MANURE, YIELD AND SOLUBLE SALTS IN SOILS. 23 



than it is in the Miami Loam, and if this more soluble potash 

 has been an influential factor in determining the yield of corn, 

 this relation is in harmony with what has been observed, 

 namely, that like amounts of manure were relatively more 

 effective on the poorer soils which have been shown to have a 

 less strong absorptive power for the potash. 



INFLUENCE OF 25, 50, 100 AND 200 TONS OF MANURE PER ACRE 

 UPON THE) WATER-SOLUBLE SALTS OF SOILS. 



In order to supplement the field studies regarding the influ- 

 ence of small amounts of stable manure upon the water-soluble 

 salts in soils, a series of experiments was started the first week 

 in July to measure the influence of 25, 50, 100 and 200 tons of 

 manure per acre upon the water-soluble salts which could be 

 recovered from the 8 soil types under investigation. 



The farm yard manure used was cow dung, taken from the 

 yard not more than two or three days after being dropped. It 

 was rendered water-free by drying at 100 O. and then ground 

 to a fine powder by running through a mill. From the water- 

 free manure the requisite amounts were weighed out at the 

 central laboratory, and sent in separate parcels to the field par- 

 ties in proper amounts to be incorporated with designated 

 amounts of soil. Like amounts of thq same manure were, 

 therefore, used on all soils. 



The 20 Ibs. of soil used were composites taken with the soil 

 tube from the surface foot of the unfertilized sub-plots of the 

 respective soil types. Where the soils were not in their opti- 

 mum moisture condition when collected,, they were rendered so 

 by the addition of water. 



After having been thoroughly mixed, the soil was weighed 

 out in 4-lb. lots and with these the prepared manure was thor- 

 oughly incorporated in the following amounts. 



Amounts of wafer-free manure added to 4-pound lots of soil. 



