Jan. 2, 1920 Relation of Moisture in Substrata to Salt Balance 2)11 



content of the cultures, from a position in the series characterized by 

 lower partial concentration of KH2PO4 to one of higher partial concen- 

 tration of this salt and correspondingly lower ones of Ca(N03)2 and 

 MgSO,. 



(3) Good physiological balance and optimum total concentration of 

 a nutrient solution for plants is not alone sufficient to produce the best 

 growth of which the solution is capable when it is diffused as a film on 

 the particles of a solid substratum. An optimum degree of moisture, 

 under such conditions, is essential to impart to the soil (sand) solution 

 its maximum physiological value. The actual plant-producing value 

 of any fertilizer treatment is thus largely determined by the moisture 

 conditions of the substratum. 



(4) The lowest degree of moisture here employed with sand cultures 

 is correlated with low yields of tops and of roots, with the lowest tran- 

 spiration rates, and with the lowest water requirement ratios. The 

 highest moisture content of the cultures, on the other hand, is associated 

 with low yields of tops and of roots, with high transpiration rates, and 

 vath the highest water requirement ratios. The medium degree of 

 moisture, which is approximately optimum for the substratum here 

 used, is correlated with the highest yields of tops and of roots, high 

 transpiration rates, and medium water requirement rations. 



LITERATURE CITED 



(i) Ayres, Arthur Hugo. 



I917. INFLUENCE OF THE COMPOSITION AND CONCENTRATION OF THE NUTRIENT 



SOLUTION ON PLANTS GROWN IN SAND CULTURES. In Univ. Cal. Pub. Agr. 

 Sci., V. 1, no. II, p. 341-394- io%-. pl- 5-15- 



(2) Briggs, Lyman J., and Shantz, H. L. 



191 1. A WAX SEAL METHOD FOR DETERMINING THE LOWER LIMIT OF AVAILABLE 



SOIL MOISTURE. In Bot. Gaz., v. 51, no. 3, p. 210-219, 2 fig. 



(3) GiLE, p. L. 



1913. LIME-MAGNESIA RATIO AS INFLUENCED BY CONCENTRATION. PortO RicO 



Agr. Exp. Sta. BuL 12, 24 p., 4 pl. 



(4) Hall, Alfred Daniel, Brenchley, Winifred Elsie, and Underwood, Lil- 



lian Marion. 



1914. THE soil solution and the mineral CONSTITUENTS OF THE SOIL. In 



Jour. Agr. Sci., v. 6, pt. 3, p. 278-301, pl. 4-8. 



(5) Harris, Franklin S. 



I914. effects of VARIATIONS IN MOISTURE CONTENT ON CERT.AIN PROPERTIES 



OF A SOIL AND ON THE GROWTH OF WHEAT. N. Y. Cornell Agr. 

 Exp. sta. Bui. 352, p. 801-868, fig. 108. Bibliography, p. 860-868. 



(6) Hibbard, R. P, 



1917. physiological balance in the soil SOLUTION. Mich. Agr. Exp. Sta. 

 Tech. Bui. 40, 44 p., 8 fig. 



(7) Hilgard, E. W. 



1918. SOILS, their FORM.'i.TlON, PROPERTIES and COMPOSITION. 593 p., 89 



fig. New York. 



