MANAGEMENT OF SPECIAL SOILS 287 



of average yard manure, resulting from perhaps two 

 tons of fresh manure, contains about 500 pounds of dry 

 matter, 10 pounds of nitrogen, 3 pounds of phosphorus, 

 and 8 pounds of potassium, one-half of the dry matter, 

 nitrogen, and potassium, and one fourth of the phos- 

 phorus having been lost. 



''In an experiment conducted at Cornell University, 

 4,000 pounds of ordinary manure from the horse stable, 

 worth $2.74 per ton for the plant food content (at com- 

 mercial prices) were exposed in a pile out of doors from 

 April 25 to September 22. At the end of that time 

 the total weight had decreased to 1,770 pounds, worth 

 only $2.34 per ton. In other words, the value of this 

 pile of manure was reduced from $5.48 to $2.03 during 

 five months' exposure. ... In no case should manure be 

 allowed to heat and ferment before being spread on the 

 land, if its full value is to be secured." 



Manure gives best results when applied thinly and 

 worked well into the soil. It is usually applied (1) as 

 a top dressing for grass land, or (2) plowed in before 

 corn, roots, potatoes or barley, or (3) on some of the 

 lighter types of soil plowed under in the fallow year. It 

 may be objectionable (1) when applied thickly in dry 

 areas and plowed under for a crop the same season, or 

 (2) when plowed under on heavy soils in the fallow year. 

 In the former case the soil may dry out, in the latter 

 the growth may be too rank and weak and the crop may 

 lodge. 



239B. The Place of Commercial Fertilizers. — Com- 

 mercial fertilizers have not yet demonstrated that 

 they have a place in our cropping system. These sub- 

 stances do not, like manure, improve the tilth or physical 

 or biological condition of the soil. They are valuable 

 only for the nitrogen, phosphorus, potassium or lime they 



