166 



SOIL PHYSICS AND MANAGEMENT 



good advantage. Calcium sulfate, laud plaster, may be dusted 

 over the manure. The sulfuric acid unites with the ammonia, 

 forming ammonium suifate, which is comparatively slowly soluble, 

 Common salt is sometimes used, but both it and land plaster are too 

 expensive for general use. 



Certain substances may be used as absorbents and also for re- 

 enforcing the manure. If the manure is to be used on land de- 

 ficient in the element potassium, kainit may be used for this pur- 

 pose and when the manure is scattered over the land will supply the 

 needed element. Finely ground rock phosphate or floats may be 

 used as an absorbent and at the same time supply the element phos- 

 phorus, in which most soils are deficient. At the Ohio Station the 

 average annual increase for stall manure and floats over stall manure 

 alone was 7.2 bushels of corn per acre, while the increase for yard 

 manure treated over untreated was 6.4 bushels. The corresponding 

 increases for wheat were 4.1 and 3.4 bushels per acre. 



The next table shows the amount of loss from manure with 

 absorbent reenforcement exposed for three months. The experi- 

 ments were made at the Ohio Station. 



Composition of Steer Manure After Exposure for Three Months Pounds 



Per Ton 6 



The value of manure in a soil depends upon three things: 

 first, the beneficial physical effect produced ; second, the plant food 

 supplied, and, third, the stimulus given to bacterial activity. Its 



