108 



Bulletin 174. 





The difference in the capacity of hinipy and fine soils to hold iilui 

 moisture is surprising to one who has not given the question t-tiidy. 

 George W. Cavanaugh, assistant chemist at the Cornell Experinu-nt 

 Station, has very graphically' shown this hy the following- 

 experiment : He put small marbles in a tumbler, as shown 

 by Fig. 22, and the total amount of lihii moisture that the 

 marbles would carry is represented in the tube placed 

 beside the tumbler. The soil in the other tumbler (Fig. 

 23) is of the same weight as the marbles in Fig, 22, and 

 it represents the marbles reduced to the fineness of 

 common sand. Its capacity for holding lilm moisture 

 is represented by the water in the standing tube (Fig. 23). 

 The weight of material is the same in eacli tumbler, and 

 the reason why one holds three times more film moisture 

 than the other is due to the increase of surface that comes 

 by dividing a coarse lump into fine particles. 



The niarbles represent the careless tillage of Mr. Black, 

 and the finer particles the thorough tillage of Mr. White- 

 Mr. White plows about one-third deeper than Mr. 

 Black, and thereby makes another addition to the capac- 

 ity of his reservoir. 



The coarse soil, as represented by the marbles, will lose 

 its film moisture by evapoi-ation much more readily than 

 the soil repi-esented by 

 Fig. 23, particularly if (\ 

 the surface of the latter 

 is covered by fine par- 

 ticles representing an 

 earth-mulch. 



16. T ill age makes 

 jplant-food availalle. — 

 Another difference in 

 the culture given by 

 Black and White is that 

 the better tillage enables the ])]ant to realize more food than all fer- 

 ilizers which may be ai)plied. Tliere is also a benefit in making 

 availal)le some of the i)lant-food that nature has put in tlie soil. 



Fig. 22.— Water lield hy a 

 coarse soil. 



Fig. 2Z.— Water Md by 



a fine soil. 



