PHYSIOLOGICAL BALANCE IN THE SOIL SOLUTION. 



BY R. H. HIBBARU. 



Considerable interest has been aroused in the subject of the mineral 

 requirement of plants by two comparatively recent publications. I refer 

 to the work of Tottingliam' and to that of Shive^. These investig;ators 

 have shown among other interesting facts that within certain limits there 

 is an optimum proportion of salts, a certain best physiological balance of 

 salts in a culture solution. They have each further shown that this 

 physiological balance is dependent on the total concentration of salts in 

 tiie solution. When the total concentration is .6% or about 2.50 atmos- 

 plieres of pressure, for example, the optimum ))roportion of salts is 

 different from that when the total concentration is .2% or .85 atmospheres 

 of pressure. This is in conformation of the conclusion obtained by both 

 (jiU ■ and McCooP concerning the antitoxic effect of calcium in over- 

 coming the toxi^'ity due to different concentrations of magnesium. The 

 ratio of lime to magnesium varies with the total concentrant of the 

 solution. 



Tottingham used Knop's four salt solution containing MgSO^, KNOj, 

 Ca(NO..)., KH0PO4, together with a few drops of a uniform suspension 

 of ferric phosphate. Such a solution contains all the essential elements 

 and fills the requirement demanded by all mineral requirement investi- 

 gators. Shive made an improvement in the method of culture solution by 

 eliminating the salt KNO... This did not take out any of the essential 

 elements since potassium is present in KH^.PO^ and the nitrate in 

 Ca(NO.).. In order to find out the effect of the various salts ratios 

 possible when each ])roportion varied by increments of one-tenth of the 

 total concentration while using four different salts there was need of 81 

 different culture solutions. When the three salt solution is considered 

 the number of cultures is reduced to 36. The Shive solution is eminently 

 suitable for wheat, oats and field and garden peas for the first few 

 weeks of growth accordirig to studies in this laboratory. 



Kitli Mich. Acad. Sci. Rept.. 1017. 



'Tottingham, W. E. — A quantitative chemical and plivsiolopical study <>)' nutrient sdIu- 

 tions for plant cultures. I'liysiol. Res. 1; 138-24.'), 19U. 



-Shive, J. W. — A study of physiological balance in nutrient media. Physiol. Res. 1: 

 327-397, 1915. 



■'Gile, P. L. — Lime ?nagnesia ratio as inttuenced by concentration, Porto Rico .Agric. Exp. 

 Sta., Bull. 12. 



^McCool, M. M. — The action of certain nutrient and non-nutrient bases on plant growth. 

 Cornell Agric. Exp. Sta. Mem. 2; 121-170, 191."!. 



