LEGUME INOCULATION AND THE LITMUS EEACTION OF SOILS. 11 



Exceptional conditions in a number of cases accounted for a reac- 

 tion the opposite of that generally produced by the soil type. Garden 

 soils, greatly improved by manure, lime, and fertilizers, have usually 

 shown no effect upon neutral litmus paper, even in regions where 

 field soils commonly cause reddening of the paper. On the otlier 

 hand, samples from run-down fields testing red to litmus on a soil 

 type normally reacting blue indicate that this behavior toward litmus 

 may develop from systems of management. Many inoculation tests 

 are made on soils where recent experience has shown that '' something 

 is the matter," inoculation being resorted to as a means of over- 

 coming the difficulty. Where the difficulty, or a part of it, can be 

 located by the reaction of the soil to litmus paper the first step has 

 been taken toward bringing the soil into such a condition that inocu- 

 lation may prove effective for alfalfa at least, and perhaps for vetch. 



CONCLUSIONS. 



(1) Tlie modified petri-dish method, using neutral litmus paper, 

 gives valuable comparative data for studying legume inoculation. 



(2) Alfalfa inoculation is most inhibited by soils which redden 

 litmus, and is most successful in soils which blue litmus or in those 

 which leave the litmus paper unchanged. Crimson clover inoculation 

 is limited little, if at all, by soils of varying litmus reaction. A'etch 

 inoculation seems midway between that of alfalfa and that of crimson 

 clover. A sharp distinction must be drawn between successful inocu- 

 lation and successful crop production. For alfalfa tlie conditions favor- 

 ing successful inoculation seem identical with tliose favoring the alfalfa 

 crop. While the limitations for either inoculation or crop production 

 with'vetch are less sharph' (h-awn, their relationship or interdepend- 

 ence is perhaps as marked as with alfalfa. Crimson clover, on the 

 other hand, may be inoculated even on soils which redden litmus, 

 yet under these conditions liming or manuring is often of great benefit 

 in croj) production. 



Approved : 



James Wilson, 



Secretary of Agriculture. 



Washington, D. C, August 26, 1910. 



[Cir. 71j 



o 



