which have found use in farm prac- 
 tice as fertilizers. Accordingly, the following organisms in pure 
 
142 University of California Publications in Agricultural Sciences [Vol. 1 
 
 culture were selected for the experiments : B. mesentericus vul- 
 gatus, Ps. putida, B. vulgatus, B. megatherium, B. mycoides, B. 
 sub t His, B. tumescens, Sarcina lutea, B. proteus vulgaris, B. 
 icteroides, B. ramosus, Streptothrix, sp., Ps. fluorescens, B. vul- 
 garis (Novy strain), Mic. tetragenus. The organic materials 
 experimented with were dried blood (13.16% N), tankage 
 (9.62% N), cottonseed meal (5.5% N), sheep and goat manure 
 (2.13% N), peptone (14.14% N), fish guano (8.63% N), and bat 
 guano (3.96% N). 
 
 Method of Experiments 
 
 Fifty-gram portions of soil were placed in tumblers and 
 thoroughly mixed with the organic material to be tested. The 
 tumblers were covered with Petri dish covers and sterilized in 
 the antoclave at a pressure of thirty pounds for three hours. 
 After cooling, the soils were each inoculated with a 1 cc. suspen- 
 sion of the organisms to be tested, made up by shaking with some 
 sterile water a young slope culture grown on bouillon agar. 
 The soil was then stirred with a sterile spatula after enough 
 sterile water had been added to make a moisture content in the 
 soil about equal to the optimum. The soil cultures thus pre- 
 pared were incubated at 28° to 30° C for twelve days. After 
 the incubation period the soils were transferred to copper dis- 
 tilling flasks, 400 cc. of distilled water and an excess of Mg O 
 added, and distilled into standard H/10 HC1. The ammonia 
 was then determined in the usual way. 
 
 No attempt was made to run all the series with the different 
 forms or organic matter at the same time, because only the 
 relative powers of the different organisms to produce ammonia 
 were sought. For the same reason amounts of organic matter 
 were chosen in the different series which would least affect the 
 physical conditions obtaining in the cultures rather than amounts 
 employed which would make the total amount of nitrogen added 
 the same in all scries. 
 
 For the reasons above given, therefore, the effects of the 
 various organisms on any given form of organic material will 
 be treated below as a separate series in the case of each soil and 
 
1914] Lipman-Burgess : Ammoniftcation in Sails by Pure Cultures 
 
 143 
 
 comparisons between the different series made only where per- 
 missible. The data, moreover, are presented so that the dupli- 
 cate determinations which were carried out in all cases may be 
 compared. The averages of duplicate determinations, however, 
 are also given as well as the percentages of nitrogen in the 
 organic matter which was transformed to ammonia. 
 
 Three different California soils were tested with each one of 
 the ammonifiable materials. The soils were a sandy soil from 
 Anaheim, a clay loam from Davis, and a black clay-adobe soil 
 from Berkeley. The mechanical and chemical analyses of these 
 soils are given in Tables I and II which follow. 
 
 
 
 TABLE 
 
 I 
 
 
 
 
 Mechanical Analyses op Soils 
 
 
 Hyd. value 
 
 Sandy 
 
 Clay-Loam 
 
 Clay-Adobe 
 
 Clay 
 
 
 5.78 
 
 
 19.12 
 
 31.93 
 
 0.25 mm. 
 
 14.59 
 
 
 40.93 
 
 25.77 
 
 0.50 
 
 
 1.04 
 
 
 3.35 
 
 3.40 
 
 1 
 
 
 2.30 
 
 
 6.60 
 
 4.77 
 
 2 
 
 
 5.28 
 
 
 7.75 
 
 7.49 
 
 4 
 
 
 9.62 
 
 
 8.78 
 
 6.20 
 
 8 
 
 
 11.58 
 
 
 8.10 
 
 .87 
 
 16 
 
 
 4.87 
 
 
 3.30 
 
 2.78 
 
 32 
 
 
 15.23 
 
 
 4.15 
 
 7.66 
 
 64 
 
 
 29.40 
 
 TABLE 
 
 II 
 
 3.07 
 
 5.44 
 
 
 Chemical Analysis 
 
 of Soils 
 
 
 
 
 Sandy 
 
 
 Clay-Loam 
 
 Clay-Adobe 
 
 Insoluble matter 
 
 73.59 
 
 
 53.55 
 
 I 77.84 
 
 Soluble 
 
 silica 
 
 11.17 
 
 
 19.77 
 
 K 2 
 
 
 .64 
 
 
 .75 
 
 .45 
 
 Na 2 
 
 
 .15 
 
 
 .11 
 
 .07 
 
 CaO 
 
 
 1.39 
 
 
 .82 
 
 1.05 
 
 MgO 
 
 
 .93 
 
 
 1.39 
 
 1.21 
 
 Mn 3 4 
 
 
 .04 
 
 
 .04 
 
 .08 
 
 Fe 2 3 
 
 
 5.10 
 
 
 7.56 
 
 1.68 
 
 A1 2 3 
 
 
 3.92 
 
 
 10.04 
 
 7.79 
 
 PA 
 
 
 .12 
 
 
 .13 
 
 .23 
 
 S0 3 
 
 
 .02 
 
 
 .03 
 
 .08 
 
 Water and 
 
 
 
 
 
 organic 
 
 matter 
 
 2.88 
 
 
 5.62 
 
 5.72 
 
144 University of California Publications in Agricultural Sciences [Vol. 1 
 
 The pure cultures of the organisms employed in these investi- 
 gations were obtained by one of us from the bacteriological 
 laboratories of the University of Illinois. Fresh strains of 
 B. subtilis and B. mycoides were, however, isolated by us from 
 California soils in order to check the stock cultures of the same 
 organisms. The same relative powers of producing ammonia 
 were, however, found to obtain with the fresh as with the old, 
 and different strains thus strengthening the validity of the 
 results below discussed. 
 
 Series I. Experiments with Dried Blood 
 Sandy Soil 
 
 Two per cent of finely sifted dried blood was added to the 
 soils in this series, or one gram per fifty grams of soil. In the 
 case of the sandy soil three series in duplicate were tried, and the 
 same relation under different conditions having been found to 
 obtain between the ammonifying powers of the different organ- 
 isms, we give only one duplicate set of the determinations. The 
 incubation period was twelve days throughout at a temperature 
 varying between 27° C and 30° C. The results of the ammoni- 
 fication determinations with all the soils using dried blood 
 throughout are given in Table III. The percentage of nitrogen 
 of the total amount added which is made available is also given 
 in every case. 
 
 The data in Table III most strikingly indicate the superiority 
 of Ps. putida, B. vulgaris and Sarcina lutea to all other organisms 
 in their efficiency at the production of ammonia from the nitrogen 
 of dried blood. The next fact of singular interest is that B. 
 mycoides, which has, in the hands of several investigators, shown 
 such marked superiority over other ammonifying organisms in 
 the production of ammonia from organic nitrogen in solutions, 
 manifests a relatively low power to transform the nitrogen of 
 dried blood in soil cultures into ammonia. This, moreover, 
 cannot be considered accidental, since different strains of B. 
 mycoides, as above explained, exhibited that same lack of vigor in 
 three duplicate sets of cultures run at different times and under 
 slightly varying conditions of temperature and period of incuba- 
 
1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 
 
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146 University of California Publications in Agricultural Sciences [Vol. 1 
 
 tion. Of the three organisms showing the highest efficiency, as 
 above indicated, in transforming the nitrogen of dried blood to 
 ammonia. B. vulgaris appears in its turn to be the most vigorous, 
 though the other two approach it closely and are about equal 
 among themselves. 
 
 Clay-Loam Soil 
 
 "When the clay-loam soil is used as the medium with dried 
 blood, marked differences are apparent in the efficiency of all 
 the organisms. The poorer air supply of the clay-loam soil, due 
 to its fineness and much greater tenacity, are evidently inimical 
 to ammonia production, even though the same source of nitrogen 
 — dried blood — is supplied for the ammonification process. The 
 largest amount of ammonia produced in this series was that by 
 B. proteus vulgaris, and even that was little more than one 
 quarter of the amount produced by B. vulgaris as above noted 
 in the sandy soil. 
 
 Moreover, the most efficient transformers of the nitrogen in 
 dried blood in the sandy soil medium are not necessarily the 
 same as those in the clay-loam soil. For example, in the case of 
 the clay-loam soil B. proteus vulgaris is the most efficient 
 ammonia producer with dried blood as ammonifiable material, 
 while in the sandy soil the same organism manifests less than half 
 the ammonifying efficiency of B. vulgaris. This latter organism, 
 however, stands second to B. proteus vulgaris in efficiency in 
 the clay-loam soil and yields 7.49 mgs. of ammonia nitrogen as 
 against 9.10 mgs. produced by the last-named organism. There 
 appear to be four other organisms which approach the efficiency 
 of the two just discussed in the clay-loam soil in the following 
 order: Mic. tetragenus, B. ramosus, Streptothrix, sp., and Ps. 
 putida. While the latter does not compare in efficiency in the 
 clay-loam soil with that shown by it in the sandy soil, it still 
 manifests a notable efficiency. Sarcina lutea, however, appears 
 to have lost in the clay-loam soil the marked ammonifying power 
 possessed by it in the sandy soil. 
 
 Of course il must be again emphasized that the amounts of 
 ammonia produced by all the organisms in the clay-loam soil 
 
1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 147 
 
 series are relatively so small that the margin allowable for safe 
 comparison must of necessity be much decreased and therefore 
 comparisons are more difficult. 
 
 Clay- Adobe Soil 
 
 Passing on to a study of the data obtained with the clay-adobe 
 soil as a medium, we find again that he physical condition of the 
 soil is a powerful factor in determining the amount of ammonia 
 produced in soils by pure cultures of organisms possessed of 
 ammonifying powers, if the fifteen different organisms used are 
 a suitable criterion. This confirms the findings of J. G. Lipman 
 in his long series of ammonification experiments with mixed cul- 
 tures. For practical purposes, we may add that most of the 
 bacteria ammonify dried-blood nitrogen equally well in the clay- 
 adobe soil and in clay-loam soil, though there does appear to be 
 a slight though consistently greater amount of ammonia produced 
 in the first-named soil. Again, we find in the clay-adobe soil 
 an organism which stands out as far superior to all others in 
 ammonifying efficiency and again also it is not the same organism 
 as manifested that superiority in the preceding soil. While the 
 duplicate determinations here do not agree as well as might be 
 desired, they indicate amounts so much greater than the quan- 
 tities of ammonia produced by the other organisms of the series 
 that there can be no doubt of the marked and superior efficiency 
 of B. tumescens as an ammonia producer from the nitrogen of 
 dried blood in the clay adobe soil as a medium. Two other 
 organisms appear to be in the second class in this series and they 
 are Mic. tetragenus and B. mycoides. The first, it can be seen 
 from Table III, occupied third place in efficiency in the clay 
 loam soil, but the second has thus far been relatively inefficient. 
 All the other organisms of the series do not manifest differences 
 in efficiency of sufficient magnitude to warrant further comment, 
 except that it is curious and interesting to note that the most 
 efficient organism in the sandy soil is the least efficient organism 
 in the adobe soil. 
 
 It should be remarked here that the generally excellent agree- 
 ment between duplicate determinations, as shown in the table. 
 
148 University of California Publications in Agricultural Sciences [Vol. 1 
 
 eliminates the fear that physical conditions in the individual 
 cultures might operate to produce the rather marked effects noted. 
 
 In a comparison of the three soils it appears that the follow- 
 ing organisms are among those which show the highest efficiency 
 in transforming the nitrogen of dried blood into ammonia: Ps. 
 putida, Sarcina lutea, B. vulgaris, B. proteus vulgaris, Mic. 
 tetragenus, B. tumescens. Of these organisms only Mic. t et ra- 
 ge nus shows a high efficiency in all three soils. Of the others 
 B. vulgaris shows a high efficiency in both the sandy and adobe 
 soils and Ps. putida in the sandy and clay-loam soil. The rest 
 namely Sarcina lutea, B. proteus vulgaris and B. tumescens, are 
 markedly efficient only in one soil each, namely, the sandy soil for 
 the first, the clay-loam soil for the second, and the clay-adobe 
 soil for the third. It appears to us particularly worthy of note, 
 also, that of the last three organisms named B. proteus vulgaris 
 and B. tumescens each holds a pre-eminent position of efficiency 
 in its own soil which no other organism of the fifteen has 
 approached; and even in the case of Sarcina lutea we find that 
 it occupies a position in efficiency in its favorite soil which is 
 second only to that of B. vulgaris and not very far behind the 
 latter. This rather remarkable condition would hardly seem to 
 be accidental and appears to us to indicate for certain organisms 
 marked preferences for certain physical characteristics in media 
 in which they are grown. 
 
 It must be added here, too, that only six of the fifteen 
 organisms show marked ammonifying efficiency as regards the 
 nitrogen of dried blood even when tested in three widely different 
 soil types. The others vary but little from one another in all 
 soils. Oddly enough, the organism which has shown the highest 
 ammonifying efficiency because it maintained it through all soils, 
 namely, Mic. tetragenus, has never before been looked upon, so 
 far as we are aware, as an important ammonifier. That it should 
 be the only one of fifteen organisms tested which should be about 
 equally efficient in all soils used is not unworthy of note. 
 
 Tt is further significant to note here that B. mycoides, which 
 has always been regarded as one of the most efficient soil organ- 
 isms at ammonification, does not in our experiments show any 
 unusual activity in that direction, at any rate when dried blood 
 
1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 149 
 
 is used as the ammonifiable material, no matter what the soil 
 medium. A possible exception to this statement may be found 
 in the case of the adobe soil, in which B. mycoides seems to be 
 superior to all but three or four of the fifteen organisms tested. 
 Such superiority, under the circumstances noted, is probably of 
 little significance. 
 
 Series II. Experiments with Tankage 
 This series was arranged in a manner similar to the preced- 
 ing, the sandy, clay loam, and clay-adobe soils again being used 
 as media, but the ammonifiable material in this case was a high- 
 grade tankage, the nitrogen content of which was 9.62 per cent. 
 The results of the ammonia determinations were as shown in 
 Table IV on page 150. 
 
 Discussion of Series II 
 
 The Sandy Soil 
 
 When we study in the foregoing table, the ammonification of 
 tankage by pure cultures of bacteria, and compare the results 
 with those of Table III, we see at once some very striking differ- 
 ences between the ability of the same micro-organisms to produce 
 ammonia from tankage and from dried blood respectively. Not 
 only do more of the organisms show a high efficiency in trans- 
 forming the tankage nitrogen to ammonia, but the point of 
 highest efficiency is not reached by the same organisms as before, 
 others having taken their places in this series with sandy soil as 
 the culture medium. For example, we find that B. mesenteric us, 
 which in the preceding series showed throughout an extremely 
 low ammonifying efficiency even in the sandy soil, now manifests 
 in the same culture medium, which, however, has tankage in 
 place of blood added to it, the highest efficiency of all of the 
 organisms tested. Indeed, it occupies a position of its own in 
 that direction, much as does B. vulgaris in the sandy soil of the 
 last series. The organism which approaches it most closely in 
 the same medium is B. proteus vulgaris which, however, falls 25 
 per cent short of producing the amount of ammonia yielded by 
 
150 University of California Publications in Agricultural Sciences [Vol. 1 
 
 
 
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1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 151 
 
 B. mesentericus. Then follow, not far behind B. proteus vulgaris, 
 B. tumescens, B. ramosus, and B. vulgaris in the order named, 
 the latter being more than 33% per cent short of the efficiency 
 exhibited by B. mesentericus. Nearly all of the other organisms 
 fall more than 50 per cent short of the efficiency of the last- 
 named organism under this set of circumstances, namely, sandy 
 soil with tankage. There are, therefore, but five organisms out of 
 the fifteen tested which can be adjudged distinctly efficient 
 ammonifying organisms under these conditions. B. mycoides 
 again exhibits a low efficiency, and not far different from, though 
 slightly below, that manifested by it in the same soil in the dried- 
 blood series. 
 
 It must be added here that, with the exception of B. mesen- 
 tericus, the efficient organisms in this part of Series II have also 
 shown more or less marked efficiency in the preceding series. 
 
 The Clay-Loam Soil 
 
 Most of the organisms tested in the clay-loam soil seem to 
 have found the latter a more congenial medium for ammonifica- 
 tion with tankage than they did when dried blood was present. 
 In this part of Series II, three of the organisms, namely, B. 
 mesentericus, B. vulgatus, and B. tumescens, were not only the 
 most efficient ammonifiers but also about equal in their ammoni- 
 fying power. It appears, therefore, that so far as tankage is 
 concerned B. mesentericus is an equally efficient ammonifier in 
 the clay-loam and sandy soils. B. tumescens has previously 
 established its pre-eminent position among the fifteen organisms 
 as an ammonifier of dried-blood nitrogen in the adobe soil, but 
 B. vulgatus enters here for the first time as a markedly efficient 
 ammonifier. 
 
 Only slightly behind the three organisms just discussed in 
 their ammonifying efficiency as regards tankage nitrogen in the 
 clay-loam soil are, in the order named, B. subtilis, B. mycoides, 
 and B. vulgaris. While the latter has manifested its high 
 efficiency in other series above described, the first two organisms 
 named for the first time in the work thus far described show 
 marked ammonifying ability. Only three organisms in this part 
 
152 University of California Publications in Agricultural Sciences [Vol. 1 
 
 of Series II have shown themselves to be really weak ammonifiers, 
 and they are B. proteus vulgaris, B. icteroides, and Mic. tetra- 
 genus. The first and the third of these, it will be remembered, 
 have given evidence of marked efficiency under other circum- 
 stances, but the second has thus far been throughout an organism 
 of low efficiency. It is striking to note the much greater uni- 
 formity which exists in this portion of Series II in the ammoni- 
 fying powers of four-fifths of the organisms tested than that 
 which obtains in other parts of this series and of other series. 
 
 The Clay-Adobe Soil 
 
 Here again we find the great uniformity in ammonifying 
 power between the larger number of bacteria tested which is 
 characteristic of the foregoing section of Series II. On the other 
 hand, the clay-loam soil seems to have been a more congenial 
 medium than the adobe soil for the ammonification of tankage 
 nitrogen, for larger amounts of ammonia are produced in it by 
 the same organisms in the same period of incubation. 
 
 Sarcina lutea shows the highest efficiency as an ammonifier 
 in this part of the series, but is only slightly more efficient than 
 B. tumescens. The organism taking third place is B. mycoides 
 which, indeed, is not far behind the other two. Next in order of 
 importance and still very efficient ammonifiers are B. subtilis and 
 Streptothrix, sp. The other organisms are considerably weaker 
 ammonifiers than those just mentioned and B. icteroides again 
 proves to be distinctly the weakest. Both Sarcina lutea and 
 B. tumescens have, as mentioned above under other circum- 
 stances, plainly evidenced their high efficiency as ammonifiers 
 and B. mycoides and B. subtilis have taken similar positions with 
 respect to tankage in the clay-loam soil. Streptothrix, sp., it will 
 be remembered, has also shown a high ammonifying power before 
 in the case of the clay-loam soil when dried blood was used. 
 
 Comparing the three soils in this series with the same ones 
 in the preceding series, it appears quite clear that taking them 
 by and Large, ammonifying bacteria manifest a much higher 
 efficiency with high-grade tankage than with dried blood under 
 similar conditions. Likewise also, in Series II a small number of 
 
1914] Lipman-Burgess: Ammonification in Soils by Pure Cultures , 153 
 
 organisms mostly identical with those in Series I seem to mani- 
 fest a distinctly high efficiency which the much larger number 
 of the balance do not in most cases even approach. It is worthy 
 of remark, moreover, that B. mycoides attains or rather ap- 
 proaches in portions of Series II its position of prime importance 
 which has thus far so generally been accorded it among ammoni- 
 fying organisms. 
 
 Series III. Cottonseed Meal 
 
 The cottonseed meal used in this series showed on analysis a 
 nitrogen content equal to 5.5 per cent. The experiment in this 
 series was otherwise conducted like those of Series I and II, 
 2 per cent of cottonseed meal being used, or 1 gram per 50 grams 
 of soil. The results are shown in Table III. 
 
 Again the efficiency of the organisms tested is much greater 
 in the sandy soil than in either the clay-loam or adobe soils. 
 
 Sandy Soil 
 
 In this part of Series III the organism of greatest ammonify- 
 ing efficiency is B. tumescens. Those approaching it closely in 
 efficiency are B. vulgatus, Sarcina luiea, and B. mycoides in the 
 order named. B. ramosus takes fifth place and the next three 
 organisms fall more than 33 % per cent short of producing the 
 amount of ammonia yielded by B. tumescens. They are B. 
 mesentericus, B. megatherium, and B. proteus vulgaris. The 
 balance of the organisms show only about half the efficiency of 
 B. tumescens and in one case, B. icteroides, which has in all pre- 
 vious series shown a very low efficiency, only about 25 per cent 
 of the maximum efficiency is manifested. Taken as a whole, the 
 data given in Table III for the Anaheim sandy soil reflects 
 favorably on cottonseed meal as a source of available nitrogen 
 under the conditions named. Again, the greatest efficiency is 
 manifested in this section of Series III by organisms which in all 
 cases have shown high efficiency in other series above reported. 
 As in the case of the heavy soil in the preceding series with 
 tankage, B. mycoides also shows marked efficiency in the light soil 
 when cottonseed meal is used. 
 
154 University of California Publications in Agricultural Sciences [Vol. i 
 
 
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1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 155 
 
 The Clay-Loam Soil 
 The most notable thing in this part of Series III is as above 
 intimated, the very low efficiency of all of the organisms tested. 
 Indeed only two organisms manifest any notable activity as 
 ammonifiers of nitrogen in cottonseed meal in the clay-loam soil 
 as a medium. These two in the order of their importance are 
 B. ramosus and Streptothrix, sp. To these, in view of the dis- 
 agreement of the duplicates as above shown, B. vulgaris may 
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 organisms are all distinctly below the first two mentioned, and 
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 tetragenus in this soil. Considering the high efficiency of the 
 latter organism in Series I, the results just discussed are puzzling. 
 
 The Clay-Adobe Soil 
 
 Even a casual glance at the data obtained in the clay-adobe 
 soil as a medium indicates the distinct superiority of that medium 
 to the clay loam soil for ammonification of the nitrogen of cotton- 
 seed meal. Not only relatively but absolutely the data obtained 
 show the production of much larger amounts of ammonia in this 
 portion of the work. 
 
 As is the case in the sandy soil with cottonseed meal as the 
 ammonifiable material, B. tumescens shows its distinct superiority 
 to the other organisms as an ammonifier in the adobe soil. The 
 next most efficient organism is B. subtilis, which, however, is con- 
 siderably less efficient ; and the next two organisms, about as far 
 below B. subtilis in efficiency as the latter is below B. tumescens, 
 are B. ramosus and B. mycoides. The other organisms are all 
 low in efficiency, though in nearly all cases absolutely better than 
 the same organisms in the clay-loam soil. Thus far we find that 
 B. subtilis shows itself markedly efficient, for the first time, in 
 the clay-adobe soil with cottonseed meal. All the other organisms 
 above named have manifested marked efficiency in some parts 
 of the foregoing series. 
 
 Looking at Series III as a whole it is interesting to note that 
 the nitrogen of cottonseed meal seems to be made available 
 through the activity of pure cultures of ammonifying bacteria, 
 
156 University of California Publications in Agricultural Sciences [Vol. 1 
 
 with much greater rapidity than has heretofore been believed. 
 The next striking fact brought out in these results is the clearly 
 indicated superiority of the clay-adobe soil to the clay-loam soil 
 as a medium for the ammonification of the nitrogen in cottonseed 
 meal. The third point worthy of mention in Series III is the fact 
 that we find again in it, as in the preceding series, only a few 
 of the fifteen organisms tested which show marked ammonifying 
 efficiency. 
 
 The culture of Ps. fluorescens died in the midst of these 
 investigations and was not replaced. 
 
 Series IV. Fish Guano 
 
 Fish guano, in accordance with the teachings of Voorhees and 
 other agricultural chemists, has always been esteemed a good 
 source of available nitrogen; in the words of Voorhees, 2 "rank- 
 ing in availability well up to blood and tankage." It seemed to 
 us therefore of importance to compare in these pure culture 
 studies fish guano with the other organic materials discussed 
 above. Accordingly a series was started similar to those above 
 described, except that 1% grams of finely sifted fish guano was 
 the ammonifiable material used per 50 grams of soil. The fish 
 guano used contained 8.63 per cent nitrogen. The results 
 obtained are shown in Table VI. 
 
 The data in Table VI not only seem to confirm the opinion of 
 Voorhees as above stated, if ammonia production by pure cul- 
 tures may be taken as a criterion for determining the availability 
 of fish guano, but they indicate in most striking fashion what 
 was not shown in any of the foregoing series for the fertilizers, 
 and particularly in the sandy soil, namely, the obliteration of 
 the marked physiological differences obtaining in other series 
 between the different organisms. Of the four nitrogenous fer- 
 tilizers thus far discussed, fish guano seems to contain the form 
 of nitrogen most generally ammonified by a large group of 
 bacteria. 
 
1914] Lipman-Burgess : Ammoniftcation in Soils by Pure Cultures 157 
 
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] 58 University of California Publications in Agricultural Sciences [Vol. 1 
 
 The Sandy Soil 
 The good ammonifying power manifested by most of the 
 organisms tested in this soil with fish guano finds its maximum 
 in the case of B. vulgaris, which, it will be remembered, has 
 already given evidence of notable ammonifying efficiency with 
 other nitrogenous fertilizers. B. tumescens, likewise an organism 
 with a record as an ammonifier well established, is a very close 
 second to B. vulgaris in its efficiency at the ammonification of the 
 nitrogen in fish guano. Four other organisms distinctly in the 
 second class, and about alike in ammonifying efficiency in this 
 part of Series IV, are, in the order of their efficiency, Ps. putida, 
 B. vulgatus, B. ramosus, and Sarcina lutea. Peculiarly enough, 
 B. icteroides shows an ammonifying efficiency here which places 
 it in the second class, a position Which it has thus far never even 
 remotely approached in the series of experiments above discussed, 
 nor, for that matter, in other series which are described below. 
 All other organisms in this part of Series IV are distinctly in 
 the third class, but nevertheles manifest notable ammonifying 
 efficiency. 
 
 In no other series of results have we obtained such sharp 
 lines of demarcation between the classes of organisms here tested, 
 and arbitrarily grouped, in accordance with their respective 
 powers of transforming organic nitrogen into ammonia. 
 
 The Clay -Loam Soil 
 
 The change in the physical condition of the soil from the sand 
 to the clay loam shows a marked effect on the ammonifying 
 power of the same organisms. Nevertheless we find, on the whole, 
 the best set of results thus far obtained with the clay loam when 
 the series with fish guano is studied. In a class by itself under 
 these conditions is B. megatherium, which is markedly superior 
 to all other organisms in this part of Series IV, except B. mesen- 
 tericus, which is a close second. The organism, however, which 
 takes third place, B. vulgaris, falls about 20 per cent short of 
 m11 fining the efficiency of B. megatherium under these conditions. 
 Distinctly lower in efficiency in this part of Series IV are, in 
 the order of their importance, but only slightly different from 
 
1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 159 
 
 one another, B. vulgatus, Ps. putida, B. ramosus, and B. tumes- 
 cens. All of these, however, fall more than 30 per cent short of 
 attaining the ammonifying efficiency of B. megatherium under 
 the conditions here considered. Two other organisms, B. subtilis 
 and Sarcina lutea, fall 40 per cent short of the efficiency of B. 
 megatherium, and the others all fall far below even that figure. 
 It is singular, here again, .that the physical nature of the soil 
 medium employed should so strikingly and so variously influence 
 the efficiency of the ammonifying bacteria. The two organisms 
 which are distinctly superior in ammonifying ability as regards 
 the nitrogen of fish guano in the clay loam soil were only of 
 moderate efficiency with the same form of nitrogen in the sandy 
 soil. And again, the organism which in the latter soil was 
 paramount in its position retreats in the clay-loam soil to third 
 place. 
 
 The Clay-Adobe Soil 
 
 This is the first series of those we have thus far considered, 
 as the data in Table VI shows, in which the clay-adobe soil proves, 
 on the whole, to be inferior to the clay-loam soil. Seven organ- 
 isms out of fourteen here show an extremely low ammonifying 
 efficiency, and two others are by no means efficient organisms. 
 That leaves five organisms in this group which may be considered 
 of importance. Of these, B. vulgaris is the most efficient, but 
 B. tumescens is not far behind it. B. subtilis belongs to the 
 second class in this group and B. proteus vulgaris and B. 
 mycoides to the third class. It is rather unfortunate that it was 
 not possible in this part of Series IV to obtain better agreement 
 between duplicate determinations. It would not appear to us, 
 however, that the discrepancies in question militate against the 
 justice of the conclusions above drawn. 
 
 B. megatherium holds a very good place in the sandy and 
 clay loam soils of Series IV and a fair place in the adobe soil. 
 The same is even more strikingly true of B. vulgaris, and in a 
 minor degree this is also true of B. tumescens. The other organ- 
 isms do not manifest such consistent efficiency under the three 
 widely varying soil conditions. 
 
160 University of California Publications in Agricultural Sciences [Vol. 1 
 
 Miscellaneous Series 
 
 For the purpose of comparing sheep and goat manure as well 
 as phosphatie guano with the other organic materials above 
 described and with peptone, it was deemed of interest to obtain 
 data exemplifying the ammonification in the same soil of all the 
 different materials above used with the three additional ones just 
 mentioned. The sandy soil was chosen for this series and when 
 peptone (Witte) was used, 0.5 gram of it was added to 50 grams 
 of soil. The peptone contained 14.14 per cent N. The sheep 
 and goat manure (2.13 per cent N), owing to its low nitrogen 
 content, was added to the extent of 3 grams per 50 grams of soil, 
 and the phosphatie guano (3.96 per cent N) was also added at 
 the rate of 3 grams per 50 grams of soil. The results obtained 
 are recorded in Table VII. 
 
 As was to be expected, the very available form of nitrogen 
 in the peptone allows of the production of much larger quantities 
 of ammonia than do the less available forms of the other materials. 
 The fineness of division and easy solubility of the peptone, as well 
 as the form of nitrogen which it contains, doubtless have con- 
 tributed to the results. The more or less uniform decomposition 
 of it, however, by most of the organisms tested shows peptone to be 
 unsuited, as has been claimed by other investigators, for ammoni- 
 fication studies with pure or mixed cultures when the application 
 of the data obtained, to field conditions, is contemplated. How- 
 ever that may be, Sarcina lutea shows the highest efficiency at 
 ammonifying peptone nitrogen and at least six other organisms 
 approach it rather closely. Relatively speaking, all but two of 
 the organisms tested are efficient ammonifiers of peptone nitrogen. 
 But their position with respect to peptone, as can be seen from 
 Table VII, is no criterion as to their efficiency with respect to 
 the other materials. 
 
 One of the interesting facts about the ammonification of the 
 sheep and goat manure by pure cultures is that only one organism 
 showed ammonifying efficiency worthy of the name, and that was 
 B. megatherium. The other organisms showed a very slight 
 power only of ammonifying the nitrogen in it. Just why this 
 large discrepancy should exist with respect to this manure 
 between B. megatherium and the other organisms still remains 
 
1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 
 
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162 University of California Publications in Agricultural Sciences [Vol. 1 
 
 to be explained. If, therefore, the readiness of the transformation 
 of its nitrogen into ammonia by pure cultures of ammonifiers is 
 to be taken as a criterion, sheep and- goat manure must be 
 adjudged to contain a relatively unavailable form of nitrogen. 
 The most amazing evidence portrayed in Table VII is the 
 very high availability of the nitrogen of bat guano, which is a 
 phosphatic guano. "While without question the fact of the large 
 amount of the guano used, as well as its low content of nitrogen, 
 preclude an accurate and wholly justifiable comparison of it with 
 the other nitrogenous materials, one cannot help being struck 
 by the large transformation of its nitrogen into ammonia which 
 nearly all of the organisms tested can accomplish. In many 
 ways, the transformation of the nitrogen of bat guano into 
 ammonia resembles that of the transformation of peptone 
 nitrogen. The differences between the ammonifying powers of 
 the different organisms are, however, unquestionably more 
 marked in the case of the bat guano. In its efficiency as an 
 ammonifier of bat guano nitrogen, B. mycoides appears for the 
 first time in all the series studied to be distinctly superior to all 
 the other organisms tested. B. vulgaris easily takes second place. 
 Not far behind, however, and about equal in efficiency, are B. 
 megatherium, B. vulgatus, B. tumescens, and Mic. tetragenus. 
 In the third class are B. ramosus, B. subtilis, and Ps. putida, B. 
 proteus vulgaris, and B. mesentericus. In the fourth class are 
 Streptothrix, sp., Sarcina lutea, B. icteroides, and Ps. fluorescens. 
 
 A Comparison of the Relative Availabilities of the Organic 
 
 Materials above Employed based on the Percentage 
 
 of Nitrogen Contained in Them that was 
 
 Transformed to Ammonia 
 
 Thus far we have been considering only the relative degrees of 
 efficiency as ammonifiers of the different organisms among them- 
 selves as respecting a given organic form of nitrogen in a given 
 soil. There is possible, however, a further very interesting study 
 of the data above given as a basis. We refer to the percentage 
 of nitrogen which is transformed in the different materials into 
 ammonia so as to give them a relative rating as to availability as 
 
1914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 
 
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164 University of California Publications in Agricultural Sciences [Vol. 1 
 
 regards the work of pure cultures. The columns on availability 
 of the various tables show a comparison in different soils of all 
 the materials as attacked by the same organisms, and give the 
 percentages of nitrogen in those materials which were trans- 
 formed to ammonia. In Table VIII all of the columns indicating 
 percentages of nitrogen of different fertilizers made available 
 are brought together from the other tables and one is enabled to 
 compare with much greater ease the different materials on the 
 basis of availability in the same soil and with the same organism 
 and in different soils, with different organisms. 
 
 The Sandy Soil 
 
 So far as this soil is concerned, the data in Table VIII 
 indicate clearly the superiority, from the point of view of the 
 availability of its nitrogen, of cottonseed meal to the other organic 
 nitrogenous fertilizers with which it is compared. Not only are 
 the absolute amounts of ammonia produced in most cases larger 
 from cottonseed meal nitrogen than from other forms, but there 
 are more organisms of the fifteen tested which can vigorously 
 ammonify this form of nitrogen. So that to illustrate, there are 
 but five organisms which have shown the power to transform 
 15 per cent or more of the nitrogen of dried blood into ammonia 
 in the sandy soil. Under similar conditions there are ten 
 organisms which hold such a record for cottonseed meal. Tank- 
 age shows itself to be the next important nitrogenous fertilizer 
 to cottonseed meal from the point of view of the availability of 
 its nitrogen. Thus, comparing it with dried blood as above, we 
 find that there are nine organisms which transform 15 per cent 
 or more of the nitrogen of tankage into ammonia. No such high 
 availability is obtained at all in the case of the fish guano. 
 
 When we consider these nitrogenous fertilizers from the point 
 of view of the transformation of 10 per cent or more of their 
 nitrogen into ammonia, we find that there are thirteen of the 
 fifteen organisms tested which possess that power as regards 
 cottonseed meal nitrogen and another comes very close to that 
 point. In the case of tankage nitrogen there are thirteen organ- 
 isms with a similar power. In the case of dried-blood nitrogen 
 
] 914] Lipman-Burgess : Ammonification in Soils by Pure Cultures 165 
 
 there are but ten organisms which can accomplish that task, and 
 but seven such in the case of fish-guano nitrogen. 
 
 From the point of view of availability by pure cultures 
 therefore in the sandy soil the four nitrogenous fertilizers are 
 to be rated as follows : cottonseed meal, tankage, dried blood, and 
 fish guano. The first two are nearly alike and are far superior 
 to the last two, which are nearly alike, but much more different 
 from each other than the first two. 
 
 The greatest efficiency at ammonification manifested by any 
 organism in the sand}^ soil is that of B. mesentericus with tankage 
 nitrogen, which transforms 32.52 per cent of the nitrogen present 
 into ammonia in twelve days. It should be noted in this con- 
 nection also that absolutely higher amounts of ammonia are 
 produced from tankage nitrogen than from any other form in 
 the sandy soil, even if there are fewer organisms which attack 
 it readily than there are in the case of the cottonseed meal. 
 
 The Clay -Loam Soil 
 
 Conditions are evidently entirely different for ammonification 
 in this soil. Not only is the ammonia production very low so 
 far as all the fertilizers are concerned, but they no longer bear 
 to one another the relation which obtained between them in the 
 sandy soil. There are thus but few organisms which possess the 
 power of transforming 10 per cent or more of the total nitrogen 
 in any of the four fertilizers into ammonia in twelve days. In 
 fact, there are none such in the case of the dried blood, only two 
 such each in the cases of cottonseed meal and fish guano, and 
 seven such in the case of the tankage. No organism attains to 
 the production of ammonia equivalent to 13 per cent of the total 
 amount present in the clay-loam soil regardless of the kind of 
 fertilizer at its disposal. 
 
 The tankage, however, is superior to the cottonseed meal in 
 the clay loam and distinctly so as above indicated. The cotton- 
 seed meal takes second place, the fish guano third place, and the 
 dried blood is by far the poorest. Indeed, no organism was 
 capable of producing an amount of ammonia in excess of 6.91 
 
166 University of California Publications in Agricultural Sciences [Vol. 1 
 
 per cent of the total amount of dried-blood nitrogen furnished, 
 and that occurred in only one case, all the other organisms pro- 
 ducing much less. 
 
 The Clay-Adobe Soil 
 
 Some very striking facts become apparent when the avail- 
 ability of the four fertilizers in clay-adobe soil are considered. 
 While on the whole dried-blood nitrogen is only slightly more 
 efficiently transformed into ammonia than in the clay-loam soil, 
 cottonseed meal and tankage, particularly the former, are more 
 vigorously acted on in the clay-adobe soil by most of the organ- 
 isms. Fish guano, while not markedly so, is none the less superior 
 here again to dried blood. 
 
 Again comparing the different fertilizers on the basis of the 
 amounts of their nitrogen transformed into ammonia by the 
 organisms tested, we find that four organisms transform 10 per 
 cent or more of the nitrogen in cottonseed meal into ammonia, 
 a like number accomplish similar results in the case of tankage, 
 and none succeeds in that direction in either fish guano or dried 
 blood. While thus cottonseed meal and tankage appear alike, 
 a study of table VIII reveals the superiority of the former in the 
 larger absolute amounts of nitrogen which are transformed there 
 than in the case of the latter. 
 
 The first striking fact shown in Table VIII is the marked 
 superiority of the sandy soil as a medium for ammonification by 
 pure cultures. Likewise the added fact of its superiority as a 
 medium for most of the organisms tested must be noted in this 
 connection. The second point of great interest is the surprising 
 fact of the superiority of the clay-adobe soil to the clay-loam 
 soil as a medium for ammonification. From its tenacious nature 
 one would suppose the former type to be a much poorer medium 
 for ammonification than the clay loam and yet it is distinctly 
 superior to the latter as regards tankage and cottonseed meal. 
 As regards fish guano, it is slightly inferior to the clay loam and 
 again as regards the dried blood about equal to the clay loam 
 or possibly slightly superior. 
 
 Considering all the data given in Table VIII from all points 
 of view, tankage must be given first place as regards the avail- 
 
1914] Lipman- Burgess : Ammonification in Soils by Pure Cultures 167 
 
 ability of its nitrogen, cottonseed meal easily takes second place 
 and, owing to its superiority in the sandy soil, dried blood takes 
 third place. Considering the superiority of the fish guano to 
 the dried blood in the other soils, however, it is probably fairer 
 to adjudge dried blood and fish guano of equal availability from 
 the point of view of the transformation of their nitrogen into 
 ammonia by pure cultures of ammonifying bacteria. 
 
 General Discussion 
 
 Several of the facts which have come to light in the investiga- 
 tions above described demand a word of comment with respect 
 to their general significance. First as regards the relative 
 efficiencies at ammonification of the different organisms tested, 
 we find that there is marked variation. Indeed it is difficult to 
 find an organism among the fifteen tested which consistently 
 stands as the best ammonifier regardless of the soil and the 
 ammonifiable material employed. There are, however, one or two 
 organisms which nearly approach such a description. In other 
 words, it appears that, viewing ammonification of organic 
 nitrogen from the standpoint of pure cultures, every organism 
 will do best with a definite combination of soil and organic 
 matter. To be sure there are some organisms of those tested, even 
 though they be in the minority, which are consistently weak 
 ammonifiers. B. icteroides and Ps. fluorescens serve to exemplify 
 such. 
 
 That B. mycoides is by no means always the most efficient of 
 ammonifying bacteria as has heretofore been believed is clearly 
 indicated above. On the other hand, it does possess and manifest 
 marked superiority in certain cases. Thus, for example, while 
 showing poor or mediocre ammonifying power in different soils 
 with dried blood, tankage and fish guano, it manifests great vigor 
 in the case of cottonseed meal and succeeds in making the record 
 for the percentage of nitrogen transformed in the case of bat 
 guano, in which it transforms to ammonia 36.06 per cent of the 
 nitrogen present. 
 
168 University of California Publications in Agricultural Sciences [Vol. 1 
 
 Comparing the organisms in any one given soil as a medium 
 we find some interesting facts. In the sandy soil, for example, 
 with dried blood B. vulgaris is the most efficient ammonifier, 
 making available or transforming into ammonia 24.36 per cent 
 of the nitrogen present. With tankage, B. mesentericus shows 
 the highest efficiency, transforming 32.52 per cent of the nitrogen 
 present into ammonia. With cottonseed meal, B. tumescens is 
 paramount, yielding an amount of ammonia equivalent to 24.30 
 per cent of the amount of nitrogen present. With fish guano, 
 B. vulgaris again manifests its superiority over the other organ- 
 isms by changing 13.09 per cent of the nitrogen present into 
 ammonia. When bat guano is used, B. mycoides stands distinctly 
 superior to all others, as above shown, by transforming 36.06 per 
 cent of the nitrogen present into ammonia. In the case of sheep 
 and goat manure there is but one efficient organism and that is 
 B. megatherium, which transforms 24.97 per cent of the nitrogen 
 present into ammonia. Lastly when peptone is used Sarcina 
 lutea stands pre-eminent, and when all materials are compared, 
 regardless of whether they were used in all soils or not, the last- 
 named organism makes the record for availability by transform- 
 ing 41.98 per cent of the nitrogen present into ammonia. There 
 are thus six organisms out of the fifteen which make records in 
 one and the same soil but with different forms of organic matter. 
 One of the six stands superior in the cases of two nitrogenous 
 materials, namely dried blood and fish guano, and that is 
 B. vulgaris. 
 
 Comparing the same organisms with the same nitrogenous 
 materials, above used, except the last three named, in the clay- 
 loam soil, we find that with dried blood B. proteus vulgaris is 
 most efficient, transforming 6.9 per cent of the nitrogen present 
 into ammonia. With tankage, B. tumescens is pre-eminent and 
 transforms 12.74 per cent of the nitrogen present into ammonia. 
 With cottonseed meal, Streptothrix, sp., is superior, transforming 
 12.84 per cent of the nitrogen present into ammonia; and lastly 
 with fish guano, B. megatherium is again pre-eminent, trans- 
 forming 11.66 per cent of the nitrogen present into ammonia. 
 We see again, therefore, that in one and the same soil, with four 
 different materials, four different organisms make records for 
 
1914] Lipman-Burgess : Ammonification in Sails by Pure Cultures 169 
 
 availability. To be sure, two of these organisms have shown 
 themselves superior to all others in the sandy soil but with 
 different materials. 
 
 In the case of the clay-adobe soil we find that with dried 
 blood B. tumescens stands at the top of the list and transforms 
 9.41 per cent of the nitrogen present into ammonia. With tank- 
 age in the same soil, Sarcina lutea is the most efficient ammonifier 
 and transforms 12.44 per cent of the nitrogen present into 
 ammonia. With cottonseed meal, B. tumescens is again superior 
 to all others and transforms 18.20 per cent of the nitrogen present 
 into ammonia ; and finally with fish guano B. vulgaris again 
 assumes the ascendency and transforms 8.64 per cent of the 
 nitrogen present into ammonia. B. tumescens is very nearly as 
 efficient in this latter case as B. vulgaris. We have thus seen 
 that organisms which in all cases have shown their superiority 
 in other soils are also very efficient in the clay-adobe soil. 
 
 It is clear, therefore, that only about half of the fifteen 
 organisms tested show greatest efficiency in some soil or with 
 some form of organic matter. Scrutinizing more closely the 
 efficiencies of each of these, we must concede to B. tumescens the 
 paramount place among them, for it has stood pre-eminent, in 
 five combinations of soil and fertilizer, out of fifteen, and has in 
 addition been close to first place in several other instances. 
 
 Comparing our findings with those of Marchal, the following 
 critical statements must be made. First, that results of solution 
 cultures are no criterion as to results to be obtained in soils. 
 Secondly, that no two forms of organic nitrogen are attacked and 
 ammonified with the same vigor by any one organism. Thirdly, 
 that different soils will modify an organism 's power to ammonify 
 any one given form of nitrogen very markedly, so that it may be 
 efficient in one case and feeble in another. Fourthly, that the 
 ammonifying efficiency of organisms is greater in sandy soil, and 
 possibly in others, than in solutions, for we have obtained a 
 transformation of 41.98 per cent of peptone nitrogen and 36.06 
 per cent of bat guano nitrogen into ammonia by Sarcina lutea 
 and B. mycoides respectively in twelve days at temperatures 
 between 27° C and 30° C, while Marchal only obtained similar 
 transformations in thirty days at 30° C in albumin solutions. 
 
170 University of California Publications in Agricultural Sciences [Vol. 1 
 
 Owing to the general distribution of the efficient ammonifying 
 organisms above described in most soils, it is extremely improb- 
 able, to judge from our results, that we may look forward 
 to a profitable form of inoculation of soils with ammonifying 
 bacteria. The choice, however, of the form of nitrogenous fer- 
 tilizer for a soil, which will be most readily made available, when 
 available nitrogen is needed, may indeed be something of much 
 greater practical significance, as our data would appear to 
 indicate. Particularly emphatic are our results in illustrating 
 that, at least so far as pure cultures are concerned, and as also 
 partly shown by J. G. Lipman 3 and others, with mixed cultures, 
 prevalent ideas with respect to the relative availability of common 
 nitrogenous fertilizers are incorrect. Both tankage and cotton- 
 seed meal, and, in some cases, fish guano, show higher avail- 
 abilities than dried blood, which we have always been in the 
 habit of regarding as the most available of organic nitrogenous 
 fertilizers (based only on vegetation tests). 
 
 Nor do we argue too far afield from our subject when we 
 make the remarks just preceding. We recognize fully that 
 availability as measured by ammonification does not necessarily 
 denote availability as measured by nitrification nor by assimila- 
 tion of nitrogen by plants. We cannot, however, help noting, 
 also, that a persistent preference exists among practical orchard- 
 ists in this state for tankage as against dried bood and we 
 therefore feel that, judged by other critera, similar conclusions, 
 must be drawn to those adduced from our experiments with pure 
 cultures of ammonifying bacteria. 
 
 We have decided, however, to go much further in these experi- 
 ments and are now prosecuting more elaborate investigations on 
 nitrogen transformation not only to ammonia but also to nitrates. 
 In these studies we shall deal with the soil flora as existing in a 
 large variety of soil types freshly collected from the field for our 
 purposes. Moreover, we shall employ the raw, unsifted fertilizer 
 material just as it is used by the farmer. From these investiga- 
 tions we hope to glean much more evidence which will be of 
 great practical significance, and, like the results above described, 
 also of marked scientific interest. 
 
1914] Lipman-Burgess : Ammonifieation in Soils by Pure Cultures 171 
 
 Summary 
 Results are above given which deal with : 
 
 1. The marked differences in ammonifying efficiency of fifteen 
 organisms in pure culture. 
 
 2. The soil was used as a medium and three types employed, 
 sandy, clay loam and clay adobe. 
 
 3. Four common fertilizers as sources of nitrogen were used, 
 in all soils, and peptone, bat guano, and sheep and goat manure 
 employed only in the sandy soil, besides. The four fertilizers 
 were dried blood, tankage, cottonseed meal and fish guano. 
 
 4. The nature of the soil, as well as the nature of the nitro- 
 genous material, markedly modify an organism's ammonifying 
 power. 
 
 5. There is no regularity in these variations and they cannot 
 be foretold. 
 
 6. While it is difficult to make an exact decision, B. tumescens 
 appears, on the whole, to have been the most efficient organism 
 above tested. 
 
 7. The highest efficiency in a single culture with a fertilizer 
 was shown by B. mycoides, which transformed in twelve days at 
 27° to 30° C, 36.06 per cent of the nitrogen in bat guano into 
 ammonia. 
 
 8. The highest efficiency in a single culture with peptone was 
 shown by Sarcina lutea, which transformed 41.98 per cent of the 
 nitrogen present into ammonia under similar conditions. 
 
 9. A comparison of availability of nitrogenous fertilizers with 
 ammonifiability as a criterion, according to our experiments, 
 markedly changes the positions of tankage, fish guano, and 
 cottonseed meal with respect to dried blood, showing them in 
 most or in many cases to be superior to the latter. 
 
 10. One half of the number of organisms tested is far superior 
 to the other half in ammonifying ability. 
 
 11. Interesting comparisons with Marchal's work are made. 
 
 12. B. icteroides has shown itself throughout to possess but 
 little ammonifying efficiency. 
 
172 University of California Publications in Agricultural Sciences [Vol. 1 
 
 13. Experiments are following those above described to make 
 the latter more complete. Elaborate tests are being made with 
 many soil types using the original soil 's mixed flora from freshly 
 collected samples in the field. Not only ammonifying powers of 
 these mixed flora in the different soil types will be studied, but 
 also the corresponding nitrifying powers. A large variety of 
 nitrogenous fertilizers as employed in practice will be tested here. 
 
 REFERENCES OF MORE OR LESS DIRECT PERTINENCE 
 
 i Bull. Acad. Roy. Soc. Belg., 3 ser., vol. 25, p. 727. 
 - Voorhees, Fertilizers, Macmillan Co., 1898. 
 
 3 N. J. Sta. Bulletin, no. 246. 
 
 4 Ann. Sci. Agron., vol. 19, p. 209. 
 s Rpt. Del. Exp. Sta., 1899, p. 76. 
 
 e Cent, fur Bakt., 2 le Abt., vol. 20, p. 322. 
 7 Ibid., vol. 15, p. 433. 
 s Ibid., vol. 29, p. 238. 
 o Ibid., vol. 31, p. 49.