May 1908. J 



461 



Scientific A griculture. 



pages 15 to 19) into "success" and 

 "failures," The third class, of "doubt- 

 ful" character, is not included in this 

 statistical study. Success, as here 

 used, means an observed increase in 

 nodule formation showing benefit to 

 the crop, while a failure is scored 

 when attempted inoculation failed to 

 produce nodules or produced so few as 

 to be of no advantage to the plant. 

 When natural inoculation proved abund- 

 ant the experiment was set aside as in- 

 conclusive, as were also crop failures 

 reported as due to poor seed, decidedly 

 adverse season, and other factors clearly 

 apart from the influence of inoculation. 

 The reports, about one thousand in all, 

 have been carefully studied, and the in- 

 fluence of the various factors upon 

 nodule formation is expressed in terms 

 of percentage in the following table :— 



Table I.— Percentages op Successful 

 and Unsuccessful Inoculations 

 under Different Soil Conditions 

 during November and December, 

 1906. 



Alfalfa. Bed Clover. 

 Conditions of Sue- Fail- Sue- Fail- 



Experiment, cesses, ures. cesses, ures. 



\ -' ' oi o/ o/ o/ 



/o lo lo la 



On new ground . . 81 19 95 5 



On sand or sandy loam ... 75 25 87 13 



On loam ... 70 30 88 12 



On clay or clayey loam... 65 35 92 8 

 On fallow or sod turned 



under ..69 31 91 9 



On old cultivated field soil 64 36 9 ) 10 



Crop new to tlie region ... 61 39 92 8 



An examination of the data here does 

 not warrant general conclusions of a 

 positive character. Apparently none of 

 the physical conditions reviewed are of 

 great importance in determining the 

 success or failure of the inoculation. 

 For the present, therefore, we must 

 assume that such differences as exist in 

 these particular cases, making one soil 

 more favourable lor inoculation than 

 another, are, in part at least, biological, 

 requiring more detailed investigation 

 and experiment. 



It is doubtless true that the cultures 

 themselves have not always been in the 

 most effective state at the time of use. 

 With the safeguards observed at each 

 point in their preparation and distri- 

 bution, however, the cultures as they go 

 from the laboratory are in a high state 

 of efficiency. To secure the desired 

 results they must, of course, be handled 

 according to directions. 



The Effect of Inoculation upon the 



Composition of the Crop. 



In some cases where there has been 

 apparent failure to improve the legume 

 crop, further examination may show a 



decided gain from inoculation. Even 

 where the lack of nodule formation does 

 not seem to hinder a healthy develop- 

 ment of the plants, careful comparisons 

 from analyses have shown the greater 

 protein content of those well supplied 

 with nodules. The amount of nitrogen 

 contained in a soy bean crop* was found 

 in one case to be 113'55 pounds to the 

 acre for the inoculated plants and 75 '98 

 pounds to the acre of those not inoculat- 

 ed, yet the appearance in the fields was 

 the same. With cowpeas, inoculated 

 and uninoculated, the nitrogen was 

 found to be 139'21 pounds to the acre for 

 the former and 11845 pounds for the 

 latter. In each case, therefore, the 

 inoculated crop, although apparently not 

 improved, was in reality much valuable 

 for feeding or for green manure than the 

 uninoculated crop. 



In addition, it shouid be noted that 

 with the inoculated plants the gain of 

 nitrogen came largely from the air, 

 while the plants lacking nodules drew 

 upon the combined nitrogen of the soil. 

 Wheu the gain in nitrogen from inocul- 

 ation is accompanied by largely in- 

 creased plant growth, the beneficial 

 effect of nodule formation is, of course, 

 most pronounced. Some chemical an- 

 alysest of Canadian field peas, inoculat- 

 ed and uninoculated serve to show in a 

 striking manner the comparatively rich 

 growth of the inoculated peas. The 

 plants bearing nodules had a nitrogen 

 content of 2-29 grams per 100 of dry sub- 

 stance ; the plants without nodules 

 grown in the same soil had 1*60 grams 

 per 100 of dry substance. The average 

 dry weight of inoculated and unin- 

 oculated plants was 11*2 and 2"3 grams 

 respectively. It is evident, therefore, 

 that the inoculated plants supplied more 

 than seven times the amount of nitrogen 

 furnished by those not inoculated, viz., 

 0"255 gram to the plant, as compared 

 with 035 gram to the plant respectively. 



Similar results were obtained with 

 wild hemp plants (Sesbania macroear- 

 pa), inoculated and uninoculated.! 

 Analyses^ of the nodules themselves and 

 of the roots from which the nodules 

 were removed show that, though the 

 noduled plants made a decided gain in 

 nitrogen in both roots and tops, by far 



* Grown at Agricultural College, Mich. For 

 description, see Bulletin 224 of the Michigan 

 Station. 



t Analyses made by the Bureau of Chemistry, 

 U. S Department of Agriculture. 



t Experiment carried on by Mr. David Fairchild '. 

 in charge of Seed and Plant Introduction 

 for the Bureau of Plant Industry. 



§ Analyses mad« by the Bureau of Chemistry, 



