6 EXPERIMENT STATION RECORD. 



remains Diucli to be learned oftheclieinical composition oftlie soil solu- 

 tion. The suggestive researches of Schlossing ' made in tlie laboratory- 

 should be repeated n])on soils in place. The intlnence of the subsoil 

 upon the moisture of the soil should be considered. The investigations 

 of Pagnoul^ are of interest in this connection to both agriculturists and 

 botanists, since they deal witli tlie effect of different soils upon the 

 spontaneous geographical distribution of plants. Here is found a key 

 to the i)references of certain plants for particular soils. The ideas 

 advanced concerning tliis question have been far from satisfactory, and 

 it is suggested that the analysis of the drainage water will materially 

 aid in its solution. 



In general the amount of water retained by a soil depends upon its 

 physical texture and chemical composition. Near the surface there is 

 ordinarily found from 25 to 35 per cent of water in soils in place, 

 although the coefficients determined in the laboratory by the method 

 of Schiibler give about 50 per cent. These numbers are given in terms 

 of weight, but from a biological standpoint the amount in terms of 

 saturation is preferable. 



Concerning the capacity of soil for water, absorption, evaporation, 

 and hygroscopicitj^ the conclusions of Wollny' are as follows : (1) A 

 compact soil loses more Avater by evaporation than a loose one, because 

 the cai)illary spaces are smaller in diameter and more easily conduct to 

 the surface the water in the deeper layers. On this account the surface 

 of a compact soil remains moist longer than a loose one. (2) A com- 

 l>act soil has a greater capacity for water than a loose one, although it 

 is less permeable. The capillary spaces are smaller, the number of 

 water pores are increased, and the penetration of water into the sub- 

 soil is hindered. (3) A comi)act soil offers more Avater for the plant 

 than a loose one. When it is desired to increase the capacity of a soil 

 for water it must be made more compact.^ 



The susceptibility of soil to drought is represented by the proportion 

 between the water lost by evaporation ami the maximum weight of 

 water it is able to hold. Schlossing'' has pointed out the important fact s 

 that the size of the soil particles and the degree of humidity exert an 

 influence on tlie amount of water transported toward the surface. The 

 fineness of the superficial layer "^ also modifies evaporation. 



It is apparent that the greater the coi^tficient of evaporation the less 

 the water capacity of the soil. The capacity for water varies directly 

 as the hygroscopicity. The hygroscopic capacity and the tension of 

 the water vapor varies with the size of the soil particles, being greatest 



' Compt. Rend., 63 (1866), p. 1007; 70 (1870), p. 98. 



-Anu. Agron., 7 (1881), p. 21. 



^Forsch. geb. agr. Phys., vol.5, p. 1. 



••Etlmond Gain, Precis de Chimie Agricole, p. 57. 



•■^Enclycl. Chiniiquc de Freiuy — Cbimie Agricole. 



*>Chabaneix, Influence de ramenldi^senient yiiperficial sur I'evaporation. 



