No. 6. DEPARTMENT OF AGRICULTURE. 203 



the bacteria and requires no inoculation. In the future it will be 

 well, however, by examination of the roots to make sure of the 

 presence of nodules on all legumes grown. Without the nodules the 

 legumes will deplete the soil like any other crop, and with the 

 nodules the growth is almost always more satisfactory and economi- 

 cal. In soil already rich in nitrogen, inoculation will not often 

 pay, as the plants will draw from this direct source instead of from 

 the air; moreover, the presence of considerable nitrogenous material 

 in the soil acts as a check upon the bacteria in their normal function 

 of forming nodules and fixing nitrogen. Their apparent refusal to 

 add further amounts of nitrogen to a soil already rich may be re- 

 garded as a kind of poetic justice; so that in this case, at least, the 

 scriptural rule, "To him that hath shall be given," does not seem 

 to apply. 



It is, therefore, pre-eminently for poor soils (low in organic matter 

 that is, nitrogen) that inoculation offers the greatest possibilities — 

 the type of soil, in fact, which is most benofitpd by lpgruminous grepp 

 manures. The fact that legumes do not thrive is not in itself an in- 

 dication that the bacteria are lacking, there are, of course, other soil 

 conditions to be considered. An examination of the roots as to the 

 presence or absence of nodules is the first and simplest criterion, 

 but, lacking this information, nothing short of an experiment in 

 inoculation will disprove the assumption that the lack of bacteria is 

 responsible for failure. Moreover, the finding of a few nodules and 

 these only on scattered plants, indicates that the soil is inadequately 

 supplied with bacteria and their wider diffusion by means of cul- 

 tures is often of distinct advantage. 



Finally, if the cultures used contain organisms of the highest 

 type, some advantages will often be found from inoculation even in 

 soils where legumes have previously made a fair growth, but not 

 satisfactory in all respects. 



Perhaps the most important application of cultures is in connec- 

 tion with sowing legumes, such as alfalfa, in regions where they are 

 entirely new. The bacteria adapted to infect the ordinary culti- 

 vated clovers and which are quite widely distributed do not produce 

 nodules on alfalfa, nor do the organisms of our common peas and 

 beans readily take to the soy bean and cowpea. In sowing alfalfa, 

 for instance, in new soil inoculation where other conditions are favor- 

 able, will usually make the difference between success and absolute 

 failure, a difference not to be reckoned in percentages. 



To illustrate the points which I have attempted to present in the 



foregoing discussion, it may be well to cite a few concrete examples 



such as are afforded by the reports received from farmers who were 



furnished with cultures for experimenting. These reports fall under 



14_6—1905 



