426 Journal of Agricultural Research voi. x, no. s 



INFLUENCE OF ORGANIC MATTER CONTENT 



In the case of the four pairs of soils D-A, C-G, E-H, and M-Iv (Table 

 VI), the surface soil and the subsoil are of similar origin and of at least 

 somewhat similar hygroscopicity, while the organic matter in the former 

 is from three to eight times as high as in the latter. The rate and distance 

 of penetration showed no distinct dependence upon the relative amounts 

 of organic matter, but with the capillary rise the rate after the first day 

 and the final height attained were, in the case of each of the four pairs, 

 greater in the case of the surface soil in all three moisture conditions. 



SUMMARY 



The relation of the rate and distance of the downward movement of 

 water in a soil to its texture has, up to the present, received very little 

 attention. Many investigators have studied the influence of the texture 

 upon the rate and distance of the upward movement from a water sur- 

 face, but in nearly all cases the soils have been used in an air-dry state, 

 a condition very rarely met with in nature at any considerable distance 

 below the surface; these studies have led to the conclusion that the finer 

 the texture the slower is the rise at first, but the greater the final distance 

 reached before movement ceases. Data showing the relation of rate and 

 distance of rise to the actually determined hygroscopicity appear entirely 

 wanting. The influence of the initial moistness upon the rate and dis- 

 tance of rise has been studied with only soils of low hygroscopicity, and 

 even with these the results obtained by the different investigators are 

 too discordant to justify definite conclusions. 



Under natural conditions in the humid region the moisture content of 

 the surface foot of soil rarely is as low as the hygroscopic coefficient, and 

 in semiarid regions it seldom falls below this value. 



Seventeen soils, ranging from a coarse sand with a hygroscopic coeffi- 

 cient of 0.6 to a silt loam vnth one of 13*3, were placed in cylinders in 

 three different degrees of moistness, 0.5, i.o, and 1.5 times- the hygro- 

 scopic coefficient, i inch of water w^as applied to the surface, the rate of 

 movement during five days observed, and finally the moisture distri- 

 bution at the end of this period determined. 



When placed in the cylinders the finer-textured soils showed a lower 

 apparent specific gravity than the coarser, but within groups of some- 

 what similar texture this value was found to show no direct dependence 

 upon the hygroscopicity. 



The moisture content of the moistened layer, even at the end of the 

 first hour, was only from one-half to two-thirds the maximum water 

 capacity, which shows that the latter has little significance as a direct 

 index of the moisture retentiveness of a soil. 



The moisture content of the moistened layer fell much more rapidly 

 with the finer-textured soils, at the end of 24 hours it being only between 

 2 and 3 times the hygroscopic coefficient, while in the coarser soils it 



