202 SYSTEMS OF PERMANENT AGRICULTURE 



nitrogen, 28.07 P er cen ^ f the phosphorus, and 28.45 P er cent f 

 the potassium, of the food consumed, the differences being prac- 

 tically accounted for by the larger amounts of milk produced by the 

 best cows. However, the poorest cow of the six, in milk produc- 

 tion, digested, during the three successive 5-day periods, 47.18 

 per cent, 44.77 per cent, and 52.54 per cent, respectively, of the 

 total phosphorus consumed in the food; or, as an average of the 

 15-day period, only 52.94 per cent of the phosphorus taken in the 

 food was recovered in the dung and urine from this cow. 



The Pennsylvania Experiment Station (Annual Report for 1899- 

 1900, page 321) reports digestion experiments with two milk cows 

 during a period of 50 days, with the results shown in Table 31. 

 The rations fed were three fifths mixed clover and timothy hay, 

 and two fifths concentrates, including corn meal, buckwheat 

 middlings, cotton-seed meal, and linseed meal. 



TABLE 31. PLANT FOOD RECOVERED FROM FOOD CONSUMED BY 



MILK Cows 

 Per Cow for 50 Days: Average for 2 Cows: Pennsylvania Experiments 



In the Pennsylvania experiments both the nitrogen and potas- 

 sium are slightly more than accounted for, but 8.12 per cent of the 

 phosphorus in the food consumed was retained by the animals, 

 probably in part for the formation of bones in unborn calves. 



As an average of both the Pennsylvania and Illinois experiments, 

 only one third (exactly 33.57 per cent) of the nitrogen consumed 

 was recovered in the dung, and nearly one half (48.91 per cent) was 

 excreted in the urine. These facts are worth remembering, and 

 also that 28 per cent of the phosphorus consumed was not recov- 

 ered in the total manurial excrements. 



