424 EXPERIMENT STATION RECORD. 



"(Ci) The ndvocatos of the statio viewpoint hold that crop yields are deereas- 

 iiij;, owiiiiLi to (h'pletion of available i)lant food. JUit croj) yields are iiicreasiiij^ 

 and factors other than the plant food supi)ly are the dominating; ones. 



"(T) To the advocates of th<' static viewpoint, soil chemistry is slmi)Ie, and 

 merely a matter of supplying enough mineral nutrients in ' available ' form for 

 the crop needs. As a matter of fact, soil chemistry is a very complex subject, 

 into which we are just beginning to get glimpses, and the supply of mineral 

 nutrients is only one of the important details in a very intricate problem. 

 Soil fertility will only become simple, if ever, when we have a much fuller and 

 more comprehensive knowledge of the physical, chemical, and biological proc- 

 esses taking i)lace in the soil. To attain this knowledge, the soil must be 

 regarded from the dynamic viewpoint." 



The soil considered as a reserve food supply, Maizieres {Engrais, 2'f (190!)), 

 No. 36, pp. 993-995; ahs. in Chem. Ahs., 4 (0)10), No. 1, p. 74).— It is pointed 

 out that ordinary cultivated soils contain sufficient amounts of nitrogen, phos- 

 phoric acid, and potash to give large yields for many years, but that as a rule 

 these constituents exist largely in unassimilable forms and that too small a 

 proportion of them becomes available each year to give maximum yields with- 

 out the use of readily available fertilizers. 



The availability of the soil potash in clay and clay loam soils, F. W. 

 Morse and B. E. Curry {New Hampshire 8ta. Bui. l-'i2, pp. 39-58, fig. 1). — The 

 data upon which this bulletin is based have already been noted (E. S. R., 21. 

 pp. 713, 714, 715). The bulletin deals particularly with the water-soluble 

 potash in soils, how to increase the availability of the soil potash, and what 

 becomes of the potash added in fertilizers. Among the more important facts 

 brought out are: 



" The clay and clay loam soils carry large quantities of potash. The potash 

 in these soils is soluble enough to supply potash for heavy crops of grass with- 

 out artificial reenforcement. 



"Additional potash when supplied in commercial fertilizers does not affect 

 the yield or the composition of the grasses. The amount of potash required 

 for a grass crop is proportional to the yield. 



"A comparison made between the amount of water-soluble potash in these 

 soils, the amount of potash in the crop, and the amount of soil water required 

 to produce the crop, shows that the addition of potash fertilizers is not neces- 

 sary. This relation stands for these soils when large yields are produced by 

 the addition of other fertilizer. 



" It is shown that when lime reacts with feldspathic minerals the potash dis- 

 solves. Also when clay is present, as in these soils, no increased amount of 

 soluble potash is produced. This is because of the action of the clay on the 

 solubility of potash. 



"A large part of the potash in fertilizers is changed to an insoluble condition 

 soon after it is applied to the soils. When the potash is rendered insoluble 

 other bases go into solution. Lime has decided effects on these by-products." 



On the fertility of soils with regard to phosphoric acid, A. Kostzyeletzkii 

 (Zhur. Opuitri. Agron. (Russ. Jour. Expt. Laiulw.), JO {1909), No. 3, pp. 321- 

 354, flffs. 5). — Two lines of investigation are reported, (1) a comparison of 

 the yields obtained in pot experiments with samples of the same soil taken at 

 different depths with the amounts of phosphoric acid found in the soil by treat- 

 ment with varying proportions of a weak solvent, and (2) the use of culttires 

 of Aspergillus niger in soil investigations. 



The physical properties of the soil samples were very similar, but, as shown 

 by chemical analysis, there was a considerable variation in the phosphoric acid 

 content. Oats was the crop grown, and the data show that there was a close 



