1910.] PUBLIC DOCUMENT — No. 31. 81 



The phosphoric acid in slag is comparable in its quickness of 

 action to nitrogen in barnyard niannre, tankage and green crops; 

 and the phosphoric acid in acid phosphate to the action of nitro- 

 gen in nitrate of soda. A combination of slag and sulfate of 

 potash (500 pounds slag and 150 pounds potash) has been 

 found to work especially well upon grass land, and to be very 

 favorable to the development of clover. 



Ql'Axtity of Slag pee Acre. 



If the soil is particularly deficient in phosphoric acid, one can 

 use as high as from 800 to 900 pounds of slag to the acre, plowed 

 in and supplemented with 200 pounds of acid phosphate in the 

 hill or drill. 



If, on the contrary, the soil is naturally rich in phosphoric 

 acid, or has been made so by large additions of slag for a series 

 of years (1,000 or more pounds yearly), then it is necessary 

 oidy to replace from year to year the amount removed by the 

 crop. In such cases Maercker states that one part of phosphoric 

 acid in basic slag is as valuable as an equal amount in acid 

 phosphate. 



