98 



may also have had an additive effect The sand, however, had 

 been repeatedly treated with disulphonic acid for the purpose 

 of removing this source of error as well as to get rid of all ni- 

 trates which might be present. 



THE INFLUENCE OF EARTH MULCHES UPON THE MOVEMENT AND 

 DISTRIBUTION OF WATER-SOLUBLE SALTS IN SOILS. 



In our earlier investigations relating to the influence of deep 

 and shallow cultivation upon the yields of crops, and in regard 

 to the influence of mulches generally, conducted at the Wiscon- 

 sin Agricultural Experiment Station, relations were observed 

 which made it appear that mulches influence yields in other 

 ways than by merely controlling the movement and amount of 

 soil moisture. 







CONDITIONS OF THE EXPERIMENT. 



Using a set of 24 cylinders, represented in Fig. 1, p. 64, the 

 effect of 3-inch earth mulches upon the movement and distribu- 

 tion of water-soluble salts in six soil types was studied during a 

 period of 70 days. Four cylinders were charged, by careful 

 and unifornn tamping, with each type of soil, in the manner al- 

 ready described, and a composite sample of each taken to give 

 the soluble salt condition of the soils when the observations were 

 begun. 



After all of the cylinders had been charged and put in place, 

 3 inches of the soil were removed from two of each set. of four 

 cylinders and so much of it returned in a loose condition as was 

 required to fill them again level full. 



The soils used were, in all cases, taken from the surface foot 

 of the respective types and were placed in the cylinders after 

 a thorough mixing of the bulk samples, in their normal moisture 

 and textual field conditions. Water was then added to the 

 reservoirs with the covers in place, until each had become cap- 

 illiarily saturated, when all were exposed to surface evapora- 

 tion under a canvas shade, which excluded the rain. 



