212 



BACTERIA AND SOIL FERTILITY 



bedding, containing varying amounts of water, and in different 

 conditions of preservation or exposure, as nitrogen ranging from 

 4.2 to 27.2 pounds per ton, phosphorus from ,9 to 6.5 pounds, 

 and potassium from 2.2 to 23.2 pounds per ton. 



Losses from Manure. — The losses sustained in manure vary 

 with the following factors : 



1. Time and condition when conveyed to the field. Manure 

 which is produced on the field suffers smaller losses than does that 

 manure produced in the stable and then conveyed to the field. 

 This in turn shows less loss than manure allowed to accumulate 

 in the barn and later carried to the soil. The loss is still greater 

 where the manure is taken from the stable into piles. The use 

 of an abundant supply of bedding material reduces the loss, as 

 considerable of the liquid manure is thus saved. 



2. The age of the manure greatly influences its composition, 

 as anyone who has observed a pile of manure in a barnyard knows 

 that it gradually diminishes in size and changes in appearance until 

 it is finally difficult to distinguish it from the soil. The loss dur- 

 ing this transformation is greater in the humid than in the arid 

 districts. The average percentage loss of sheep manure kept in 

 piles for the semi-arid region as reported by Headden is as fol- 

 lows: 



Time 



Dry 

 Weight 



Total 

 Nitrogen 



Total 

 Phosphorus 



Total 

 Potassium 



15 months 

 2 years 



56.7 



48.6 

 68.0 



42.0 

 59.0 



3S'0 



That is, during one year the total dry weight decreases one- 

 third and the total nitrogen and phosphorus about one-half. By 

 the end of the second year nearly three-fifths of the dry matter, 

 total nitrogen and phosphorus have been lost and one third of the 

 potassium. Although old manure is richer in the essential ele- 

 ments of plant-food, pound for pound, than is fresh manure, 



