452 



SCIENCE. 



[N. S. Vol. XXII. No. 563. 



field conditions, when the introduced or- 

 ganisms are subject to the competition both 

 of kindred bacteria and of the enormous 

 bacterial flora of any soil. Up to the pres- 

 ent all evidence of greater nodule-forming 

 power and increased virulence of the arti- 

 ficial cultures has been derived from ex- 

 periments made, under laboratory condi- 

 tions without the concurrence of the mass 

 of soil organisms. 



In the other case, however, where new 

 land is being brought under cultivation and 

 leguminous crops are being grown for the 

 first time, there can be no doubt of the 

 great value of inoculation with these pure 

 cultures of the nitrogen-fixing organism. 

 An example is afforded in Egypt, where 

 land that is 'salted,' alkali or 'brak' soil, is 

 being reclaimed by washing out the salt; 

 inoculation may be necessary before a 

 leguminous crop can be started on such 

 new land, though in many cases the Nile 

 water used for irrigation is quite capable 

 of effecting inoculation. The body of evi- 

 dence brought together by the United 

 States Department of Agriculture is very 

 convincing, and shows in repeated ex- 

 amples that the use of Moore's cultures 

 has enabled farmers to obtain a growth of 

 lucerne and kindred plants, which before 

 had been impossible. In view of the eco- 

 nomic importance the lucerne or alfalfa 

 crop is assuming in all semiarid climates, 

 the financial benefit to the farming com- 

 munity is likely to be great and immediate. 

 And since in the development of South 

 African farming the lucerne crop is likely 

 to become very prominent, both as the 

 most trustworthy of all the fodder crops 

 and as the one which brings about the 

 maximum enrichment pf the soil by its 

 growth, the behavior of the lucerne plant 

 as regards bacterial infection in South 

 African soils is worthy of most careful 

 investigation. It is necessary to know to 

 what extent nodules are formed when 



lucerne is planted on new soils in South 

 Africa, as, for example, on freshly broken- 

 up veldt; the condition of the organisms 

 within the nodule should be investigated, 

 so as to ascertain if improvement be pos- 

 sible by inoculation from pure cultures, 

 either imported or prepared de novo from 

 lucerne within the country. These and 

 kindred questions connected with the sym- 

 biosis of the nitrogen-fixing organism and 

 the leguminous plants must to a large ex- 

 tent be worked out afresh in each country, 

 and South Africa, with its special condi- 

 tions of soil and climate, can not take on 

 trust the results arrived at in Europe or 

 America. 



I have spoken of the enrichment of the 

 soil due to growing lucerne, caused by the 

 decay of the great root residues containing 

 nitrogen derived from the atmosphere ; an 

 enrichment which is quite independent of 

 the amount of similarly combined nitrogen 

 taken away in the successive crops of leafy 

 growth. Some of the Rothamsted experi- 

 ments show very clearly how great the 

 gain may be. In the first place I will 

 call your attention to the effect of a crop 

 of red clover grown in rotation upon the 

 crops which succeeded it, since in the 

 Agdell rotation-field we get a comparison 

 between plots growing red clover once every 

 four years and other plots on which a bare 

 fallow is substituted for the clover. 



The table shows that in one particular 

 case, when an extra large crop of clover 

 was grown, notwithstanding the fact that 

 the clover plots yielded between three and 

 four tons per acre of clover hay, yet the 

 wheat crop which followed this growth of 

 clover was 15 per cent, better than the 

 wheat crop following the bare fallow. The 

 swede turnip crop, which followed the 

 wheat, although similarly and heavily 

 manured on both plots, continued to be 

 better where the clover had been grown 

 two years previously; and even the barley,. 



