1921.] 



Artificial Farmyard Manure. 



401 



on the making of farmyard manure.* Three equal portions of 

 straw were saturated either with water or urine and allowed 

 to ferment for three months in the laboratory, the two portiojis 

 with urine being subjected to different temperatures. As will 

 be seen from the following table, these two portions fermented 

 to dilferent degrees — the dry matter losses being 49 and 60 

 per cent, respectively, hut the final nitrogen content was almost 

 identical, and practically three-fom'ths of the nitrogen supplied 

 as urine was lost. 



Loss of Dry 



Matter. Xitrogen. 

 Temp. per cent. Initial. Final. Loss— or 



Gain + 



in grin. mgrm. rngrra. 



Straw with water ... (36°C. = 97°F.) 40-1 71 97 +26 

 Straw „ urine ... (26°C. = 80T.) 49-1 507 178 -329 

 Straw (36C.==97F.) 59-8 507 176 -331 



It would be erroneous, however, to assume that such losses 

 are inevitably connected with a satisfactory breakdown of 

 straw, or that the conditions ordinarily obtaining in the farm- 

 yard at all represent optimum proportions between the straw 

 which is to be decomposed, and the concentration of nitrogen 

 in the urine which eventually serves for this decomposition. 

 That equally good rotting may be obtained w^ithout loss of 

 nitrogen is shown by the cases given in the table below\ In 

 the experiments to which the table refers, straw was incubated 

 with urine in different concentrations for periods up to 86 days. 

 Even after this period the losses that occurred with satisfactory 

 rotting and within the lower concentrations were only about 4 

 per cent, of the total nitrogen of the final product. The ordinary 

 losses of the manure heap are frequently more than tenfold this 

 amount. 



Number of Experiment. 



At beginning 



(1) (2) (3) 



(4) 



Straw and urine nitrogen 



77-5 157-6 £.37'6 



317*6 



After 86 days 







Total nitrogen 



77-3 1.53-1 .226 S 



262-1 



In addition to the two phases already mentioned, (a) in which 

 straw overloaded with nitrogen loses it to a definite degree, and 

 (h) in which straw with the requisite amount of nitrogen u.ay 

 undergo rotting without appreciable loss and is therefore in a state 

 of equilibrium, there exists a third phase in which under-saturated 

 straw, by the agency of micro-organisms, exhibits a well- 

 marked property of picking up nitrogen, particularly in the 



* See, for example, Russell & Richards, Journ. Agn'c. Set., 1917, Vol. VIII, 

 p. 495. 



B 



