151 



t:iiniii« a larixor iiiiiount. Wheats containliij; a low porccntaso of nitroj;en are 

 iiivarialilv of pour bivad-iuaking value, as are also oecasioiially those of average, 

 even lii,t;h. iiltroi,'eii eoutent. A. D. Hall, of the Kothainstetl lOxperiment 

 Stiitioii." recoiimieiids the deteninnation of nitrogen as a means of selecting 

 "stri>n.ir wlie.-its." provided the whe.ats are grown under similar conditions. 

 '• r.ut this cnrrelation is only a|ipro.\imate and true for an average of samples, 

 often failing entirely when applied to individual cases." 



In determining tiie relation of gliadin to the hread-making v.-ilue of flour, 

 experiments have shown that, like the total nitrogen.'' it is valuable in a g(>neral 

 way, hut taken alone and as the only means for determining commercial value, 

 it fails, as do all other single tests, in absolutely determining the bread-making 

 value of a flour. 



Mr. A. E. Humphries'-, at the recent International Conference of the Milling 

 Industry, held at Paris, in speaking of t^le relation of gliadin results to the 

 bread-niaking vahie of fl(mr. said: "In a general way they agree relatively 

 with the gluten ligui-es : perhaps of the two sets of figures they more uearly 

 approximati'd to liaking results." 



It is quite evident that at the present time there are no laboratory methods 

 based on the analysis of the wheat alone that can be used for determining the 

 bread-making or conunercial value of wheat. It appears that this can best be 

 .arrived at by actual bread-making t«'sts of the flour made from the wheat. 



A number of different kinds of miniature experimental roller mills have been 

 devised for wheat-testing i)ui-poses. These mills, when jjroperly manipulated, 

 .•ire valuaiile for preparing the flour s.amples for determining the comparative 

 bre.-ul-making v;ilu(> of a samph' of wheat, but they fail to give the actual flour 

 yield. This, however, can be aii])roximately determined from the weight per 

 bushel of the grain. 



The committee begs leave to reserve for future reiiorts reconnnendatious of 

 methods for prei>aring the flour ;ind making the technical tests. 



The report was act-epted. 



A paper by A. M. Peter, of Lexington, Ky., was read by the si>cretary of the 

 section, as follows : 



Some Results of an Old Method fou Determining Available Plant Food 



IN Soils. 



Happily the day has passed when a chemist may devise a method of analysis 

 from purely theoretical considerations, often imperfectly understood, and then 

 feel justified in putting forward his method as the true and iufallible standard, 

 with()ut having tested its accuracy by the determination of known quantities 

 under working conditions. He who inirsues this course in these days may 

 expect just criticism at the hands of his contemporaries. Nevertheless, soil 

 chemistry, and even analytical chemistry generally, is still burdened and 

 clogged with the debris of many such methods. 



The conditions affecting the availal)ility of plant foods in soils are so complex 

 that theory alone would be a dangerous guide. The amount of available plant 

 food in a given soil is not in field practice an absolute and fixed (luantity, like 

 the ])ercentage of gold in a given sample of ore. for instance, the exact amount 

 of which may be determined with great accui-acy. The que.stiou of availability 

 is rather a qviestion of relative soluI)ilities. and it will now be generally admitted 

 that any method for the determination of available ])lant food in soils to be of 

 practical value umst be comparative, and gauged by experience in the field. 

 And at the present time a vast auKjunt and great variety of material suitable 

 for such comparative studies is within the reach of our agricultural chemists 

 in the experimental fields of the agricultural colleges and experiment stations. 

 The Association of Official Agricultural Chemists has done well to engage in 

 this work, but when, at its annual convention in 1804, it made the beginning 

 by instructing its reporter on soils and asli to make a study of methods for 

 determining the available plant food in soils after the ideas of Dyer, Deherain, 

 and others, it was not even then necessary to go abroad for a precedent to 

 justify this measure, for an extensive investigation upon the proposed lines had 

 i»een undertaken forty years before in this country and carried out on an 

 extensive scale under State auspices — an investigation which clearly proved 



a. Tour. Bd. Agr. [London], 11 (1905). p. 327. 

 & Jour. Anier. Chenu Soc. 27 (irXJ5), p. 1068. 



