No. 7. DEPARTMENT OF AGRICULTURE. 449 



value determined by computing from the value of the increase which 

 it produces iu the different crops. 



The plant food in a ton of manure varies greatly ith the materials 

 used for feed and bedding. Thus, wheat straw contains per ton 

 about ten pounds of nitrogen, two pounds of phosphorus and seven- 

 teen pounds of potassium; while clover hay contains about forty 

 pounds of nitrogen, five pounds of phosphorus and thirty pounds of 

 potassium. At fifteen cents a pound for nitrogen, twelve cents 

 for phosphorus and six cents for potassium, the value of these ele- 

 ments is |2.76 a ton of wheat straw, ^5.40 in timothy hay, $8.40 in 

 clover hay and ?9.42 in a ton of alfalfa hay. 



The following facts may well be kept in mind : 



1- In grain crops about two-thirds of the nitrogen, three-fourths 

 of the phosphorus and one-fourth of the potassium required for the 

 crop will be contained in the grain, while about one-third of the ni- 

 trogen, one-fourth of the phosphorus and three-fourths of the po- 

 tassium required for the crop will be found in the straw or stalks. 



2. In nitrogen and phosphorus, clover and other legume crops are 

 about as rich as grains, nearly twice as rich as timothy or red 

 top and more than twice as rich as straw or stalks, 



3. When crops are fed to live stock about three-fourths of the ni- 

 trogen, three-fourths of the phosphorus and practically all of the 

 potassium contained in the feed will be returned in the solid and 

 liquid manure, the animals retaining only about one-fourth of the ni- 

 trogen and one-fourth of the phosphorus, as a general average. 



From these facts it becomes very plain that the quality or richness 

 of manure must depend very largely upon the kind of feed used. 



The value of a given supply of manure varies greatly with the ex- 

 posure it suffers under weather conditions. 



If ordinary fresh farm manure contains ten pounds of nitrogen, 

 two pounds of phosphorus and ten pounds of potassium per ton of 

 manure with a dry matter basis of 25 per cent, (and 75 per cent, 

 water), the manure that will result from holding such fresh manure 

 until it becomes more or less rotted will vary greatly in composition, 

 depending upon the conditions to which it is subjected. 



If the fresh manure is exposed for a few weeks to the leaching 

 of heavy rains, half of the nitrogen and potassium may be leached 

 out, while smaller losses of phosphorus and dry matter occur, so that 

 a full ton of the resulting manure, in which the urine (which usually 

 contains about half the nitrogen and potassium) has been replaced 

 by rain water, may contain only six pounds of nitrogen, two pounds 

 of phosphorus and six pounds of potassium. This difference of four 

 pounds each of nitrogen and potassium does not represent the total 

 loss, because if the pile contained ten tons of fresh manure there will 

 be left perhaps only eight tons of the leached manure, even with the 

 same percentages or dry matter and water. 



If, however, the pile of manure suffers less from leaching but 

 more from fermentation and heating for several months, the loss of 

 dry matter and nitrogen will be great, while the loss of phosphorus 

 and potassium will be less. Rotted manure produced in this way is 

 usually richer per ton than fresh manure, but the total amount of 

 manure has been so reduced that the loss is very great. 



These simple principles should be kept in mind: 



29—7—1906. 



