Scientific Agriculture. 



332 



[October, 1909. 



estates, the returns showed no difference 

 whatever in favour of inoculation. At 

 two other estates the returns from the 

 inoculated plots were slightly superior 

 to those which had not been treated. 

 Finally, at the two remaining estates, 

 Dougaldston and Diamond, the reports 

 state that the inoculated areas gave 

 yields considerably higher than the 

 untreated plots. No actual figures as to 

 the weights of produce reaped are given, 

 but it is mentioned that on Diamond 

 estate, the plants on the inoculated plot 

 were about one-fourth as large again as 

 on the uninoculated land. 



Reference has been made to Professor 

 Bottomley's culture preparation for 

 inoculating sugar-cane plants, It may 

 be added that a number of cane 

 plants were inoculated at Antigua and 

 Barbados in accordance with the direc- 

 tions supplied, but that in no case could 

 inoculation be observed to have any 

 effect whatever. 



From the facts which have been emr 

 merated, it will be seen that the histoiy 

 of past attempts at soil inoculation by 

 artificial cultures, forms a record chiefly 

 of failures, although numerous instances 

 have been reported in which a certain 

 measure of success has resulted. The 

 failures which have been recorded can- 

 not be regarded as indicating that the 

 operation is in itself valueless, since the 

 importance of ensuring that the nitrogen- 

 gathering organisms are present in the 

 soil is obvious. But it is evident 

 that the earlier and more enthusiastic 

 advocates of the process formed an 

 exaggerated idea of the advantages 

 which they believed would in general 

 follow soil inoculation, and later re- 

 searches have enabled a truer estimate 

 to be formed of the conditions and 

 circumstances under which the process 

 is likely to be followed by beneficial 

 results. It was at one time hoped and 

 even claimed, that inoculation of any 

 soil on which a leguminous crop was to 

 be grown, would undoubtedly lead to a 

 satisfactory increase in its crop-yielding 

 capacity. Experimental results soon 

 showed the fallacy of this belief, and 

 indicated that the advantages of the 

 process are not general, but may be 

 expected only under certain limited 

 conditions. Briefly stated, the condi- 

 tions under which inoculation may be 

 expected to prove distinctly advan- 

 tageous are on vii gin soils newly brought 

 under cultivation, on reclaimed peat 

 lands, and also on cultivated farm lands 

 when the leguminous crop to be planted 

 has not previously been grown in the 

 neighbourhood, and on the soil in 

 question. For inoculation to have its 

 full effect, these soils must be properly 



drained, and contain suitable propor- 

 tions of lime, phosphates, and potash. 

 But in the majority of cases it would 

 appear that the process is not capable 

 of increasing to any appreciable extent 

 the crop-yielding capacity of most 

 cultivated farm and estate lands, more 

 especially if ordinary leguminous crops 

 have been regularly included in the 

 rotations followed. This is due to the 

 fact that the nitrogen-fixing bacteria 

 which the culture preparations are 

 designed to introduce, are already pre- 

 sent in the great bulk of such soils, and 

 inoculation can only prove of benefit if 

 the organisms introduced are more effi- 

 cient (their 'efficiency' being measured 

 by the quantity of nitrogen fixed than 

 those already present in the soil). 



Reference has been made to the 

 question of the possibility of increasing 

 the amount of nitrogen-fixation by culti- 

 vating and introducing into the soil 

 races of bacteria superior in vigour to 

 those which already exist there. This 

 is a phase of the subject of soil inocu- 

 lation which has of late years received 

 a good deal of attention. It has been 

 found that the capacity of the Pseudo- 

 monas organisms to assimilate nitrogen 

 is not fixed and unalterable, but that 

 this power varies with changed condi- 

 tions of growth. Under certain condi- 

 tions they are liable to lose their power 

 of fixing nitrogen, while at the same 

 time retaining the capacity to multiply 

 at a rapid rate. From this consideration 

 it will be seen that the number of 

 nodules on the roots of the legumes in 

 association with which the bacteria 

 live, does not always form a basis from 

 which deductions can be made as to the 

 amount of nitrogen fixed. The bacteria 

 may lose their power of fixing nitrogen 

 as the result of cultivation on unsuitable 

 media, such as gelatine, among other 

 causes. 



A German Investigator, Suchting, 

 found that the amount of nitrogen 

 assimilated by legumes varied with the 

 source of the bacteria, whether these 

 were derived from the soil, from crushed 

 nodules, or from cultures grown on 

 suitable media. He reports that the 

 efficiency of the last was greater than 

 that of the other two, while the 

 organisms direct from the crushed 

 nodules were superior to those in a 

 watery extract of the soil. Similarly 

 his experiments confirmed the obser- 

 vation, that the most 'efficient' races of 

 Pseudomonas radicicola, when grown 

 upon unsuitable media, rapidly lost 

 their power of nitrogen-fixation, with- 

 out diminishing their power of multi- 

 plication. The source of the infecting 

 organisms, and the manner in which 



