108 



Bulletin 174. 



The difference in the capacity of himpy and fine soils to hold film 

 moisture is surprising to one who has not given the question study. 

 George AY. Cavanaugh, assistant chemist at the Cornell Experiment 

 Station, has very graphically shown this by the following 

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

 by Fig. 22, and the total amount of film 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 film moisture 

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

 The weight of material is the same in each 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 marbles 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 evaporation much more readily than 



the soil represented by 

 Fig. 23, particularly if 

 the surface of the latter 

 is covered by fine par- 

 ticles representing an 

 earth-mulch. 



16. Tillage wMhes 

 jylant-food availahle. — 

 Another difference in 

 the culture given by 

 Black and White is that 

 the better tillage enables the plant to realize more food than all fer- 

 ilizers which may be applied. There is also a benefit in making 

 available some of the plant-food that nature has put in the soil. 



Fig. 2'i.— Water held by a 

 coarse soil. 



Fig. 2^. — Water held by 

 a fine soil. 



