1114 EXPERIMENT STATION EECOED. 



i'xi)ei-iments on this siilijeet which have been carried on at the station since 

 1804 are summarized and discussed in consideralile detail in this article. The 

 completion of certain features of the woi'k. particularly the chemical examina- 

 tion of the crops jimwu with reference to mineral constitnents, was made pos- 

 sible by the assistance of the Bureau of Soils of this Deiiartment. The work of 

 other investigators bearing upon the subject is reviewed. The details of the 

 plan of the experiment and of the crop yields have been given in previous pub- 

 lications of tlie station (E. S. R., 17, p. .34.5). 



The results of the experiment to date are sunnnarized as follows : 



" These experiments show that in the presence of very limited supplies of 

 potassium salts, sodium salts may greatly increase the yields of certain crops. • 



" In the case of the mangel-wurzel, similar benefit from sodium salts occurred 

 when as much as 3.32 lbs. of muriate of potash, or its equivalent of potassium 

 carbonate, were employed per acre. Also, in connection with certain other 

 plants similar though less marked benefit from sodium salts was observed 

 even when the applications of potassium salt were large. 



" Sodium salts were found to increase the percentage of i)hosphorus in the 

 plant. In this respect the carbonate was more efficient than the chlorid. The 

 results furnish much evidence to show that this was an incidental accompani- 

 ment of the employment of the sodium salts rather than the cause of the 

 increased growth which resulted. This feature should uevei'theless be further 

 investigated. 



" Little evidence was secured to indicate that the benefit to plant growth 

 caused by the sodium salts was due to changing the ratio of lime and magnesia 

 in the plants. 



"The sodium salts undoubtedly acted as indirect manures by virtue of lib- 

 erating potash, yet strong evidence was afforded that the potassium taken up 

 by the plant was often more economically utilized, or, in other words, a greater 

 crop was produced when sodium salts were applied in the manures and when 

 relatively more sodium entered the plant. 



" The water-culture investigations show unquestionable benefit, under certain 

 conditions, from the employment of sodium salts in the presence of limited sup- 

 plies of potassium, which is not attributable to liberation of plant food, effect 

 upon soil moisture, etc. This benefit does not seem to be wholly or chiefiy 

 explainable uiion the ground that the sodium salts had increased the osmotic 

 pressure, for calcium salts failed to have the same marked effect. 



" In the dry season of IS!)'.) strong evidence was afforded that applications of 

 sodium salts to the soil prevented the plants from taking up and removing 

 inmecessary amounts of potash, or in other words the sodium seemed to conserve 

 the potassium of the soil. In the wet season of 1001 the contrary apparently 

 resulted. This indicates the necessity of a more careful study of the conditions 

 affecting the beneficial action of .sodium salts and the danger of drawing definite 

 and final conclusions from a single experiment. 



" The results do not indicate that it would be wise to purposely cut down the 

 supplies of potassium enough to make sodium salts beneficial, for fear of de- 

 pressing the crops, nor to buy common salt nor sodium carbonate for the purpose 

 of attempting to conserve the potassium in the soil ; yet the sodium in the 

 potash salts and in nitrate of soda, which practically costs nothing, may often 

 increase certain ero]>s if a shortage of potassium occurs. 



"The results go to show that the beneficial infiuence of sodium salts is largely 

 conditioned upon the variety Of plant, and this is a field of investigation that 

 has as yet remained grossly neglected, not only in this country but also in Euro])e. 



"It is proposed to further study the influence of sodium salts upon the 

 reaction of the medium and the bearing' of this influence upon the growth of 



