March 1909.] 



271 



Scientific Agriculture. 



them. If the root tubercles are not 

 formed, then leguminous plants are as 

 dependent upou supplies of combined 

 nitrogen (nitrates, etc.) as are ordinary 

 plants, so that whenever a leguminous 

 crop, which usually does well on a parti- 

 cular soil in the. absence of nitrates, fails 

 to grow well, the first investigation to 

 make is to pull up some of the plants 

 and see whether the failure is due to 

 the absence or deficiency of root nodules. 

 In this connection it must be remembered 

 that the use of nitrates as manures 

 tends to suppress the formation of 

 root nodules, since these are then less 

 necessary. 



If a leguminous crop fails owing to 

 the non-formation of root tubercles, it 

 may succeed if the necessary bacteria 

 are supplied to the soil or young seed- 

 lings. The root tubercle bacteria appear 

 all to belong to a single species, Bacillus 

 radicicola : but several varieties grow on 

 different plants, and these are not 

 mutually interchangeable. Thus, the 

 variety from the pea will infect the 

 bean, but not clover. The soja plant of 

 Japan usually forms no tubercles in 

 Europe, although they are abundantly 

 produced in Japan, where the appro- 

 priate variety of bacterium occurs. In 

 such cases the bacterium may be supplied 

 to the soil from a plant of the same 

 kind as that which is to be grown by 

 crushing its root tubercles to a thin 

 paste with cold water and either spray- 

 ing the diluted mixture over the land or 

 soaking the seeds in it before planting. 

 A single large root tubercle may contaiu 

 several million bacteria, and only one 

 bacterium is needed to start each fresh 

 root tubercle, so that the root tubercles 

 from a small number of plants would be 

 sufficient to infect an acre of soil or 

 several bushels of seeds. Once added to 

 the soil they appear, however, to die 

 out before long in the absence of an 

 appropriate host plant, so that the direct 

 application to the soil usually involves 

 considerable waste and may be quite 

 ineffective. 



Cultures of nitrogen fixing bacteria, 

 usually termed nitragin,* juive been 

 placed upon the market and extensively 

 boomed both for direct application to 

 the soil and to the seeds before planting. 

 These cultures are only effective when 

 they contain the particular variety of 

 bacterium required, and they are no 

 better than the material which can be 

 derived directly from the root nodules. 



* A very unfortunate term, well adapted for 

 booming a commercial product, but highly con- 

 fusing to farmers since " nitragin " is the phonetic 

 spelling of the chemical element, nitrogen, as 

 customarily pronounced, and all farmers now realize 

 the importance of nitrogen in plant nutrition, 



The cultures soon lose their efficacy, 

 and in many cases have been shown to 

 contain none of the required bacteria 

 at all. 



In fact, in certain cases, unscrupulous 

 persons have taken advantage of a 

 useful scientific discovery to make money 

 by palming off ivorthless rubbish upon 

 .farmers eager to adopt scientific methods. 

 It cannot be too strongly emphasized 

 that no heavy outlay for a supply of 

 " nitragin " is justified unless the farmer : 



Firstly, is unable to grow certain 

 leguminous crops satisfactorily, even in 

 the presence of lime, potash and phos- 

 phoric acid in sufficient amount in the 

 soil. 



Secondly, finds by direct observation 

 that this is due to the non-formation of 

 root tubercles. 



Thirdly, is unable to procure a supply 

 of the same plant-bearing living root 

 tubercles which can be directly used for 

 infecting the seed or soil. 



Some of the forms of " nitragin" have 

 been supposed to contain the bacteria 

 which live freely in the soil and enrich 

 it with nitrogen, This is probably a 

 misstatement. In any case, the use of 

 such cultures would not be profitable, 

 because these soil bacteria are usually 

 present in all soils capable of maintain- 

 ing them, and when added to a soil from 

 which they were originally absent, they 

 usually rapidly tend to disappear again. 



Further, the net result of the activity 

 of soil bacteria in rich, well-manured 

 soils is to produce a loss rather than a 

 gain of nitrogen, and hence no advan- 

 tage is to be expected by the addition of 

 cultures of any kind of bacterium to 

 such soils. 



To sum up, in the present condition of 

 our knowledge, the use of "nitragin " in 

 agriculture is not at present to be re- 

 commended except under very special 

 conditions. Even then the same results 

 might be obtained by the far better and 

 cheaper methods indicated above.— 

 Journal of Agriculture oj Victoria, Vol. 

 VII., Pt. 1, January, 1909. 



NOTES ON THE NUTRITION OF 

 PLANTS. 



By T. Wilson Main. 



A knowledge of the physical properties 

 of soil and the substances necessary for 

 the effective nutrition of plants is of the 

 utmost value to the Agriculturist. In 

 practice soils become impoverished, more 

 or less rapidly, according to the require- 

 ments of the various crops, and as no soil 



