BULLETIN 919, U. S, DEPARTMENT OF AGRICULTURE. 



To determine the fertilizing constituents in the manure the feeds 

 used throughout the winter were classified so that their average com- 

 position could be obtained. This was done by referring to standard 

 tables containing the analyses of the various classes of feeds. 



Since a cow in the process of digestion utilizes on the average only 

 approximately 25 per cent of the nitrogen, 30 per cent of the phos- 

 phorus, and 15 per cent of the potash, it is evident that 75 per cent 

 of the nitrogen, TO per cent of the phosphorus, and 85 per cent of the 

 potash is available for fertilizers. By knowing the weights of the 

 feeds and their average composition it was possible to determine the 

 approximate amounts of the three fertilizing elements consumed. 

 From these figures deductions were made for that utilized by the 

 cows to obtain the total amounts of the fertilizing elements voided. In 

 figuring the amount of fertilizing constituents saved the same factors 

 were considered that determined the weight of manure credited to 

 cows, namely, the time the cattle were out, making the fertilizer 

 unreclaimable, the amount of liquid lost through holes in the gut- 

 ters, and the loss in leaching while stored in the yards. 



A ton of average manure during the winter was estimated to have 

 the following constituents : 



Pounds. 



Nitrogen 9.9 



Commercial phosphoric acid 4. 2 



Potash 11. 5 



No credit was allowed for bedding, as the large acreage of oats and 

 a superabundance of straw from the fertile soil makes the farm price 

 of the straw less than the value of the fertilizing constituents in it. 

 The farm price of the straw is little more than enough to pay for 

 bringing the straw to the barn. It might be hauled directly from 

 the stack to the field instead of the barn, thereby distributing the fer- 

 tilizing elements on the soil at the same expense. 



Table 3. — Manure and fertilizing constituents credited to the herds during the 

 two winters and the tico summers. 





Winter. 



Summer. 



Item. 



1917-18 



1919-20 



Average. 



1917-18 i 



1919 



Average. 



Total manure saved tons. . 



Manure credited per 100 pounds of milk, 



1, 128. 2 

 4,200.0 



802.3 

 3,200.0 



965.2 

 3,800.0 



115 



179.1 

 600.0 



126.8 

 400.0 



153.0 

 600.0 



13 















Winter average. 



Summer average. 





Nitrogen. 



Phos- 

 phoric 

 acid. 



Potash. 



Nitrogen. 



Phos- 

 phoric 

 acid. 



Potash. 



Fertilizing constituents in manure, 



9,474 

 18.2 



4,003 



7.7 



11,134 

 21.3 



1,500 

 2.9 



634 

 1.2 



1,765 



Credit per cow pounds . . 



3.4 



i The summer of 1917-18 included the months of September and October, 1917, and May, June, July, and 

 August, 1918. 



